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Electronic Tuning in the Hidden Order Compound URu2Si2 through Si → P Substitution

Title: Electronic Tuning in the Hidden Order Compound URu2Si2 through Si → P Substitution.
Name(s): Gallagher, Andrew, author
Baumbach, Ryan Eagle, professor co-directing dissertation
Hill, Stephen (Professor of Physics), professor co-directing dissertation
Siegrist, Theo, university representative
Boebinger, Gregory S. (Gregory Scott), committee member
Piekarewicz, Jorge, committee member
Florida State University, degree granting institution
College of Arts and Sciences, degree granting college
Department of Physics, degree granting department
Type of Resource: text
Genre: Text
Doctoral Thesis
Issuance: monographic
Date Issued: 2017
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (112 pages)
Language(s): English
Abstract/Description: Crystalline materials that include 4f- and 5f-electron elements frequently exhibit a variety of intriguing phenomena including spin and charge orderings, spin and valence fluctuations, heavy fermion behavior, breakdown of Fermi liquid behavior, and unconventional superconductivity. [5, 6, 7, 8, 9, 10, 11, 12, 13] Amongst such materials, the Kondo lattice system URu2Si2 stands out as being particularly unusual. [14, 15, 16] While at high temperature it exhibits behavior that is typical for an f-electron lattice immersed in a sea of conduction electrons, at T0 = 17:5 K there is a second order phase transition that is followed by unconventional superconductivity near Tc 1:5 K. [15] Despite three decades of work, the order parameter for the transition at T0 remains unknown and hence, it has been named "hidden order". There have been a multitude of experimental attempts to unravel hidden order, mainly through tuning of the electronic state via pressure, applied magnetic field, and chemical substitution. [17, 18] While these strategies reveal interesting phase diagrams, a longstanding challenge is that any such approach explores the phase space along an unknown vector: i.e., many different factors are affected. To address this issue, we developed a new organizational map for the U-based ThCr2Si2-type compounds that are related to URu2Si2 and thus guided, we explored a new chemical tuning axis: Si -> P. Our studies were enabled by the development of a new molten metal crystal growth method for URu2Si2 which produces high quality single crystals and allows us to introduce high vapor pressure elements, such as phosphorous. [19, 20] Si -> P tuning reveals that while the high temperature Kondo lattice behavior is robust, the low temperature phenomena are remarkably sensitive to electronic tuning. [21, 22] In the URu2Si2-xPx phase diagram we find that while hidden order is monotonically suppressed and destroyed for x < 0.035, the superconducting strength evolves non-monotonically with a maximum near x = 0.01 and that superconductivity is destroyed near x = 0.028. For 0.03 < x < 0.26 there is a region with Kondo coherence but no ordered state. Antiferromagnetism abruptly appears for x = 0.26. This phase diagram differs significantly from those produced by most other tuning strategies in URu2Si2, including applied pressure, and isoelectronic chemical substitution (i.e. Ru -> Fe and Os), where hidden order and magnetism share a common phase boundary. [2, 23, 24] We discuss implications for understanding hidden order, its relationship to magnetism, and prospects for uncovering novel sibling electronic states.
Identifier: FSU_SUMMER2017_Gallagher_fsu_0071E_13976 (IID)
Submitted Note: A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Degree Awarded: Summer Semester 2017.
Date of Defense: May 19, 2017.
Keywords: correlated electrons, heavy fermion, hidden order, molten metal flux, URu2Si2
Bibliography Note: Includes bibliographical references.
Advisory Committee: Ryan Baumbach, Professor Co-Directing Dissertation; Stephen Hill, Professor Co-Directing Dissertation; Theo Siegrist, University Representative; Greg Boebinger, Committee Member; Jorge Piekarewicz, Committee Member.
Subject(s): Condensed matter
Persistent Link to This Record:
Owner Institution: FSU

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Gallagher, A. (2017). Electronic Tuning in the Hidden Order Compound URu2Si2 through Si → P Substitution. Retrieved from