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Metz T, Bae S, Ran S, Liu IL, Eo YS, Fuhrman WT, Agterberg DF, Anlage SM, Butch NP, Paglione J. Point-node gap structure of the spin-triplet superconductor UTe 2. PHYSICAL REVIEW. B 2019; 100:10.1103/PhysRevB.100.220504. [PMID: 34136735 PMCID: PMC8204512 DOI: 10.1103/physrevb.100.220504] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Low-temperature electrical and thermal transport, magnetic penetration depth, and heat capacity measurements were performed on single crystals of the actinide superconductor UTe2 to determine the structure of the superconducting energy gap. Heat transport measurements performed with currents directed along both crystallographic a and b axes reveal a vanishingly small residual fermionic component of the thermal conductivity. The magnetic field dependence of the residual term follows a rapid, quasilinear increase consistent with the presence of nodal quasiparticles, rising toward the a-axis upper critical field where the Wiedemann-Franz law is recovered. Together with a quadratic temperature dependence of the magnetic penetration depth up to T/T c = 0.3, these measurements provide evidence for an unconventional spin-triplet superconducting order parameter with point nodes. Millikelvin specific heat measurements performed on the same crystals used for thermal transport reveal an upturn below 300 mK that is well described by a divergent quantum-critical contribution to the density of states (DOS). Modeling this contribution with a T -1/3 power law allows restoration of the full entropy balance in the superconducting state and a resultant cubic power law for the electronic DOS below T c , consistent with the point-node gap structure determined by thermal conductivity and penetration depth measurements.
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Affiliation(s)
- Tristin Metz
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Seokjin Bae
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Sheng Ran
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - I-Lin Liu
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Yun Suk Eo
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Wesley T. Fuhrman
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Daniel F. Agterberg
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53201, USA
| | - Steven M. Anlage
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Nicholas P. Butch
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Johnpierre Paglione
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
- Canadian Institute for Advanced Research, Toronto, Ontario, Canada M5G 1Z8
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