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Lee S, Kim DY, Rosa PFS, Bauer ED, Ronning F, Thompson JD, Lin SZ, Movshovich R. Normal Fermi Surface in the Nodal Superconductor CeCoIn_{5} Revealed via Thermal Conductivity. PHYSICAL REVIEW LETTERS 2024; 132:236002. [PMID: 38905643 DOI: 10.1103/physrevlett.132.236002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 05/06/2024] [Indexed: 06/23/2024]
Abstract
The thermal conductivity of heavy-fermion superconductor CeCoIn_{5} was measured with a magnetic field rotating in the tetragonal a-b plane, with the heat current in the antinodal direction, J|| [100]. We observe a sharp resonance in thermal conductivity for the magnetic field at an angle Θ≈12°, measured from the heat current direction [100]. This resonance corresponds to the reported resonance at an angle Θ^{'}≈33° from the direction of the heat current applied along the nodal direction, J||[110]. Both resonances, therefore, occur when the magnetic field is applied in the same crystallographic orientation in the two experiments, regardless of the direction of the heat current, proving conclusively that these resonances are due to the structure of the Fermi surface of CeCoIn_{5}. We argue that the uncondensed Landau quasiparticles, emerging with field, are responsible for the observed resonance. We support our experimental results with density-functional-theory model calculations of the density of states in a rotating magnetic field. Our calculations, using a model Fermi surface of CeCoIn_{5}, reveal several sharp peaks as a function of the field direction. Our study demonstrates that the thermal-conductivity measurement in rotating magnetic field can probe the normal parts of the Fermi surface deep inside the superconducting state.
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2
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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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3
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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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4
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Abstract
AbstractA long-standing theoretical prediction is that in clean, nodal unconventional superconductors the magnetic penetration depth λ, at zero temperature, varies linearly with magnetic field. This non-linear Meissner effect is an equally important manifestation of the nodal state as the well studied linear-in-T dependence of λ, but has never been convincingly experimentally observed. Here we present measurements of the nodal superconductors CeCoIn5 and LaFePO which clearly show this non-linear Meissner effect. We further show how the effect of a small dc magnetic field on λ(T) can be used to distinguish gap nodes from non-nodal deep gap minima. Our measurements of KFe2As2 suggest that this material has such a non-nodal state.
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Paul S, Chandra LSS, Chattopadhyay MK. Renormalization of electron-phonon coupling in the Mott-Ioffe-Regel limit due to point defects in the V 1-x Ti x alloy superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:475801. [PMID: 31342931 DOI: 10.1088/1361-648x/ab3515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report here the temperature dependence of electrical resistivity ([Formula: see text](T)), heat capacity (C(T)) and thermal conductivity ([Formula: see text](T)) of superconducting V1-x Ti x alloys in the absence and presence of external applied magnetic fields. The [Formula: see text](T) changes from positive temperature coefficient of resistivity (TCR) to negative TCR at about x = 0.7 indicating that many of these alloys lie close to the Mott-Ioffe-Regel (MIR) limit. The jump in the C(T) across the superconducting transition temperature ([Formula: see text]) indicates that these alloys are in the intermediate coupling limit. The [Formula: see text](T) increases in certain V1-x Ti x alloys as the temperature decreases below the [Formula: see text] indicating that the phonons dominate the heat conduction in the superconducting state, whereas we found that the electrons are the major carriers of heat in the normal state. Our analysis suggests that the unusual features of thermal conductivity have origin in (i) the electron mean free path approaching the inter atomic distances (MIR limit) and (ii) the renormalization of the phonon mean free path due to the presence of point defects and the electron-phonon interaction.
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Affiliation(s)
- Sabyasachi Paul
- Free Eelectron Laser Utilization Laboratory, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh, 452 013, India. Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400 094, India
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Abstract
A self-consistent two-gap γ -model is used to quantitatively describe several thermodynamic properties of MgB 2 superconductor. The superconducting coupling matrix, ν i j , was obtained from the fitting of the superfluid density in the entire superconducting temperature range. Using this input, temperature-dependent superconducting gaps, specific heat, and upper critical fields were calculated with no adjustable parameters and compared with the experimental data as well as with the first-principles calculations. The observed agreement between fit and data shows that γ -model provides adequate quantitative description of the two-gap superconductivity in MgB 2 and may serve as a relatively simple and versatile self-consistent description of the thermodynamic quantities in multi-gap superconductors.
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7
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Paglione J, Tanatar MA, Reid JP, Shakeripour H, Petrovic C, Taillefer L. Quantum Critical Quasiparticle Scattering within the Superconducting State of CeCoIn_{5}. PHYSICAL REVIEW LETTERS 2016; 117:016601. [PMID: 27419578 DOI: 10.1103/physrevlett.117.016601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Indexed: 06/06/2023]
Abstract
The thermal conductivity κ of the heavy-fermion metal CeCoIn_{5} was measured in the normal and superconducting states as a function of temperature T and magnetic field H, for a current and field parallel to the [100] direction. Inside the superconducting state, when the field is lower than the upper critical field H_{c2}, κ/T is found to increase as T→0, just as in a metal and in contrast to the behavior of all known superconductors. This is due to unpaired electrons on part of the Fermi surface, which dominate the transport above a certain field. The evolution of κ/T with field reveals that the electron-electron scattering (or transport mass m^{⋆}) of those unpaired electrons diverges as H→H_{c2} from below, in the same way that it does in the normal state as H→H_{c2} from above. This shows that the unpaired electrons sense the proximity of the field-tuned quantum critical point of CeCoIn_{5} at H^{⋆}=H_{c2} even from inside the superconducting state. The fact that the quantum critical scattering of the unpaired electrons is much weaker than the average scattering of all electrons in the normal state reveals a k-space correlation between the strength of pairing and the strength of scattering, pointing to a common mechanism, presumably antiferromagnetic fluctuations.
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Affiliation(s)
- Johnpierre Paglione
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- Canadian Institute for Advanced Research, Toronto, Canada M5G 1Z8
| | - M A Tanatar
- Département de physique & RQMP, Université de Sherbrooke, Sherbrooke, Canada J1K 2R1
- Ames Laboratory USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - J-Ph Reid
- Département de physique & RQMP, Université de Sherbrooke, Sherbrooke, Canada J1K 2R1
| | - H Shakeripour
- Department of Physics, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - C Petrovic
- Canadian Institute for Advanced Research, Toronto, Canada M5G 1Z8
- Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Louis Taillefer
- Canadian Institute for Advanced Research, Toronto, Canada M5G 1Z8
- Département de physique & RQMP, Université de Sherbrooke, Sherbrooke, Canada J1K 2R1
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8
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Raymond S, Lapertot G. Ising Incommensurate Spin Resonance of CeCoIn5: A Dynamical Precursor of the Q Phase. PHYSICAL REVIEW LETTERS 2015; 115:037001. [PMID: 26230821 DOI: 10.1103/physrevlett.115.037001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Indexed: 06/04/2023]
Abstract
It is shown through detailed inelastic neutron scattering experiments that the gapped collective magnetic excitation of the unconventional superconductor CeCoIn5, the spin resonance mode, is incommensurate and that the corresponding fluctuations are of an Ising nature. The incommensurate peak position of these fluctuations corresponds to the propagation vector of the adjacent field induced static magnetic ordered phase, the so-called Q phase. Furthermore, the direction of the magnetic moment fluctuations is also the direction of the ordered magnetic moments of the Q phase. Hence, the resonance mode and the Q phase share the same symmetry and this strongly supports a scenario where the static order is realized by a condensation of the magnetic excitation.
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Affiliation(s)
- S Raymond
- Université Grenoble Alpes, INAC-SPSMS, F-38000 Grenoble, France and CEA, INAC-SPSMS, F-38000 Grenoble, France
| | - G Lapertot
- Université Grenoble Alpes, INAC-SPSMS, F-38000 Grenoble, France and CEA, INAC-SPSMS, F-38000 Grenoble, France
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9
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Sundar S, Sharath Chandra LS, Chattopadhyay MK, Roy SB. Evidence of multiband superconductivity in the β-phase Mo1-xRex alloys. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:045701. [PMID: 25563211 DOI: 10.1088/0953-8984/27/4/045701] [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
We present a detailed study of the superconducting properties in the β-phase Mo(1-x)Re(x) (x = 0.25 and 0.4) solid solution alloys pursued through magnetization and heat capacity measurements. The temperature dependence of the upper critical field H(C2)(T) in these binary alloys shows a deviation from the prediction of the Werthamer-Helfand-Hohenberg (WHH) theory. The temperature dependence of superfluid density estimated from the variation of lower critical field H(C1) with temperature, cannot be explained within the framework of a single superconducting energy gap. The heat capacity also shows an anomalous feature in its temperature dependence. All these results can be reasonably explained by considering the existence of two superconducting energy gaps in these Mo(1-x)Re(x) alloys. Initial results of electronic structure calculations and resonant photoelectron spectroscopy measurements support this possibility and suggest that the Re-5d like states at the Fermi level may not intermix with the Mo-5p and 5s like states in the β-phase Mo(1-x)Re(x) alloys and contribute quite distinctly to the superconductivity of these alloys.
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Affiliation(s)
- Shyam Sundar
- Homi Bhabha National Institute at RRCAT, Indore, Madhya Pradesh 452 013, India
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10
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Kim H, Tanatar MA, Flint R, Petrovic C, Hu R, White BD, Lum IK, Maple MB, Prozorov R. Nodal to nodeless superconducting energy-gap structure change concomitant with fermi-surface reconstruction in the heavy-fermion compound CeCoIn(5). PHYSICAL REVIEW LETTERS 2015; 114:027003. [PMID: 25635560 DOI: 10.1103/physrevlett.114.027003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Indexed: 06/04/2023]
Abstract
The London penetration depth λ(T) was measured in single crystals of Ce_{1-x}R_{x}CoIn_{5}, R=La, Nd, and Yb down to T_{min}≈50 mK (T_{c}/T_{min}∼50) using a tunnel-diode resonator. In the cleanest samples Δλ(T) is best described by the power law Δλ(T)∝T^{n}, with n∼1, consistent with the existence of line nodes in the superconducting gap. Substitutions of Ce with La, Nd, and Yb lead to similar monotonic suppressions of T_{c}; however, the effects on Δλ(T) differ. While La and Nd substitution leads to an increase in the exponent n and saturation at n∼2, as expected for a dirty nodal superconductor, Yb substitution leads to n>3, suggesting a change from nodal to nodeless superconductivity. This superconducting gap structure change happens in the same doping range where changes of the Fermi-surface topology were reported, implying that the nodal structure and Fermi-surface topology are closely linked.
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Affiliation(s)
- Hyunsoo Kim
- Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - M A Tanatar
- Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - R Flint
- Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - C Petrovic
- Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Rongwei Hu
- Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - B D White
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - I K Lum
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - M B Maple
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - R Prozorov
- Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA
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11
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Tokiwa Y, Bauer ED, Gegenwart P. Zero-field quantum critical point in CeCoIn5. PHYSICAL REVIEW LETTERS 2013; 111:107003. [PMID: 25166697 DOI: 10.1103/physrevlett.111.107003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 08/02/2013] [Indexed: 06/03/2023]
Abstract
Quantum criticality in the normal and superconducting states of the heavy-fermion metal CeCoIn5 is studied by measurements of the magnetic Grüneisen ratio ΓH and specific heat in different field orientations and temperatures down to 50 mK. A universal temperature over magnetic field scaling of ΓH in the normal state indicates a hidden quantum critical point at zero field. Within the superconducting state, the quasiparticle entropy at constant temperature increases upon reducing the field towards zero, providing additional evidence for zero-field quantum criticality.
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Affiliation(s)
- Y Tokiwa
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
| | - E D Bauer
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - P Gegenwart
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
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12
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Machida Y, Tomokuni K, Izawa K, Lapertot G, Knebel G, Brison JP, Flouquet J. Verification of the Wiedemann-Franz law in YbRh2Si2 at a quantum critical point. PHYSICAL REVIEW LETTERS 2013; 110:236402. [PMID: 25167518 DOI: 10.1103/physrevlett.110.236402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 02/04/2013] [Indexed: 06/03/2023]
Abstract
The thermal conductivity measurements are performed on the heavy-fermion compound YbRh(2)Si(2) down to 0.04 K and under magnetic fields through a quantum critical point (QCP) at B(c)=0.66 T∥c axis. In the limit as T→0, we find that the Wiedemann-Franz law is satisfied within experimental error at the QCP despite the destruction of the standard signature of Fermi liquid. Our results place strong constraints on models that attempt to describe the nature of the unconventional quantum criticality of YbRh(2)Si(2).
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Affiliation(s)
- Y Machida
- Department of Physics, Tokyo Institute of Technology, Meguro 152-8551, Japan
| | - K Tomokuni
- Department of Physics, Tokyo Institute of Technology, Meguro 152-8551, Japan
| | - K Izawa
- Department of Physics, Tokyo Institute of Technology, Meguro 152-8551, Japan
| | - G Lapertot
- SPSMS, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble, F-38054, France
| | - G Knebel
- SPSMS, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble, F-38054, France
| | - J-P Brison
- SPSMS, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble, F-38054, France
| | - J Flouquet
- SPSMS, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble, F-38054, France
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13
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Howald L, Maisuradze A, de Réotier PD, Yaouanc A, Baines C, Lapertot G, Mony K, Brison JP, Keller H. Strong pressure dependence of the magnetic penetration depth in single crystals of the heavy-fermion superconductor CeCoIn5 studied by muon spin rotation. PHYSICAL REVIEW LETTERS 2013; 110:017005. [PMID: 23383830 DOI: 10.1103/physrevlett.110.017005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Indexed: 06/01/2023]
Abstract
In the tetragonal heavy fermion system CeCoIn(5) the unconventional superconducting state is probed by means of muon spin rotation. The pressure dependence (0-1 GPa) of the basal-plane magnetic penetration depth (λ(a)), the penetration depth anisotropy (γ = λ(c)/λ(a)) and the temperature dependence of 1/λ(i)(2) (i = a, c) were studied in single crystals. A strong decrease of λ(a) with pressure was observed, while γ and λ(i)(2)(0)/λ(i)(2)(T) are pressure independent. A linear relationship between 1/λ(a)(2)(270 mK) and T(c) was also found. The large decrease of λ(a) with pressure is the signature of an increase of the number of superconducting quasiparticles by a factor of about 2.
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Affiliation(s)
- L Howald
- Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
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14
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Tokiwa Y, Bauer ED, Gegenwart P. Quasiparticle entropy in the high-field superconducting phase of CeCoIn(5). PHYSICAL REVIEW LETTERS 2012; 109:116402. [PMID: 23005654 DOI: 10.1103/physrevlett.109.116402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Revised: 06/22/2012] [Indexed: 06/01/2023]
Abstract
The heavy-fermion superconductor CeCoIn(5) displays an additional transition within its superconducting (SC) state, whose nature is characterized by high-precision studies of the isothermal field dependence of the entropy, derived from combined specific heat and magnetocaloric effect measurements at temperatures T≥100 mK and fields H≤12 T aligned along different directions. For any of these conditions, we do not observe an additional entropy contribution upon tuning at constant temperature by magnetic field from the homogeneous SC into the presumed Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) SC state. By contrast, for H∥[100] a reduction of entropy was found that quantitatively agrees with the expectation for spin-density-wave order without FFLO superconductivity. Our data exclude the formation of a FFLO state in CeCoIn(5) for out-of-plane field directions, where no spin-density-wave order exists.
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Affiliation(s)
- Y Tokiwa
- I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
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15
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Ronning F, Zhu JX, Das T, Graf MJ, Albers RC, Rhee HB, Pickett WE. Superconducting gap structure of the 115s revisited. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:294206. [PMID: 22773378 DOI: 10.1088/0953-8984/24/29/294206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Density functional theory calculations of the electronic structure of Ce- and Pu-based heavy fermion superconductors in the so-called 115 family are performed. The gap equation is used to consider which superconducting order parameters are most favorable assuming a pairing interaction that is peaked at (π, π, qz)—the wavevector for the antiferromagnetic ordering found in close proximity. In addition to the commonly accepted dx2−y2 order parameter, there is evidence that an extended s-wave order parameter with nodes is also plausible. We discuss whether these results are consistent with current observations and possible measurements that could help distinguish between these scenarios.
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Affiliation(s)
- F Ronning
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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16
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Bauer ED, Yang YF, Capan C, Urbano RR, Miclea CF, Sakai H, Ronning F, Graf MJ, Balatsky AV, Movshovich R, Bianchi AD, Reyes AP, Kuhns PL, Thompson JD, Fisk Z. Electronic inhomogeneity in a Kondo lattice. Proc Natl Acad Sci U S A 2011; 108:6857-6861. [PMCID: PMC3084059 DOI: 10.1073/pnas.1103965108] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023] Open
Abstract
Inhomogeneous electronic states resulting from entangled spin, charge, and lattice degrees of freedom are hallmarks of strongly correlated electron materials; such behavior has been observed in many classes of d -electron materials, including the high-T c copper-oxide superconductors, manganites, and most recently the iron–pnictide superconductors. The complexity generated by competing phases in these materials constitutes a considerable theoretical challenge—one that still defies a complete description. Here, we report a manifestation of electronic inhomogeneity in a strongly correlated f -electron system, using CeCoIn5 as an example. A thermodynamic analysis of its superconductivity, combined with nuclear quadrupole resonance measurements, shows that nonmagnetic impurities (Y, La, Yb, Th, Hg, and Sn) locally suppress unconventional superconductivity, generating an inhomogeneous electronic “Swiss cheese” due to disrupted periodicity of the Kondo lattice. Our analysis may be generalized to include related systems, suggesting that electronic inhomogeneity should be considered broadly in Kondo lattice materials.
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Affiliation(s)
- E. D. Bauer
- Los Alamos National Laboratory, Los Alamos, NM 87545
| | - Yi-feng Yang
- Los Alamos National Laboratory, Los Alamos, NM 87545
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - C. Capan
- Department of Physics and Astronomy, University of California, Irvine, CA 92697
| | - R. R. Urbano
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306
| | - C. F. Miclea
- Los Alamos National Laboratory, Los Alamos, NM 87545
| | - H. Sakai
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan; and
| | - F. Ronning
- Los Alamos National Laboratory, Los Alamos, NM 87545
| | - M. J. Graf
- Los Alamos National Laboratory, Los Alamos, NM 87545
| | | | - R. Movshovich
- Los Alamos National Laboratory, Los Alamos, NM 87545
| | - A. D. Bianchi
- Department de Physique, Universite de Montreal, Montreal, QC, Canada H3C 3J7
| | - A. P. Reyes
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306
| | - P. L. Kuhns
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306
| | | | - Z. Fisk
- Department of Physics and Astronomy, University of California, Irvine, CA 92697
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17
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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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18
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Lu F, Wang WH, Liu DY, Wang CZ, Zou LJ. Orbital polarizations and superconducting phase diagrams in two-orbital asymmetric t-J models. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:355603. [PMID: 21403294 DOI: 10.1088/0953-8984/22/35/355603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present the zero-temperature superconducting (SC) phase diagrams of the two-orbital asymmetric t-J model on a square lattice by means of the auxiliary-boson approach. Besides the two-gap SC and normal phases, we find an orbital dependent intermediate SC phase, in which one orbit is fully SC and another orbit is exponentially vanishing gapped SC. Such an intermediate phase is stable only for sufficient asymmetry in orbital space and doping concentration. The implication of the present scenario on the iron-based and other multi-orbital superconductors is discussed.
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Affiliation(s)
- Feng Lu
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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19
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O'Farrell ECT, Tompsett DA, Sebastian SE, Harrison N, Capan C, Balicas L, Kuga K, Matsuo A, Kindo K, Tokunaga M, Nakatsuji S, Csányi G, Fisk Z, Sutherland ML. Role of f electrons in the Fermi surface of the heavy fermion superconductor beta-YbAlB4. PHYSICAL REVIEW LETTERS 2009; 102:216402. [PMID: 19519118 DOI: 10.1103/physrevlett.102.216402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Indexed: 05/27/2023]
Abstract
We present a detailed quantum oscillation study of the Fermi surface of the recently discovered Yb-based heavy fermion superconductor beta-YbAlB4. We compare the data, obtained at fields from 10 to 45 T, to band structure calculations performed using the local density approximation. Analysis of the data suggests that f holes participate in the Fermi surface up to the highest magnetic fields studied. We comment on the significance of these findings for the unconventional superconducting properties of this material.
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Affiliation(s)
- E C T O'Farrell
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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20
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Koutroulakis G, Mitrović VF, Horvatić M, Berthier C, Lapertot G, Flouquet J. Field dependence of the ground state in the exotic superconductor CeCoIn5: a nuclear magnetic resonance investigation. PHYSICAL REVIEW LETTERS 2008; 101:047004. [PMID: 18764359 DOI: 10.1103/physrevlett.101.047004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Indexed: 05/26/2023]
Abstract
We report 115In nuclear magnetic resonance (NMR) measurements in CeCoIn5 at low temperature (T approximately 70 mK) as a function of the magnetic field (H0) from 2 to 13.5 T applied perpendicular to the c axis. A NMR line shift reveals that below 10 T the spin susceptibility increases as sqrt[H0]. We associate this with an increase of the density of states due to the Zeeman and Doppler-shifted quasiparticles extended outside the vortex cores in a d-wave superconductor. Above 10 T a new superconducting state is stabilized, possibly the modulated phase predicted by Fulde, Ferrell, Larkin, and Ovchinnikov. This phase is clearly identified by a strong and linear increase of the NMR shift with the field, before a jump at the first order transition to the normal state.
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Affiliation(s)
- G Koutroulakis
- Department of Physics, Brown University, Providence, Rhode Island 02912, USA
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