1
|
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.
Collapse
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
| |
Collapse
|
2
|
On the Superconducting Critical Temperature of Heavily Disordered Interfaces Hosting Multi-Gap Superconductivity. COATINGS 2021. [DOI: 10.3390/coatings12010030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
LaAlO3/SrTiO3 interfaces are a nice example of a two-dimensional electron gas, whose carrier density can be varied by top- and back-gating techniques. Due to the electron confinement near the interface, the two-dimensional band structure is split into sub-bands, and more than one sub-band can be filled when the carrier density increases. These interfaces also host superconductivity, and the interplay of two-dimensionality, multi-band character, with the possible occurrence of multi-gap superconductivity and disorder calls for a better understanding of finite-bandwidth effects on the superconducting critical temperature of heavily disordered multi-gap superconductors.
Collapse
|
3
|
Ghosh SK, Smidman M, Shang T, Annett JF, Hillier AD, Quintanilla J, Yuan H. Recent progress on superconductors with time-reversal symmetry breaking. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:033001. [PMID: 32721940 DOI: 10.1088/1361-648x/abaa06] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 07/28/2020] [Indexed: 06/11/2023]
Abstract
Superconductivity and magnetism are adversarial states of matter. The presence of spontaneous magnetic fields inside the superconducting state is, therefore, an intriguing phenomenon prompting extensive experimental and theoretical research. In this review, we discuss recent experimental discoveries of unconventional superconductors which spontaneously break time-reversal symmetry and theoretical efforts in understanding their properties. We discuss the main experimental probes and give an extensive account of theoretical approaches to understand the order parameter symmetries and the corresponding pairing mechanisms, including the importance of multiple bands.
Collapse
Affiliation(s)
- Sudeep Kumar Ghosh
- Physics of Quantum Materials, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - Michael Smidman
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, People's Republic of China
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Tian Shang
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - James F Annett
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - Adrian D Hillier
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, United Kingdom
| | - Jorge Quintanilla
- Physics of Quantum Materials, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - Huiqiu Yuan
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, People's Republic of China
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China
- State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People's Republic of China
| |
Collapse
|
4
|
Ayino Y, Yue J, Wang T, Jalan B, Pribiag VS. Effects of paramagnetic pair-breaking and spin-orbital coupling on multi-band superconductivity. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:38LT02. [PMID: 32422615 DOI: 10.1088/1361-648x/ab940c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
The BCS picture of superconductivity describes pairing between electrons originating from a single band. A generalization of this picture occurs in multi-band superconductors, where electrons from two or more bands contribute to superconductivity. The contributions of the different bands can result in an overall enhancement of the critical field and can lead to qualitative changes in the temperature dependence of the upper critical field when compared to the single-band case. While the role of orbital pair-breaking on the critical field of multi-band superconductors has been explored extensively, paramagnetic and spin-orbital scattering effects have received comparatively little attention. Here we investigate this problem using thin films of Nd-doped SrTiO3. We furthermore propose a model for analyzing the temperature-dependence of the critical field in the presence of orbital, paramagnetic and spin-orbital effects, and find a very good agreement with our data. Interestingly, we also observe a dramatic enhancement in the out-of-plane critical field to values well in excess of the Chandrasekhar-Clogston (Pauli) paramagnetic limit, which can be understood as a consequence of multi-band effects in the presence of spin-orbital scattering.
Collapse
Affiliation(s)
- Yilikal Ayino
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jin Yue
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Tianqi Wang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Bharat Jalan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Vlad S Pribiag
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
Falkowski M, Strydom AM. A new ternary magnetically ordered heavy fermion compound Pr 2Rh 3Ge: magnetic, electronic and thermodynamic properties. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:395601. [PMID: 28682301 DOI: 10.1088/1361-648x/aa7e1d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The results of the magnetic, electron transport, heat capacity and heat conduction measurements on the new rhombohedral ternary compound Pr2Rh3Ge have been investigated. The synthesized polycrystalline compound was found to crystallize in the ternary ordered variant of the cubic Laves phase [Formula: see text]-type of structure with the space group R[Formula: see text]m, as previously reported. Pr2Rh3Ge exhibits a ferromagnetic behaviour below [Formula: see text] K, which was found to be unstable in low applied magnetic fields, revealing characteristics usually attributed to the long-range order. In the entire paramagnetic region electrical resistivity shows monotonous metallic conductivity character. We estimated that the Sommerfeld coefficient γ = 315 mJ/Pr-mol · [Formula: see text] of [Formula: see text] [Formula: see text]Ge is very large with comparison to ordinary metals which indicate the existence of heavy fermion behaviour of itinerant charge carriers at low temperatures or enhanced density of the quasi-particle state at the Fermi level. The crucial role of the crystalline electric field effects on the ground state properties of [Formula: see text] (J = 4) has been also observed. We think that the heavy fermion behaviour in [Formula: see text] [Formula: see text]Ge results from the dynamic low-lying crystal-field fluctuations, since there is no sign of Kondo effect in electrical resistivity and no enhancement of the slope S(T)/T in thermoelectric power data at low temperatures. It suggests that the conduction electrons at the Fermi level does not correlate with the 4f 2 states of [Formula: see text] atoms and hence there is no place for a typical spin Kondo effect, as it is commonly observed in Ce- and Yb-based heavy fermion systems.
Collapse
Affiliation(s)
- M Falkowski
- Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland. Physics Department, Highly Correlated Matter Research Group, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | | |
Collapse
|
7
|
Griffith MA, Puel TO, Continentino MA, Martins GB. Multiband superconductivity in BiS 2-based layered compounds. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:305601. [PMID: 28573976 DOI: 10.1088/1361-648x/aa76ac] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A mean-field treatment is presented of a square lattice two-orbital-model for [Formula: see text] taking into account intra- and inter-orbital superconductivity. A rich phase diagram involving both types of superconductivity is presented as a function of the ratio between the couplings of electrons in the same and different orbitals ([Formula: see text]) and electron doping x. With the help of a quantity we call orbital-mixing ratio, denoted as [Formula: see text], the phase diagram is analyzed using a simple and intuitive picture based on how [Formula: see text] varies as electron doping increases. The predictive power of [Formula: see text] suggests that it could be a useful tool in qualitatively (or even semi-quantitatively) analyzing multiband superconductivity in BCS-like superconductors.
Collapse
Affiliation(s)
- M A Griffith
- Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, Urca, 22290-180 Rio de Janeiro, RJ, Brazil
| | | | | | | |
Collapse
|
8
|
Kozii V, Venderbos JWF, Fu L. Three-dimensional Majorana fermions in chiral superconductors. SCIENCE ADVANCES 2016; 2:e1601835. [PMID: 27957543 PMCID: PMC5142806 DOI: 10.1126/sciadv.1601835] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 11/03/2016] [Indexed: 05/31/2023]
Abstract
Using a systematic symmetry and topology analysis, we establish that three-dimensional chiral superconductors with strong spin-orbit coupling and odd-parity pairing generically host low-energy nodal quasiparticles that are spin-nondegenerate and realize Majorana fermions in three dimensions. By examining all types of chiral Cooper pairs with total angular momentum J formed by Bloch electrons with angular momentum j in crystals, we obtain a comprehensive classification of gapless Majorana quasiparticles in terms of energy-momentum relation and location on the Fermi surface. We show that the existence of bulk Majorana fermions in the vicinity of spin-selective point nodes is rooted in the nonunitary nature of chiral pairing in spin-orbit-coupled superconductors. We address experimental signatures of Majorana fermions and find that the nuclear magnetic resonance spin relaxation rate is significantly suppressed for nuclear spins polarized along the nodal direction as a consequence of the spin-selective Majorana nature of nodal quasiparticles. Furthermore, Majorana nodes in the bulk have nontrivial topology and imply the presence of Majorana bound states on the surface, which form arcs in momentum space. We conclude by proposing the heavy fermion superconductor PrOs4Sb12 and related materials as promising candidates for nonunitary chiral superconductors hosting three-dimensional Majorana fermions.
Collapse
Affiliation(s)
- Vladyslav Kozii
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jörn W. F. Venderbos
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| |
Collapse
|
9
|
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.
Collapse
Affiliation(s)
- Shi-Zeng Lin
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| |
Collapse
|
10
|
Yang M, Liu WM. The d-p band-inversion topological insulator in bismuth-based skutterudites. Sci Rep 2014; 4:5131. [PMID: 24875345 PMCID: PMC4038835 DOI: 10.1038/srep05131] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 05/14/2014] [Indexed: 11/08/2022] Open
Abstract
Skutterudites, a class of materials with cage-like crystal structure which have received considerable research interest in recent years, are the breeding ground of several unusual phenomena such as heavy fermion superconductivity, exciton-mediated superconducting state and Weyl fermions. Here, we predict a new topological insulator in bismuth-based skutterudites, in which the bands involved in the topological band-inversion process are d- and p-orbitals, which is distinctive with usual topological insulators, for instance in Bi2Se3 and BiTeI the bands involved in the topological band-inversion process are only p-orbitals. Due to the present of large d-electronic states, the electronic interaction in this topological insulator is much stronger than that in other conventional topological insulators. The stability of the new material is verified by binding energy calculation, phonon modes analysis, and the finite temperature molecular dynamics simulations. This new material can provide nearly zero-resistivity signal current for devices and is expected to be applied in spintronics devices.
Collapse
Affiliation(s)
- Ming Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wu-Ming Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| |
Collapse
|
11
|
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.
Collapse
Affiliation(s)
- L Howald
- Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
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.
Collapse
Affiliation(s)
- Y Machida
- Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
| | | | | | | | | |
Collapse
|
13
|
Taylor BJ, Maple MB. Formula for the critical temperature of superconductors based on the electronic density of states and the effective mass. PHYSICAL REVIEW LETTERS 2009; 102:137003. [PMID: 19392396 DOI: 10.1103/physrevlett.102.137003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Indexed: 05/27/2023]
Abstract
A formula for the superconducting transition temperature T(c) is developed by comparing the total condensation energy contained within the coherence volume of a Cooper pair to the number of electronic states at the Fermi surface within the same coherence volume. It is found that T(c) is proportional to the ratio of the condensation energy density and normal state charge carrier density. We find that this relation holds for over 2 orders of magnitude in temperature for numerous well-known superconducting compounds belonging to distinctly different classes.
Collapse
Affiliation(s)
- B J Taylor
- Department of Physics and Institute for Pure and Applied Physical Sciences, University of California, San Diego, La Jolla, California 92093, USA
| | | |
Collapse
|
14
|
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]
|
15
|
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.
Collapse
Affiliation(s)
- R W Hill
- Guelph-Waterloo Physics Institute, University of Waterloo, Waterloo, Ontario, Canada.
| | | | | | | |
Collapse
|
16
|
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.
Collapse
Affiliation(s)
- G Seyfarth
- CNRS, Néel Institute, 25 avenue des Martyrs, BP166, 38042 Grenoble Cedex 9, France
| | | | | | | | | | | |
Collapse
|
17
|
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).
Collapse
Affiliation(s)
- Y Nakajima
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
| | | | | | | |
Collapse
|
18
|
Khasanov R, Strässle S, Di Castro D, Masui T, Miyasaka S, Tajima S, Bussmann-Holder A, Keller H. Multiple gap symmetries for the order parameter of cuprate superconductors from penetration depth measurements. PHYSICAL REVIEW LETTERS 2007; 99:237601. [PMID: 18233411 DOI: 10.1103/physrevlett.99.237601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Indexed: 05/25/2023]
Abstract
The temperature dependence of the London penetration depth lambda was measured for an untwinned single crystal of YBa_{2}Cu_{3}O_{7-delta} along the three principal crystallographic directions (a, b, and c). Both in-plane components (lambda_{a};{-2} and lambda_{b};{-2}) show an inflection point in their temperature dependence which is absent in the component along the c direction (lambda_{c};{-2}). The data provide convincing evidence that the in-plane superconducting order parameter is a mixture of (s+d)-wave symmetry whereas it is mainly s wave along the c direction. In conjunction with previous results it is concluded that coupled s+d-order parameters are universal and intrinsic to cuprate superconductors.
Collapse
Affiliation(s)
- R Khasanov
- Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Kasahara Y, Iwasawa T, Shishido H, Shibauchi T, Behnia K, Haga Y, Matsuda TD, Onuki Y, Sigrist M, Matsuda Y. Exotic superconducting properties in the electron-hole-compensated heavy-fermion "Semimetal" URu2Si2. PHYSICAL REVIEW LETTERS 2007; 99:116402. [PMID: 17930455 DOI: 10.1103/physrevlett.99.116402] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Indexed: 05/25/2023]
Abstract
We show that the charge and thermal transport measurements on ultraclean crystals of URu2Si2 reveal a number of unprecedented superconducting properties. The uniqueness is best highlighted by the peculiar field dependence of thermal conductivity including the first-order transition at Hc2 with a reduction of entropy flow. This is a consequence of multiband superconductivity with compensated electronic structure in the hidden order state of this system. We provide strong evidence for a new type of unconventional superconductivity with two distinct gaps having different nodal topology.
Collapse
Affiliation(s)
- Y Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Seyfarth G, Brison JP, Méasson MA, Braithwaite D, Lapertot G, Flouquet J. Superconducting PrOs4Sb12: a thermal conductivity study. PHYSICAL REVIEW LETTERS 2006; 97:236403. [PMID: 17280219 DOI: 10.1103/physrevlett.97.236403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Indexed: 05/13/2023]
Abstract
The superconducting state of the heavy fermion PrOs4Sb12 is studied by heat transport measurements on a highly homogeneous single crystal exhibiting only one transition peak in the specific heat. The field and temperature dependence of the thermal conductivity confirm multiband superconductivity and point to fully open gaps on the whole Fermi surface.
Collapse
Affiliation(s)
- G Seyfarth
- CRTBT, CNRS, 25 avenue des Martyrs, B.P. 166, 38042 Grenoble CEDEX 9, France
| | | | | | | | | | | |
Collapse
|