Title: Point-node gap structure of the spin-triplet superconductor ${\mathrm{UTe}}_2$

Abstract

In this work, low-temperature electrical and thermal transport, magnetic penetration depth, and heat capacity measurements were performed on single crystals of the actinide superconductor ${\mathrm{UTe}}_2$ 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.

Authors:

Metz, Tristin ^[1]; Bae, Seokjin  ^[1];

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Ran, Sheng ^[2]; Liu, I-Lin ^[2]; Eo, Yun Suk ^[1]; Fuhrman, Wesley T. ^[1]; Agterberg, Daniel F. ^[3]; Anlage, Steven M.  ^[1];

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Butch, Nicholas P. ^[2]; Paglione, Johnpierre  ^[4]

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• Search DOE PAGES for ORCID "0000-0001-7257-014X"
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+ Show Author Affiliations

1. Univ. of Maryland, College Park, MD (United States)
2. Univ. of Maryland, College Park, MD (United States); National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
3. Univ. of Wisconsin, Milwaukee, WI (United States)
4. Univ. of Maryland, College Park, MD (United States); Canadian Inst. for Advanced Research, Toronto, ON (Canada)

Publication Date:

2019-12-19

Research Org.:

Univ. of Maryland, College Park, MD (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE Office of Science (SC), High Energy Physics (HEP); US Air Force Office of Scientific Research (AFOSR); National Science Foundation (NSF); Gordon and Betty Moore Foundation

OSTI Identifier:

1604581

Grant/Contract Number:  

SC0018788; SC0019154; SC0017931; FA9550-14-1-0332; DMR-1410712; GBMF4419

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 100; Journal Issue: 22; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; UTe2; penetration depth; electrical transport; thermal transport; heat capacity