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arXiv · 2309.12457

Time-Reversal Symmetry Breaking Superconductivity in CaSb$_2$

M. Oudah·Y. Cai·M. V. De Toro Sanchez·J. Bannies·M. C. Aronson·K. M. Kojima·D. A. Bonn
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Abstract

CaSb$_2$ is a bulk superconductor and a topological semimetal, making it a great platform for realizing topological superconductivity. In this work, we investigate the superconducting upper and lower critical field anisotropy using magnetic susceptibility, and study the superconducting state using muon spin-relaxation. The temperature dependence of transverse-field relaxation rate can be fitted with a single-gap model or two-gap model. Zero-field relaxation shows little temperature dependence when the muon-spin is parallel to the $c*$-axis, while an increase in relaxation appears below 1 K when the muon-spin is parallel to the $ab$-plane. We conclude an $s+is$ order parameter considering the breaking of time-reversal symmetry (TRS), which originates from competing interband interactions between the three bands of CaSb$_2$. To explain the direction-dependent breaking of TRS we suggest loop currents developing in the plane of distorted square-net of Sb atoms.

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M. Oudah, Y. Cai, M. V. De Toro Sanchez, J. Bannies, M. C. Aronson, K. M. Kojima, D. A. Bonn. 2023-09-21. Time-Reversal Symmetry Breaking Superconductivity in CaSb$_2$. https://arxiv.org/abs/2309.12457

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