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Point-Node Gap Structure of Spin-Triplet Superconductor UTe2



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


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 Tc1/3 power law allows restoration of the full entropy balance in the superconducting state below Tc = 1.6 K, revealing a perfect T3 power law for the electronic DOS below Tc. 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/Tc = 0.3, these measurements provide definitive evidence for an unconventional spin-triplet superconducting order parameter with point nodes positioned along the crystallographic a-axis.
Physical Review B




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 UTe<sub>2</sub>, Physical Review B, [online], (Accessed May 25, 2024)


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Created December 18, 2019, Updated October 12, 2021