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Lewin SK, Frank CE, Ran S, Paglione J, Butch NP. A review of UTe 2at high magnetic fields. Rep Prog Phys 2023; 86:114501. [PMID: 37729901 DOI: 10.1088/1361-6633/acfb93] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 09/20/2023] [Indexed: 09/22/2023]
Abstract
Uranium ditelluride (UTe2) is recognized as a host material to unconventional spin-triplet superconductivity, but it also exhibits a wealth of additional unusual behavior at high magnetic fields. One of the most prominent signatures of the unconventional superconductivity is a large and anisotropic upper critical field that exceeds the paramagnetic limit. This superconductivity survives to 35 T and is bounded by a discontinuous magnetic transition, which itself is also field-direction-dependent. A different, reentrant superconducting phase emerges only on the high-field side of the magnetic transition, in a range of angles between the crystallographicbandcaxes. This review discusses the current state of knowledge of these high-field phases, the high-field behavior of the heavy fermion normal state, and other phases that are stabilized by applied pressure.
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Affiliation(s)
- Sylvia K Lewin
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, United States of America
- Department of Physics, Quantum Materials Center, University of Maryland, College Park, MD, United States of America
| | - Corey E Frank
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, United States of America
- Department of Physics, Quantum Materials Center, University of Maryland, College Park, MD, United States of America
| | - Sheng Ran
- Department of Physics, Washington University in St. Louis, St. Louis, MO, United States of America
| | - Johnpierre Paglione
- Department of Physics, Quantum Materials Center, University of Maryland, College Park, MD, United States of America
| | - Nicholas P Butch
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, United States of America
- Department of Physics, Quantum Materials Center, University of Maryland, College Park, MD, United States of America
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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. J Phys Condens Matter 2022; 34:243002. [PMID: 35203074 DOI: 10.1088/1361-648x/ac5863] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Haga Y, Opletal P, Tokiwa Y, Yamamoto E, Tokunaga Y, Kambe S, Sakai H. Effect of uranium deficiency on normal and superconducting properties in unconventional superconductor UTe 2. J Phys Condens Matter 2022; 34:175601. [PMID: 35120343 DOI: 10.1088/1361-648x/ac5201] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/04/2022] [Indexed: 06/14/2023]
Abstract
Single crystals of the unconventional superconductor UTe2have been grown in various conditions which result in different superconducting transition temperature as well as normal state properties. Stoichiometry of the samples has been characterized by the single-crystal x-ray crystallography and electron microprobe analyses. Superconducting samples are nearly stoichiometric within an experimental error of about 1%, while non-superconducting sample significantly deviates from the ideal composition. The superconducting UTe2showed that the large density of states was partially gapped in the normal state, while the non-superconducting sample is characterized by the relatively large electronic specific heat as reported previously.
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Affiliation(s)
- Y Haga
- Advanced Science Research Center, Japan Atomic Energy Agency, Japan
| | - P Opletal
- Advanced Science Research Center, Japan Atomic Energy Agency, Japan
| | - Y Tokiwa
- Advanced Science Research Center, Japan Atomic Energy Agency, Japan
| | - E Yamamoto
- Advanced Science Research Center, Japan Atomic Energy Agency, Japan
| | - Y Tokunaga
- Advanced Science Research Center, Japan Atomic Energy Agency, Japan
| | - S Kambe
- Advanced Science Research Center, Japan Atomic Energy Agency, Japan
| | - H Sakai
- Advanced Science Research Center, Japan Atomic Energy Agency, Japan
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Cairns LP, Stevens CR, O'Neill CD, Huxley A. Composition dependence of the superconducting properties of UTe 2. J Phys Condens Matter 2020; 32:415602. [PMID: 32531764 DOI: 10.1088/1361-648x/ab9c5d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 06/12/2020] [Indexed: 06/11/2023]
Abstract
A better understanding of the synthesis conditions, composition and physical properties of UTe2are required to interpret previously reported unconventional superconductivity. Here we report how the superconducting properties of single crystals depend on the ratio of elements present in their synthesis by chemical vapour transport. We have obtained crystals with the highest reported ambient pressureTcand a larger superconducting heat capacity jump from a growth with a U:Te ratio different from that widely used in the literature. For these crystals, the ratio of residual heat capacity in the superconducting state to that of the normal state,γ*/γN, is significantly lower than 0.5, reported elsewhere. An upturn in the heat capacity below 200 mK is also reduced compared to other studies and is well described by a Schottky anomaly and residual Sommerfeld term rather than quantum critical behaviour.
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Affiliation(s)
- Luke Pritchard Cairns
- School of Physics and Astronomy and CSEC, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
| | - Callum R Stevens
- School of Physics and Astronomy and CSEC, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
| | - Christopher D O'Neill
- School of Physics and Astronomy and CSEC, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
| | - Andrew Huxley
- School of Physics and Astronomy and CSEC, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
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Hutanu V, Deng H, Ran S, Fuhrman WT, Thoma H, Butch NP. Low-temperature crystal structure of the unconventional spin-triplet superconductor UTe 2 from single-crystal neutron diffraction. Acta Crystallogr B Struct Sci Cryst Eng Mater 2020; 76:137-143. [PMID: 32831248 PMCID: PMC8202135 DOI: 10.1107/s2052520619016950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 12/18/2019] [Indexed: 06/01/2023]
Abstract
The crystal structure of a new superconductor UTe2 has been investigated using single-crystal neutron diffraction for the first time at the low temperature (LT) of 2.7 K, just above the superconducting transition temperature of ∼1.6 K, in order to clarify whether the orthorhombic structure of type Immm (No. 71), reported for the room-temperature (RT) structure persists down to the superconducting phase and can be considered as a parent symmetry for the development of spin-triplet superconductivity. In contrast to the previously reported phase transition at about 100 K [Stöwe (1996). J. Solid State Chem. 127, 202-210], our high-precision LT neutron diffraction data show that the body-centred RT symmetry is indeed maintained down to 2.7 K. No sign of a structural change from RT down to 2.7 K was observed. The most significant change depending on temperature was observed for the U ion position and the U-U distance along the c direction, implying its potential importance as a magnetic interaction path. No magnetic order could be deduced from the neutron diffraction data refinement at 2.7 K, consistent with bulk magnetometry. Assuming normal thermal evolution of the lattice parameters, moderately large linear thermal expansion coefficients of about α = 2.8 (7) × 10-5 K-1 are estimated.
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Affiliation(s)
- Vladimir Hutanu
- Institute of Crystallography, RWTH Aachen University and Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Lichtenbergstrasse 1, Garching, 85748, Germany
| | - Hao Deng
- Institute of Crystallography, RWTH Aachen University and Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Lichtenbergstrasse 1, Garching, 85748, Germany
| | - Sheng Ran
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Wesley T. Fuhrman
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Henrik Thoma
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Lichtenbergstrasse 1, Garching, 85748, Germany
| | - Nicholas P. Butch
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, MD 20742, USA
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