Multigap Superconductivity in Chiral Noncentrosymmetric TaRh${}_2$B${}_2$

Abstract

We report the first observation of multigap superconductivity in TaRh${}_2$B${}_2$. We show TaRh${}_2$B${}_2$ is a bulk type-II superconductor with a transition temperature, $T_{\mathrm{c}}=6.00(5)$ K. We present transverse-field muon spin relaxation data where the superconducting gap can be fit using a two-gap $\left(s+s\right)$-wave model. We also report the zero-field electronic specific heat in the superconducting state that is best described by the same $\left(s+s\right)$ model providing further evidence of multiband behavior in this superconductor. Zero-field muon spin relaxation measurements show time-reversal symmetry is preserved in the superconducting state. We demonstrate that TaRh${}_2$B${}_2$ has an upper critical field of $15.2(1)$ T, which is significantly higher than previously reported and exceeds the Pauli limit.

5 pages, 3 figures. Accepted for publication in Physical Review B