Pair wave function symmetry in UTe<sub>2</sub> from zero-energy surface state visualization.

Gu, Qiangqiang; Wang, Shuqiu; Carroll, Joseph P; Zhussupbekov, Kuanysh; Broyles, Christopher; Ran, Sheng; Butch, Nicholas P; Horn, Jarryd A et al. · Science · 2025

basic_science · Level V

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Abstract

Although nodal spin-triplet topological superconductivity appears probable in uranium ditelluride (UTe<sub>2</sub>), its superconductive order parameter Δ<b><sub>k</sub></b> remains unestablished. In theory, a distinctive identifier would be the existence of a superconductive topological surface band, which could facilitate zero-energy Andreev tunneling to an s-wave superconductor and also distinguish a chiral from a nonchiral Δ<sub><b>k</b></sub> through enhanced s-wave proximity. In this study, we used s-wave superconductive scan tips and detected intense zero-energy Andreev conductance at the UTe<sub>2</sub> (0-11) termination surface. Imaging revealed subgap quasiparticle scattering interference signatures with <i>a</i>-axis orientation. The observed zero-energy Andreev peak splitting with enhanced s-wave proximity signifies that Δ<b><sub>k</sub></b> of UTe<sub>2</sub> is a nonchiral state: <i>B</i><sub>1</sub><i><sub>u</sub></i>, <i>B</i><sub>2</sub><i><sub>u</sub></i>, or <i>B</i><sub>3</sub><i><sub>u</sub></i>. However, if the quasiparticle scattering along the <i>a</i> axis is internodal, then a nonchiral <i>B</i><sub>3</sub><i><sub>u</sub></i> state is the most consistent for UTe<sub>2</sub>.