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arXiv · 1806.03768

Fully-gapped superconductivity in single crystals of noncentrosymmetric Re$_6$Zr with broken time-reversal symmetry

G. M. Pang·Z. Y. Nie·A. Wang·D. Singh·W. Xie·W. B. Jiang·Y. Chen·R. P. Singh·M. Smidman·H. Q. Yuan
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Abstract

The noncentrosymmetric superconductor Re$_6$Zr has attracted much interest due to the observation of broken time-reversal symmetry in the superconducting state. Here we report an investigation of the superconducting gap structure of Re$_6$Zr single crystals by measuring the magnetic penetration depth shift $Δλ(T)$ and electronic specific heat $C_e(T)$. $Δλ(T)$ exhibits an exponential temperature dependence behavior for $T~\ll~T_c$, which indicates a fully-open superconducting gap. Our analysis shows that a single gap $s$-wave model is sufficient to describe both the superfluid density $ρ_s(T)$ and $C_e(T)$ results, with a fitted gap magnitude larger than the weak coupling BCS value, providing evidence for fully-gapped superconductivity in Re$_6$Zr with moderate coupling.

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G. M. Pang, Z. Y. Nie, A. Wang, D. Singh, W. Xie, W. B. Jiang, Y. Chen, R. P. Singh, M. Smidman, H. Q. Yuan. 2018-06-11. Fully-gapped superconductivity in single crystals of noncentrosymmetric Re$_6$Zr with broken time-reversal symmetry. https://doi.org/10.1103/physrevb.97.224506

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