Point-Node Gap Structure of Spin-Triplet Superconductor UTe2

Published

December 19, 2019

Author(s)

Tristin Metz, Seokjin Bae, Sheng NMN Ran, I-Lin Liu, Yun Suk Eo, Wesley T. Fuhrman, Daniel F. Agterberg, Steven M. Anlage, Nicholas Butch, Johnpierre Paglione

Abstract

Low-temperature electrical and thermal transport, heat capacity and magnetic penetration depth measurements were performed on single crystals of the actinide superconductor UTe₂ to determine the structure of the superconducting energy gap. Millikelvin specific heat measurements reveal an upturn below 300 mK that is is well described by a divergent quantum-critical contribution to the density of states (DOS). Modeling this contribution with a T_c1/3 power law allows restoration of the full entropy balance in the superconducting state below T_c = 1.6 K, revealing a perfect T³ power law for the electronic DOS below T_c. 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 that grows as T³ for both directions and exhibits an a/b anisotropy ratio of 2:5 in the T = 0 limit. The magnetic field dependence of the residual term follows a quasilinear increase consistent with the presence of nodal quasiparticles, rising rapidly toward the a-axis upper critical field where the Wiedemann-Franz (WF) law is recovered. Together with a quadratic temperature dependence of the magnetic penetration depth up to T/T_c = 0.3, these measurements provide definitive evidence for an unconventional spin-triplet superconducting order parameter with point nodes positioned along the crystallographic a-axis.

Citation

Physical Review B

Volume

100

Issue

11

Pub Type

Journals

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Keywords

superconductivity

Citation

Metz, T. , Bae, S. , Ran, S. , Liu, I. , Eo, Y. , Fuhrman, W. , Agterberg, D. , Anlage, S. , Butch, N. and Paglione, J. (2019), Point-Node Gap Structure of Spin-Triplet Superconductor UTe₂, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=928829 (Accessed October 14, 2024)