自旋轨道耦合Su-Schrieffer-Heeger原子链系统的电子输运特性

在Su-Schrieffer-Heeger (SSH)原子链中,电子在胞内和胞间的跳跃依赖于其自旋时,即SSH原子链存在自旋轨道耦合作用时,存在不同缠绕数的非平庸拓扑边缘态.如何探测自旋轨道耦合SSH原子链不同缠绕数的边缘态是一个重要问题.本文在紧束缚近似下研究了自旋轨道耦合SSH原子链的非平庸拓扑边缘态性质及其零能附近的电子输运特性.研究发现四重和二重简并边缘态的缠绕数分别为2和1;并且仅当源极入射电子的自旋被极化(铁磁电极)时,自旋轨道耦合SSH原子链在零能附近的电子输运特性才能反映其边缘态的能谱特性.尤其是,随着自旋轨道耦合SSH原子链与左、右导线之间的耦合强度由弱到强改变,对于缠绕数为2的四重简并边缘态,入射电子在零能附近的透射峰数目将从4个变为0;而对于缠绕数为1的二重简并边缘态情形,其透射峰数目将从2个变为0.因此,在源极为铁磁电极的情形下,通过观察自旋轨道耦合SSH原子链在零能附近电子共振透射峰的数目随着其与左、右导线之间耦合强度的变化,来探测其不同缠绕数的边缘态.上述结果为基于电子输运特性探测自旋轨道耦合SSH原子链不同拓扑性质的边缘态提供了一种可选择的理论方案.

Electron transport through Su-Schrieffer-Heeger chain with spin-orbit coupling

In the Su-Schrieffer-Heeger(SSH)chain,the nontrivial topological edge states will have different winding numbers when the intra-cell and inter-cell hopping amplitudes are spin-dependent ones.Consequently,how to detect the edge states with different winding numbers theoretically and experimentally has become one of important topics in condensed matter physics.In this paper,in the framework of the tight-binding approximation,we study the topological properties and the electron transport properties of the edge states of the SSH chain with the spin-orbit coupling.It is demonstrated that the winding numbers of the quadrupledegenerate and twofold-degenerate edge states are two and one,respectively.Importantly,the electron transport properties in the vicinity of the zero energy can characterize the energy spectra of the edge states,when the spin-polarized electrons tunnel into the SSH chain from the source lead,namely,the source lead is a ferromagnetic one.With increasing the tunneling coupling strengths between the SSH chain and the two leads from the weak coupling regime to the strong coupling one,the number of transmission resonance peaks of the quadruple-degenerate with the winding numbers being two and twofold-degenerate edge states with the winding numbers being one will be reduced by four and two,respectively.In other words,the transmission resonance peaks related to the edge states will disappear when the SSH chain is strongly coupled to the two leads.Therefore,these results suggest an alternative way of detecting the nontrivial topological ones with different winding numbers by changing the number of transmission resonance peaks of edge states.