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 Title
 Absence Of Dirac States In Baznbi2 Induced By Spinorbit Coupling.
 Creator

Ren, Weijun, Wang, Aifeng, Graf, D., Liu, Yu, Zhang, Zhidong, Yin, WeiGuo, 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 spinorbit coupling (SOC) and consequently electronic transport is dominated by the small hole and electron pockets. Our results are consistent with not only threedimensional, but also with quasitwodimensional portions of the Fermi surface. The SOCinduced 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 spinorbit coupling (SOC) and consequently electronic transport is dominated by the small hole and electron pockets. Our results are consistent with not only threedimensional, but also with quasitwodimensional portions of the Fermi surface. The SOCinduced gap in Dirac states is much larger when compared to isostructural SrMnBi2. This suggests that not only longrange magnetic order, but also mass of the alkalineearth atoms A in ABX(2) (A = alkalineearth, B = transitionmetal, and X = Bi/Sb) are important for the presence of lowenergy states obeying the relativistic Dirac equation at the Fermi surface.
Show less  Date Issued
 20180122
 Identifier
 FSU_libsubv1_wos_000423341500001, 10.1103/PhysRevB.97.035147
 Format
 Citation
 Title
 Anisotropic Antiferromagnetic Order In The Spinorbit Coupled Trigonallattice 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 singlecrystal xray 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 longrange antiferromagnetic order below TN = 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 singlecrystal xray 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 longrange antiferromagnetic order below TN = 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 edgesharing 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.
Show less  Date Issued
 20180611
 Identifier
 FSU_libsubv1_wos_000434761900004, 10.1103/PhysRevB.97.235116
 Format
 Citation
 Title
 Detailed Study Of The Fermi Surfaces Of The Typeii 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.
Show less  Abstract/Description

We present a detailed quantum oscillatory study on the Dirac typeII semimetallic candidates PdTe2 and PtTe2 via the temperature and the angular dependence of the de Haasvan Alphen and Shubnikovde Haas effects. In highquality 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 typeII semimetallic candidates PdTe2 and PtTe2 via the temperature and the angular dependence of the de Haasvan Alphen and Shubnikovde Haas effects. In highquality 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 H0 = 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 crosssectional 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 typeII 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 typeII 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 typeII node. Therefore, it should yield a trivial Berry phase.
Show less  Date Issued
 20180629
 Identifier
 FSU_libsubv1_wos_000436907600002, 10.1103/PhysRevB.97.235154
 Format
 Citation
 Title
 Fieldinduced Spin Splitting And Anomalous Photoluminescence Circular Polarization In Ch3nh3pbi3 Films At High Magnetic Field.
 Creator

Zhang, Chuang, Sun, Dali, Yu, ZhiGang, Sheng, ChuanXiang, McGill, Stephen, Semenov, Dmitry, Vardeny, Zeev Valy
 Abstract/Description

The organicinorganic hybrid perovskites show excellent optical and electrical properties for photovoltaic and a myriad of other optoelectronics applications. Using highfield magnetooptical measurements up to 17.5 T at cryogenic temperatures, we have studied the spindependent optical transitions in the prototype CH3NH3PbI3, which are manifested in the fieldinduced circularly polarized photoluminescence emission. The energy splitting between left and right circularly polarized emission...
Show moreThe organicinorganic hybrid perovskites show excellent optical and electrical properties for photovoltaic and a myriad of other optoelectronics applications. Using highfield magnetooptical measurements up to 17.5 T at cryogenic temperatures, we have studied the spindependent optical transitions in the prototype CH3NH3PbI3, which are manifested in the fieldinduced 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 fieldinduced 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 effectivemass approximation.
Show less  Date Issued
 20180416
 Identifier
 FSU_libsubv1_wos_000430055800003, 10.1103/PhysRevB.97.134412
 Format
 Citation
 Title
 Fermi Surface Reconstruction And Dimensional Topology Change In Nddoped 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 lowtemperature de Haasvan Alphen effect measurements on a Ce1xNdxCoIn5 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 quasitwodimensional topology for Nd2% to a rather threedimensional one for Nd5%, thus reducing the possibility of perfect FS nesting. The FS evolves further with increasing Nd content with no observed divergence of...
Show moreWe performed lowtemperature de Haasvan Alphen effect measurements on a Ce1xNdxCoIn5 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 quasitwodimensional topology for Nd2% to a rather threedimensional one for Nd5%, 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 Nd2% 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% Nddoping level [Raymond et al., T. Phys. Soc. Jpn. 83, 013707 (2014)].
Show less  Date Issued
 20180809
 Identifier
 FSU_libsubv1_wos_000441234900001, 10.1103/PhysRevB.98.081105
 Format
 Citation
 Title
 Observation Of Two Critical Points Linked To The Highfield 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 Tc and at two secondorder transitions TA,TB 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 Tc and at two secondorder transitions TA,TB into ordered phases A and B. Our measurements establish the boundary of phase B at high field and low temperature. No evidence for additional highfield 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 spindensity wave type and (ii) the firstorder phase transition between A and B is caused by Fermisurface reconstruction. We furthermore identify a quantum critical point at Hc similar or equal to 17 T, where TB is suppresssed to zero, and a bicritical point at (0.35 K, 7.0 T), where phase lines TA(H) and TB(H) meet.
Show less  Date Issued
 20180808
 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 rareearth monopnictides, the field dependence of resistivity in HoBi is nonmonotonic and reveals clear signatures of every metamagnetic transition in the lowtemperature and lowfield 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 rareearth monopnictides, the field dependence of resistivity in HoBi is nonmonotonic and reveals clear signatures of every metamagnetic transition in the lowtemperature and lowfield 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 rareearth monopnictides. Therefore, HoBi provides a unique opportunity to understand the electrical transport in magnetic XMR semimetals.
Show less  Date Issued
 20180727
 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 threedimensional topological insulator Bi2Te3. Magnetoreflectance response of singlecrystal Bi2Te3 was studied in 18T 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 threedimensional topological insulator Bi2Te3. Magnetoreflectance response of singlecrystal Bi2Te3 was studied in 18T 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.
Show less  Date Issued
 20180920
 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 spinorbit interaction. Recent Na23 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 spinorbit interaction. Recent Na23 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 Na23 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.
Show less  Date Issued
 20180614
 Identifier
 FSU_libsubv1_wos_000435332500001, 10.1103/PhysRevB.97.224103
 Format
 Citation
 Title
 Nodal Superconductivity Coexists With Lowmoment Static Magnetism In Singlecrystalline 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 Tc. TF mu SR results indicate a linear temperature dependence of the superfluid density at low temperature, consistent with nodal superconductivity. The s+dwave model gives the best fit to the observed temperature and field dependencies, and yields an inplane penetration depth value lambda(ab) (T=0) = 241(3) nm.
Show less  Date Issued
 20180531
 Identifier
 FSU_libsubv1_wos_000433907600005, 10.1103/PhysRevB.97.174524
 Format
 Citation
 Title
 Dissipation In Quantum Turbulence In Superfluid He4 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 He4 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 He4 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)L2, 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 L2(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.
Show less  Date Issued
 20180529
 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 metalpnictide 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 metalpnictide 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.
Show less  Date Issued
 20180510
 Identifier
 FSU_libsubv1_wos_000432031700002, 10.1103/PhysRevB.97.174410
 Format
 Citation
 Title
 Multistability In An Unusual Phase Diagram Induced By The Competition Between Antiferromagneticlike Shortrange And Ferromagneticlike Longrange Interactions.
 Creator

Nishino, Masamichi, Rikvold, Per Arne, Omand, Conor, Miyashita, Seiji
 Abstract/Description

The interplay between competing shortrange (SR) and longrange (LR) interactions can cause nontrivial structures in phase diagrams. Recently, hornshaped unusual structures were found by Monte Carlo simulations in the phase diagram of the Ising antiferromagnet (IA) with infiniterange ferromagneticlike (F) interactions [Phys. Rev. B 93, 064109 (2016); 96, 174428 (2017)], and also in an IA with LR interactions of elastic origin modeling spincrossover materials [Phys. Rev. B 96, 144425 (2017...
Show moreThe interplay between competing shortrange (SR) and longrange (LR) interactions can cause nontrivial structures in phase diagrams. Recently, hornshaped unusual structures were found by Monte Carlo simulations in the phase diagram of the Ising antiferromagnet (IA) with infiniterange ferromagneticlike (F) interactions [Phys. Rev. B 93, 064109 (2016); 96, 174428 (2017)], and also in an IA with LR interactions of elastic origin modeling spincrossover 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 infiniterange F interactions by applying a variational free energy in a cluster meanfield (CMF) approximation. While the simple BraggWilliams meanfield 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 ferromagneticlike, antiferromagneticlike, and disordered phases coexist, and also six tristable regions accompanying the horn structure. We also point out that several characteristic endpoints of firstorder 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 latticegas model, in which solid, liquid, and gas phases can coexist.
Show less  Date Issued
 20181002
 Identifier
 FSU_libsubv1_wos_000446296400003, 10.1103/PhysRevB.98.144402
 Format
 Citation
 Title
 Fieldinduced 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, lowtemperature magnetic structures, and the magnetic field effect on the electrical resistivity of the binary intermetallic compound Tb3Ni. The incommensurate magnetic structure of the spindensitywave 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 TN = 61 K. Further cooling below 58 K results in the...
Show moreIn this paper we report the detailed study of magnetic phase diagrams, lowtemperature magnetic structures, and the magnetic field effect on the electrical resistivity of the binary intermetallic compound Tb3Ni. The incommensurate magnetic structure of the spindensitywave 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 TN = 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 lockedin incommensurate component in the temperature range 48 < T < 51 K; and (iii) a lowtemperature 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 lowtemperature 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.
Show less  Date Issued
 20180426
 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, ShouShu, 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 halffilling, which has a quadratic band touching in the absence of interaction. In the presence of strong nearestneighbor (V1) and nextnearestneighbor (V2...
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 halffilling, which has a quadratic band touching in the absence of interaction. In the presence of strong nearestneighbor (V1) and nextnearestneighbor (V2) 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 timereversal 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 V1 and V2 on equal footing, as well as the weak coupling renormalization group. Our analytical results reveal that not only the repulsive V1 interaction, but also the V2 interaction (both repulsive and attractive), can drive the quantum anomalous Hall phase. We also determine the phase boundary in the V1V2 plane that separates the semimetal from the quantum anomalous Hall state. Finally, we show that the nematic semimetal, which was proposed for vertical bar V2 vertical bar >> V1 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.
Show less  Date Issued
 20180926
 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 O2 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 O2 for different durations of time. With increasing annealing time, the films developed significant strains of opposite signs along the two orthogonal inplane directions. The static temperaturedependent resistivity, p(T), was measured simultaneously along the two orthogonal directions. With increasing annealing time, both zerofieldcooled and fieldcooled p(T) show significant increases, suggesting straintriggered EPS and appearance of antiferromagnetic insulating (AFI) phases in a ferromagnetic metallic (FMM) ground state. Meanwhile, p(T) along the tensilestrained [010] direction becomes progressively larger than that along the compressivestrained [100]. The enhanced resistivity anisotropy indicates that the EPS is characterized by phaseseparated 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 phaseseparated 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.
Show less  Date Issued
 20180625
 Identifier
 FSU_libsubv1_wos_000436190900003, 10.1103/PhysRevB.97.214428
 Format
 Citation
 Title
 Quench Dynamics Across Topological Quantum Phase Transitions.
 Creator

Liou, ShiuanFan, 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 bandtouching structures leading to topology changes. The generation of bulk excitations is found to obey the powerlaw relation KibbleZurek and LandauZener theories predict. However, an antiKibbleZurek...
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 bandtouching structures leading to topology changes. The generation of bulk excitations is found to obey the powerlaw relation KibbleZurek and LandauZener theories predict. However, an antiKibbleZurek behavior is observed in the edge excitations. The mechanism of excitation generation on edge states is revealed, which explains the antiKibbleZurek behavior.
Show less  Date Issued
 20180625
 Identifier
 FSU_libsubv1_wos_000436192300003, 10.1103/PhysRevB.97.235144
 Format
 Citation
 Title
 Topological Phase Transition In A Twospecies Fermion System: Effects Of A Rotating Trap Potential Or A Synthetic Gauge Field.
 Creator

Liou, ShiuanFan, Hu, ZiXiang, 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 swave 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 swave 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 fieldtheoretical predictions and the case of pwave pairing.
Show less  Date Issued
 20180625
 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 maingroup 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 spinorbit coupling and proper external magnetic field. The...
Show moreThe square lattices formed by maingroup 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 spinorbit 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 Haasvan Alphen (dHvA) oscillations. The dHvA study also reveals YSn2 has a complicated Fermi surface, consisting of several threedimensional (3D) and one 2D pocket. Our firstprinciples 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.
Show less  Date Issued
 20180716
 Identifier
 FSU_libsubv1_wos_000438674700001, 10.1103/PhysRevB.98.035117
 Format
 Citation
 Title
 Energylevel Statistics In Strongly Disordered Systems With Powerlaw 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 longrange interactions, we study energylevel statistics of quasiparticles with the powerlaw hopping Hamiltonian proportional to 1/r(alpha) in a strong random potential. In solidstate systems such quasiparticles, which are exemplified by neutral dipolar excitations, lead to longrange 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 longrange interactions, we study energylevel statistics of quasiparticles with the powerlaw hopping Hamiltonian proportional to 1/r(alpha) in a strong random potential. In solidstate systems such quasiparticles, which are exemplified by neutral dipolar excitations, lead to longrange correlations of local observables and may dominate energy transport. Focusing on the excitations in disordered electronic systems, we compute the energylevel correlation function R2(omega) in a finite system in the limit of sufficiently strong disorder. At small energy differences, the correlations exhibit WignerDyson statistics. In particular, in the limit of very strong disorder the energylevel correlation function is given by R2(omega, V) = A(3) omega/omega(V) for small frequencies omega << omega(V) and R2(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 Valpha/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 energylevel 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.
Show less  Date Issued
 20180716
 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 statess 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 statess 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 spinorbit coupling in the effective lowenergy Hamiltonian.
Show less  Date Issued
 20180706
 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 rareearth 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 rareearth 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 spinorbit 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 firstprinciple findings should form a foundation for effective models describing the lowtemperature properties of this material whose true ground state remains controversial.
Show less  Date Issued
 20180611
 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., LezamaPacheco, 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., LezamaPacheco, J., Mocko, V., Ditter, A. S., Kozimor, S. A., Seidler, G. T., Nelson, W. L., Chiu, Y.C., Huang, K., Potter, W., Graf, D., AlbrechtSchmitt, T. E., Baumbach, R. E.
Show less  Abstract/Description

An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1x Nix)(2)P2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperatureconcentration (Tx) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and RudermanKittelKasuya Yosida (RKKY) interactions, and the introduction...
Show moreAn investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1x Nix)(2)P2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperatureconcentration (Tx) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and RudermanKittelKasuya 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, xray 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 Fermiliquid 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 BelitzKirkpatrickVojta model for ferromagnetic quantum criticality, where distinct behaviors are expected in the dirty and clean limits.
Show less  Date Issued
 20180606
 Identifier
 FSU_libsubv1_wos_000434256700002, 10.1103/PhysRevB.97.224406
 Format
 Citation
 Title
 Dipolaroctupolar 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.
Show less  Abstract/Description

Over the past two decades, the magnetic ground states of all rareearth 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 rareearth 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 dipolaroctupolar doublet with Ising anisotropy. Neutron diffraction experiments reveal that Sm2Ti2O7 orders into the allin, allout magnetic structure with an ordered moment of 0.44(7)mu(B) below TN = 0.35 K, consistent with expectations for antiferromagnetically coupled Ising spins on the pyrochlore lattice. Zerofield muon spin relaxation measurements reveal an absence of spontaneous oscillations and persistent spin fluctuations down to 0.03 K. The combination of the dipolaroctupolar nature of the Sm3+ moment, the allin, allout ordered state, and the lowtemperature persistent spin dynamics make this material an intriguing candidate for moment fragmentation physics.
Show less  Date Issued
 20180905
 Identifier
 FSU_libsubv1_wos_000443672100001, 10.1103/PhysRevB.98.100401
 Format
 Citation
 Title
 Sensitivity Of Tc To Pressure And Magnetic Field In The Cuprate Superconductor Yba2cu3oy: Evidence Of Chargeorder Suppression By Pressure.
 Creator

CyrChoiniere, O., LeBoeuf, D., Badoux, S., DufourBeausejour, S., Bonn, D. A., Hardy, W. N., Liang, R., Graf, D., DoironLeyraud, N., Taillefer, Louis
 Abstract/Description

Cuprate superconductors have a universal tendency to form charge densitywave (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 densitywave (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 Tc of YBCO in the same way as a function of dopingbut in opposite directionsand 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 highpressure data and our own work, we observe that when CDW order is fully suppressed at high pressure, the socalled "1/8 anomaly" in the superconducting dome vanishes, revealing a smooth Tc dome which now peaks at p similar or equal to 0.13. We propose that this Tc 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.
Show less  Date Issued
 20180830
 Identifier
 FSU_libsubv1_wos_000443139600006, 10.1103/PhysRevB.98.064513
 Format
 Citation
 Title
 Observation Of A Pressureinduced 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 RuddlesdenPopper compound with triple RuO perovskite layers separated by SrO rocksalt layers. This compound presents a rare coexistence of interlayer (caxis) ferromagnetism and intralayer (basalplane) metamagnetism at ambient pressure. Here we report the observation of pressureinduced, 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 RuddlesdenPopper compound with triple RuO perovskite layers separated by SrO rocksalt layers. This compound presents a rare coexistence of interlayer (caxis) ferromagnetism and intralayer (basalplane) metamagnetism at ambient pressure. Here we report the observation of pressureinduced, 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 caxis ferromagnetism and basalplane metamagnetism, and induce a basalplane antiferromagnetic state. The unusually large magnetoelastic coupling and pressure tunability of Sr4Ru3O10 makes it a model system for studies of itinerant magnetism.
Show less  Date Issued
 20180821
 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 socalled 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 magneticfieldinduced, quantum Wigner crystal forms in a dilute, twodimensional electron layer when a second, highdensity 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 socalled 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 magneticfieldinduced, quantum Wigner crystal forms in a dilute, twodimensional electron layer when a second, highdensity 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 singlelayer twodimensional electron systems. The measured nu(c) exhibits a strong dependence on the interlayer distance, reflecting the interaction and screening from the adjacent, highdensity layer.
Show less  Date Issued
 20180816
 Identifier
 FSU_libsubv1_wos_000441857700001, 10.1103/PhysRevB.98.081111
 Format
 Citation
 Title
 Timereversal Symmetrybreaking Nematic Superconductivity In Fese.
 Creator

Kang, Jian, Chubukov, Andrey, Fernandes, Rafael M.
 Abstract/Description

FeSe is a unique member of the family of ironbased superconductors, not only because of the high values of Tc in FeSe monolayer, but also because in bulk FeSe superconductivity emerges inside a nematic phase without competing with longrange magnetic order. Near Tc, superconducting order necessarily has s + d symmetry, because nematic order couples linearly the swave and dwave harmonics of the superconducting order parameter. Here we argue that the neardegeneracy between swave and d...
Show moreFeSe is a unique member of the family of ironbased superconductors, not only because of the high values of Tc in FeSe monolayer, but also because in bulk FeSe superconductivity emerges inside a nematic phase without competing with longrange magnetic order. Near Tc, superconducting order necessarily has s + d symmetry, because nematic order couples linearly the swave and dwave harmonics of the superconducting order parameter. Here we argue that the neardegeneracy between swave and dwave pairing instabilities in FeSe, combined with the signchange of the nematic order parameter between hole and electron pockets, allows the superconducting order to break timereversal 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.
Show less  Date Issued
 20180820
 Identifier
 FSU_libsubv1_wos_000442194600005, 10.1103/PhysRevB.98.064508
 Format
 Citation
 Title
 Variational Monte Carlo Study Of Chiral Spin Liquid In Quantum Antiferromagnet On The Triangular Lattice.
 Creator

Hu, WenJun, Gong, ShouShu, Sheng, D. N.
 Abstract/Description

By using Gutzwiller projected fermionic wave functions and variational Monte Carlo technique, we study the spin1/2 Heisenberg model with the firstneighbor (J(1)), secondneighbor (J(2)), and additional scalar chiral interaction J(chi)S(i) . (Sj x Sk) on the triangular lattice. In the nonmagnetic phase of the J(1)J(2) triangular model with 0.08 less than or similar to J(2)/J(1) less than or similar to 0.16, recent densitymatrix renormalization group (DMRG) studies [Zhu and White, Phys....
Show moreBy using Gutzwiller projected fermionic wave functions and variational Monte Carlo technique, we study the spin1/2 Heisenberg model with the firstneighbor (J(1)), secondneighbor (J(2)), and additional scalar chiral interaction J(chi)S(i) . (Sj x Sk) on the triangular lattice. In the nonmagnetic phase of the J(1)J(2) triangular model with 0.08 less than or similar to J(2)/J(1) less than or similar to 0.16, recent densitymatrix renormalization group (DMRG) studies [Zhu and White, Phys. Rev. B 92, 041105(R) (2015) and Hu, Gong, Zhu, and Sheng, Phys. Rev. B 92, 140403(R) (2015)] find a possible gapped spin liquid with the signal of a competition between a chiral and a Z(2) spin liquid. Motivated by the DMRG results, we consider the chiral interaction J(chi)S(i) . (Sj x Sk) as a perturbation for this nonmagnetic phase. We find that with growing J(chi), the gapless U(1) Dirac spin liquid, which has the best variational energy for J(chi) = 0, exhibits the energy instability towards a gapped spin liquid with nontrivial magnetic fluxes and nonzero chiral order. We calculate topological Chern number and groundstate degeneracy, both of which identify this flux state as the chiral spin liquid with fractionalized Chern number C = 1/2 and twofold topological degeneracy. Our results indicate a positive direction to stabilize a chiral spin liquid near the nonmagnetic phase of the J(1)J(2) triangular model.
Show less  Date Issued
 20160815
 Identifier
 FSU_libsubv1_wos_000381482600002, 10.1103/PhysRevB.94.075131
 Format
 Citation
 Title
 WiedemannFranz law in the underdoped cuprate superconductor YBa2Cu3Oy.
 Creator

Grissonnanche, G., Laliberte, F., DufourBeausejour, S., Matusiak, M., Badoux, S., Tafti, F. F., Michon, B., Riopel, A., CyrChoiniere, O., Baglo, J. C., Ramshaw, B. J., Liang,...
Show moreGrissonnanche, G., Laliberte, F., DufourBeausejour, S., Matusiak, M., Badoux, S., Tafti, F. F., Michon, B., Riopel, A., CyrChoiniere, O., Baglo, J. C., Ramshaw, B. J., Liang, R., Bonn, D. A., Hardy, W. N., Kraemer, S., LeBoeuf, D., Graf, D., DoironLeyraud, N., Taillefer, Louis
Show less  Abstract/Description

The electrical and thermal Hall conductivities of the cuprate superconductor YBa2Cu3Oy, sigma(xy) and kappa(xy), were measured in a magnetic field up to 35 T, at a hole concentration (doping) p = 0.11. In the T = 0 limit, we find that the WiedemannFranz law, kappa(xy)/T = (pi(2)/3)(k(B)/e)(2)sigma(xy), is satisfied for fields immediately above the vortexmelting field Hvs. This rules out the existence of a vortex liquid at T = 0 and it puts a clear constraint on the nature of the normal...
Show moreThe electrical and thermal Hall conductivities of the cuprate superconductor YBa2Cu3Oy, sigma(xy) and kappa(xy), were measured in a magnetic field up to 35 T, at a hole concentration (doping) p = 0.11. In the T = 0 limit, we find that the WiedemannFranz law, kappa(xy)/T = (pi(2)/3)(k(B)/e)(2)sigma(xy), is satisfied for fields immediately above the vortexmelting field Hvs. This rules out the existence of a vortex liquid at T = 0 and it puts a clear constraint on the nature of the normal state in underdoped cuprates, in a region of the doping phase diagram where chargedensitywave order is known to exist. As the temperature is raised, the Lorenz ratio, Lxy = kappa(xy)/(sigma Txy), decreases rapidly, indicating that strong smallq scattering processes are involved.
Show less  Date Issued
 20160222
 Identifier
 FSU_libsubv1_wos_000370793000005, 10.1103/PhysRevB.93.064513
 Format
 Citation
 Title
 Possible Devil's Staircase In The Kondo Lattice Cesbse.
 Creator

Chen, K.W., Lai, Y., Chiu, Y.C., Steven, S., Besara, T., Graf, D., Siegrist, T., AlbrechtSchmitt, T. E., Balicas, L., Baumbach, R. E.
 Abstract/Description

The temperature (T) magneticfield (H) phase diagram for the tetragonal layered compound CeSbSe is determined from magnetization, specific heat, and electrical resistivity measurements. This system exhibits complex magnetic ordering at TM = 3 K and the application of a magnetic field results in a cascade of magnetically ordered states for H less than or similar to 1.8 T which are characterized by fractional integer size steps: i.e., a possible devil's staircase is observed. Electrical...
Show moreThe temperature (T) magneticfield (H) phase diagram for the tetragonal layered compound CeSbSe is determined from magnetization, specific heat, and electrical resistivity measurements. This system exhibits complex magnetic ordering at TM = 3 K and the application of a magnetic field results in a cascade of magnetically ordered states for H less than or similar to 1.8 T which are characterized by fractional integer size steps: i.e., a possible devil's staircase is observed. Electrical transport measurements show a weak temperature dependence and large residual resistivity which suggest a small chargecarrier density and strong scattering from the f moments. These features reveal Kondo lattice behavior where the f moments are screened incompletely, resulting in a fine balanced magnetic interaction between different Ce neighbors that is mediated by the RudermanKittelKasuyaYosida interaction. This produces the nearly degenerate magnetically ordered states that are accessed under an applied magnetic field.
Show less  Date Issued
 20170717
 Identifier
 FSU_libsubv1_wos_000405697200002, 10.1103/PhysRevB.96.014421
 Format
 Citation
 Title
 Possible Nematic Spin Liquid In Spin1 Antiferromagnetic System On The Square Lattice: Implications For The Nematic Paramagnetic State Of Fese.
 Creator

Gong, ShouShu, Zhu, W., Sheng, D. N., Yang, Kun
 Abstract/Description

The exotic normal state of iron chalcogenide superconductor FeSe, which exhibits vanishing magnetic order and possesses an electronic nematic order, triggered extensive explorations of its magnetic ground state. To understand its novel properties, we study the ground state of a highly frustrated spin1 system with bilinearbiquadratic interactions using an unbiased largescale density matrix renormalization group. Remarkably, with increasing biquadratic interactions, we find a paramagnetic...
Show moreThe exotic normal state of iron chalcogenide superconductor FeSe, which exhibits vanishing magnetic order and possesses an electronic nematic order, triggered extensive explorations of its magnetic ground state. To understand its novel properties, we study the ground state of a highly frustrated spin1 system with bilinearbiquadratic interactions using an unbiased largescale density matrix renormalization group. Remarkably, with increasing biquadratic interactions, we find a paramagnetic phase between Neel and stripe magnetic ordered phases. We identify this phase as a candidate of nematic quantum spin liquid by the compelling evidences, including vanished spin and quadrupolar orders, absence of lattice translational symmetry breaking, and a persistent nonzero lattice nematic order in the thermodynamic limit. The established quantum phase diagram naturally explains the observations of enhanced spin fluctuations of FeSe in neutron scattering measurement and the phase transition with increasing pressure. This identified paramagnetic phase provides a possibility to understand the novel properties of FeSe.
Show less  Date Issued
 20170519
 Identifier
 FSU_libsubv1_wos_000401654300004, 10.1103/PhysRevB.95.205132
 Format
 Citation
 Title
 Probing The Magnetic Field Dependence Of The Light Hole Transition In Gaas/algaas Quantum Wells Using Optically Pumped Nmr.
 Creator

Willmering, Matthew M., Sesti, Erika L., Hayes, Sophia E., Wood, Ryan M., Bowers, Clifford R., Thapa, Sunil K., Stanton, Christopher J., Reyes, Arneil P., Kuhns, Philip, McGill,...
Show moreWillmering, Matthew M., Sesti, Erika L., Hayes, Sophia E., Wood, Ryan M., Bowers, Clifford R., Thapa, Sunil K., Stanton, Christopher J., Reyes, Arneil P., Kuhns, Philip, McGill, Stephen
Show less  Abstract/Description

Optically pumped NMR (OPNMR) of the NMRactive Ga69/71 species has been shown to be a unique method to probe electronic energy bands in GaAs, with sensitivity to the light holetoconduction band transition. This transition is often obscured in other optical measurements such as magnetoabsorption. Using OPNMR, we exploit the hyperfine interaction between conduction band electrons (and their spin states) and nuclear spins, which are detected through phasesensitive radiofrequency (NMR)...
Show moreOptically pumped NMR (OPNMR) of the NMRactive Ga69/71 species has been shown to be a unique method to probe electronic energy bands in GaAs, with sensitivity to the light holetoconduction band transition. This transition is often obscured in other optical measurements such as magnetoabsorption. Using OPNMR, we exploit the hyperfine interaction between conduction band electrons (and their spin states) and nuclear spins, which are detected through phasesensitive radiofrequency (NMR) spectroscopy. Measurements were made over a range of external magnetic fields (B0) in two different labs with separate experimental setups to obtain the magnetic field dependence of the light holetoconduction band transition energy. In addition, k . p theory was used to interpret the experimental results, mapping out this specific transition's magnetic field dependence in an AlGaAs/GaAs quantum well. The combination of theory and experiment point to a mixing of valence bands at a field of approximately B0 = 4.7 T, swapping the dominant character of the absorption transition and, thus, explaining the magnetic field dependence. Lastly, the experimental dependence of the light holetoconduction band transition energy on B0 is found to be less steep compared to the calculated trend, indicating that inclusion of additional effects may be necessary to accurately model the spinsplit band structure. The additional insight gained by Ga69/71 OPNMR about the light hole states will facilitate future testing of more complex band structure models.
Show less  Date Issued
 20180207
 Identifier
 FSU_libsubv1_wos_000424376500004, 10.1103/PhysRevB.97.075303
 Format
 Citation
 Title
 Probing critical surfaces in momentum space using realspace entanglement entropy: Bose versus Fermi.
 Creator

Lai, HsinHua, Yang, Kun
 Abstract/Description

A codimensionone critical surface in momentum space can be either a familiar Fermi surface, which separates occupied states from empty ones in the noninteracting fermion case, or a novel Bose surface, where gapless bosonic excitations are anchored. The presence of such surfaces gives rise to logarithmic violation of entanglement entropy area law. When they are convex, we show that the shape of these critical surfaces can be determined by inspecting the leading logarithmic term of realspace...
Show moreA codimensionone critical surface in momentum space can be either a familiar Fermi surface, which separates occupied states from empty ones in the noninteracting fermion case, or a novel Bose surface, where gapless bosonic excitations are anchored. The presence of such surfaces gives rise to logarithmic violation of entanglement entropy area law. When they are convex, we show that the shape of these critical surfaces can be determined by inspecting the leading logarithmic term of realspace entanglement entropy. The fundamental difference between a Fermi surface and a Bose surface is revealed by the fact that the logarithmic terms in entanglement entropies differ by a factor of 2: Slog(Bose) = 2S(log)(Fermi), even when they have identical geometry. Our method has remarkable similarity with determining Fermi surface shape using quantum oscillation. We also discuss possible probes of concave critical surfaces in momentum space.
Show less  Date Issued
 20160323
 Identifier
 FSU_libsubv1_wos_000372716500001, 10.1103/PhysRevB.93.121109
 Format
 Citation
 Title
 Search For A Nematic Phase In The Quasitwodimensional Antiferromagnet Cucro2 By Nmr In An Electric Field.
 Creator

Sakhratov, Yu A., Kweon, J. J., Choi, E. S., Zhou, H. D., Svistov, L. E., Reyes, A. P.
 Abstract/Description

The magnetic phase diagram of CuCrO2 was studied with an alternative method of simultaneous Cu NMR and electric polarization techniques with the primary goal of demonstrating that, regardless of cooling history of the sample, the magnetic phase with specific helmetshaped NMR spectra associated with interplanar disorder possesses electric polarization. Our result unequivocally confirms the assumption of Sakhratov et al. [Phys. Rev. B 94, 094410 ( 2016)] that the highfield lowtemperature...
Show moreThe magnetic phase diagram of CuCrO2 was studied with an alternative method of simultaneous Cu NMR and electric polarization techniques with the primary goal of demonstrating that, regardless of cooling history of the sample, the magnetic phase with specific helmetshaped NMR spectra associated with interplanar disorder possesses electric polarization. Our result unequivocally confirms the assumption of Sakhratov et al. [Phys. Rev. B 94, 094410 ( 2016)] that the highfield lowtemperature phase is in fact a threedimensional (3D) polar phase characterized by a 3D magnetic order with tensor order parameter. In comparison with the results obtained in pulsed fields, a modified phase diagram is introduced defining the upper boundary of the firstorder transition from the 3D spiral to the 3D polar phase.
Show less  Date Issued
 20180312
 Identifier
 FSU_libsubv1_wos_000427111700001, 10.1103/PhysRevB.97.094409
 Format
 Citation
 Title
 Simultaneous Metalinsulator And Antiferromagnetic Transitions In Orthorhombic Perovskite Iridate Sr0.94ir0.78o2.68 Single Crystals.
 Creator

Zheng, H., Terzic, J., Ye, Feng, Wan, X. G., Wang, D., Wang, Jinchen, Wang, Xiaoping, Schlottmann, P., Yuan, S. J., Cao, G.
 Abstract/Description

The orthorhombic perovskite SrIrO3 is a semimetal, an intriguing exception in iridates where the strong spinorbit interaction coupled with electron correlations tends to impose an insulating state. We report results of our investigation of bulk singlecrystal Sr0.94Ir0.78O2.68 or Irdeficient, orthorhombic perovskite SrIrO3. It retains the same crystal structure as stoichiometric SrIrO3 but exhibits a sharp, simultaneous antiferromagnetic (AFM) and metalinsulator (MI) transition occurring...
Show moreThe orthorhombic perovskite SrIrO3 is a semimetal, an intriguing exception in iridates where the strong spinorbit interaction coupled with electron correlations tends to impose an insulating state. We report results of our investigation of bulk singlecrystal Sr0.94Ir0.78O2.68 or Irdeficient, orthorhombic perovskite SrIrO3. It retains the same crystal structure as stoichiometric SrIrO3 but exhibits a sharp, simultaneous antiferromagnetic (AFM) and metalinsulator (MI) transition occurring in the basalplane resistivity at 185 K. Above it, the basalplane resistivity features an extended regime of almost linear temperature dependence up to 800 K but the strong electronic anisotropy renders an insulating behavior in the outofplane resistivity. The Hall resistivity undergoes an abrupt sign change and grows below 40 K, which along with the Sommerfeld constant of 20 mJ/mol K2 suggests a multiband effect. All results including our firstprinciples calculations underscore a delicacy of the paramagnetic, metallic state in SrIrO3 that is in close proximity to an AFM insulating state. The contrasting ground states in isostructural Sr0.94Ir0.78O2.68 and SrIrO3 illustrate a critical role of lattice distortions and Ir deficiency in rebalancing the ground state in the iridates. Finally, the concurrent AFM and MI transitions reveal a direct correlation between the magnetic transition and formation of an activation gap in the iridate, which is conspicuously absent in Sr2IrO4.
Show less  Date Issued
 20160627
 Identifier
 FSU_libsubv1_wos_000378813800008, 10.1103/PhysRevB.93.235157
 Format
 Citation
 Title
 Spin correlations and topological entanglement entropy in a nonAbelian spinone spin liquid.
 Creator

Wildeboer, Julia, Bonesteel, N. E.
 Abstract/Description

We analyze the properties of a nonAbelian spinone chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 MooreRead Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a threedimensional space of these states corresponding to the topological degeneracy of the bosonic MooreRead state on the...
Show moreWe analyze the properties of a nonAbelian spinone chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 MooreRead Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a threedimensional space of these states corresponding to the topological degeneracy of the bosonic MooreRead state on the torus. We show that spin correlations for different states in this space become indistinguishable for large system size. We also calculate the Renyi entanglement entropy for different system partitions to extract the topological entanglement entropy and provide evidence that the topological order of the lattice spinliquid state is the same as that of the continuum MooreRead state from which it is constructed.
Show less  Date Issued
 20160718
 Identifier
 FSU_libsubv1_wos_000380104300008, 10.1103/PhysRevB.94.045125
 Format
 Citation
 Title
 Transport, magnetic, and optical properties of electrochemically doped poly(1, 4dimethoxy phenylene vinylene).
 Creator

Schlenoff, Joseph B., Obrzut, Jan, Karasz, F.
 Abstract/Description

A coordinated study on electrochemical, magnetic, optical, and transport properties of poly(1, 4 dimethoxy phenylene vinylene) (PDMPV) using in situ electrochemical doping techniques is presented. Properties are correlated through a common axis of applied voltage. Electrochemical doping shows approx. 100% Coulombic efficiency up to an applied potential of 3.8 V versus lithium in propylene carbonate electrolyte. Conductivity increases in a reversible manner to a maximum of 250 0 ' cm ' and an...
Show moreA coordinated study on electrochemical, magnetic, optical, and transport properties of poly(1, 4 dimethoxy phenylene vinylene) (PDMPV) using in situ electrochemical doping techniques is presented. Properties are correlated through a common axis of applied voltage. Electrochemical doping shows approx. 100% Coulombic efficiency up to an applied potential of 3.8 V versus lithium in propylene carbonate electrolyte. Conductivity increases in a reversible manner to a maximum of 250 0 ' cm ' and an applied potential of 3.9 V. Potentials in excess of 3.9 V cause an irreversible decrease in conductivity. Spin and charge show a 1:1 relation on/y to very low doping levels. Two paramagnetic species are produced on doping. A maximum spin concentration is observed at =3.7 V. The ultraviolet —visible —nearinfrared spectra of doped PDMPV show at least five absorption bands, at 4.8, 3.7, 2.5, 1.7, and 0.6 eV. The first three bands decrease with doping and the latter two increase. When analyzed by the polaron or bipolaron model, the optical data imply significant symmetry breaking, Contributions to the optical activity from polarons and bipolarons are determined from the EPR results and are found to be di6'erent for both peaks, implying greater symmetrybreaking eA'ects for polarons. An electrochemical analysis of EPR results suggests that polaron interaction energies are =0.4S eV greater than those for bipolarons.
Show less  Date Issued
 1989
 Identifier
 FSU_migr_chm_faculty_publications0006
 Format
 Citation
 Title
 Thermodynamic Constraints On The Amplitude Of Quantum Oscillations.
 Creator

Shekhter, Arkady, Modic, K. A., McDonald, R. D., Ramshaw, B. J.
 Abstract/Description

Magnetoquantum oscillation experiments in hightemperature superconductors show a strong thermally induced suppression of the oscillation amplitude approaching the critical dopings [B.J. Ramshaw et al., Science 348, 317 (2014); H. Shishido et al., Phys. Rev. Lett. 104, 057008 (2010); P. Walmsley et al., Phys. Rev. Lett. 110, 257002 (2013)]in support of a quantumcritical origin of their phase diagrams. We suggest that, in addition to a thermodynamic mass enhancement, these experiments may...
Show moreMagnetoquantum oscillation experiments in hightemperature superconductors show a strong thermally induced suppression of the oscillation amplitude approaching the critical dopings [B.J. Ramshaw et al., Science 348, 317 (2014); H. Shishido et al., Phys. Rev. Lett. 104, 057008 (2010); P. Walmsley et al., Phys. Rev. Lett. 110, 257002 (2013)]in support of a quantumcritical origin of their phase diagrams. We suggest that, in addition to a thermodynamic mass enhancement, these experiments may directly indicate the increasing role of quantum fluctuations that suppress the quantum oscillation amplitude through inelastic scattering. We show that the traditional theoretical approaches beyond LifshitzKosevich to calculate the oscillation amplitude in correlated metals result in a contradiction with the third law of thermodynamics and suggest a way to rectify this problem.
Show less  Date Issued
 20170323
 Identifier
 FSU_libsubv1_wos_000399220000001, 10.1103/PhysRevB.95.121106
 Format
 Citation
 Title
 Thicknesstuned Transition Of Band Topology In Zrte5 Nanosheets.
 Creator

Lu, Jianwei, Zheng, Guolin, Zhu, Xiangde, Ning, Wei, Zhang, Hongwei, Yang, Jiyong, Du, Haifeng, Yang, Kun, Lu, Haizhou, Zhang, Yuheng, Tian, Mingliang
 Abstract/Description

We report thicknesstuned electrical transport in highly anisotropic threedimensional Dirac semimetal ZrTe5 nanosheets with thickness down to 10 nm. We find that the resistivity peak temperature T* can be significantly tuned by the nanosheet thickness. When the thickness is reduced from 160 to 40 nm, T* reduces systematically from 145 to 100 K. However, with the thickness further reducing to 10 nm, T* shifts up to a higher temperature. From our analysis, the system transitions from a...
Show moreWe report thicknesstuned electrical transport in highly anisotropic threedimensional Dirac semimetal ZrTe5 nanosheets with thickness down to 10 nm. We find that the resistivity peak temperature T* can be significantly tuned by the nanosheet thickness. When the thickness is reduced from 160 to 40 nm, T* reduces systematically from 145 to 100 K. However, with the thickness further reducing to 10 nm, T* shifts up to a higher temperature. From our analysis, the system transitions from a topological semimetal with two types of carriers to a single band with conventional hole carriers when the thickness is less than 40 nm. Furthermore, by tracking the thickness dependence of the carrier density, we find that the Fermi level shifts continuously downward from the conduction band to the valence band with decreasing the thickness. Our experiment reveals a thicknesstuned transition of band topology in ZrTe5 nanosheets which may be helpful for the understanding of the contrast observations in this material.
Show less  Date Issued
 20170329
 Identifier
 FSU_libsubv1_wos_000399142500003, 10.1103/PhysRevB.95.125135
 Format
 Citation
 Title
 Transport evidence for the threedimensional Dirac semimetal phase in ZrTe5.
 Creator

Zheng, Guolin, Lu, Jianwei, Zhu, Xiangde, Ning, Wei, Han, Yuyan, Zhang, Hongwei, Zhang, Jinglei, Xi, Chuanying, Yang, Jiyong, Du, Haifeng, Yang, Kun, Zhang, Yuheng, Tian, Mingliang
 Abstract/Description

Topological Dirac semimetal is a newly discovered class of materials which has attracted intense attention. This material can be viewed as a threedimensional (3D) analog of graphene and has linear energy dispersion in bulk, leading to a range of exotic transport properties. Here we report direct quantum transport evidence of the 3D Dirac semimetal phase of layered material ZrTe5 by angulardependent magnetoresistance measurements under high magnetic fields up to 31 T. We observed very clear...
Show moreTopological Dirac semimetal is a newly discovered class of materials which has attracted intense attention. This material can be viewed as a threedimensional (3D) analog of graphene and has linear energy dispersion in bulk, leading to a range of exotic transport properties. Here we report direct quantum transport evidence of the 3D Dirac semimetal phase of layered material ZrTe5 by angulardependent magnetoresistance measurements under high magnetic fields up to 31 T. We observed very clear negative longitudinal magnetoresistance induced by chiral anomaly under the condition of the magnetic field aligned only along the current direction. Pronounced Shubnikovde Hass (SdH) quantum oscillations in both longitudinal magnetoresistance and transverse Hall resistance were observed, revealing anisotropic light cyclotron masses and high mobility of the system. In particular, a nontrivial piBerry phase in the SdH oscillations gives clear evidence for the 3D Dirac semimetal phase. Furthermore, we observed clear Landau level splitting under high magnetic field, suggesting possible splitting of the Dirac point into Weyl points due to broken timereversal symmetry. Our results indicate that ZrTe5 is an ideal platform to study 3D massless Dirac and Weyl fermions in a layered compound.
Show less  Date Issued
 20160309
 Identifier
 FSU_libsubv1_wos_000371734800006, 10.1103/PhysRevB.93.115414
 Format
 Citation
 Title
 Coulombinteraction Induced Coupling Of Landau Levels In Intrinsic And Modulationdoped Quantum Wells.
 Creator

Paul, J., Stevens, C. E., Zhang, H., Dey, P., McGinty, D., McGill, S. A., Smith, R. P., Reno, J. L., Turkowski, V., Perakis, I. E., Hilton, D. J., Karaiskaj, D.
 Abstract/Description

We have performed two dimensional Fourier transform spectroscopy on intrinsic and modulation doped quantum wells in external magnetic fields up to 10 T. In the undoped sample, the strong Coulomb interactions and the increasing separations of the electron and hole charge distributions with increasing magnetic fields lead to a nontrivial inplane dispersion of the magnetoexcitons. Thus, the discrete and degenerate Landau levels are coupled to a continuum. The signature of this continuum is...
Show moreWe have performed two dimensional Fourier transform spectroscopy on intrinsic and modulation doped quantum wells in external magnetic fields up to 10 T. In the undoped sample, the strong Coulomb interactions and the increasing separations of the electron and hole charge distributions with increasing magnetic fields lead to a nontrivial inplane dispersion of the magnetoexcitons. Thus, the discrete and degenerate Landau levels are coupled to a continuum. The signature of this continuum is the emergence of elongated spectral line shapes at the Landau level energies, which are exposed by the multidimensional nature of our technique. Surprisingly, the elongation of the peaks is completely absent in the lowest Landau level spectra obtained from the modulation doped quantum well at high fields.
Show less  Date Issued
 20170628
 Identifier
 FSU_libsubv1_wos_000404469700004, 10.1103/PhysRevB.95.245314
 Format
 Citation
 Title
 Decoherence In Semiconductor Nanostructures With Typeii Band Alignment: Alloptical Measurements Using Aharonovbohm Excitons.
 Creator

Kuskovsky, I. L., Mourokh, L. G., Roy, B., Ji, H., Dhomkar, S., Ludwig, J., Smirnov, D., Tamargo, M. C.
 Abstract/Description

We examine the temperature dependence of the visibility of the excitonic AharonovBohm peak in typeII quantum dots. We obtain a functional temperature dependence that is similar to that determined by transport experiments, namely, with the T1 term due to electronelectron collisions and the T3 term due to electronphonon interactions. However, the magnitude of the latter term is much smaller than that for the transport electrons and similar to the interaction strength of the excitonphonon...
Show moreWe examine the temperature dependence of the visibility of the excitonic AharonovBohm peak in typeII quantum dots. We obtain a functional temperature dependence that is similar to that determined by transport experiments, namely, with the T1 term due to electronelectron collisions and the T3 term due to electronphonon interactions. However, the magnitude of the latter term is much smaller than that for the transport electrons and similar to the interaction strength of the excitonphonon coupling. Such suppressed electronphonon interaction ushers a way for alloptical studies of decoherence processes in semiconductor nanostructures as other dephasing mechanisms become more pronounced.
Show less  Date Issued
 20170426
 Identifier
 FSU_libsubv1_wos_000400064400006, 10.1103/PhysRevB.95.165445
 Format
 Citation
 Title
 Determination Of The Effective Kinematic Viscosity For The Decay Of Quasiclassical Turbulence In Superfluid He4.
 Creator

Gao, J., Guo, W., Vinen, W. F.
 Abstract/Description

The energy dissipation of quasiclassical homogeneous turbulence in superfluid He4 (He II) is controlled by an effective kinematic viscosity nu', which relates the energy decay rate dE / dt to the density of quantized vortex lines L as dE / dt = nu'(kappa L)(2). The precise value of nu' is of fundamental importance in developing our understanding of the dissipation mechanism in He II, and it is also needed in many highReynoldsnumber turbulence experiments and model testing that use He II...
Show moreThe energy dissipation of quasiclassical homogeneous turbulence in superfluid He4 (He II) is controlled by an effective kinematic viscosity nu', which relates the energy decay rate dE / dt to the density of quantized vortex lines L as dE / dt = nu'(kappa L)(2). The precise value of nu' is of fundamental importance in developing our understanding of the dissipation mechanism in He II, and it is also needed in many highReynoldsnumber turbulence experiments and model testing that use He II as the working fluid. However, a reliable determination of nu' requires the measurements of both E(t) and L(t), which was never achieved. Here we discuss our study of the quasiclassical turbulence that emerges in the decay of thermal counterflow in He II above 1 K. We were able to measure E(t) by using a recently developed flowvisualization technique and L(t) via secondsound attenuation. We report the nu' values in a wide temperature range determined from a comparison of the time evolution of E(t) and L(t).
Show less  Date Issued
 20160901
 Identifier
 FSU_libsubv1_wos_000383033500004, 10.1103/PhysRevB.94.094502
 Format
 Citation
 Title
 Cyclotron decay time of a twodimensional electron gas from 0.4 to 100 K.
 Creator

Curtis, Jeremy A., Tokumoto, Takahisa, Hatke, A. T., Cherian, Judy G., Reno, John L., McGill, Stephen A., Karaiskaj, Denis, Hilton, David J.
 Abstract/Description

We have studied the cyclotron decay time of a Landauquantized twodimensional electron gas as a function of temperature (0.4100 K) at a fixed magnetic field (+/ 1.25 T) using terahertz timedomain spectroscopy in a gallium arsenide quantum well with a mobility of mu(dc) = 3.6 x 10(6) cm(2) V1 s(1) and a carrier concentration of n(s) = 2 x 10(11) cm(2). We find a cyclotron decay time that is limited by superradiant decay of the cyclotron ensemble and a temperature dependence that may...
Show moreWe have studied the cyclotron decay time of a Landauquantized twodimensional electron gas as a function of temperature (0.4100 K) at a fixed magnetic field (+/ 1.25 T) using terahertz timedomain spectroscopy in a gallium arsenide quantum well with a mobility of mu(dc) = 3.6 x 10(6) cm(2) V1 s(1) and a carrier concentration of n(s) = 2 x 10(11) cm(2). We find a cyclotron decay time that is limited by superradiant decay of the cyclotron ensemble and a temperature dependence that may result from both dissipative processes as well as a decrease in n(s) below 1.5K. Shubnikovde Haas characterization determines a quantum lifetime, tau(q) = 1.1 ps, which is significantly faster than the corresponding dephasing time, tau(s) = 66.4 ps, in our cyclotron data. This is consistent with smallangle scattering as the dominant contribution in this sample, where scattering angles below theta <= 13 degrees. do not efficiently contribute to dephasing. Above 50 K, the cyclotron oscillations show a strong reduction in both the oscillation amplitude and lifetime that result from polar optical phonon scattering.
Show less  Date Issued
 20160429
 Identifier
 FSU_libsubv1_wos_000375202600004, 10.1103/PhysRevB.93.155437
 Format
 Citation
 Title
 Crystal Structure And Partial Isinglike Magnetic Ordering Of Orthorhombic Dy2tio5.
 Creator

Shamblin, Jacob, Calder, Stuart, Dun, Zhiling, Lee, Minseong, Choi, Eun Sang, Neuefeind, Joerg, Zhou, Haidong, Lang, Maik
 Abstract/Description

The structure andmagnetic properties of orthorhombic Dy2TiO5 have been investigated using xray diffraction, neutron diffraction, and alternating current (ac)/direct current (dc) magnetic susceptibility measurements. We report a continuous structural distortion below 100 K characterized by negative thermal expansion in the [0 1 0] direction. Neutron diffraction and magnetic susceptibility measurements revealed that twodimensional (2D) magnetic ordering begins at 3.1 K, which is followed by a...
Show moreThe structure andmagnetic properties of orthorhombic Dy2TiO5 have been investigated using xray diffraction, neutron diffraction, and alternating current (ac)/direct current (dc) magnetic susceptibility measurements. We report a continuous structural distortion below 100 K characterized by negative thermal expansion in the [0 1 0] direction. Neutron diffraction and magnetic susceptibility measurements revealed that twodimensional (2D) magnetic ordering begins at 3.1 K, which is followed by a threedimensional magnetic transition at 1.7 K. The magnetic structure has been solved through a representational analysis approach and can be indexed with the propagation vector k = [0 1/2 0]. The spin structure corresponds to a coplanar model of interwoven 2D "sheets" extending in the [0 1 0] direction. The local crystal field is different for each Dy3+ ion (Dy1 and Dy2), one of which possesses strong uniaxial symmetry indicative of Isinglike magnetic ordering. Consequently, two succeeding transitions under magnetic field are observed in the ac susceptibility, which are associated with flipping each Dy3+ spin independently.
Show less  Date Issued
 20160712
 Identifier
 FSU_libsubv1_wos_000379500900004, 10.1103/PhysRevB.94.024413
 Format
 Citation
 Title
 Charge avalanches and depinning in the Coulomb glass: The role of longrange interactions.
 Creator

Andresen, Juan Carlos, Pramudya, Yohanes, Katzgraber, Helmut G., Thomas, Creighton K., Zimanyi, Gergely T., Dobrosavljevic, V.
 Abstract/Description

We explore the stability of farfromequilibrium metastable states of a threedimensional Coulomb glass at zero temperature by studying charge avalanches triggered by a slowly varying external electric field. Surprisingly, we identify a sharply defined dynamical ("depinning") phase transition from stationary to nonstationary charge displacement at a critical value of the external electric field. Using particleconserving dynamics, scalefree systemspanning avalanches are observed only at the...
Show moreWe explore the stability of farfromequilibrium metastable states of a threedimensional Coulomb glass at zero temperature by studying charge avalanches triggered by a slowly varying external electric field. Surprisingly, we identify a sharply defined dynamical ("depinning") phase transition from stationary to nonstationary charge displacement at a critical value of the external electric field. Using particleconserving dynamics, scalefree systemspanning avalanches are observed only at the critical field. We show that the qualitative features of this depinning transition are completely different for an equivalent shortrange model, highlighting the key importance of longrange interactions for nonequilibrium dynamics of Coulomb glasses.
Show less  Date Issued
 20160324
 Identifier
 FSU_libsubv1_wos_000372712000002, 10.1103/PhysRevB.93.094429
 Format
 Citation
 Title
 Effects Of Uniaxial Pressure On The Quantum Tunneling Of Magnetization In A Highsymmetry Mn12 Singlemolecule Magnet.
 Creator

Atkinson, James H., Fournet, Adeline D., Bhaskaran, Lakshmi, Myasoedov, Yuri, Zeldov, Eli, del Barco, Enrique, Hill, Stephen, Christou, George, Friedman, Jonathan R.
 Abstract/Description

The symmetry of singlemolecule magnets dictates their spin quantum dynamics, influencing how such systems relax via quantum tunneling of magnetization (QTM). By reducing a system's symmetry, through the application of a magnetic field or uniaxial pressure, these dynamics can be modified. We report measurements of the magnetization dynamics of a crystalline sample of the highsymmetry [Mn12O12(O2CMe)(16)(MeOH)(4)] center dot MeOH singlemolecule magnet as a function of uniaxial pressure...
Show moreThe symmetry of singlemolecule magnets dictates their spin quantum dynamics, influencing how such systems relax via quantum tunneling of magnetization (QTM). By reducing a system's symmetry, through the application of a magnetic field or uniaxial pressure, these dynamics can be modified. We report measurements of the magnetization dynamics of a crystalline sample of the highsymmetry [Mn12O12(O2CMe)(16)(MeOH)(4)] center dot MeOH singlemolecule magnet as a function of uniaxial pressure applied either parallel or perpendicular to the sample's "easy" magnetization axis. At temperatures between 1.8 and 3.3 K, magnetic hysteresis loops exhibit the characteristic steplike features that signal the occurrence of QTM. After applying uniaxial pressure to the sample in situ, both the magnitude and field position of the QTM steps changed. The step magnitudes were observed to grow as a function of pressure in both arrangements of pressure, while pressure applied along (perpendicular to) the sample's easy axis caused the resonanttunneling fields to increase (decrease). These observations were compared with simulations in which the system's Hamiltonian parameters were changed. From these comparisons, we determined that parallel pressure induces changes to the secondorder axial anisotropy parameter as well as either the fourthorder axial or fourthorder transverse parameter, or to both. In addition, we find that pressure applied perpendicular to the easy axis induces a rhombic anisotropy E approximate to D/2000 per kbar that can be understood as deriving from a symmetrybreaking distortion of the molecule.
Show less  Date Issued
 20170504
 Identifier
 FSU_libsubv1_wos_000400657600001, 10.1103/PhysRevB.95.184403
 Format
 Citation
 Title
 Effective twodimensional thickness for the BerezinskiiKosterlitzThoulesslike transition in a highly underdoped La2xSrxCuO4.
 Creator

Baity, P. G., Shi, Xiaoyan, Shi, Zhenzhong, Benfatto, L., Popovic, Dragana
 Abstract/Description

The nature of the superconducting transition in highly underdoped thick films of La2xSrxCuO4 (x = 0.07 and 0.08) has been investigated using the inplane transport measurements. The contribution of superconducting fluctuations to the conductivity in zero magnetic field, or paraconductivity, was determined from the magnetoresistance measured in fields applied perpendicular to the CuO2 planes. Both the temperature dependence of the paraconductivity above the transition and the nonlinear...
Show moreThe nature of the superconducting transition in highly underdoped thick films of La2xSrxCuO4 (x = 0.07 and 0.08) has been investigated using the inplane transport measurements. The contribution of superconducting fluctuations to the conductivity in zero magnetic field, or paraconductivity, was determined from the magnetoresistance measured in fields applied perpendicular to the CuO2 planes. Both the temperature dependence of the paraconductivity above the transition and the nonlinear currentvoltage (I  V) characteristics measured across it exhibit the main signatures of the BerezinskiiKosterlitzThouless (BKT) transition. The quantitative comparison of the superfluid stiffness, extracted from the I  V data, with the renormalizationgroup results for the BKT theory, reveals a large value of the vortexcore energy. This finding is confirmed by the analysis of the paraconductivity obtained using different methods. The results strongly suggest that the characteristic energy scale controlling the BKT behavior in this layered system corresponds to the superfluid stiffness of a few layers.
Show less  Date Issued
 20160125
 Identifier
 FSU_libsubv1_wos_000369218500009, 10.1103/PhysRevB.93.024519
 Format
 Citation
 Title
 Electrical Transport Properties Of Singlecrystal Cab6, Srb6, And Bab6.
 Creator

Stankiewicz, Jolanta, Rosa, Priscila F. S., Schlottmann, Pedro, Fisk, Zachary
 Abstract/Description

The electrical resistivity and Hall effect of alkalineearthmetal hexaboride single crystals are measured as a function of temperature, hydrostatic pressure, and magnetic field. The transport properties vary weakly with the external parameters and are modeled in terms of intrinsic variablevalence defects. These defects can stay either in (1) delocalized shallow levels or in (2) localized levels resonant with the conduction band, which can be neutral or negatively charged. Satisfactory...
Show moreThe electrical resistivity and Hall effect of alkalineearthmetal hexaboride single crystals are measured as a function of temperature, hydrostatic pressure, and magnetic field. The transport properties vary weakly with the external parameters and are modeled in terms of intrinsic variablevalence defects. These defects can stay either in (1) delocalized shallow levels or in (2) localized levels resonant with the conduction band, which can be neutral or negatively charged. Satisfactory agreement is obtained for electronic transport properties in a broad temperature and pressure range, although fitting the magnetoresistance is less straightforward and a combination of various mechanisms is needed to explain the field and temperature dependences.
Show less  Date Issued
 20160922
 Identifier
 FSU_libsubv1_wos_000383865700005, 10.1103/PhysRevB.94.125141
 Format
 Citation