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Title: Absence Of Dirac States In Baznbi2 Induced By Spin-orbit Coupling.
Creator: Ren, Weijun, Wang, Aifeng, Graf, D., Liu, Yu, Zhang, Zhidong, Yin, Wei-Guo, Petrovic, C.
Abstract/Description: We report magnetotransport properties of BaZnBi2 single crystals. Whereas electronic structure features Dirac states, such states are removed from the Fermi level by spin-orbit coupling (SOC) and consequently electronic transport is dominated by the small hole and electron pockets. Our results are consistent with not only three-dimensional, but also with quasi-two-dimensional portions of the Fermi surface. The SOC-induced gap in Dirac states is much larger when compared to isostructural...
Show moreWe report magnetotransport properties of BaZnBi2 single crystals. Whereas electronic structure features Dirac states, such states are removed from the Fermi level by spin-orbit coupling (SOC) and consequently electronic transport is dominated by the small hole and electron pockets. Our results are consistent with not only three-dimensional, but also with quasi-two-dimensional portions of the Fermi surface. The SOC-induced gap in Dirac states is much larger when compared to isostructural SrMnBi2. This suggests that not only long-range magnetic order, but also mass of the alkaline-earth atoms A in ABX(2) (A = alkaline-earth, B = transition-metal, and X = Bi/Sb) are important for the presence of low-energy states obeying the relativistic Dirac equation at the Fermi surface.
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Date Issued: 2018-01-22
Identifier: FSU_libsubv1_wos_000423341500001, 10.1103/PhysRevB.97.035147
Format: Citation

Title: Anisotropic Antiferromagnetic Order In The Spin-orbit Coupled Trigonal-lattice Ca2sr2iro6.
Creator: Sheng, Jieming, Ye, Feng, Hoffmann, Christina, Cooper, Valentino R., Okamoto, Satoshi, Terzic, Jasminka, Zheng, Hao, Zhao, Hengdi, Cao, G.
Abstract/Description: We used single-crystal x-ray and neutron diffraction to investigate the crystal and magnetic structures of trigonal lattice iridate Ca2Sr2IrO6. The crystal structure is determined to be R (3) over bar with two distinct Ir sites. The system exhibits long-range antiferromagnetic order below T-N = 13.1 K. The magnetic wave vector is identified as (0,0.5,1) with ferromagnetic coupling along the a axis and antiferromagnetic correlation along the b axis. Spins align dominantly within the basal...
Show moreWe used single-crystal x-ray and neutron diffraction to investigate the crystal and magnetic structures of trigonal lattice iridate Ca2Sr2IrO6. The crystal structure is determined to be R (3) over bar with two distinct Ir sites. The system exhibits long-range antiferromagnetic order below T-N = 13.1 K. The magnetic wave vector is identified as (0,0.5,1) with ferromagnetic coupling along the a axis and antiferromagnetic correlation along the b axis. Spins align dominantly within the basal plane along the [1,2,0] direction and tilt 34 degrees toward the c axis. The ordered moment is 0.66(3) mu(B) /Tr, larger than other iridates where iridium ions form corner- or edge-sharing IrO6 octahedral networks. The tilting angle is reduced to approximate to 19 degrees when a magnetic field of 4.9 T is applied along the c axis. Density functional theory calculations confirm that the experimentally determined magnetic configuration is the most probable ground state with an insulating gap similar to 0.5 eV.
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Date Issued: 2018-06-11
Identifier: FSU_libsubv1_wos_000434761900004, 10.1103/PhysRevB.97.235116
Format: Citation

Title: Detailed Study Of The Fermi Surfaces Of The Type-ii Dirac Semimetallic Candidates Xte2 (x=pd,pt).
Creator: Zheng, W., Schonemann, R., Aryal, N., Zhou, Q., Rhodes, D., Chiu, Y.-C., Chen, K.-W., Kampert, E., Foerster, T., Martin, T. J., McCandless, G. T., Chan, J. Y., Manousakis, E.,...
Show moreZheng, W., Schonemann, R., Aryal, N., Zhou, Q., Rhodes, D., Chiu, Y.-C., Chen, K.-W., Kampert, E., Foerster, T., Martin, T. J., McCandless, G. T., Chan, J. Y., Manousakis, E., Balicas, L.
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Abstract/Description: We present a detailed quantum oscillatory study on the Dirac type-II semimetallic candidates PdTe2 and PtTe2 via the temperature and the angular dependence of the de Haas-van Alphen and Shubnikov-de Haas effects. In high-quality single crystals of both compounds, i.e., displaying carrier mobilities between 10(3) and 10(4) cm(2)/Vs, we observed a large nonsaturating magnetoresistivity which in PtTe2 at a temperature T = 1.3 K leads to an increase in the resistivity up to (5 x 10(4))% under a...
Show moreWe present a detailed quantum oscillatory study on the Dirac type-II semimetallic candidates PdTe2 and PtTe2 via the temperature and the angular dependence of the de Haas-van Alphen and Shubnikov-de Haas effects. In high-quality single crystals of both compounds, i.e., displaying carrier mobilities between 10(3) and 10(4) cm(2)/Vs, we observed a large nonsaturating magnetoresistivity which in PtTe2 at a temperature T = 1.3 K leads to an increase in the resistivity up to (5 x 10(4))% under a magnetic field mu H-0 = 62 T. These high mobilities correlate with their light effective masses in the range of 0.04 to 1 bare electron mass according to our measurements. For PdTe2 the experimentally determined Fermi surface cross-sectional areas show excellent agreement with those resulting from band structure calculations. Surprisingly, this is not the case for PtTe2, whose agreement between calculations and experiments is relatively poor even when electronic correlations are included in the calculations. Therefore, our study provides strong support for the existence of a Dirac type-II node in PdTe2 and probably also for PtTe2. Band structure calculations indicate that the topologically nontrivial bands of PtTe2 do not cross the Fermi level epsilon(F). In contrast, for PdTe2 the Dirac type-II cone does intersect Bp, although our calculations also indicate that the associated cyclotron orbit on the Fermi surface is located in a distinct k(z) plane with respect to that of the Dirac type-II node. Therefore, it should yield a trivial Berry phase.
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Date Issued: 2018-06-29
Identifier: FSU_libsubv1_wos_000436907600002, 10.1103/PhysRevB.97.235154
Format: Citation

Title: Field-induced Spin Splitting And Anomalous Photoluminescence Circular Polarization In Ch3nh3pbi3 Films At High Magnetic Field.
Creator: Zhang, Chuang, Sun, Dali, Yu, Zhi-Gang, Sheng, Chuan-Xiang, McGill, Stephen, Semenov, Dmitry, Vardeny, Zeev Valy
Abstract/Description: The organic-inorganic hybrid perovskites show excellent optical and electrical properties for photovoltaic and a myriad of other optoelectronics applications. Using high-field magneto-optical measurements up to 17.5 T at cryogenic temperatures, we have studied the spin-dependent optical transitions in the prototype CH3NH3PbI3, which are manifested in the field-induced circularly polarized photoluminescence emission. The energy splitting between left and right circularly polarized emission...
Show moreThe organic-inorganic hybrid perovskites show excellent optical and electrical properties for photovoltaic and a myriad of other optoelectronics applications. Using high-field magneto-optical measurements up to 17.5 T at cryogenic temperatures, we have studied the spin-dependent optical transitions in the prototype CH3NH3PbI3, which are manifested in the field-induced circularly polarized photoluminescence emission. The energy splitting between left and right circularly polarized emission bands is measured to be similar to 1.5 meV at 17.5 T, from which we obtained an exciton effective g factor of similar to 1.32. Also from the photoluminescence diamagnetic shift we estimate the exciton binding energy to be similar to 17 meV at low temperature. Surprisingly, the corresponding field-induced circular polarization is "anomalous" in that the photoluminescence emission of the higher split energy band is stronger than that of the lower split band. This "reversed" intensity ratio originates from the combination of long electron spin relaxation time and hole negative g factor in CH3NH3PbI3, which are in agreement with a model based on the k.p effective-mass approximation.
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Date Issued: 2018-04-16
Identifier: FSU_libsubv1_wos_000430055800003, 10.1103/PhysRevB.97.134412
Format: Citation

Title: Fermi Surface Reconstruction And Dimensional Topology Change In Nd-doped Cecoin5.
Creator: Klotz, J., Goetze, K., Sheikin, I., Foerster, T., Graf, D., Park, J.-H., Choi, E. S., Hu, R., Petrovic, C., Wosnitza, J., Green, E. L.
Abstract/Description: We performed low-temperature de Haas-van Alphen effect measurements on a Ce1-xNdxCoIn5 series, for x = 0.02, 0.05, 0.1, and 1, down to T = 40 mK using torque magnetometry in magnetic fields up to 35 T. Our results indicate that a Fermi surface (FS) reconstruction occurs from a quasi-two-dimensional topology for Nd-2% to a rather three-dimensional one for Nd-5%, thus reducing the possibility of perfect FS nesting. The FS evolves further with increasing Nd content with no observed divergence of...
Show moreWe performed low-temperature de Haas-van Alphen effect measurements on a Ce1-xNdxCoIn5 series, for x = 0.02, 0.05, 0.1, and 1, down to T = 40 mK using torque magnetometry in magnetic fields up to 35 T. Our results indicate that a Fermi surface (FS) reconstruction occurs from a quasi-two-dimensional topology for Nd-2% to a rather three-dimensional one for Nd-5%, thus reducing the possibility of perfect FS nesting. The FS evolves further with increasing Nd content with no observed divergence of the effective mass between Nd-2% and 10%, consistent with the crossing of a spin density wave type of quantum critical point. Our results elucidate the origin of the Q phase observed at the 5% Nd-doping level [Raymond et al., T. Phys. Soc. Jpn. 83, 013707 (2014)].
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Date Issued: 2018-08-09
Identifier: FSU_libsubv1_wos_000441234900001, 10.1103/PhysRevB.98.081105
Format: Citation

Title: Observation Of Two Critical Points Linked To The High-field Phase B In Cecu2si2.
Creator: Weickert, Franziska, Gegenwart, Philipp, Geibel, Christoph, Assmus, Wolf, Steglich, Frank
Abstract/Description: We present thermal expansion and magnetostriction measurements on a CeCu2Si2 single crystal of A/S type up to 17.9 T magnetic field applied along the crystallographic a direction (Delta L parallel to a parallel to H) and down to 0.015 K temperature. We identify clear thermodynamic anomalies at the superconducting transition T-c and at two second-order transitions T-A,T-B into ordered phases A and B. Our measurements establish the boundary of phase B at high field and low temperature. No...
Show moreWe present thermal expansion and magnetostriction measurements on a CeCu2Si2 single crystal of A/S type up to 17.9 T magnetic field applied along the crystallographic a direction (Delta L parallel to a parallel to H) and down to 0.015 K temperature. We identify clear thermodynamic anomalies at the superconducting transition T-c and at two second-order transitions T-A,T-B into ordered phases A and B. Our measurements establish the boundary of phase B at high field and low temperature. No evidence for additional high-field phases above B is found up to the maximum field. We speculate based on our experimental results that (i) phase B is similar to phase A of spin-density wave type and (ii) the first-order phase transition between A and B is caused by Fermi-surface reconstruction. We furthermore identify a quantum critical point at H-c similar or equal to 17 T, where T-B is suppresssed to zero, and a bicritical point at (0.35 K, 7.0 T), where phase lines T-A(H) and T-B(H) meet.
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Date Issued: 2018-08-08
Identifier: FSU_libsubv1_wos_000441108600002, 10.1103/PhysRevB.98.085115
Format: Citation

Title: Interplay Of Magnetism And Transport In Hobi.
Creator: Yang, H.-Y., Gaudet, J., Aczel, A. A., Graf, D. E., Blaha, P., Gaulin, B. D., Tafti, Fazel
Abstract/Description: We report the observation of an extreme magnetoresistance (XMR) in HoBi with a large magnetic moment from Ho f electrons. Neutron scattering is used to determine the magnetic wave vectors across several metamagnetic transitions on the phase diagram of HoBi. Unlike other magnetic rare-earth monopnictides, the field dependence of resistivity in HoBi is nonmonotonic and reveals clear signatures of every metamagnetic transition in the low-temperature and low-field regime, at T < 2 K and H < 2.3 T...
Show moreWe report the observation of an extreme magnetoresistance (XMR) in HoBi with a large magnetic moment from Ho f electrons. Neutron scattering is used to determine the magnetic wave vectors across several metamagnetic transitions on the phase diagram of HoBi. Unlike other magnetic rare-earth monopnictides, the field dependence of resistivity in HoBi is nonmonotonic and reveals clear signatures of every metamagnetic transition in the low-temperature and low-field regime, at T < 2 K and H < 2.3 T. The XMR appears at H > 2.3 T after all the metamagnetic transitions are complete and the system is spin polarized by the external magnetic field. The existence of an onset field for XMR and the intimate connection between magnetism and transport in HoBi are unprecedented among the magnetic rare-earth monopnictides. Therefore, HoBi provides a unique opportunity to understand the electrical transport in magnetic XMR semimetals.
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Date Issued: 2018-07-27
Identifier: FSU_libsubv1_wos_000439974200002, 10.1103/PhysRevB.98.045136
Format: Citation

Title: Observation Of Cyclotron Antiresonance In The Topological Insulator Bi2te3.
Creator: Dordevic, S., Lei, Hechang, Petrovic, C., Ludwig, J., Li, Z. Q., Smirnov, D.
Abstract/Description: We report on the experimental observation of a cyclotron antiresonance in a canonical three-dimensional topological insulator Bi2Te3. Magnetoreflectance response of single-crystal Bi2Te3 was studied in 18-T magnetic field, and compared to other topological insulators studied before, the main spectral feature is inverted. We refer to it as an antiresonance. In order to describe this unconventional behavior we propose the idea of an imaginary cyclotron resonance frequency, which on the other...
Show moreWe report on the experimental observation of a cyclotron antiresonance in a canonical three-dimensional topological insulator Bi2Te3. Magnetoreflectance response of single-crystal Bi2Te3 was studied in 18-T magnetic field, and compared to other topological insulators studied before, the main spectral feature is inverted. We refer to it as an antiresonance. In order to describe this unconventional behavior we propose the idea of an imaginary cyclotron resonance frequency, which on the other hand indicates that the form of the Lorentz force that magnetic field exerts on charge carriers takes an unconventional form.
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Date Issued: 2018-09-20
Identifier: FSU_libsubv1_wos_000445173200003, 10.1103/PhysRevB.98.115138
Format: Citation

Title: Nature Of Lattice Distortions In The Cubic Double Perovskite Ba2naoso6.
Creator: Liu, W., Cong, R., Reyes, A. P., Fisher, I. R., Mitrovic, V. F.
Abstract/Description: We present detailed calculations of the electric field gradient (EFG) using a point charge approximation in Ba2NaOsO6, a Mott insulator with strong spin-orbit interaction. Recent Na-23 nuclear magnetic resonance (NMR) measurements found that the onset of local point symmetry breaking, likely caused by the formation of quadrupolar order [Chen, Pereira, and Balents, Phys. Rev. B 82, 174440 (2010)], precedes the formation of long range magnetic order in this compound [Lu et al., Nat. Commun. 8,...
Show moreWe present detailed calculations of the electric field gradient (EFG) using a point charge approximation in Ba2NaOsO6, a Mott insulator with strong spin-orbit interaction. Recent Na-23 nuclear magnetic resonance (NMR) measurements found that the onset of local point symmetry breaking, likely caused by the formation of quadrupolar order [Chen, Pereira, and Balents, Phys. Rev. B 82, 174440 (2010)], precedes the formation of long range magnetic order in this compound [Lu et al., Nat. Commun. 8, 14407 (2017); Liu et al., Physica B 536, 863 (2018)]. An extension of the static Na-23 NMR measurements as a function of the orientation of a 15 T applied magnetic field at 8 K in the magnetically ordered phase is reported. Broken local cubic symmetry induces a nonspherical electronic charge distribution around the Na site and thus finite EFG, affecting the NMR spectral shape. We combine the spectral analysis as a function of the orientation of the magnetic field with calculations of the EFG to determine the exact microscopic nature of the lattice distortions present in low temperature phases of this material. We establish that orthorhombic distortions, constrained along the cubic axes of the perovskite reference unit cell, of oxygen octahedra surrounding Na nuclei are present in the magnetic phase. Other common types of distortions often observed in oxide structures are considered as well.
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Date Issued: 2018-06-14
Identifier: FSU_libsubv1_wos_000435332500001, 10.1103/PhysRevB.97.224103
Format: Citation

Title: Nodal Superconductivity Coexists With Low-moment Static Magnetism In Single-crystalline Tetragonal Fes: A Muon Spin Relaxation And Rotation Study.
Creator: Tan, C., Ying, T. P., Ding, Z. F., Zhang, J., MacLaughlin, D. E., Bernal, O. O., Ho, P. C., Huang, K., Watanabe, I., Li, S. Y., Shu, L.
Abstract/Description: We report muon spin relaxation and rotation (mu SR) measurements on hydrothermally grown single crystals of superconducting tetragonal FeS, which help to clarify the controversial magnetic state and superconducting gap symmetry of this compound. mu SR time spectra were obtained from 280 K down to 0.025 K in zero field (ZF) and applied fields up to 75 mT. In ZF, the observed loss of initial asymmetry (signal amplitude) and increase of depolarization rate Lambda(ZF) below 13 K indicate the...
Show moreWe report muon spin relaxation and rotation (mu SR) measurements on hydrothermally grown single crystals of superconducting tetragonal FeS, which help to clarify the controversial magnetic state and superconducting gap symmetry of this compound. mu SR time spectra were obtained from 280 K down to 0.025 K in zero field (ZF) and applied fields up to 75 mT. In ZF, the observed loss of initial asymmetry (signal amplitude) and increase of depolarization rate Lambda(ZF) below 13 K indicate the onset of static magnetism, which coexists with superconductivity below T-c. TF mu SR results indicate a linear temperature dependence of the superfluid density at low temperature, consistent with nodal superconductivity. The s+d-wave model gives the best fit to the observed temperature and field dependencies, and yields an in-plane penetration depth value lambda(ab) (T=0) = 241(3) nm.
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Date Issued: 2018-05-31
Identifier: FSU_libsubv1_wos_000433907600005, 10.1103/PhysRevB.97.174524
Format: Citation

Title: Dissipation In Quantum Turbulence In Superfluid He-4 Above 1 K.
Creator: Gao, J., Guo, W., Yui, S., Tsubota, M., Vinen, W. F.
Abstract/Description: There are two commonly discussed forms of quantum turbulence in superfluid He-4 above 1 K: in one there is a random tangle of quantized vortex lines, existing in the presence of a nonturbulent normal fluid; in the second there is a coupled turbulent motion of the two fluids, often exhibiting quasiclassical characteristics on scales larger than the separation between the quantized vortex lines in the superfluid component. The decay of vortex line density, L, in the former case is often...
Show moreThere are two commonly discussed forms of quantum turbulence in superfluid He-4 above 1 K: in one there is a random tangle of quantized vortex lines, existing in the presence of a nonturbulent normal fluid; in the second there is a coupled turbulent motion of the two fluids, often exhibiting quasiclassical characteristics on scales larger than the separation between the quantized vortex lines in the superfluid component. The decay of vortex line density, L, in the former case is often described by the equation dL/dt = -chi 2 (kappa/2 pi)L-2, where kappa is the quantum of circulation and chi(2). is a dimensionless parameter of order unity. The decay of total turbulent energy, E, in the second case is often characterized by an effective kinematic viscosity, v', such that dE/dt = -v'kappa L-2(2). We present values of chi(2 )derived from numerical simulations and from experiment, which we compare with those derived from a theory developed by Vinen and Niemela. We summarize what is presently known about the values of v' from experiment, and we present a brief introductory discussion of the relationship between chi(2 )and v', leaving a more detailed discussion to a later paper.
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Date Issued: 2018-05-29
Identifier: FSU_libsubv1_wos_000433287200005, 10.1103/PhysRevB.97.184518
Format: Citation

Title: Coas: The Line Of 3d Demarcation.
Creator: Campbell, Daniel J., Wang, Limin, Eckberg, Chris, Graf, Dave, Hodovanets, Halyna, Paglione, Johnpierre
Abstract/Description: Transition metal-pnictide compounds have received attention for their tendency to combine magnetism and unconventional superconductivity. Binary CoAs lies on the border of paramagnetism and the more complex behavior seen in isostructural CrAs, MnP, FeAs, and FeP. Here we report the properties of CoAs single crystals grown with two distinct techniques along with density functional theory calculations of its electronic structure and magnetic ground state. While all indications are that CoAs is...
Show moreTransition metal-pnictide compounds have received attention for their tendency to combine magnetism and unconventional superconductivity. Binary CoAs lies on the border of paramagnetism and the more complex behavior seen in isostructural CrAs, MnP, FeAs, and FeP. Here we report the properties of CoAs single crystals grown with two distinct techniques along with density functional theory calculations of its electronic structure and magnetic ground state. While all indications are that CoAs is paramagnetic, both experiment and theory suggest proximity to a ferromagnetic instability. Quantum oscillations are seen in torque measurements up to 31.5 T and support the calculated paramagnetic Fermiology.
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Date Issued: 2018-05-10
Identifier: FSU_libsubv1_wos_000432031700002, 10.1103/PhysRevB.97.174410
Format: Citation

Title: Multistability In An Unusual Phase Diagram Induced By The Competition Between Antiferromagnetic-like Short-range And Ferromagnetic-like Long-range Interactions.
Creator: Nishino, Masamichi, Rikvold, Per Arne, Omand, Conor, Miyashita, Seiji
Abstract/Description: The interplay between competing short-range (SR) and long-range (LR) interactions can cause nontrivial structures in phase diagrams. Recently, horn-shaped unusual structures were found by Monte Carlo simulations in the phase diagram of the Ising antiferromagnet (IA) with infinite-range ferromagnetic-like (F) interactions [Phys. Rev. B 93, 064109 (2016); 96, 174428 (2017)], and also in an IA with LR interactions of elastic origin modeling spin-crossover materials [Phys. Rev. B 96, 144425 (2017...
Show moreThe interplay between competing short-range (SR) and long-range (LR) interactions can cause nontrivial structures in phase diagrams. Recently, horn-shaped unusual structures were found by Monte Carlo simulations in the phase diagram of the Ising antiferromagnet (IA) with infinite-range ferromagnetic-like (F) interactions [Phys. Rev. B 93, 064109 (2016); 96, 174428 (2017)], and also in an IA with LR interactions of elastic origin modeling spin-crossover materials [Phys. Rev. B 96, 144425 (2017)]. To clarify the nature of the phases associated with the horn structures, we study the phase diagram of the IA model with infinite-range F interactions by applying a variational free energy in a cluster mean-field (CMF) approximation. While the simple Bragg-Williams mean-field theory for each sublattice does not produce a horn structure, we find such structures with the CMF method. This confirms that the local thermal fluctuations enabled by the multisite clusters are essential for this phenomenon. We investigate in detail the structure of metastable phases in the phase diagram. In contrast to the phase diagram obtained by the Monte Carlo studies, we find a triple point, at which ferromagnetic-like, antiferromagnetic-like, and disordered phases coexist, and also six tristable regions accompanying the horn structure. We also point out that several characteristic endpoints of first-order transitions appear in the phase diagram. We propose three possible scenarios for the transitions related to the tristable regions. Finally, we discuss the relation between the triple point in this phase diagram and that of a possible lattice-gas model, in which solid, liquid, and gas phases can coexist.
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Date Issued: 2018-10-02
Identifier: FSU_libsubv1_wos_000446296400003, 10.1103/PhysRevB.98.144402
Format: Citation

Title: Field-induced Magnetic Phase Transitions And Metastable States In Tb3ni.
Creator: Gubkin, A. F., Wu, L. S., Nikitin, S. E., Suslov, A. V., Podlesnyak, A., Prokhnenko, O., Prokes, K., Yokaichiya, F., Keller, L., Baranov, N. V.
Abstract/Description: In this paper we report the detailed study of magnetic phase diagrams, low-temperature magnetic structures, and the magnetic field effect on the electrical resistivity of the binary intermetallic compound Tb3Ni. The incommensurate magnetic structure of the spin-density-wave type described with magnetic superspace group P112(1)/a1'(ab0)0ss and propagation vector k(IC) = [0.506, 0.299,0] was found to emerge just below Neel temperature T-N = 61 K. Further cooling below 58 K results in the...
Show moreIn this paper we report the detailed study of magnetic phase diagrams, low-temperature magnetic structures, and the magnetic field effect on the electrical resistivity of the binary intermetallic compound Tb3Ni. The incommensurate magnetic structure of the spin-density-wave type described with magnetic superspace group P112(1)/a1'(ab0)0ss and propagation vector k(IC) = [0.506, 0.299,0] was found to emerge just below Neel temperature T-N = 61 K. Further cooling below 58 K results in the appearance of multicomponent magnetic states: (i) a combination of k(1) = [1/2, 1/2, 0] and k(IC) in the temperature range 51 < T < 58 K; (ii) a mixed magnetic state of k(IC), k(1), and k(2) = [1/2, 1/4, 0] with the partially locked-in incommensurate component in the temperature range 48 < T < 51 K; and (iii) a low-temperature magnetic structure that is described by the intersection of two isotropy subgroups associated with the irreducible representations of two coupled primary order parameters (OPs) k(2) = [1/2, 1/4, 0] and k(3) = [1/2, 1/3, 0] and involves irreducible representations of the secondary OPs k(1) = [1/2, 1/2, 0] and k(4) = [1/2, 0, 0] below 48 K. An external magnetic field suppresses the complex low-temperature antiferromagnetic states and induces metamagnetic transitions towards a forced ferromagnetic state that are accompanied by a substantial magnetoresistance effect due to the magnetic superzone effect. The forced ferromagnetic state induced after application of an external magnetic field along the b and c crystallographic axes was found to be irreversible below 3 and 8 K, respectively.
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Date Issued: 2018-04-26
Identifier: FSU_libsubv1_wos_000430908700001, 10.1103/PhysRevB.97.134425
Format: Citation

Title: Quantum Anomalous Hall Insulator Stabilized By Competing Interactions.
Creator: Sur, Shouvik, Gong, Shou-Shu, Yang, Kun, Vafek, Oskar
Abstract/Description: We study the quantum phases driven by interaction in a semimetal with a quadratic band touching at the Fermi level. By combining the density matrix renormalization group (DMRG), analytical power expanded Gibbs potential method, and the weak coupling renormalization group, we study a spinless fermion system on a checkerboard lattice at half-filling, which has a quadratic band touching in the absence of interaction. In the presence of strong nearest-neighbor (V-1) and next-nearest-neighbor (V-2...
Show moreWe study the quantum phases driven by interaction in a semimetal with a quadratic band touching at the Fermi level. By combining the density matrix renormalization group (DMRG), analytical power expanded Gibbs potential method, and the weak coupling renormalization group, we study a spinless fermion system on a checkerboard lattice at half-filling, which has a quadratic band touching in the absence of interaction. In the presence of strong nearest-neighbor (V-1) and next-nearest-neighbor (V-2) interactions, we identify a site nematic insulator phase, a stripe insulator phase, and a phase separation region, in agreement with the phase diagram obtained analytically in the strong coupling limit (i.e., in the absence of fermion hopping). In the intermediate interaction regime we establish a quantum anomalous Hall phase in the DMRG as evidenced by the spontaneous time-reversal symmetry breaking and the appearance of a quantized Chern number C = 1. For weak interaction we utilize the power expanded Gibbs potential method that treats V-1 and V-2 on equal footing, as well as the weak coupling renormalization group. Our analytical results reveal that not only the repulsive V-1 interaction, but also the V-2 interaction (both repulsive and attractive), can drive the quantum anomalous Hall phase. We also determine the phase boundary in the V-1-V-2 plane that separates the semimetal from the quantum anomalous Hall state. Finally, we show that the nematic semimetal, which was proposed for vertical bar V-2 vertical bar >> V-1 at weak coupling in a previous study, is absent, and the quantum anomalous Hall state is the only weak coupling instability of the spinless quadratic band touching semimetal.
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Date Issued: 2018-09-26
Identifier: FSU_libsubv1_wos_000445726500005, 10.1103/PhysRevB.98.125144
Format: Citation

Title: Static And Dynamic Signatures Of Anisotropic Electronic Phase Separation In La2/3ca1/3mno3 Thin Films Under Anisotropic Strain.
Creator: Hu, L., Yu, L. Q., Xiong, P., Wang, X. L., Zhao, J. H., Wang, L. F., Huang, Z., Wu, W. B.
Abstract/Description: The electronic phase separation (EPS) of optimally doped La2/3Ca1/3MnO3 (LCMO) thin films under various degrees of anisotropic strain is investigated by static magnetotransport and dynamic relaxation measurements. Three LCMO films were grown simultaneously on (001) NdGaO3 substrates by pulsed laser deposition, and then postgrowth annealed at 780 degrees C in O-2 for different durations of time. With increasing annealing time, the films developed significant strains of opposite signs along the...
Show moreThe electronic phase separation (EPS) of optimally doped La2/3Ca1/3MnO3 (LCMO) thin films under various degrees of anisotropic strain is investigated by static magnetotransport and dynamic relaxation measurements. Three LCMO films were grown simultaneously on (001) NdGaO3 substrates by pulsed laser deposition, and then postgrowth annealed at 780 degrees C in O-2 for different durations of time. With increasing annealing time, the films developed significant strains of opposite signs along the two orthogonal in-plane directions. The static temperature-dependent resistivity, p(T), was measured simultaneously along the two orthogonal directions. With increasing annealing time, both zero-field-cooled and field-cooled p(T) show significant increases, suggesting strain-triggered EPS and appearance of antiferromagnetic insulating (AFI) phases in a ferromagnetic metallic (FMM) ground state. Meanwhile, p(T) along the tensile-strained [010] direction becomes progressively larger than that along the compressive-strained [100]. The enhanced resistivity anisotropy indicates that the EPS is characterized by phase-separated FMM entities with a preferred orientation along [100], possibly due to the cooperative deformation and rotation/tilting of the MnO6 octahedra under the enhanced anisotropic strain. The anisotropic EPS can also be tuned by an external magnetic field. During a field cycle at several fixed temperatures, the AFI phases are melted at high fields and recovered at low fields, resulting in sharp resistance changes of ratio as high as 10(4). Furthermore, the resistivity was found to exhibit glasslike behavior, relaxing logarithmically in the phase-separated states. Fitting the data to a phenomenological model, the resulting resistive viscosity and characteristic relaxation time are found to evolve with temperature, showing a close correlation with the static measurements in the EPS states.
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Date Issued: 2018-06-25
Identifier: FSU_libsubv1_wos_000436190900003, 10.1103/PhysRevB.97.214428
Format: Citation

Title: Quench Dynamics Across Topological Quantum Phase Transitions.
Creator: Liou, Shiuan-Fan, Yang, Kun
Abstract/Description: We study the dynamics of systems quenched through topological quantum phase transitions and investigate the behavior of the bulk and edge excitations with various quench rates. Specifically, we consider the Haldane model and checkerboard model in slow quench processes with distinct band-touching structures leading to topology changes. The generation of bulk excitations is found to obey the power-law relation Kibble-Zurek and Landau-Zener theories predict. However, an anti-Kibble-Zurek...
Show moreWe study the dynamics of systems quenched through topological quantum phase transitions and investigate the behavior of the bulk and edge excitations with various quench rates. Specifically, we consider the Haldane model and checkerboard model in slow quench processes with distinct band-touching structures leading to topology changes. The generation of bulk excitations is found to obey the power-law relation Kibble-Zurek and Landau-Zener theories predict. However, an anti-Kibble-Zurek behavior is observed in the edge excitations. The mechanism of excitation generation on edge states is revealed, which explains the anti-Kibble-Zurek behavior.
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Date Issued: 2018-06-25
Identifier: FSU_libsubv1_wos_000436192300003, 10.1103/PhysRevB.97.235144
Format: Citation

Title: Topological Phase Transition In A Two-species Fermion System: Effects Of A Rotating Trap Potential Or A Synthetic Gauge Field.
Creator: Liou, Shiuan-Fan, Hu, Zi-Xiang, Yang, Kun
Abstract/Description: We numerically investigate the quantum phases and phase transition in a system made of two species of fermionic atoms that interact with each other via s-wave Feshbach resonance and are subject to rotation or a synthetic gauge field that puts the fermions at Landau level filling factor v(f) = 2. We show that the system undergoes a continuous quantum phase transition from a v(f) = 2 fermionic integer quantum Hall state formed by atoms to a v(b) = 1/2 bosonic fractional quantum Hall state...
Show moreWe numerically investigate the quantum phases and phase transition in a system made of two species of fermionic atoms that interact with each other via s-wave Feshbach resonance and are subject to rotation or a synthetic gauge field that puts the fermions at Landau level filling factor v(f) = 2. We show that the system undergoes a continuous quantum phase transition from a v(f) = 2 fermionic integer quantum Hall state formed by atoms to a v(b) = 1/2 bosonic fractional quantum Hall state formed by bosonic diatomic molecules. In the disk geometry we use, these two different topological phases are distinguished by their different gapless edge excitation spectra, and the quantum phase transition between them is signaled by the closing of the energy gap in the bulk. Comparisons will be made with field-theoretical predictions and the case of p-wave pairing.
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Date Issued: 2018-06-25
Identifier: FSU_libsubv1_wos_000436192800006, 10.1103/PhysRevB.97.245140
Format: Citation

Title: Multiple Topologically Nontrivial Bands In Noncentrosymmetric Ysn2.
Creator: Zhu, Yanglin, Zhang, Tiantian, Hu, Jin, Kidd, Jamin, Graf, David, Gui, Xin, Xie, Weiwei, Zhu, Mengze, Ke, Xianglin, Cao, Huibo, Fang, Zhong, Weng, Hongming, Mao, Zhiqiang
Abstract/Description: The square lattices formed by main-group elements such as Bi, Sb, Sn, and Si in layered materials have attracted a lot of interest, since they can create rich topological phases. In this paper, we report the slightly distorted square lattice of Sn in a noncentrosymmetric compound YSn2 generates multiple topologically nontrivial bands, one of which likely hosts a nodal line and tunable Weyl semimetal state induced by the Rashba spin-orbit coupling and proper external magnetic field. The...
Show moreThe square lattices formed by main-group elements such as Bi, Sb, Sn, and Si in layered materials have attracted a lot of interest, since they can create rich topological phases. In this paper, we report the slightly distorted square lattice of Sn in a noncentrosymmetric compound YSn2 generates multiple topologically nontrivial bands, one of which likely hosts a nodal line and tunable Weyl semimetal state induced by the Rashba spin-orbit coupling and proper external magnetic field. The quasiparticles described as relativistic fermions from these bands are manifested by nearly zero mass and nontrivial Berry phases probed in de Haas-van Alphen (dHvA) oscillations. The dHvA study also reveals YSn2 has a complicated Fermi surface, consisting of several three-dimensional (3D) and one 2D pocket. Our first-principles calculations show the pointlike 3D pocket at Y point on the Brillouin zone boundary hosts the possible Weyl state. Our findings establish YSn2 as a new interesting platform for observing novel topological phases and studying their underlying physics.
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Date Issued: 2018-07-16
Identifier: FSU_libsubv1_wos_000438674700001, 10.1103/PhysRevB.98.035117
Format: Citation

Title: Energy-level Statistics In Strongly Disordered Systems With Power-law Hopping.
Creator: Titum, Paraj, Quito, Victor L., Syzranov, Sergey
Abstract/Description: Motivated by neutral excitations in disordered electronic materials and systems of trapped ultracold particles with long-range interactions, we study energy-level statistics of quasiparticles with the power-law hopping Hamiltonian proportional to 1/r(alpha) in a strong random potential. In solid-state systems such quasiparticles, which are exemplified by neutral dipolar excitations, lead to long-range correlations of local observables and may dominate energy transport. Focusing on the...
Show moreMotivated by neutral excitations in disordered electronic materials and systems of trapped ultracold particles with long-range interactions, we study energy-level statistics of quasiparticles with the power-law hopping Hamiltonian proportional to 1/r(alpha) in a strong random potential. In solid-state systems such quasiparticles, which are exemplified by neutral dipolar excitations, lead to long-range correlations of local observables and may dominate energy transport. Focusing on the excitations in disordered electronic systems, we compute the energy-level correlation function R-2(omega) in a finite system in the limit of sufficiently strong disorder. At small energy differences, the correlations exhibit Wigner-Dyson statistics. In particular, in the limit of very strong disorder the energy-level correlation function is given by R-2(omega, V) = A(3) omega/omega(V) for small frequencies omega << omega(V) and R-2(omega, V) = 1 - (alpha - d)A(1) (omega(V)/omega)(d/alpha) - A(2) (omega(V)/omega)(2) for large frequencies omega << omega(V), where omega(V) proportional to V-alpha/d is the characteristic matrix element of excitation hopping in a system of volume V, and A(1), A(2), and A(3) are coefficients of order unity which depend on the shape of the system. The energy-level correlation function, which we study, allows for a direct experimental observation, for example, by measuring the correlations of the ac conductance of the system at different frequencies.
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Date Issued: 2018-07-16
Identifier: FSU_libsubv1_wos_000438672400001, 10.1103/PhysRevB.98.014201
Format: Citation

Title: Classification Of Symmetry Derived Pairing At The M Point In Fese.
Creator: Eugenio, P. Myles, Vafek, Oskar
Abstract/Description: Using the constraints imposed by the crystalline symmetry of FeSe and the experimentally observed phenomenology, we analyze the possible pairing symmetry of the superconducting order parameter focusing on intercalated and monolayer FeSe compounds. Such analysis leads to three possible pairing symmetry states-s wave, d wave, and helical p wave. Despite the differences in the pairing symmetry, each of these states is fully gapped with gap minimum centered above the normal state Fermi surface,...
Show moreUsing the constraints imposed by the crystalline symmetry of FeSe and the experimentally observed phenomenology, we analyze the possible pairing symmetry of the superconducting order parameter focusing on intercalated and monolayer FeSe compounds. Such analysis leads to three possible pairing symmetry states-s wave, d wave, and helical p wave. Despite the differences in the pairing symmetry, each of these states is fully gapped with gap minimum centered above the normal state Fermi surface, in agreement with photoemission data of Zhang et al. [Phys. Rev. Lett. 117, 117001 (2016)]. The analysis provides additional insights into the possible pairing mechanism for each of these states, highlighting the detrimental role of the renormalized repulsive intraorbital Hubbard U and interorbital U' and the beneficial role of the pair hopping J' and the Hund's J terms, as well as the spin-orbit coupling in the effective low-energy Hamiltonian.
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Date Issued: 2018-07-06
Identifier: FSU_libsubv1_wos_000437735000001, 10.1103/PhysRevB.98.014503
Format: Citation

Title: Effects Of Stuffing On The Atomic And Electronic Structure Of The Pyrochlore Yb2ti2o7.
Creator: Ghosh, Soham S., Manousakis, Efstratios
Abstract/Description: There are reasons to believe that the ground state of the magnetic rare-earth pyrochlore Yb(2)Ti2O(7) is on the boundary between competing ground states. We have carried out ab initio density functional calculations to determine the most stable chemical formula as a function of the oxygen chemical potential and the likely location of the oxygen atoms in the unit cell of the "stuffed" system. We find that it is energetically favorable in the stuffed crystal (with an Yb replacement on a Ti site...
Show moreThere are reasons to believe that the ground state of the magnetic rare-earth pyrochlore Yb(2)Ti2O(7) is on the boundary between competing ground states. We have carried out ab initio density functional calculations to determine the most stable chemical formula as a function of the oxygen chemical potential and the likely location of the oxygen atoms in the unit cell of the "stuffed" system. We find that it is energetically favorable in the stuffed crystal (with an Yb replacement on a Ti site) to contain oxygen vacancies which dope the Yb 4f orbitals and qualitatively change the electronic properties of the system. In addition, with the inclusion of the contribution of spin-orbit coupling (SOC) on top of the GGA + U approach, we investigated the electronic structure and the magnetic moments of the most stable stuffed system. In our determined stuffed structure the valence bands as compared to those of the pure system are pushed down and a change in hybridization between the O 2p orbitals and the metal ion states is found. Our first-principle findings should form a foundation for effective models describing the low-temperature properties of this material whose true ground state remains controversial.
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Date Issued: 2018-06-11
Identifier: FSU_libsubv1_wos_000434762500006, 10.1103/PhysRevB.97.245117
Format: Citation

Title: Ferromagnetic Quantum Critical Point In Cepd2p2 With Pd -> Ni Substitution.
Creator: Lai, Y., Bone, S. E., Minasian, S., Ferrier, M. G., Lezama-Pacheco, J., Mocko, V., Ditter, A. S., Kozimor, S. A., Seidler, G. T., Nelson, W. L., Chiu, Y.-C., Huang, K., Potter,...
Show moreLai, Y., Bone, S. E., Minasian, S., Ferrier, M. G., Lezama-Pacheco, J., Mocko, V., Ditter, A. S., Kozimor, S. A., Seidler, G. T., Nelson, W. L., Chiu, Y.-C., Huang, K., Potter, W., Graf, D., Albrecht-Schmitt, T. E., Baumbach, R. E.
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Abstract/Description: An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1-x Ni-x)(2)P-2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration (T-x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman-KittelKasuya- Yosida (RKKY) interactions, and the introduction...
Show moreAn investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1-x Ni-x)(2)P-2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration (T-x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman-KittelKasuya- Yosida (RKKY) interactions, and the introduction of disorder through alloying. Near the critical region at x(cr) approximate to 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium f valence crosses over from trivalent to a noninteger value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd2P2 has a purely trivalent cerium f state, CeNi2P2 has a small (<10 %) tetravalent contribution. In a broad region around xcr, there is a breakdown of Fermi-liquid temperature dependences, signaling the influence of quantum critical fluctuations and disorder effects. Measurements of clean CePd2P2 furthermore showthat applied pressure has an initial effect similar to alloying on the ferromagnetic order. From these results, CePd2P2 emerges as a keystone system to test theories such as the Belitz-Kirkpatrick-Vojta model for ferromagnetic quantum criticality, where distinct behaviors are expected in the dirty and clean limits.
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Date Issued: 2018-06-06
Identifier: FSU_libsubv1_wos_000434256700002, 10.1103/PhysRevB.97.224406
Format: Citation

Title: Dipolar-octupolar Ising Antiferromagnetism In Sm2ti2o7: A Moment Fragmentation Candidate.
Creator: Mauws, C., Hallas, A. M., Sala, G., Aczel, A. A., Sarte, P. M., Gaudet, J., Ziat, D., Quilliam, J. A., Lussier, J. A., Bieringer, M., Zhou, H. D., Wildes, A., Stone, I. M. B.,...
Show moreMauws, C., Hallas, A. M., Sala, G., Aczel, A. A., Sarte, P. M., Gaudet, J., Ziat, D., Quilliam, J. A., Lussier, J. A., Bieringer, M., Zhou, H. D., Wildes, A., Stone, I. M. B., Abernathy, D., Luke, G. M., Gaulin, B. D., Wiebe, C. R.
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Abstract/Description: Over the past two decades, the magnetic ground states of all rare-earth titanate pyrochlores have been extensively studied, with the exception of Sm2Ti2O7. This is, in large part, due to the very high absorption cross section of naturally occurring samarium, which renders neutron scattering infeasible. To combat this, we have grown a large, isotopically enriched single crystal of Sm2Ti2O7. Using inelastic neutron scattering, we determine that the crystal field ground state for Sm3+ is a...
Show moreOver the past two decades, the magnetic ground states of all rare-earth titanate pyrochlores have been extensively studied, with the exception of Sm2Ti2O7. This is, in large part, due to the very high absorption cross section of naturally occurring samarium, which renders neutron scattering infeasible. To combat this, we have grown a large, isotopically enriched single crystal of Sm2Ti2O7. Using inelastic neutron scattering, we determine that the crystal field ground state for Sm3+ is a dipolar-octupolar doublet with Ising anisotropy. Neutron diffraction experiments reveal that Sm2Ti2O7 orders into the all-in, all-out magnetic structure with an ordered moment of 0.44(7)mu(B) below T-N = 0.35 K, consistent with expectations for antiferromagnetically coupled Ising spins on the pyrochlore lattice. Zero-field muon spin relaxation measurements reveal an absence of spontaneous oscillations and persistent spin fluctuations down to 0.03 K. The combination of the dipolar-octupolar nature of the Sm3+ moment, the all-in, all-out ordered state, and the low-temperature persistent spin dynamics make this material an intriguing candidate for moment fragmentation physics.
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Date Issued: 2018-09-05
Identifier: FSU_libsubv1_wos_000443672100001, 10.1103/PhysRevB.98.100401
Format: Citation

Title: Sensitivity Of T-c To Pressure And Magnetic Field In The Cuprate Superconductor Yba2cu3oy: Evidence Of Charge-order Suppression By Pressure.
Creator: Cyr-Choiniere, O., LeBoeuf, D., Badoux, S., Dufour-Beausejour, S., Bonn, D. A., Hardy, W. N., Liang, R., Graf, D., Doiron-Leyraud, N., Taillefer, Louis
Abstract/Description: Cuprate superconductors have a universal tendency to form charge density-wave (CDW) order which competes with superconductivity and is strongest at a doping p similar or equal to 0.12. Here we show that in the archetypal cuprate YBa2Cu3Oy (YBCO) pressure suppresses charge order but does not affect the pseudogap phase. This is based on transport measurements under pressure, which reveal that the onset of the pseudogap at T* is independent of pressure, while the negative Hall effect, a clear...
Show moreCuprate superconductors have a universal tendency to form charge density-wave (CDW) order which competes with superconductivity and is strongest at a doping p similar or equal to 0.12. Here we show that in the archetypal cuprate YBa2Cu3Oy (YBCO) pressure suppresses charge order but does not affect the pseudogap phase. This is based on transport measurements under pressure, which reveal that the onset of the pseudogap at T* is independent of pressure, while the negative Hall effect, a clear signature of CDW order in YBCO, is suppressed by pressure. We also find that pressure and magnetic field shift the superconducting transition temperature T-c of YBCO in the same way as a function of doping-but in opposite directions-and most effectively at p similar or equal to 0.12. This shows that the competition between superconductivity and CDW order can be tuned in two ways, either by suppressing superconductivity with field or suppressing CDW order by pressure. Based on existing high-pressure data and our own work, we observe that when CDW order is fully suppressed at high pressure, the so-called "1/8 anomaly" in the superconducting dome vanishes, revealing a smooth T-c dome which now peaks at p similar or equal to 0.13. We propose that this T-c dome is shaped by the competing effects of the pseudogap phase below its critical point p* similar to 0.19 and spin order at low doping.
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Date Issued: 2018-08-30
Identifier: FSU_libsubv1_wos_000443139600006, 10.1103/PhysRevB.98.064513
Format: Citation

Title: Observation Of A Pressure-induced Transition From Interlayer Ferromagnetism To Intralayer Antiferromagnetism In Sr4ru3o10.
Creator: Zheng, H., Song, W. H., Terzic, J., Zhao, H. D., Zhang, Y., Ni, Y. F., DeLong, L. E., Schlottmann, P., Cao, G.
Abstract/Description: Sr4Ru3O10 is a Ruddlesden-Popper compound with triple Ru-O perovskite layers separated by Sr-O rock-salt layers. This compound presents a rare coexistence of interlayer (c-axis) ferromagnetism and intralayer (basal-plane) metamagnetism at ambient pressure. Here we report the observation of pressure-induced, intralayer itinerant antiferromagnetism arising from the interlayer ferromagnetism. The application of modest hydrostatic pressure generates an anisotropy that may cause a flattening and a...
Show moreSr4Ru3O10 is a Ruddlesden-Popper compound with triple Ru-O perovskite layers separated by Sr-O rock-salt layers. This compound presents a rare coexistence of interlayer (c-axis) ferromagnetism and intralayer (basal-plane) metamagnetism at ambient pressure. Here we report the observation of pressure-induced, intralayer itinerant antiferromagnetism arising from the interlayer ferromagnetism. The application of modest hydrostatic pressure generates an anisotropy that may cause a flattening and a tilting of RuO6 octahedra. All magnetic and transport results from this study indicate these lattice distortions diminish the c-axis ferromagnetism and basal-plane metamagnetism, and induce a basal-plane antiferromagnetic state. The unusually large magnetoelastic coupling and pressure tunability of Sr4Ru3O10 makes it a model system for studies of itinerant magnetism.
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Date Issued: 2018-08-21
Identifier: FSU_libsubv1_wos_000442341200003, 10.1103/PhysRevB.98.064418
Format: Citation

Title: Critical Filling Factor For The Formation Of A Quantum Wigner Crystal Screened By A Nearby Layer.
Creator: Deng, H., Engel, L. W., Pfeiffer, L. N., West, K. W., Baldwin, K. W., Shayegan, M.
Abstract/Description: One of the most fascinating ground states of an interacting electron system is the so-called Wigner crystal where the electrons, in order to minimize their repulsive Coulomb energy, form an ordered array. Here, we report measurements of the critical filling factor (nu(c)) below which a magnetic-field-induced, quantum Wigner crystal forms in a dilute, two-dimensional electron layer when a second, high-density electron layer is present in close proximity. The data reveal that the Wigner crystal...
Show moreOne of the most fascinating ground states of an interacting electron system is the so-called Wigner crystal where the electrons, in order to minimize their repulsive Coulomb energy, form an ordered array. Here, we report measurements of the critical filling factor (nu(c)) below which a magnetic-field-induced, quantum Wigner crystal forms in a dilute, two-dimensional electron layer when a second, high-density electron layer is present in close proximity. The data reveal that the Wigner crystal forms at a significantly smaller nu(c) compared to the nu(c) (similar or equal to 0.20) in single-layer two-dimensional electron systems. The measured nu(c) exhibits a strong dependence on the interlayer distance, reflecting the interaction and screening from the adjacent, high-density layer.
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Date Issued: 2018-08-16
Identifier: FSU_libsubv1_wos_000441857700001, 10.1103/PhysRevB.98.081111
Format: Citation

Title: Time-reversal Symmetry-breaking Nematic Superconductivity In Fese.
Creator: Kang, Jian, Chubukov, Andrey, Fernandes, Rafael M.
Abstract/Description: FeSe is a unique member of the family of iron-based superconductors, not only because of the high values of T-c in FeSe monolayer, but also because in bulk FeSe superconductivity emerges inside a nematic phase without competing with long-range magnetic order. Near T-c, superconducting order necessarily has s + d symmetry, because nematic order couples linearly the s-wave and d-wave harmonics of the superconducting order parameter. Here we argue that the near-degeneracy between s-wave and d...
Show moreFeSe is a unique member of the family of iron-based superconductors, not only because of the high values of T-c in FeSe monolayer, but also because in bulk FeSe superconductivity emerges inside a nematic phase without competing with long-range magnetic order. Near T-c, superconducting order necessarily has s + d symmetry, because nematic order couples linearly the s-wave and d-wave harmonics of the superconducting order parameter. Here we argue that the near-degeneracy between s-wave and d-wave pairing instabilities in FeSe, combined with the sign-change of the nematic order parameter between hole and electron pockets, allows the superconducting order to break time-reversal symmetry at a temperature T* < T(c. )The transition from an s + d state to an s + e(i alpha)d state should give rise to a peak in the specific heat and to the emergence of a soft collective mode that can be potentially detected by Raman spectroscopy.
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Date Issued: 2018-08-20
Identifier: FSU_libsubv1_wos_000442194600005, 10.1103/PhysRevB.98.064508
Format: Citation

$Acoustic wave absorption as a probe of dynamical geometrical response of fractional quantum Hall liquids$

Title: Acoustic wave absorption as a probe of dynamical geometrical response of fractional quantum Hall liquids.
Creator: Yang, Kun
Abstract/Description: We show that an acoustic crystalline wave gives rise to an effect similar to that of a gravitational wave to an electron gas. Applying this idea to a two-dimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intra-Landau level dynamical response in the long-wavelength limit. To study such response we generalize Haldane's geometrical description of fractional quantum Hall states to situations where the external metric is time dependent. We...
Show moreWe show that an acoustic crystalline wave gives rise to an effect similar to that of a gravitational wave to an electron gas. Applying this idea to a two-dimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intra-Landau level dynamical response in the long-wavelength limit. To study such response we generalize Haldane's geometrical description of fractional quantum Hall states to situations where the external metric is time dependent. We show that such time-dependent metric (generated by acoustic wave) couples to collective modes of the system, including a quadrapolar mode at long wavelength, and magnetoroton at finite wavelength. Energies of these modes can be revealed in spectroscopic measurements, controlled by strain-induced Fermi velocity anisotropy. We argue that such geometrical probe provides a potentially highly useful alternative probe of quantum Hall liquids, in addition to the usual electromagnetic response.
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Date Issued: 2016-04-15
Identifier: FSU_libsubv1_wos_000374297500001, 10.1103/PhysRevB.93.161302
Format: Citation

Title: Evidence For Impact Ionization In Vanadium Dioxide.
Creator: Holleman, Joshua, Bishop, Michael M., Garcia, Carlos, Winfred, J. S. R. Vellore, Lee, Shinbuhm, Lee, Ho Nyung, Beekman, Christianne, Manousakis, Efstratios, McGill, Stephen A.
Abstract/Description: Pump-probe optical spectroscopy was used to investigate proposed charge-carrier multiplication via impact ionization in the M-1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed a larger ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple time scales within the charge dynamics and...
Show morePump-probe optical spectroscopy was used to investigate proposed charge-carrier multiplication via impact ionization in the M-1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed a larger ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple time scales within the charge dynamics and analyzed how these changed when the pump and probe wavelengths were varied. This experiment provided evidence that a fast carrier multiplication process, i.e., impact ionization, acts efficiently in this prototypical strongly correlated insulator, as was recently predicted by theoretical calculations.
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Date Issued: 2016-10-17
Identifier: FSU_libsubv1_wos_000386097100004, 10.1103/PhysRevB.94.155129
Format: Citation

Title: Equilibrium, metastability, and hysteresis in a model spin-crossover material with nearest-neighbor antiferromagnetic-like and long-range ferromagnetic-like interactions.
Creator: Rikvold, Per Arne, Brown, Gregory, Miyashita, Seiji, Omand, Conor, Nishino, Masamichi
Abstract/Description: Phase diagrams and hysteresis loops were obtained by Monte Carlo simulations and a mean- field method for a simplified model of a spin-crossovermaterialwith a two-step transition between the high-spin and low-spin states. This model is a mapping onto a square-lattice S = 1/2 Ising model with antiferromagnetic nearest-neighbor and ferromagnetic Husimi-Temperley ( equivalent-neighbor) long-range interactions. Phase diagrams obtained by the two methods for weak and strong long-range interactions...
Show morePhase diagrams and hysteresis loops were obtained by Monte Carlo simulations and a mean- field method for a simplified model of a spin-crossovermaterialwith a two-step transition between the high-spin and low-spin states. This model is a mapping onto a square-lattice S = 1/2 Ising model with antiferromagnetic nearest-neighbor and ferromagnetic Husimi-Temperley ( equivalent-neighbor) long-range interactions. Phase diagrams obtained by the two methods for weak and strong long-range interactions are found to be similar. However, for intermediate-strength long-range interactions, the Monte Carlo simulations show that tricritical points decompose into pairs of critical end points and mean-field critical points surrounded by horn-shaped regions of metastability. Hysteresis loops along paths traversing the horn regions are strongly reminiscent of thermal two-step transition loops with hysteresis, recently observed experimentally in several spin-crossover materials. We believe analogous phenomena should be observable in experiments and simulations for many systems that exhibit competition between local antiferromagnetic-like interactions and long-range ferromagnetic-like interactions caused by elastic distortions.
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Date Issued: 2016-02-16
Identifier: FSU_libsubv1_wos_000370244600002, 10.1103/PhysRevB.93.064109
Format: Citation

Title: Forbidden Coherent Transfer Observed Between Two Realizations Of Quasiharmonic Spin Systems.
Creator: Bertaina, S., Yue, G., Dutoit, C.-E., Chiorescu, I.
Abstract/Description: The multilevel system Mn-55(2 vertical bar) is used to generate two pseudoharmonic level systems, as representations of the same electronic sextuplet at different nuclear spin projections. The systems are coupled using a forbidden nuclear transition induced by the crystalline anisotropy. We demonstrate Rabi oscillations between the two representations in conditions similar to two coupled pseudoharmonic quantum oscillators. Rabi oscillations are performed at a detuned pumping frequency which...
Show moreThe multilevel system Mn-55(2 vertical bar) is used to generate two pseudoharmonic level systems, as representations of the same electronic sextuplet at different nuclear spin projections. The systems are coupled using a forbidden nuclear transition induced by the crystalline anisotropy. We demonstrate Rabi oscillations between the two representations in conditions similar to two coupled pseudoharmonic quantum oscillators. Rabi oscillations are performed at a detuned pumping frequency which matches the energy difference between electronuclear states of different oscillators. We measure a coupling stronger than the decoherence rate to indicate the possibility of fast information exchange between the systems.
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Date Issued: 2017-07-20
Identifier: FSU_libsubv1_wos_000405913900004, 10.1103/PhysRevB.96.024428
Format: Citation

Title: Ground-state tuning of metal-insulator transition by compositional variations in BaIr1-xRuxO3 (0 <= x <= 1).
Creator: Yuan, S. J., Butrouna, K., Terzic, J., Zheng, H., Aswartham, S., DeLong, L. E., Ye, Feng, Schlottmann, P., Cao, G.
Abstract/Description: Hexagonal BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO3 is an enhanced paramagnetic metal. Our investigation of structural, magnetic, transport, and thermal properties reveals that substitution of Ru4+ (4d(4)) ions for Ir4+ (5d(5)) ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural distortion and rebalances the competition between the SOI and the lattice degrees of freedom to render an evolution from a magnetic insulting...
Show moreHexagonal BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO3 is an enhanced paramagnetic metal. Our investigation of structural, magnetic, transport, and thermal properties reveals that substitution of Ru4+ (4d(4)) ions for Ir4+ (5d(5)) ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural distortion and rebalances the competition between the SOI and the lattice degrees of freedom to render an evolution from a magnetic insulting state to a robust metallic state. The central findings of this paper are as follows: (1) light Ru doping (0 < x <= 0.15) prompts simultaneous, precipitous drops in both the magnetic ordering temperature T-N and the electrical resistivity, and (2) heavier Ru doping (0.41 <= x <= 0.9) induces a robust metallic state without any long-range magnetic order. All results suggest a critical role of the lattice degrees of freedom in determining the ground state in the heavy transition-metal oxides.
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Date Issued: 2016-04-25
Identifier: FSU_libsubv1_wos_000374950300008, 10.1103/PhysRevB.93.165136
Format: Citation

Title: Fermi surface reconstruction in FeSe under high pressure.
Creator: Terashima, Taichi, Kikugawa, Naoki, Kiswandhi, Andhika, Graf, David, Choi, Eun-Sang, Brooks, James S., Kasahara, Shigeru, Watashige, Tatsuya, Matsuda, Yuji, Shibauchi, Takasada,...
Show moreTerashima, Taichi, Kikugawa, Naoki, Kiswandhi, Andhika, Graf, David, Choi, Eun-Sang, Brooks, James S., Kasahara, Shigeru, Watashige, Tatsuya, Matsuda, Yuji, Shibauchi, Takasada, Wolf, Thomas, Boehmer, Anna E., Hardy, Frederic, Meingast, Christoph, Loehneysen, Hilbert V., Uji, Shinya
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Abstract/Description: We report Shubnikov-de Haas (SdH) oscillation measurements on FeSe under high pressure up to P = 16.1 kbar. We find a sudden change in SdH oscillations at the onset of the pressure-induced antiferromagnetism at P similar to 8 kbar. We argue that this change can be attributed to a reconstruction of the Fermi surface by the antiferromagnetic order. The negative dT(c)/dP observed in a range between P similar to 8 and 12 kbar may be explained by the reduction in the density of states due to the...
Show moreWe report Shubnikov-de Haas (SdH) oscillation measurements on FeSe under high pressure up to P = 16.1 kbar. We find a sudden change in SdH oscillations at the onset of the pressure-induced antiferromagnetism at P similar to 8 kbar. We argue that this change can be attributed to a reconstruction of the Fermi surface by the antiferromagnetic order. The negative dT(c)/dP observed in a range between P similar to 8 and 12 kbar may be explained by the reduction in the density of states due to the reconstruction. The ratio of the transition temperature to the effective Fermi energy remains high under high pressure: k(B)T(c)/E-F similar to 0.1 even at P = 16.1 kbar.
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Date Issued: 2016-03-03
Identifier: FSU_libsubv1_wos_000371401700003, 10.1103/PhysRevB.93.094505
Format: Citation

Title: Evidence For Correlated Dynamics Near The Berezinskii-kosterlitz-thouless-like Transition In Highly Underdoped La2-xsrxcuo4.
Creator: Shi, Zhenzhong, Shi, Xiaoyan, Popovic, Dragana
Abstract/Description: A low-frequency resistance noise study in highly underdoped thick films of La2-xSrxCuO4 (x = 0.07 and 0.08) reveals slow, correlated dynamics and breaking of ergodicity near the superconducting transition of the Berezinskii-Kosterlitz-Thouless type. The observed correlated behavior is strongly suppressed by disorder.
Date Issued: 2016-10-05
Identifier: FSU_libsubv1_wos_000385239900002, 10.1103/PhysRevB.94.134503
Format: Citation

Title: Extremely Large Nonsaturating Magnetoresistance And Ultrahigh Mobility Due To Topological Surface States In The Metallic Bi2te3 Topological Insulator.
Creator: Shrestha, K., Chou, M., Graf, D., Yang, H. D., Lorenz, B., Chu, C. W.
Abstract/Description: Weak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge-carrier concentrations. At low charge-carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge-carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to...
Show moreWeak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge-carrier concentrations. At low charge-carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge-carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to topological surface states shows no dependence on the nature (electrons or holes) of the bulk charge carriers. The observations of an extremely large nonsaturating magnetoresistance and ultrahigh mobility in the samples with lower carrier density further support the presence of surface states. The physical parameters characterizing the WAL effects are calculated using the Hikami-LarkinNagaoka formula. At high charge-carrier concentrations, there is a greater number of conduction channels and a decrease in the phase coherence length compared to low charge-carrier concentrations. The extremely large magnetoresistance and high mobility of topological insulators have great technological value and can be exploited in magnetoelectric sensors and memory devices.
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Date Issued: 2017-05-08
Identifier: FSU_libsubv1_wos_000401229000004, 10.1103/PhysRevB.95.195113
Format: Citation

Title: Entanglement Entropy And Topological Order In Resonating Valence-bond Quantum Spin Liquids.
Creator: Wildeboer, Julia, Seidel, Alexander, Melko, Roger G.
Abstract/Description: On the triangular and kagome lattices, short-ranged resonating valence-bond wave functions can be sampled without the sign problem using a recently developed Pfaffian Monte Carlo scheme. In this Rapid Communication, we study the Renyi entanglement entropy in these wave functions using a replica-trick method. Using various spatial bipartitions, including the Levin-Wen construction, our finite-size scaled Renyi entropy gives a topological contribution consistent with. gamma = ln( 2), as...
Show moreOn the triangular and kagome lattices, short-ranged resonating valence-bond wave functions can be sampled without the sign problem using a recently developed Pfaffian Monte Carlo scheme. In this Rapid Communication, we study the Renyi entanglement entropy in these wave functions using a replica-trick method. Using various spatial bipartitions, including the Levin-Wen construction, our finite-size scaled Renyi entropy gives a topological contribution consistent with. gamma = ln( 2), as expected for a gapped Z(2) quantum spin liquid. We prove that the mutual statistics is consistent with the toric code anyon model and rule out any other quasiparticle statistics such as the double semion model.
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Date Issued: 2017-03-06
Identifier: FSU_libsubv1_wos_000396000700001, 10.1103/PhysRevB.95.100402
Format: Citation

Title: Frustrated Magnetism In The Tetragonal Cose Analog Of Superconducting Fese.
Creator: Wilfong, Brandon, Zhou, Xiuquan, Vivanco, Hector, Campbell, Daniel J., Wang, Kefeng, Graf, Dave, Paglione, Johnpierre, Rodriguez, Efrain
Abstract/Description: Recently synthesized metastable tetragonal CoSe, isostructural to the FeSe superconductor, offers a new avenue for investigating systems in close proximity to the iron-based superconductors. We present magnetic and transport property measurements on powders and single crystals of CoSe. High field magnetic susceptibility measurements indicate a suppression of the previously reported 10 K ferromagnetic transition with the magnetic susceptibility, exhibiting time dependence below the proposed...
Show moreRecently synthesized metastable tetragonal CoSe, isostructural to the FeSe superconductor, offers a new avenue for investigating systems in close proximity to the iron-based superconductors. We present magnetic and transport property measurements on powders and single crystals of CoSe. High field magnetic susceptibility measurements indicate a suppression of the previously reported 10 K ferromagnetic transition with the magnetic susceptibility, exhibiting time dependence below the proposed transition. Dynamic scaling analysis of the time dependence yields a critical relaxation time of tau* = 0.064 +/- 0.008 s which in turn yields activation energy E-a(*) = 14.84 +/- 0.59 K and an ideal glass temperature T-0(*) = 8.91 +/- 0.09 K from Vogel-Fulcher analysis. No transition is observed in resistivity and specific heat measurements, but both measurements indicate that CoSe is metallic. These results are interpreted on the basis of CoSe exhibiting frustrated magnetic ordering arising from competing magnetic interactions. Arrott analysis of single crystal magnetic susceptibility has indicated the transition temperature occurs in close proximity to previous reports and that the magnetic moment lies solely in the ab plane. The results have implications for understanding the relationship between magnetism and transport properties in the iron chalcogenide superconductors.
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Date Issued: 2018-03-08
Identifier: FSU_libsubv1_wos_000426901700002, 10.1103/PhysRevB.97.104408
Format: Citation

Title: Gutzwiller renormalization group.
Creator: Lanata, Nicola, Yao, Yong-Xin, Deng, Xiaoyu, Wang, Cai-Zhuang, Ho, Kai-Ming, Kotliar, Gabriel
Abstract/Description: We develop a variational scheme called the "Gutzwiller renormalization group" (GRG), which enables us to calculate the ground state of Anderson impurity models (AIM) with arbitrary numerical precision. Our method exploits the low-entanglement property of the ground state of local Hamiltonians in combination with the framework of the Gutzwiller wave function and indicates that the ground state of the AIM has a very simple structure, which can be represented very accurately in terms of a...
Show moreWe develop a variational scheme called the "Gutzwiller renormalization group" (GRG), which enables us to calculate the ground state of Anderson impurity models (AIM) with arbitrary numerical precision. Our method exploits the low-entanglement property of the ground state of local Hamiltonians in combination with the framework of the Gutzwiller wave function and indicates that the ground state of the AIM has a very simple structure, which can be represented very accurately in terms of a surprisingly small number of variational parameters. We perform benchmark calculations of the single-band AIM that validate our theory and suggest that the GRG might enable us to study complex systems beyond the reach of the other methods presently available and pave the way to interesting generalizations, e.g., to nonequilibrium transport in nanostructures.
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Date Issued: 2016-01-06
Identifier: FSU_libsubv1_wos_000367665400002, 10.1103/PhysRevB.93.045103
Format: Citation

Title: Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe.
Creator: Yakunin, M. V., Suslov, A. V., Popov, M. R., Novik, E. G., Dvoretsky, S. A., Mikhailov, N. N.
Abstract/Description: We present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage V-g. This large overlap manifests itself in a much higher critical field B-c separating the range above it with a plain behavior of the Hall...
Show moreWe present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage V-g. This large overlap manifests itself in a much higher critical field B-c separating the range above it with a plain behavior of the Hall magnetoresistance rho(xy) (B), where the quantum peculiarities shift linearly with V-g, and the range below with a complicated behavior. In the latter case, specific structures in rho(xy) (B) are formed like a double-N-shaped rho(xy) (B), reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state, etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative V-g as revealed (i) from fits to the low-field N-shaped rho(xy) (B), (ii) from the Fourier analysis of oscillations in rho(xx) (B), and (iii) from a specific behavior of rho(xy) (B) at high positive V-g. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated V-g while the hole density p drops down from the value a factor of 6 larger than n at extreme negative V-g to almost zero at extreme positive V-g passing through the charge-neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an oscillating behavior of the valence subband top versus field due to lateral maxima in the energy spectrum, (ii) a reduced gap between the lowest-electron and the highest-hole magnetic levels where the electron- and hole-type localized states are superposed, and (iii) a possible formation of the interlayer electron-hole excitons.
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Date Issued: 2016-02-12
Identifier: FSU_libsubv1_wos_000370025100005, 10.1103/PhysRevB.93.085308
Format: Citation

Title: Magnetoinfrared spectroscopic study of thin Bi2Te3 single crystals.
Creator: Tung, L.-C., Yu, W., Cadden-Zimansky, P., Miotkowski, I., Chen, Y. P., Smirnov, D., Jiang, Z.
Abstract/Description: Thin Bi2Te3 single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at 4 K and in a magnetic field up to 35 T. The magnetotransmittance spectra of the Bi2Te3/tape composite are analyzed as a stacked-slab system, and the average thickness of Bi2Te3 is estimated to be 6.4 +/- 1.7 mu m. The optical conductivity of Bi2Te3 at different magnetic fields is then extracted, and we find that the magnetic field modifies the optical conductivity in the following...
Show moreThin Bi2Te3 single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at 4 K and in a magnetic field up to 35 T. The magnetotransmittance spectra of the Bi2Te3/tape composite are analyzed as a stacked-slab system, and the average thickness of Bi2Te3 is estimated to be 6.4 +/- 1.7 mu m. The optical conductivity of Bi2Te3 at different magnetic fields is then extracted, and we find that the magnetic field modifies the optical conductivity in the following ways: (1) Field-induced transfer of the optical weight from the lower-frequency regime (< 250 cm(-1)) to the higher-frequency regime (> 250 cm(-1)) due to the redistribution of charge carriers across the Fermi surface. (2) Evolving of a Fano-resonance-like spectral feature from an antiresonance to a resonance with increasing magnetic field. Such behavior can be attributed to the electron-phonon interactions between the E-u(1) optical phonon mode and the continuum of electronic transitions. (3) Cyclotron resonance resulting from the intervalence band Landau level transitions, which can be described by the electrodynamics of massive Dirac holes.
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Date Issued: 2016-02-29
Identifier: FSU_libsubv1_wos_000371398500002, 10.1103/PhysRevB.93.085140
Format: Citation

Title: Magnetochromic Sensing And Size-dependent Collective Excitations In Iron Oxide Nanoparticles.
Creator: O'Neal, Kenneth R., Patete, Jonathan M., Chen, Peng, Nanavati, Ruhani, Holinsworth, Brian S., Smith, Jacqueline M., Marques, Carlos, Simonson, Jack W., Aronson, Meigan C.,...
Show moreO'Neal, Kenneth R., Patete, Jonathan M., Chen, Peng, Nanavati, Ruhani, Holinsworth, Brian S., Smith, Jacqueline M., Marques, Carlos, Simonson, Jack W., Aronson, Meigan C., McGill, Stephen A., Wong, Stanislaus S., Musfeldt, Janice L.
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Abstract/Description: We combine optical and magneto-optical spectroscopies with complementary vibrational and magnetic property measurements to reveal finite length scale effects in nanoscale alpha-Fe2O3. Analysis of the d-to-d on-site excitations uncovers enhanced color contrast at particle sizes below approximately 75 nm due to size-induced changes in spin-charge coupling that are suppressed again below the superparamagnetic limit. These findings provide a general strategy for amplifying magnetochromism in...
Show moreWe combine optical and magneto-optical spectroscopies with complementary vibrational and magnetic property measurements to reveal finite length scale effects in nanoscale alpha-Fe2O3. Analysis of the d-to-d on-site excitations uncovers enhanced color contrast at particle sizes below approximately 75 nm due to size-induced changes in spin-charge coupling that are suppressed again below the superparamagnetic limit. These findings provide a general strategy for amplifying magnetochromism in alpha-Fe2O3 and other iron-containing nanomaterials that may be useful for advanced sensing applications. We also unravel the size dependence of collective excitations in this iconic antiferromagnet.
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Date Issued: 2017-03-10
Identifier: FSU_libsubv1_wos_000396013400006, 10.1103/PhysRevB.95.125416
Format: Citation

Title: Magnetic Properties Of The Triangular Lattice Magnets A(4)b ' B2o12 (a=ba, Sr, La; B '=co, Ni, Mn; B=w, Re).
Creator: Rawl, R., Lee, M., Choi, E. S., Li, G., Chen, K. W., Baumbach, R., dela Cruz, C. R., Ma, J., Zhou, H. D.
Abstract/Description: The geometrically frustrated two-dimensional triangular lattice magnets A(4)B'B2O12 (A=Ba, Sr, La; B'=Co, Ni, Mn; B=W, Re) have been studied by x-ray diffraction, ac and dc susceptibilities, powder neutron diffraction, and specific-heat measurements. The results reveal the following: (i) The samples containing Co2+ (effective spin-1/2) and Ni2+ (spin-1) ions with small spin numbers exhibit ferromagnetic (FM) behavior and ordering, respectively, while the sample containing Mn2+ (spin-5/2) ions...
Show moreThe geometrically frustrated two-dimensional triangular lattice magnets A(4)B'B2O12 (A=Ba, Sr, La; B'=Co, Ni, Mn; B=W, Re) have been studied by x-ray diffraction, ac and dc susceptibilities, powder neutron diffraction, and specific-heat measurements. The results reveal the following: (i) The samples containing Co2+ (effective spin-1/2) and Ni2+ (spin-1) ions with small spin numbers exhibit ferromagnetic (FM) behavior and ordering, respectively, while the sample containing Mn2+ (spin-5/2) ions with a large spin number exhibits antiferromagnetic (AFM) ordering. We ascribe these spin-number-manipulated ground states to the competition between the AFM B'-O-O-B' and FM B'-O-B-O-B' superexchange interactions. (ii) The chemical pressure introduced into the Co-containing samples through the replacement of different-size ions on the A site finely tunes the FM behavior temperature of the system. This effect is not simply governed by the lattice parameters and requires more precise structural measurements to elucidate.
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Date Issued: 2017-05-25
Identifier: FSU_libsubv1_wos_000401998500003, 10.1103/PhysRevB.95.174438
Format: Citation

Title: Magnetic Phases Of The Quasi-two-dimensional Antiferromagnet Cucro2 On A Triangular Lattice.
Creator: Sakhratov, Yu A., Svistov, L. E., Kuhns, P. L., Zhou, H. D., Reyes, A. P.
Abstract/Description: We have carried out Cu-63,Cu-65 NMR spectra measurements in a magnetic field up to about 45 T on a single crystal of a multiferroic triangular antiferromagnet CuCrO2. The measurements were performed for magnetic fields aligned along the crystal c axis. Field and temperature evolution of the spectral shape demonstrates a number of phase transitions. It was found that the 3D magnetic ordering takes place in the low field range (H less than or similar to 15 T). At higher fields magnetic...
Show moreWe have carried out Cu-63,Cu-65 NMR spectra measurements in a magnetic field up to about 45 T on a single crystal of a multiferroic triangular antiferromagnet CuCrO2. The measurements were performed for magnetic fields aligned along the crystal c axis. Field and temperature evolution of the spectral shape demonstrates a number of phase transitions. It was found that the 3D magnetic ordering takes place in the low field range (H less than or similar to 15 T). At higher fields magnetic structures form within individual triangular planes whereas the spin directions of the magnetic ions from neighboring planes are not correlated. It is established that the 2D-3D transition is hysteretic in field and temperature. Line-shape analysis reveals several possible magnetic structures existing within individual planes for different phases of CuCrO2. Within certain regions on the magnetic H-T phase diagram of CuCrO2 a 3D magnetic ordering with tensor order parameter is expected.
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Date Issued: 2016-09-12
Identifier: FSU_libsubv1_wos_000383138700003, 10.1103/PhysRevB.94.094410
Format: Citation

Title: Magnetic Ground States And Magnetodielectric Effect In Rcr(bo3)(2) (r = Y And Ho).
Creator: Sinclair, R., Zhou, H. D., Lee, M., Choi, S., Li, G., Hong, T., Calder, S.
Abstract/Description: The layered perovskites RCr(BO3)(2) (R = Y and Ho) with magnetic triangular lattices were studied by performing ac/dc susceptibility, specific heat, elastic and inelastic neutron scattering, and dielectric constant measurements. The results show (i) both samples' Cr3+ spins order in a canted antiferromagnetic structure with TN around 8-9 K, while the Ho3+ ions do not order down to T = 1.5 K in HoCr(BO3)(2); (ii) when a critical magnetic field HC around 2-3 T is applied below TN, the Cr3+...
Show moreThe layered perovskites RCr(BO3)(2) (R = Y and Ho) with magnetic triangular lattices were studied by performing ac/dc susceptibility, specific heat, elastic and inelastic neutron scattering, and dielectric constant measurements. The results show (i) both samples' Cr3+ spins order in a canted antiferromagnetic structure with TN around 8-9 K, while the Ho3+ ions do not order down to T = 1.5 K in HoCr(BO3)(2); (ii) when a critical magnetic field HC around 2-3 T is applied below TN, the Cr3+ spins in the Y compound and both the Cr3+ and Ho3+ spins in the Ho compound order in a ferromagnetic state; (iii) both samples exhibit dielectric constant anomalies around the transition temperature and critical field, but the Ho compound displays a much stronger magnetodielectric response. We speculate that this is due to the magnetostriction, which depends on both the Cr3+ and the Ho3+ ions' ordering in the Ho compound. Moreover, by using linear spin-wave theory to simulate the inelastic neutron scattering data, we estimated the Y compound's intralayer and interlayer exchange strengths as ferromagnetic J(1) = -0.12 meV and antiferromagnetic J(2) = 0.014 meV, respectively. The competition between different kinds of superexchange interactions results in the ferromagnetic intralayer interaction.
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Date Issued: 2017-05-08
Identifier: FSU_libsubv1_wos_000401223700002, 10.1103/PhysRevB.95.174410
Format: Citation

Title: Interlayer Electronic Transport In Camnbi2 Antiferromagnet.
Creator: Wang, Aifeng, Graf, D., Wu, Lijun, Wang, Kefeng, Bozin, E., Zhu, Yimei, Petrovic, C.
Abstract/Description: We report interlayer electronic transport in CaMnBi2 single crystals. Quantum oscillations and angular magnetoresistance suggest coherent electronic conduction and valley polarized conduction of Dirac states. The small cyclotron mass, high mobility of carriers, and nontrivial Berry's phase are consistent with the presence of Dirac fermions on the side wall of the warped cylindrical Fermi surface. Similarly to SrMnBi2, which features an anisotropic Dirac cone, our results suggest that magnetic...
Show moreWe report interlayer electronic transport in CaMnBi2 single crystals. Quantum oscillations and angular magnetoresistance suggest coherent electronic conduction and valley polarized conduction of Dirac states. The small cyclotron mass, high mobility of carriers, and nontrivial Berry's phase are consistent with the presence of Dirac fermions on the side wall of the warped cylindrical Fermi surface. Similarly to SrMnBi2, which features an anisotropic Dirac cone, our results suggest that magnetic-field-induced changes in interlayer conduction are also present in layered bismuth-based materials with a zero-energy line in momentum space created by the staggered alkaline earth atoms.
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Date Issued: 2016-09-12
Identifier: FSU_libsubv1_wos_000383145300004, 10.1103/PhysRevB.94.125118
Format: Citation

$Interaction-driven fractional quantum Hall state of hard-core bosons on kagome lattice at one-third filling$

Title: Interaction-driven Fractional Quantum Hall State Of Hard-core Bosons On Kagome Lattice At One-third Filling.
Creator: Zhu, W., Gong, S. S., Sheng, D. N.
Abstract/Description: There has been a growing interest in realizing topologically nontrivial states of matter in band insulators, where a quantum Hall effect can appear as an intrinsic property of the band structure. While ongoing progress is under way with a number of directions, the possibility of realizing novel interaction-generated topological phases, without the requirement of a nontrivial invariant encoded in single-particle wave function or band structure, can significantly extend the class of topological...
Show moreThere has been a growing interest in realizing topologically nontrivial states of matter in band insulators, where a quantum Hall effect can appear as an intrinsic property of the band structure. While ongoing progress is under way with a number of directions, the possibility of realizing novel interaction-generated topological phases, without the requirement of a nontrivial invariant encoded in single-particle wave function or band structure, can significantly extend the class of topological materials and is thus of great importance. Here, we show an interaction-driven topological phase emerging in an extended Bose-Hubbard model on a kagome lattice, where the noninteracting band structure is topological trivial with zero Berry curvature in the Brillouin zone. By means of an unbiased state-of-the-art density-matrix renormalization group technique, we identify that the ground state in a broad parameter region is equivalent to a bosonic fractional quantum Hall Laughlin state, based on the characterization of universal properties including ground-state degeneracy, edge excitations, and anyonic quasiparticle statistics. Our work paves a way to finding an interaction-induced topological phase at the phase boundary of conventionally ordered solid phases.
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Date Issued: 2016-07-13
Identifier: FSU_libsubv1_wos_000379502800001, 10.1103/PhysRevB.94.035129
Format: Citation

Title: Jain-2/5 Parent Hamiltonian: Structure Of Zero Modes, Dominance Patterns, And Zero Mode Generators.
Creator: Chen, Li, Bandyopadhyay, Sumanta, Seidel, Alexander
Abstract/Description: We analyze general zero mode properties of the parent Hamiltonian of the unprojected Jain-2/5 state. We characterize the zero mode condition associated to this Hamiltonian via projection onto a four-dimensional two-particle subspace for given pair angular momentum, for the disk and similarly for the spherical geometry. Earlier numerical claims in the literature about ground-state uniqueness on the sphere are substantiated on analytic grounds, and related results are derived. Preference is...
Show moreWe analyze general zero mode properties of the parent Hamiltonian of the unprojected Jain-2/5 state. We characterize the zero mode condition associated to this Hamiltonian via projection onto a four-dimensional two-particle subspace for given pair angular momentum, for the disk and similarly for the spherical geometry. Earlier numerical claims in the literature about ground-state uniqueness on the sphere are substantiated on analytic grounds, and related results are derived. Preference is given to second-quantized methods, where zero mode properties are derived not from given analytic wave functions, but from a "lattice" Hamiltonian and associated zero mode conditions. This method reveals new insights into the guiding-center structure of the unprojected Jain-2/5 state, in particular, a system of dominance patterns following a "generalized Pauli principle," which establishes a complete one-to-one correspondence with the edge mode counting. We also identify one-body operators that function as generators of zero modes.
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Date Issued: 2017-05-31
Identifier: FSU_libsubv1_wos_000402463500001, 10.1103/PhysRevB.95.195169
Format: Citation

Title: Hybridization Gap In The Heavy-fermion Compound Upd2al3 Via Quasiparticle Scattering Spectroscopy.
Creator: Jaggi, N. K., Mehio, O., Dwyer, M., Greene, L. H., Baumbach, R. E., Tobash, P. H., Bauer, E. D., Thompson, J. D., Park, W. K.
Abstract/Description: We present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd2Al3: Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature andmagnetic field and analyzed using a theory of cotunneling into anAnderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi...
Show moreWe present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd2Al3: Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature andmagnetic field and analyzed using a theory of cotunneling into anAnderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi liquid is formed. Both the hybridization gap, found to be 7.2 +/- 0.3meV at 4 K, and the conductance enhancement above a flat background decrease upon increasing temperature. While the hybridization gap is extrapolated to remain finite up to similar to 28 K, close to the temperature around which the magnetic susceptibility displays a broad peak, the conductance enhancement vanishes at similar to 18 K, slightly above the antiferromagnetic transition temperature (T-N approximate to 14 K). This rapid decrease of the conductance enhancement is understood as a consequence of the junction drifting away from the ballistic regime due to increased scattering off magnons associated with the localized U 5f electrons. This shows that while the hybridization gap opening is not directly associated with the antiferromagnetic ordering, its visibility in the conductance is greatly affected by the temperature-dependent magnetic excitations. Our findings are not only consistent with the 5f dual-nature picture in the literature but also shed new light on the interplay between the itinerant and localized electrons in UPd2Al3.
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Date Issued: 2017-04-17
Identifier: FSU_libsubv1_wos_000399799500004, 10.1103/PhysRevB.95.165123
Format: Citation

Title: Incommensurate crystal supercell and polarization flop observed in the magnetoelectric ilmenite MnTiO3.
Creator: Silverstein, Harlyn J., Skoropata, Elizabeth, Sarte, Paul M., Mauws, Cole, Aczel, Adam A., Choi, Eun Sang, van Lierop, Johan, Wiebe, Christopher R., Zhou, Haidong
Abstract/Description: MnTiO3 has been studied for many decades, but it was only in the last few years that its magnetoelectric behavior had been observed. Here, we use neutron scattering on two separately grown single crystals and two powder samples to show the presence of a supercell that breaks R (3) over bar symmetry. We also present the temperature and field dependence of the dielectric constant and pyroelectric current and show evidence of nonzero off-diagonal magnetoelectric tensor elements (forbidden by R ...
Show moreMnTiO3 has been studied for many decades, but it was only in the last few years that its magnetoelectric behavior had been observed. Here, we use neutron scattering on two separately grown single crystals and two powder samples to show the presence of a supercell that breaks R (3) over bar symmetry. We also present the temperature and field dependence of the dielectric constant and pyroelectric current and show evidence of nonzero off-diagonal magnetoelectric tensor elements (forbidden by R (3) over bar symmetry) followed by a polarization flop accompanying the spin flop transition at mu H-0(SF) = 6.5T. Mossbauer spectroscopy on MnTiO3 gently doped with Fe-57 was used to help shed light on the impact of the supercell on the observed behavior. Although the full supercell structure could not be solved at this time due to a lack of visible reflections, the full scope of the results presented here suggest that the role of local spin-lattice coupling in the magnetoelectric properties of MnTiO3 is likely more important than previously thought.
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Date Issued: 2016-02-19
Identifier: FSU_libsubv1_wos_000370485900001, 10.1103/PhysRevB.93.054416
Format: Citation

National High Magnetic Field Laboratory (84)	+ -
Department of Physics (47)	+ -
Department of Chemical and Biomedical Engineering (3)	+ -
Department of Chemistry and Biochemistry (3)	+ -
Department of Mechanical Engineering (1)	+ -

text (103)	+ -
journal article (53)	+ -

Yang, Kun (12)	+ -
Graf, D. (11)	+ -
Zhou, H. D. (9)	+ -
Baumbach, R. E. (7)	+ -
Balicas, L. (6)	+ -

Reyes, A. P. (6)	+ -
Choi, E. S. (5)	+ -
Gong, Shou-Shu (5)	+ -
Petrovic, C. (5)	+ -
Aczel, A. A. (4)	+ -
Besara, T. (4)	+ -
Cao, G. (4)	+ -
Chen, K.-W. (4)	+ -
Kuhns, P. L. (4)	+ -
Lee, M. (4)	+ -
Sheng, D. N. (4)	+ -
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Pfeiffer, L. N. (3)	+ -
Rhodes, D. (3)	+ -
Schlottmann, P. (3)	+ -
Siegrist, T. (3)	+ -
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