Cook Ashley M
Department of Physics, University of California, Berkeley, CA 94720, United States of America.
Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany.
J Phys Condens Matter. 2023 Mar 9;35(18). doi: 10.1088/1361-648X/acbffd.
We introduce topological phases of matter defined by skyrmions in the ground state spin-or pseudospin-expectation value textures in the Brillouin zone, the chiral and helical topological skyrmion phases of matter. These phases are protected by a symmetry present in centrosymmetric superconductors. We consider a tight-binding model for spin-triplet superconductivity in transition metal oxides and find it realizes each of these topological skyrmion phases. The chiral phase is furthermore realized for a parameter set characterizing SrRuOwith spin-triplet superconductivity. We also find two types of topological phase transitions by which the skyrmion number can change. The second type occurs without the closing of energy gaps in a system described by a quadratic Hamiltonian without breaking the protecting symmetries when atomic spin-orbit coupling is non-negligible and there is a suitable additional degree of freedom. This contradicts the 'flat band' limit assumption important in use of entanglement spectrum and Wilson loops, and in construction of the ten-fold way classification scheme of topological phases of matter. We furthermore predict two kinds of bulk-boundary correspondence signatures-one for measurements which execute a partial trace over degrees of freedom other than spin, which yields quantized transport signatures-and a second resulting from skyrmions trapping defects with their own non-trivial topology that is discussed in a second work, which yields generalizations of unpaired Majorana zero-modes.
我们介绍了由布里渊区基态自旋或赝自旋期望值纹理中的斯格明子所定义的物质拓扑相，即手性和螺旋拓扑斯格明子物质相。这些相由中心对称超导体中存在的一种对称性保护。我们考虑了过渡金属氧化物中自旋三重态超导的紧束缚模型，并发现它实现了这些拓扑斯格明子相中的每一种。此外，对于具有自旋三重态超导特性的SrRuO的一组参数，实现了手性相。我们还发现了两种拓扑相变，通过它们斯格明子数可以改变。第二种类型发生在由二次哈密顿量描述的系统中，在不破坏保护对称性的情况下能隙不闭合，此时原子自旋轨道耦合不可忽略且存在合适的附加自由度。这与在使用纠缠谱和威尔逊圈以及构建物质拓扑相的十重方式分类方案中重要的“平带”极限假设相矛盾。此外，我们预测了两种体-边界对应特征——一种用于对自旋以外的自由度进行部分求迹的测量，这会产生量子化的输运特征；另一种是由斯格明子捕获具有自身非平凡拓扑结构的缺陷导致的，这在第二篇论文中进行了讨论，它产生了未配对马约拉纳零模的推广。
