NbReSi：一种具有大上临界场的非中心对称超导体
NbReSi: A Noncentrosymetric Superconductor with Large Upper Critical Field
摘要：
本文报道了在非中心对称的NbReSi中发现的超导电性。NbReSi具有六方ZrNiAl型晶体结构，空间群为$P\bar{6}2m$（No.~ 189）。体超导性，与$T_c$ = 6.5 K，其特征在于通过电阻率，磁化强度和热容量测量。低温电子比热表明NbReSi处于完全带隙的超导态，同时获得了$μ_0H_\mathrm{c2}(0)$ $\sim$ 12.6 T的大上临界场，与弱耦合泡利极限相当.电子能带结构计算表明，费米能级的态密度主要由Re和Nb的$d$轨道控制，反对称自旋-轨道耦合导致了相当大的能带分裂. NbReSi代表了另一种候选材料，用于揭示在某些Re基超导体中观察到的时间反演对称性破缺的难题及其与缺乏反演对称性的关系。
英文摘要：
We report the discovery of superconductivity in noncentrosymmetric NbReSi, which crystallizes in a hexagonal ZrNiAl-type crystal structure with space group $P\bar{6}2m$ (No.~189). Bulk superconductivity, with $T_c$ = 6.5 K was characterized via electrical-resistivity, magnetization, and heat-capacity measurements. The low-temperature electronic specific heat suggests a fully gapped superconducting state in NbReSi, while a large upper critical field of $μ_0H_\mathrm{c2}(0)$ $\sim$ 12.6 T is obtained, which is comparable to the weak-coupling Pauli limit. The electronic band-structure calculations show that the density of states at the Fermi level are dominated by Re and Nb $d$-orbitals, with a sizeable band splitting induced by the antisymmetric spin-orbit coupling. NbReSi represents another candidate material for revealing the puzzle of time-reversal symmetry breaking observed in some Re-based superconductors and its relation to the lack of inversion symmetry.
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