Superconductivity in noncentrosymmetric SrAuSi3
Superconductivity in noncentrosymmetric SrAuSi3
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DOI：
10.1103/physrevb.93.054519
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发表时间：
2016-02-22
影响因子：
3.7
通讯作者：
Shirakawa, Naoki
中科院分区：
文献类型：
--
作者：
Isobe, Masaaki;Arai, Masao;Shirakawa, Naoki
用电阻率、磁化率、比热测量和从头算方法研究了非中心对称化合物SrAuSi_3 [BaNiSn_3型，I_（4 mm），a = 4.4024（9）埃，c = 9.942（2）埃]的超导电性。这些物理性质的测量证实了SrAuSi 3相显示出体超导电性，其临界温度T-C接近1.6K，上临界场H-C2接近1.8kOe。在超导状态下，电子比热表现出热激活型的温度依赖性和索末菲常数γ线性响应于低能量激发磁场。这些结果清楚地表明SrAuSi 3是一种全能隙s波超导体，在超导序参数中没有能隙节点。密度泛函理论从头算能带计算表明，该电子体系由三种费米面组成：圆柱形、哑铃形和异形空穴袋.在布里渊区中，自旋轨道耦合引起的费米面分裂仅沿沿着有限的方向存在。总的来说，分裂能量的大小是小的，不足以实现非常规的各向异性超导归因于空间反演对称性破缺。
Superconductivity in the noncentrosymmetric compound SrAuSi3 [BaNiSn3 type, I4mm, a = 4.4024(9) angstrom, and c = 9.942(2) angstrom] was studied by electrical resistivity, magnetic susceptibility, and specific heat measurements using single-phase polycrystalline samples, and ab initio band calculation. These measurements of the physical properties confirmed that the SrAuSi3 phase shows bulk superconductivity with a critical temperature of T-C similar to 1.6K and an upper critical field of H-C2 similar to 1.8 kOe. In the superconducting state, the electronic specific heat exhibits a thermal-activation-type temperature dependence and the Sommerfeld constant gamma linearly responds to magnetic fields for low-energy excitation. These results clearly indicate that SrAuSi3 is a full-gap s-wave superconductor without a gap node in the superconducting order parameter. The density functional theory ab initio band calculation revealed that the electron system is composed of three kinds of Fermi surface: a cylindrical shape, a dumbbell shape, and a peculiar-shaped hole pocket. Fermi-surface splitting due to spin-orbit coupling exists only along limited directions in the Brillouin zone. Overall, the splitting energy size is small, insufficient to realize unconventional anisotropic superconductivity attributed to space-inversion symmetry breaking.