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arXiv · 2209.03187

Time reversal invariant single gap superconductivity with upper critical field larger than Pauli limit in NbIr$_2$B$_2$

Debarchan Das·Karolina Górnicka·Zurab Guguchia·Jan Jaroszynski·Robert J. Cava·Weiwei Xie·Hubertus Luetkens·Tomasz Klimczuk
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Abstract

Recently, compounds with noncentrosymmetric crystal structure have attracted much attention for providing a rich playground in search for unconventional superconductivity. NbIr$_2$B$_2$ is a new member to this class of materials harboring superconductivity below $T_{\rm c} = 7.3(2)$~K and very high upper critical field that exceeds Pauli limit. Here we report on muon spin rotation ($μ$SR) experiments probing the temperature and field dependence of effective magnetic penetration depth in this compound. Our transverse-field -$μ$SR results suggest a fully gaped $s$-wave superconductvity. Further, the estimated high value of upper critical field is also supplemented by high field transport measurements. Remarkably, the ratio $T_{\rm c}$/$λ^{-2}(0)$ obtained for NbIr$_2$B$_2$ ($\sim$2) is comparable to those of unconventional superconductors. Zero-field $μ$SR data reveals no significant change in the muon spin relaxation rate above and below $T_{\rm c}$, evincing that time-reversal symmetry is preserved in the superconducting state. The presented results will stimulate theoretical investigations to obtain a microscopic understanding of the origin of superconductivity with preserved time reversal symmetry in this unique noncentrosymmetric system.

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Debarchan Das, Karolina Górnicka, Zurab Guguchia, Jan Jaroszynski, Robert J. Cava, Weiwei Xie, Hubertus Luetkens, Tomasz Klimczuk. 2022-09-16. Time reversal invariant single gap superconductivity with upper critical field larger than Pauli limit in NbIr$_2$B$_2$. https://doi.org/10.1103/physrevb.106.094507

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