1
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Suetsugu S, Shimomura M, Kamimura M, Asaba T, Asaeda H, Kosuge Y, Sekino Y, Ikemori S, Kasahara Y, Kohsaka Y, Lee M, Yanase Y, Sakai H, Opletal P, Tokiwa Y, Haga Y, Matsuda Y. Fully gapped pairing state in spin-triplet superconductor UTe 2. SCIENCE ADVANCES 2024; 10:eadk3772. [PMID: 38324692 PMCID: PMC10849587 DOI: 10.1126/sciadv.adk3772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 01/05/2024] [Indexed: 02/09/2024]
Abstract
The recently discovered superconductor UTe2 is a promising candidate for spin-triplet superconductors, but the symmetry of the superconducting order parameter remains highly controversial. Here, we determine the superconducting gap structure by the thermal conductivity of ultraclean UTe2 single crystals. We find that the a-axis thermal conductivity divided by temperature κ/T in zero-temperature limit is vanishingly small for both magnetic field H‖a and H‖c axes up to H/Hc2 ∼ 0.2, demonstrating the absence of nodes around the a axis contrary to the previous belief. The present results, combined with the reduction of nuclear magnetic resonance Knight shift, indicate that the superconducting order parameter belongs to the isotropic Au representation with a fully gapped pairing state, analogous to the B phase of superfluid 3He. These findings reveal that UTe2 is likely to be a long-sought three-dimensional strong topological superconductor, hosting helical Majorana surface states on any crystal plane.
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Affiliation(s)
- Shota Suetsugu
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | | | | | - Tomoya Asaba
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Hiroto Asaeda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Yuki Kosuge
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Yuki Sekino
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Shun Ikemori
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Yuichi Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Yuhki Kohsaka
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Minhyea Lee
- Department of Physics, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Youichi Yanase
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - Hironori Sakai
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Petr Opletal
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Yoshifumi Tokiwa
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Yoshinori Haga
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Yuji Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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2
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Aoki D, Brison JP, Flouquet J, Ishida K, Knebel G, Tokunaga Y, Yanase Y. Unconventional superconductivity in UTe 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:243002. [PMID: 35203074 DOI: 10.1088/1361-648x/ac5863] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 02/24/2022] [Indexed: 06/14/2023]
Abstract
The novel spin-triplet superconductor candidate UTe2was discovered only recently at the end of 2018 and already attracted enormous attention. We review key experimental and theoretical progress which has been achieved in different laboratories. UTe2is a heavy-fermion paramagnet, but following the discovery of superconductivity, it has been expected to be close to a ferromagnetic instability, showing many similarities to the U-based ferromagnetic superconductors, URhGe and UCoGe. This view might be too simplistic. The competition between different types of magnetic interactions and the duality between the local and itinerant character of the 5fUranium electrons, as well as the shift of the U valence appear as key parameters in the rich phase diagrams discovered recently under extreme conditions like low temperature, high magnetic field, and pressure. We discuss macroscopic and microscopic experiments at low temperature to clarify the normal phase properties at ambient pressure for field applied along the three axis of this orthorhombic structure. Special attention will be given to the occurrence of a metamagnetic transition atHm= 35 T for a magnetic field applied along the hard magnetic axisb. Adding external pressure leads to strong changes in the magnetic and electronic properties with a direct feedback on superconductivity. Attention is paid on the possible evolution of the Fermi surface as a function of magnetic field and pressure. Superconductivity in UTe2is extremely rich, exhibiting various unconventional behaviors which will be highlighted. It shows an exceptionally huge superconducting upper critical field with a re-entrant behavior under magnetic field and the occurrence of multiple superconducting phases in the temperature-field-pressure phase diagrams. There is evidence for spin-triplet pairing. Experimental indications exist for chiral superconductivity and spontaneous time reversal symmetry breaking in the superconducting state. Different theoretical approaches will be described. Notably we discuss that UTe2is a possible example for the realization of a fascinating topological superconductor. Exploring superconductivity in UTe2reemphasizes that U-based heavy fermion compounds give unique examples to study and understand the strong interplay between the normal and superconducting properties in strongly correlated electron systems.
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Affiliation(s)
- D Aoki
- IMR, Tohoku University, Oarai, Ibaraki, 311-1313, Japan
| | - J-P Brison
- Univ. Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, F-38000 Grenoble, France
| | - J Flouquet
- Univ. Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, F-38000 Grenoble, France
| | - K Ishida
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - G Knebel
- Univ. Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, F-38000 Grenoble, France
| | - Y Tokunaga
- ASRC, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Y Yanase
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
- Institute for Molecular Science, Okazaki 444-8585, Japan
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3
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Oh H, Agterberg DF, Moon EG. Using Disorder to Identify Bogoliubov Fermi-Surface States. PHYSICAL REVIEW LETTERS 2021; 127:257002. [PMID: 35029417 DOI: 10.1103/physrevlett.127.257002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 11/16/2021] [Indexed: 06/14/2023]
Abstract
We argue that a superconducting state with a Fermi surface of Bogoliubov quasiparticles, a Bogoliubov Fermi surface (BG-FS), can be identified by the dependence of physical quantities on disorder. In particular, we show that a linear dependence of the residual density of states at weak disorder distinguishes a BG-FS state from other nodal superconducting states. We further demonstrate the stability of supercurrent against impurities and a characteristic Drude-like behavior of the optical conductivity. Our results can be directly applied to electron irradiation experiments on candidate materials of BG-FSs, including Sr_{2}RuO_{4}, FeSe_{1-x}S_{x}, and UBe_{13}.
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Affiliation(s)
- Hanbit Oh
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
| | - Daniel F Agterberg
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53201, USA
| | - Eun-Gook Moon
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea
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4
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Grinenko V, Das D, Gupta R, Zinkl B, Kikugawa N, Maeno Y, Hicks CW, Klauss HH, Sigrist M, Khasanov R. Unsplit superconducting and time reversal symmetry breaking transitions in Sr 2RuO 4 under hydrostatic pressure and disorder. Nat Commun 2021; 12:3920. [PMID: 34168141 PMCID: PMC8225887 DOI: 10.1038/s41467-021-24176-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 06/01/2021] [Indexed: 11/23/2022] Open
Abstract
There is considerable evidence that the superconducting state of Sr2RuO4 breaks time reversal symmetry. In the experiments showing time reversal symmetry breaking, its onset temperature, TTRSB, is generally found to match the critical temperature, Tc, within resolution. In combination with evidence for even parity, this result has led to consideration of a dxz ± idyz order parameter. The degeneracy of the two components of this order parameter is protected by symmetry, yielding TTRSB = Tc, but it has a hard-to-explain horizontal line node at kz = 0. Therefore, s ± id and d ± ig order parameters are also under consideration. These avoid the horizontal line node, but require tuning to obtain TTRSB ≈ Tc. To obtain evidence distinguishing these two possible scenarios (of symmetry-protected versus accidental degeneracy), we employ zero-field muon spin rotation/relaxation to study pure Sr2RuO4 under hydrostatic pressure, and Sr1.98La0.02RuO4 at zero pressure. Both hydrostatic pressure and La substitution alter Tc without lifting the tetragonal lattice symmetry, so if the degeneracy is symmetry-protected, TTRSB should track changes in Tc, while if it is accidental, these transition temperatures should generally separate. We observe TTRSB to track Tc, supporting the hypothesis of dxz ± idyz order.
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Affiliation(s)
- Vadim Grinenko
- Institute for Solid State and Materials Physics, Technische Universität Dresden, Dresden, Germany.
- Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden, Dresden, Germany.
| | - Debarchan Das
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland
| | - Ritu Gupta
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland
| | - Bastian Zinkl
- Institute for Theoretical Physics, ETH Zurich, Zurich, Switzerland
| | - Naoki Kikugawa
- National Institute for Materials Science, Tsukuba, Japan
| | | | - Clifford W Hicks
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
- School of Physics and Astronomy, University of Birmingham, Birmingham, UK
| | - Hans-Henning Klauss
- Institute for Solid State and Materials Physics, Technische Universität Dresden, Dresden, Germany
| | - Manfred Sigrist
- Institute for Theoretical Physics, ETH Zurich, Zurich, Switzerland.
| | - Rustem Khasanov
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland.
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5
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Jaoui A, Fauqué B, Behnia K. Thermal resistivity and hydrodynamics of the degenerate electron fluid in antimony. Nat Commun 2021; 12:195. [PMID: 33420029 PMCID: PMC7794374 DOI: 10.1038/s41467-020-20420-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 11/30/2020] [Indexed: 11/09/2022] Open
Abstract
Detecting hydrodynamic fingerprints in the flow of electrons in solids constitutes a dynamic field of investigation in contemporary condensed matter physics. Most attention has been focused on the regime near the degeneracy temperature when the thermal velocity can present a spatially modulated profile. Here, we report on the observation of a hydrodynamic feature in the flow of quasi-ballistic degenerate electrons in bulk antimony. By scrutinizing the temperature dependence of thermal and electric resistivities, we detect a size-dependent departure from the Wiedemann-Franz law, unexpected in the momentum-relaxing picture of transport. This observation finds a natural explanation in the hydrodynamic picture, where upon warming, momentum-conserving collisions reduce quadratically in temperature both viscosity and thermal diffusivity. This effect has been established theoretically and experimentally in normal-state liquid 3He. The comparison of electrons in antimony and fermions in 3He paves the way to a quantification of momentum-conserving fermion-fermion collision rate in different Fermi liquids. Viscous fermionic flow appears in liquid helium but rarely appears in metallic solid. Here, Jaoui et al. report a T-square thermal resistivity due to momentum conserving electronic scattering in semi-metallic antimony, which is in agreement with the hydrodynamic scenario.
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Affiliation(s)
- Alexandre Jaoui
- JEIP, USR 3573 CNRS, Collège de France, PSL Research University, 11, Place Marcelin Berthelot, Paris, Cedex 05, 75231, France. .,Laboratoire de Physique et Etude des Matériaux (CNRS/UPMC), Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, Paris, 75005, France.
| | - Benoît Fauqué
- JEIP, USR 3573 CNRS, Collège de France, PSL Research University, 11, Place Marcelin Berthelot, Paris, Cedex 05, 75231, France
| | - Kamran Behnia
- Laboratoire de Physique et Etude des Matériaux (CNRS/UPMC), Ecole Supérieure de Physique et de Chimie Industrielles, 10 Rue Vauquelin, Paris, 75005, France
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6
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Mydosh JA, Oppeneer PM, Riseborough PS. Hidden order and beyond: an experimental-theoretical overview of the multifaceted behavior of URu 2Si 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:143002. [PMID: 31801118 DOI: 10.1088/1361-648x/ab5eba] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This topical review describes the multitude of unconventional behaviors in the hidden order, heavy fermion, antiferromagnetic and superconducting phases of the intermetallic compound URu2Si2 when tuned with pressure, magnetic field, and substitutions for all three elements. Such 'perturbations' result in a variety of new phases beyond the mysterious hidden order that are only now being slowly understood through a series of state-of-the-science experimentation, along with an array of novel theoretical approaches. Despite all these efforts spanning more than 30 years, hidden order (HO) remains puzzling and non-clarified, and the search continues in 2019 into a fourth decade for its final resolution. Here we attempt to update the present situation of URu2Si2 importing the latest experimental results and theoretical proposals. First, let us consider the pristine compound as a function of temperature and report the recent measurements and models relating to its heavy Fermi liquid crossover, its HO and superconductivity (SC). Recent experiments and theories are surmized that address four-fold symmetry breaking (or nematicity), Isingness and unconventional excitation modes. Second, we review the pressure dependence of URu2Si2 and its transformation to antiferromagnetic long-range order. Next we confront the dramatic high magnetic-field phases requiring fields above 40 T. And finally, we attempt to answer how does random substitutions of other 5f elements for U, and 3d, 4d, and 5d elements for Ru, and even P for Si affect and transform the HO. Commensurately, recent theoretical models are summarized and then related to the intriguing experimental behavior.
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Affiliation(s)
- J A Mydosh
- Institute Lorentz and Kamerlingh Onnes Laboratory, Leiden University, NL-2300 RA Leiden, The Netherlands
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7
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Kasahara S, Sato Y, Licciardello S, Čulo M, Arsenijević S, Ottenbros T, Tominaga T, Böker J, Eremin I, Shibauchi T, Wosnitza J, Hussey NE, Matsuda Y. Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov State with Segmented Vortices in the BCS-BEC-Crossover Superconductor FeSe. PHYSICAL REVIEW LETTERS 2020; 124:107001. [PMID: 32216412 DOI: 10.1103/physrevlett.124.107001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 02/05/2020] [Indexed: 06/10/2023]
Abstract
We present resistivity and thermal-conductivity measurements of superconducting FeSe in intense magnetic fields up to 35 T applied parallel to the ab plane. At low temperatures, the upper critical field μ_{0}H_{c2}^{ab} shows an anomalous upturn, while thermal conductivity exhibits a discontinuous jump at μ_{0}H^{*}≈24 T well below μ_{0}H_{c2}^{ab}, indicating a first-order phase transition in the superconducting state. This demonstrates the emergence of a distinct field-induced superconducting phase. Moreover, the broad resistive transition at high temperatures abruptly becomes sharp upon entering the high-field phase, indicating a dramatic change of the magnetic-flux properties. We attribute the high-field phase to the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state, where the formation of planar nodes gives rise to a segmentation of the flux-line lattice. We point out that strongly orbital-dependent pairing as well as spin-orbit interactions, the multiband nature, and the extremely small Fermi energy are important for the formation of the FFLO state in FeSe.
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Affiliation(s)
- S Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - Y Sato
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - S Licciardello
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - M Čulo
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - S Arsenijević
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - T Ottenbros
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - T Tominaga
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
| | - J Böker
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
| | - I Eremin
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, D-44801 Bochum, Germany
- National University of Science and Technology MISiS, 119049 Moscow, Russian Federation
| | - T Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan
| | - J Wosnitza
- Hochfeld-Magnetlabor Dresden (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - N E Hussey
- High Field Magnet Laboratory (HFML-EMFL) and Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL, United Kingdom
| | - Y Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502 Japan
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8
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Juraszek J, Wawryk R, Henkie Z, Konczykowski M, Cichorek T. Symmetry of Order Parameters in Multiband Superconductors LaRu_{4}As_{12} and PrOs_{4}Sb_{12} Probed by Local Magnetization Measurements. PHYSICAL REVIEW LETTERS 2020; 124:027001. [PMID: 32004020 DOI: 10.1103/physrevlett.124.027001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 11/04/2019] [Indexed: 06/10/2023]
Abstract
The temperature dependencies of the lower critical field H_{c1}(T) of several filled-skutterudite superconductors were investigated by local magnetization measurements. While LaOs_{4}As_{12} and PrRu_{4}As_{12} exhibit the H_{c1}(T) dependencies consistent with the single-band BCS prediction, for LaRu_{4}As_{12} (the superconducting temperature T_{c}=10.4 K) with a similar three-dimensional Fermi surface, we observe a sudden increase in H_{c1}(T) deep in a superconducting state below about 0.32T_{c}. Remarkably, a rapid rise of H_{c1}(T) at approximately the same reduced temperature 0.27T_{c} is also found for the heavy-fermion compound PrOs_{4}Sb_{12} (T_{c}≃1.78 K), in fair accord with the earlier macroscopic study. We attribute the unusual H_{c1}(T) dependencies of LaRu_{4}As_{12} and PrOs_{4}Sb_{12} to a kink structure in their superfluid densities due to different contributions from two nearly decoupled bands. Whereas LaRu_{4}As_{12} is established as a two-band isotropic s-wave superconductor, nonsaturating behavior of H_{c1}(T) is observed for PrOs_{4}Sb_{12}, indicative of an anisotropic structure of a smaller gap. For this superconductor with broken time-reversal symmetry, our findings suggest a superconducting state with multiple symmetries of the order parameters.
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Affiliation(s)
- J Juraszek
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wrocław, Poland
| | - R Wawryk
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wrocław, Poland
| | - Z Henkie
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wrocław, Poland
| | - M Konczykowski
- Laboratoire des Solides Irradiés, CEA/DRF/IRAMIS, École Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France
| | - T Cichorek
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wrocław, Poland
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9
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Kobayashi T, Matsushita T, Mizushima T, Tsuruta A, Fujimoto S. Negative Thermal Magnetoresistivity as a Signature of a Chiral Anomaly in Weyl Superconductors. PHYSICAL REVIEW LETTERS 2018; 121:207002. [PMID: 30500245 DOI: 10.1103/physrevlett.121.207002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Indexed: 06/09/2023]
Abstract
We propose that the chiral anomaly of Weyl superconductors gives rise to negative thermal magnetoresistivity induced by emergent magnetic fields, which are generated by vortex textures of order parameters or lattice strain. We establish this scenario by combining the argument based on Berry curvatures and the quasiclassical theory of the Eilenberger equation with quantum corrections arising from inhomogeneous structures. It is found that the chiral anomaly contribution of the thermal conductivity exhibits characteristic temperature dependence, which can be a smoking-gun signature of this effect.
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Affiliation(s)
- Takuro Kobayashi
- Department of Materials Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| | - Taiki Matsushita
- Department of Materials Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| | - Takeshi Mizushima
- Department of Materials Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| | - Atsushi Tsuruta
- Department of Materials Engineering Science, Osaka University, Toyonaka 560-8531, Japan
| | - Satoshi Fujimoto
- Department of Materials Engineering Science, Osaka University, Toyonaka 560-8531, Japan
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10
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Pressure induced superconductivity bordering a charge-density-wave state in NbTe 4 with strong spin-orbit coupling. Sci Rep 2018; 8:6298. [PMID: 29674609 PMCID: PMC5908920 DOI: 10.1038/s41598-018-24572-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/06/2018] [Indexed: 11/12/2022] Open
Abstract
Transition-metal chalcogenides host various phases of matter, such as charge-density wave (CDW), superconductors, and topological insulators or semimetals. Superconductivity and its competition with CDW in low-dimensional compounds have attracted much interest and stimulated considerable research. Here we report pressure induced superconductivity in a strong spin-orbit (SO) coupled quasi-one-dimensional (1D) transition-metal chalcogenide NbTe4, which is a CDW material under ambient pressure. With increasing pressure, the CDW transition temperature is gradually suppressed, and superconducting transition, which is fingerprinted by a steep resistivity drop, emerges at pressures above 12.4 GPa. Under pressure p = 69 GPa, zero resistance is detected with a transition temperature Tc = 2.2 K and an upper critical field μ0Hc2 = 2 T. We also find large magnetoresistance (MR) up to 102% at low temperatures, which is a distinct feature differentiating NbTe4 from other conventional CDW materials.
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11
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Hattori T, Sakai H, Tokunaga Y, Kambe S, Matsuda TD, Haga Y. Evidence for Spin Singlet Pairing with Strong Uniaxial Anisotropy in URu_{2}Si_{2} Using Nuclear Magnetic Resonance. PHYSICAL REVIEW LETTERS 2018; 120:027001. [PMID: 29376726 DOI: 10.1103/physrevlett.120.027001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Indexed: 06/07/2023]
Abstract
In order to identify the spin contribution to superconducting pairing compatible with the so-called "hidden order", ^{29}Si nuclear magnetic resonance measurements have been performed using a high-quality single crystal of URu_{2}Si_{2}. A clear reduction of the ^{29}Si Knight shift in the superconducting state has been observed under a magnetic field applied along the crystalline c axis, corresponding to the magnetic easy axis. These results provide direct evidence for the formation of spin-singlet Cooper pairs. Consequently, results indicating a very tiny change of the in-plane Knight shift reported previously demonstrate extreme uniaxial anisotropy for the spin susceptibility in the hidden order state.
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Affiliation(s)
- T Hattori
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - H Sakai
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Y Tokunaga
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - S Kambe
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - T D Matsuda
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Y Haga
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
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12
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Agterberg DF, Brydon PMR, Timm C. Bogoliubov Fermi Surfaces in Superconductors with Broken Time-Reversal Symmetry. PHYSICAL REVIEW LETTERS 2017; 118:127001. [PMID: 28388193 DOI: 10.1103/physrevlett.118.127001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Indexed: 06/07/2023]
Abstract
It is commonly believed that, in the absence of disorder or an external magnetic field, there are three possible types of superconducting excitation gaps: The gap is nodeless, it has point nodes, or it has line nodes. Here, we show that, for an even-parity nodal superconducting state which spontaneously breaks time-reversal symmetry, the low-energy excitation spectrum generally does not belong to any of these categories; instead, it has extended Bogoliubov Fermi surfaces. These Fermi surfaces can be visualized as two-dimensional surfaces generated by "inflating" point or line nodes into spheroids or tori, respectively. These inflated nodes are topologically protected from being gapped by a Z_{2} invariant, which we give in terms of a Pfaffian. We also show that superconducting states possessing these Fermi surfaces can be energetically stable. A crucial ingredient in our theory is that more than one band is involved in the pairing; since all candidate materials for even-parity superconductivity with broken time-reversal symmetry are multiband systems, we expect these Z_{2}-protected Fermi surfaces to be ubiquitous.
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Affiliation(s)
- D F Agterberg
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53201, USA
| | - P M R Brydon
- Department of Physics, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - C Timm
- Institute of Theoretical Physics, Technische Universität Dresden, 01062 Dresden, Germany
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13
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Abstract
The second-order phase transition into a hidden order phase in URu2Si2 goes along with an order parameter that is still a mystery, despite 30 years of research. However, it is understood that the symmetry of the order parameter must be related to the symmetry of the low-lying local electronic [Formula: see text]-states. Here, we present results of a spectroscopic technique, namely core-level nonresonant inelastic X-ray scattering (NIXS). This method allows for the measurement of local high-multipole excitations and is bulk-sensitive. The observed anisotropy of the scattering function unambiguously shows that the 5[Formula: see text] ground-state wave function is composed mainly of the [Formula: see text] with majority [Formula: see text] = [Formula: see text] + [Formula: see text] and/or [Formula: see text] singlet states. The incomplete dichroism indicates the possibility that quantum states of other irreducible representation are mixed into the ground state.
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14
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Knafo W, Duc F, Bourdarot F, Kuwahara K, Nojiri H, Aoki D, Billette J, Frings P, Tonon X, Lelièvre-Berna E, Flouquet J, Regnault LP. Field-induced spin-density wave beyond hidden order in URu 2Si 2. Nat Commun 2016; 7:13075. [PMID: 27762260 PMCID: PMC5080431 DOI: 10.1038/ncomms13075] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 08/31/2016] [Indexed: 11/09/2022] Open
Abstract
URu2Si2 is one of the most enigmatic strongly correlated electron systems and offers a fertile testing ground for new concepts in condensed matter science. In spite of >30 years of intense research, no consensus on the order parameter of its low-temperature hidden-order phase exists. A strong magnetic field transforms the hidden order into magnetically ordered phases, whose order parameter has also been defying experimental observation. Here, thanks to neutron diffraction under pulsed magnetic fields up to 40 T, we identify the field-induced phases of URu2Si2 as a spin-density-wave state. The transition to the spin-density wave represents a unique touchstone for understanding the hidden-order phase. An intimate relationship between this magnetic structure, the magnetic fluctuations and the Fermi surface is emphasized, calling for dedicated band-structure calculations. The strongly-correlated electron system URu2Si2 possesses a hidden-order phase whose order parameter remains unidentified. Here, the authors demonstrate the development of spin-density-wave phases in URu2Si2 under high magnetic fields, providing a potential in-road to understanding this system.
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Affiliation(s)
- W Knafo
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UPS-INSA-UGA, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - F Duc
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UPS-INSA-UGA, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - F Bourdarot
- Service de Modélisation et d'Exploration des Matériaux, Université Grenoble Alpes et Commissariat á l'Energie Atomique, INAC, 17 rue des Martyrs, 38054 Grenoble, France
| | - K Kuwahara
- Institute of Quantum Beam Science, Ibaraki University, Mito 310-8512, Japan
| | - H Nojiri
- Institute for Materials Research, Tohoku University, Sendai 980-8578, Japan
| | - D Aoki
- Institute for Materials Research, Tohoku University, Ibaraki 311-1313, Japan.,Service Photonique, Electronique et Ingénierie Quantiques, Université Grenoble Alpes et Commissariat à l'Energie Atomique, INAC, 17 rue des Martyrs, 38054 Grenoble, France
| | - J Billette
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UPS-INSA-UGA, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - P Frings
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UPS-INSA-UGA, 143 Avenue de Rangueil, 31400 Toulouse, France
| | - X Tonon
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble, France
| | - E Lelièvre-Berna
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble, France
| | - J Flouquet
- Service Photonique, Electronique et Ingénierie Quantiques, Université Grenoble Alpes et Commissariat à l'Energie Atomique, INAC, 17 rue des Martyrs, 38054 Grenoble, France
| | - L-P Regnault
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble, France
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15
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Sakakibara T, Kittaka S, Machida K. Angle-resolved heat capacity of heavy fermion superconductors. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:094002. [PMID: 27482621 DOI: 10.1088/0034-4885/79/9/094002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Owing to a strong Coulomb repulsion, heavy electron superconductors mostly have anisotropic gap functions which have nodes for certain directions in the momentum space. Since the nodal structure is closely related to the pairing mechanism, its experimental determination is of primary importance. This article discusses the experimental methods of the gap determination by bulk heat capacity measurements in a rotating magnetic field. The basic idea is based on the fact that the quasiparticle density of states in the vortex state of nodal superconductors is field and direction dependent. We present our recent experimental results of the field-orientation dependence of the heat capacity in heavy fermion superconductors CeTIn5 (T = Co, Ir), UPt3, CeCu2Si2, and UBe13 and discuss their gap structures.
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Affiliation(s)
- Toshiro Sakakibara
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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16
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Schnyder AP, Brydon PMR. Topological surface states in nodal superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:243201. [PMID: 26000466 DOI: 10.1088/0953-8984/27/24/243201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Topological superconductors have become a subject of intense research due to their potential use for technical applications in device fabrication and quantum information. Besides fully gapped superconductors, unconventional superconductors with point or line nodes in their order parameter can also exhibit nontrivial topological characteristics. This article reviews recent progress in the theoretical understanding of nodal topological superconductors, with a focus on Weyl and noncentrosymmetric superconductors and their protected surface states. Using selected examples, we review the bulk topological properties of these systems, study different types of topological surface states, and examine their unusual properties. Furthermore, we survey some candidate materials for topological superconductivity and discuss different experimental signatures of topological surface states.
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Affiliation(s)
- Andreas P Schnyder
- Max-Planck-Institut für Festkörperforschung, Heißenbergstrasse 1, D-70569 Stuttgart, Germany
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17
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Tada Y, Nie W, Oshikawa M. Orbital angular momentum and spectral flow in two-dimensional chiral superfluids. PHYSICAL REVIEW LETTERS 2015; 114:195301. [PMID: 26024177 DOI: 10.1103/physrevlett.114.195301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Indexed: 06/04/2023]
Abstract
We study the orbital angular momentum (OAM) L_{z} in two-dimensional chiral (p_{x}+ip_{y})^{ν}-wave superfluids (SFs) of N fermions on a disk at zero temperature, in terms of spectral asymmetry and spectral flow. It is shown that L_{z}=νN/2 for any integer ν, in the Bose-Einstein condensation regime. In contrast, in the BCS limit, while the OAM is L_{z}=N/2 for the p+ip-wave SF, for chiral SFs with ν≥2, the OAM is remarkably suppressed as L_{z}=N×O(Δ_{0}/ϵ_{F})≪N, where Δ_{0} is the gap amplitude and ϵ_{F} is the Fermi energy. We demonstrate that the difference between the p+ip-wave SF and the other chiral SFs in the BCS regimes originates from the nature of edge modes and related depairing effects.
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Affiliation(s)
- Yasuhiro Tada
- Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
| | - Wenxing Nie
- Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
| | - Masaki Oshikawa
- Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
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18
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Lin SZ. Ground state, collective mode, phase soliton and vortex in multiband superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:493202. [PMID: 25398159 DOI: 10.1088/0953-8984/26/49/493202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This article reviews theoretical and experimental work on the novel physics in multiband superconductors. Multiband superconductors are characterized by multiple superconducting energy gaps in different bands with interaction between Cooper pairs in these bands. The discovery of prominent multiband superconductors MgB2 and later iron-based superconductors, has triggered enormous interest in multiband superconductors. The most recently discovered superconductors exhibit multiband features. The multiband superconductors possess novel properties that are not shared with their single-band counterpart. Examples include: the time-reversal symmetry broken state in multiband superconductors with frustrated interband couplings; the collective oscillation of number of Cooper pairs between different bands, known as the Leggett mode; and the phase soliton and fractional vortex, which are the main focus of this review. This review presents a survey of a wide range of theoretical exploratory and experimental investigations of novel physics in multiband superconductors. A vast amount of information derived from these studies is shown to highlight unusual and unique properties of multiband superconductors and to reveal the challenges and opportunities in the research on the multiband superconductivity.
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Affiliation(s)
- Shi-Zeng Lin
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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19
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Momentum-resolved hidden-order gap reveals symmetry breaking and origin of entropy loss in URu2Si2. Nat Commun 2014; 5:4326. [PMID: 25014432 DOI: 10.1038/ncomms5326] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 06/06/2014] [Indexed: 11/08/2022] Open
Abstract
Spontaneous symmetry breaking in physical systems leads to salient phenomena at all scales, from the Higgs mechanism and the emergence of the mass of the elementary particles, to superconductivity and magnetism in solids. The hidden-order state arising below 17.5 K in URu2Si2 is a puzzling example of one of such phase transitions: its associated broken symmetry and gap structure have remained longstanding riddles. Here we directly image how, across the hidden-order transition, the electronic structure of URu2Si2 abruptly reconstructs. We observe an energy gap of 7 meV opening over 70% of a large diamond-like heavy-fermion Fermi surface, resulting in the formation of four small Fermi petals, and a change in the electronic periodicity from body-centred tetragonal to simple tetragonal. Our results explain the large entropy loss in the hidden-order phase, and the similarity between this phase and the high-pressure antiferromagnetic phase found in quantum-oscillation experiments.
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20
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Takatsu H, Ishikawa JJ, Yonezawa S, Yoshino H, Shishidou T, Oguchi T, Murata K, Maeno Y. Extremely large magnetoresistance in the nonmagnetic metal PdCoO2. PHYSICAL REVIEW LETTERS 2013; 111:056601. [PMID: 23952426 DOI: 10.1103/physrevlett.111.056601] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Indexed: 06/02/2023]
Abstract
Extremely large magnetoresistance is realized in the nonmagnetic layered metal PdCoO(2). In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35,000% for the field along the [11[over ¯]0] direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction. Such severe and anisotropic destruction of the interlayer coherence by a magnetic field on a simple Fermi surface is ascribable to orbital motion of carriers on the Fermi surface driven by the Lorentz force, but seems to have been largely overlooked until now.
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Affiliation(s)
- Hiroshi Takatsu
- Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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21
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Tonegawa S, Hashimoto K, Ikada K, Lin YH, Shishido H, Haga Y, Matsuda TD, Yamamoto E, Onuki Y, Ikeda H, Matsuda Y, Shibauchi T. Cyclotron resonance in the hidden-order phase of URu2Si2. PHYSICAL REVIEW LETTERS 2012; 109:036401. [PMID: 22861875 DOI: 10.1103/physrevlett.109.036401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Indexed: 06/01/2023]
Abstract
We report the first observation of cyclotron resonance in the hidden-order phase of ultraclean URu2Si2 crystals, which allows the full determination of angle-dependent electron-mass structure of the main Fermi-surface sheets. We find an anomalous splitting of the sharpest resonance line under in-plane magnetic-field rotation. This is most naturally explained by the domain formation, which breaks the fourfold rotational symmetry of the underlying tetragonal lattice. The results reveal the emergence of an in-plane mass anisotropy with hot spots along the [110] direction, which can account for the anisotropic in-plane magnetic susceptibility reported recently. This is consistent with the "nematic" Fermi liquid state, in which itinerant electrons have unidirectional correlations.
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Affiliation(s)
- S Tonegawa
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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22
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Machida Y, Sakai S, Izawa K, Okuyama H, Watanabe T. Enhanced quasiparticle heat conduction in the multigap superconductor Lu2Fe3Si5 . PHYSICAL REVIEW LETTERS 2011; 106:107002. [PMID: 21469825 DOI: 10.1103/physrevlett.106.107002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Indexed: 05/30/2023]
Abstract
Thermal transport measurements have been made on the Fe-based superconductor Lu2Fe3Si5 (T(c) ∼ 6 K) down to a very low temperature T(c)/120. The field and temperature dependences of the thermal conductivity confirm the multigap superconductivity with fully opened gaps on the whole Fermi surfaces. In comparison to MgB2, Lu2Fe3Si5 reveals a remarkably enhanced quasiparticle heat conduction in the mixed state. The results can be interpreted as a consequence of the unequal weight of the Fe 3d-electron character among the distinct bands.
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Affiliation(s)
- Y Machida
- Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
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23
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Okazaki R, Shimozawa M, Shishido H, Konczykowski M, Haga Y, Matsuda TD, Yamamoto E, Onuki Y, Yanase Y, Shibauchi T, Matsuda Y. Anomalous low-field diamagnetic response in ultraclean URu2Si2superconductor. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/273/1/012081] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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24
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Okazaki R, Shibauchi T, Shi HJ, Haga Y, Matsuda TD, Yamamoto E, Onuki Y, Ikeda H, Matsuda Y. Rotational symmetry breaking in the hidden-order phase of URu2Si2. Science 2011; 331:439-42. [PMID: 21273481 DOI: 10.1126/science.1197358] [Citation(s) in RCA: 212] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A second-order phase transition is characterized by spontaneous symmetry breaking. The nature of the broken symmetry in the so-called "hidden-order" phase transition in the heavy-fermion compound URu(2)Si(2), at transition temperature T(h) = 17.5 K, has posed a long-standing mystery. We report the emergence of an in-plane anisotropy of the magnetic susceptibility below T(h), which breaks the four-fold rotational symmetry of the tetragonal URu(2)Si(2). Two-fold oscillations in the magnetic torque under in-plane field rotation were sensitively detected in small pure crystals. Our findings suggest that the hidden-order phase is an electronic "nematic" phase, a translationally invariant metallic phase with spontaneous breaking of rotational symmetry.
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Affiliation(s)
- R Okazaki
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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25
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Aoki D, Bourdarot F, Hassinger E, Knebel G, Miyake A, Raymond S, Taufour V, Flouquet J. Field re-entrant hidden-order phase under pressure in URu2Si2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:164205. [PMID: 21386411 DOI: 10.1088/0953-8984/22/16/164205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We succeeded in growing high quality single crystals of URu(2)Si(2) and performed thermal expansion measurements under pressure. Applying a magnetic field along the [001] direction in the tetragonal structure, the so-called hidden-order phase reappears after the suppression of the antiferromagnetic phase above the critical pressure P(x). We determined the pressure-temperature-field phase diagram for the paramagnetic, hidden-order and antiferromagnetic states for the [Formula: see text] direction. We also present the temperature dependence of the upper critical field H(c2) for [Formula: see text] and [100] determined by the AC specific heat measurements, corresponding to the bulk superconductivity in a high quality single crystal.
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Affiliation(s)
- D Aoki
- INAC/SPSMS, CEA-Grenoble, 17 rue des Martyrs, F-38054 Grenoble, France.
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26
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Shishido H, Hashimoto K, Shibauchi T, Sasaki T, Oizumi H, Kobayashi N, Takamasu T, Takehana K, Imanaka Y, Matsuda TD, Haga Y, Onuki Y, Matsuda Y. Possible phase transition deep inside the hidden order phase of ultraclean URu2Si2. PHYSICAL REVIEW LETTERS 2009; 102:156403. [PMID: 19518659 DOI: 10.1103/physrevlett.102.156403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2008] [Indexed: 05/27/2023]
Abstract
To elucidate the underlying nature of the hidden order (HO) state in heavy-fermion compound URu(2)Si(2), we measure electrical transport properties of ultraclean crystals in a high field, low temperature regime. Unlike previous studies, the present system with much less impurity scattering resolves a distinct anomaly of the Hall resistivity at H;{*} = 22.5 T, well below the destruction field of the HO phase = or approximately 36 T. In addition, a novel quantum oscillation appears above a magnetic field slightly below H;{*}. These results indicate an abrupt reconstruction of the Fermi surface, which implies a possible phase transition well within the HO phase caused by a band-dependent destruction of the HO parameter.
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Affiliation(s)
- H Shishido
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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27
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Elgazzar S, Rusz J, Amft M, Oppeneer PM, Mydosh JA. Hidden order in URu2Si2 originates from Fermi surface gapping induced by dynamic symmetry breaking. NATURE MATERIALS 2009; 8:337-341. [PMID: 19234447 DOI: 10.1038/nmat2395] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 01/20/2009] [Indexed: 05/27/2023]
Abstract
Spontaneous, collective ordering of electronic degrees of freedom leads to second-order phase transitions that are characterized by an order parameter driving the transition. The notion of a 'hidden order' has recently been used for a variety of materials where a clear phase transition occurs without a known order parameter. The prototype example is the heavy-fermion compound URu(2)Si(2), where a mysterious hidden-order transition occurs at 17.5 K. For more than twenty years this system has been studied theoretically and experimentally without a firm grasp of the underlying physics. Here, we provide a microscopic explanation of the hidden order using density-functional theory calculations. We identify the Fermi surface 'hot spots' where degeneracy induces a Fermi surface instability and quantify how symmetry breaking lifts the degeneracy, causing a surprisingly large Fermi surface gapping. As the mechanism for the hidden order, we deduce spontaneous symmetry breaking through a dynamic mode of antiferromagnetic moment excitations.
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Affiliation(s)
- S Elgazzar
- Department of Physics and Materials Science, Uppsala University, Box 530, S-751 21 Uppsala, Sweden
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28
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Okazaki R, Kasahara Y, Shishido H, Konczykowski M, Behnia K, Haga Y, Matsuda TD, Onuki Y, Shibauchi T, Matsuda Y. Vortex lattice melting in the ultraclean heavy-fermion superconductor URu2Si2. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/150/5/052198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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29
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Kasahara Y, Iwasawa T, Shishido H, Shibauchi T, Behnia K, Matsuda TD, Haga Y, Onuki Y, Sigrist M, Matsuda Y. Gap structure and exotic superconducting state of URu2Si2. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/150/5/052098] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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30
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Behnia K. The Nernst effect and the boundaries of the Fermi liquid picture. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:113101. [PMID: 21693905 DOI: 10.1088/0953-8984/21/11/113101] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Following the observation of an anomalous Nernst signal in cuprates, the Nernst effect has been explored in a variety of metals and superconductors during the past few years. This paper reviews the results obtained during this exploration, focusing on the Nernst response of normal quasi-particles as opposed to the one generated by superconducting vortices or by short-lived Cooper pairs. Contrary to what has been often assumed, the so-called Sondheimer cancelation does not imply a negligible Nernst response in a Fermi liquid. In fact, the amplitude of the Nernst response measured in various metals in the low-temperature limit is scattered over six orders of magnitude. According to the data, this amplitude is roughly set by the ratio of electron mobility to Fermi energy, in agreement with the implications of semi-classical transport theory.
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Affiliation(s)
- Kamran Behnia
- Laboratoire Photons et Matière (UPR5-CNRS), ESPCI, 10 Rue Vauquelin, F-75005 Paris, France
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31
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Hill RW, Li S, Maple MB, Taillefer L. Multiband order parameters for the PrOs4Sb12 and PrRu4Sb12 skutterudite superconductors from thermal conductivity measurements. PHYSICAL REVIEW LETTERS 2008; 101:237005. [PMID: 19113585 DOI: 10.1103/physrevlett.101.237005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Indexed: 05/27/2023]
Abstract
Thermal conductivity measurements were performed on single crystal samples of the superconducting filled-skutterudite compounds PrOs4Sb12 and PrRu4Sb12 both as a function of temperature and transverse magnetic field. In a zero magnetic field, the low temperature electronic thermal conductivity of PrRu4Sb12 is consistent with a fully gapped Fermi surface. For PrOs4Sb12, residual electronic conduction in the zero-temperature limit is consistent with the presence of nodes in the superconducting energy gap. The electronic thermal conductivity for both compounds shows a rapid rise at low magnetic fields. In PrRu4Sb12, this is interpreted in terms of multiband effects. In PrOs4Sb12, we consider the Doppler shift of nodal quasiparticles and multiband effects.
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Affiliation(s)
- R W Hill
- Guelph-Waterloo Physics Institute, University of Waterloo, Waterloo, Ontario, Canada.
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32
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Seyfarth G, Brison JP, Knebel G, Aoki D, Lapertot G, Flouquet J. Multigap superconductivity in the heavy-Fermion system CeCoIn5. PHYSICAL REVIEW LETTERS 2008; 101:046401. [PMID: 18764344 DOI: 10.1103/physrevlett.101.046401] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Indexed: 05/26/2023]
Abstract
New thermal conductivity experiments on the heavy-fermion superconductor CeCoIn5 down to 10 mK rule out the suggested existence of unpaired electrons. Moreover, they reveal strong multigap effects with a remarkably low "critical" field Hc2S for the small gap band, showing that the complexity of heavy-fermion band structure has a direct impact on their response under magnetic field.
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Affiliation(s)
- G Seyfarth
- CNRS, Néel Institute, 25 avenue des Martyrs, BP166, 38042 Grenoble Cedex 9, France
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33
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Tewari S, Zhang C, Yakovenko VM, Das Sarma S. Time-reversal symmetry breaking by a (d+id) density-wave state in underdoped cuprate superconductors. PHYSICAL REVIEW LETTERS 2008; 100:217004. [PMID: 18518628 DOI: 10.1103/physrevlett.100.217004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Indexed: 05/26/2023]
Abstract
It was proposed that the id(x(2)-y(2)) density-wave state (DDW) may be responsible for the pseudogap behavior in the underdoped cuprates. Here we show that the admixture of a small d(xy) component to the DDW state breaks the symmetry between the counterpropagating orbital currents of the DDW state and, thus, violates the macroscopic time-reversal symmetry. This symmetry breaking results in a nonzero polar Kerr effect, which has recently been observed in the pseudogap phase.
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Affiliation(s)
- Sumanta Tewari
- Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
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34
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Nakajima Y, Nakagawa T, Tamegai T, Harima H. Specific-heat evidence for two-gap superconductivity in the ternary-iron silicide Lu2Fe3Si5. PHYSICAL REVIEW LETTERS 2008; 100:157001. [PMID: 18518144 DOI: 10.1103/physrevlett.100.157001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Indexed: 05/26/2023]
Abstract
We report low-temperature specific-heat studies on the single-crystalline ternary-iron silicide superconductor Lu(2)Fe(3)Si(5) with T(c)=6.1 K down to approximately T(c)/20. We confirm a reduced normalized jump in specific heat at T(c), and find that the specific heat divided by temperature C/T shows a sudden drop at approximately T(c)/5 and goes to zero with further decreasing temperature. These results indicate the presence of two distinct superconducting gaps in Lu(2)Fe(3)Si(5), similar to the typical two-gap superconductor MgB(2). We also report Hall coefficients, band structure calculations, and the anisotropy of upper critical fields for Lu(2)Fe(3)Si(5), which support the anisotropic multiband nature and reinforce the existence of two superconducting gaps in Lu(2)Fe(3)Si(5).
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Affiliation(s)
- Y Nakajima
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
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Okazaki R, Kasahara Y, Shishido H, Konczykowski M, Behnia K, Haga Y, Matsuda TD, Onuki Y, Shibauchi T, Matsuda Y. Flux line lattice melting and the formation of a coherent quasiparticle Bloch state in the ultraclean URu2Si2 superconductor. PHYSICAL REVIEW LETTERS 2008; 100:037004. [PMID: 18233028 DOI: 10.1103/physrevlett.100.037004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Indexed: 05/25/2023]
Abstract
We find that in the ultraclean heavy-fermion superconductor URu(2)Si(2) (T_{c0}=1.45 K) a distinct flux line lattice melting transition with outstanding characters occurs well below the mean-field upper critical fields. We show that a very small number of carriers with heavy mass in this system results in exceptionally large thermal fluctuations even at sub-Kelvin temperatures, which are witnessed by a sizable region of the flux line liquid phase. The uniqueness is further highlighted by an enhancement of the quasiparticle mean free path below the melting transition, implying a possible formation of a quasiparticle Bloch state in the periodic flux line lattice.
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Affiliation(s)
- R Okazaki
- Department of Physics, Kyoto University, Kyoto, Japan.
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Yano K, Sakakibara T, Tayama T, Yokoyama M, Amitsuka H, Homma Y, Miranović P, Ichioka M, Tsutsumi Y, Machida K. Field-angle-dependent specific heat measurements and gap determination of a heavy fermion superconductor URu2Si2. PHYSICAL REVIEW LETTERS 2008; 100:017004. [PMID: 18232809 DOI: 10.1103/physrevlett.100.017004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Indexed: 05/25/2023]
Abstract
To identify the superconducting gap structure in URu2Si2, we perform field-angle-dependent specific heat measurements for the two principal orientations in addition to field rotations, and a theoretical analysis based on microscopic calculations. The Sommerfeld coefficient gamma(H)'s in the mixed state exhibit a distinctly different field dependence. This comes from point nodes and the substantial Pauli paramagnetic effect of URu2Si2. These two features combined give rise to a consistent picture of superconducting properties, including a possible first order transition of Hc2 at low temperatures.
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Affiliation(s)
- K Yano
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 270-8581, Japan
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