Rotational Symmetry Breaking in a Trigonal Superconductor Nb-doped Bi2Se3
Rotational Symmetry Breaking in a Trigonal Superconductor Nb-doped Bi2Se3
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DOI：
10.1103/physrevx.7.011009
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发表时间：
2017-01-27
影响因子：
12.5
通讯作者：
Li, Lu
中科院分区：
文献类型：
--
作者：
Asaba, Tomoya;Lawson, B. J.;Li, Lu
对非常规超导性的研究主要集中在具有强自旋轨道耦合和独特晶格的材料上。考虑到母体化合物的拓扑绝缘体性质及其三角形晶格，掺杂硒化铋（Bi2Se3）是一个强有力的候选者。超导状态下的物理性质与其潜在的晶体对称性之间的耦合是非常规超导性的关键测试。在本文中，我们报告了最近发现的具有三角晶体结构的超导体铌（Nb）掺杂Bi2Se3的超导磁响应与潜在的三角晶体对称性强烈耦合的直接证据。因此，面内磁转矩信号每60度消失一次。更重要的是，超导磁滞回线的振幅沿着一个优先方向增强，自发地破坏了旋转对称性。这一观察结果表明，铌掺杂Bi2Se3的超导基态中存在向列序。
The search for unconventional superconductivity has been focused on materials with strong spin-orbit coupling and unique crystal lattices. Doped bismuth selenide (Bi2Se3) is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb)-doped Bi2Se3. As a result, the in-plane magnetic torque signal vanishes every 60 degrees. More importantly, the superconducting hysteresis loop amplitude is enhanced along one preferred direction, spontaneously breaking the rotational symmetry. This observation indicates the presence of nematic order in the superconducting ground state of Nb-doped Bi2Se3.