报告题目：Quantized transport signature for second-order topological insulators
报告摘要Topological phases have corresponding signatures in various spatial domains. For instance, Chern insulator is characterized by Chern number in bulk systems; when it is confined with boundaries, spinless edge states emerges; transport measurements show quantized Hall conductance for open systems. Such a bulk-boundary-transport correspondence is also valid for topological insulators (TI, or quantum spin Hall effect), which is manifested by Z2 invariance, helical edge states, and quantized spin Hall conductance. For higher-order topological insulators (HOTI), the bulk-boundary correspondence has been well established, but quantized transport signature is still absent. We demonstrate that, for a second-order TI induced by applying an in-plane magnetic field in the Z2 invariant first-order TI, integer spin quanta are pumped out per cycle when this magnetic field is rotating, giving rise to quantized spin transport. Numerical results show that for finite systems the onset of quantized spin current corresponds to the formation of topological corner states labeling 2nd-order TI, suggesting that the quantized spin pump can serve as the quantized transport signature for HOTI that evolved from Z2 invariant first-order TI. The quantized spin current has been verified in different model systems including various versions of BHZ and Kane-Mele models, which is shown as a universal feature and robust against disorders.
报告人简介：许富明，深圳大学物理与光电工程学院副教授，博士生导师。2011年于香港大学获得博士学位，2011年至2014年在香港大学物理系从事博士后研究工作，2014年入职深圳大学。主要从事纳米结构和介观系统量子输运特性的理论研究，包括拓扑物态的输运特性和无序系统的普适性统计规律等。在Phys. Rev. B、New J. Phys.等物理学期刊发表论文30余篇。