自旋简并节线半金属中表面态诱导的自旋相关散射

Spin-dependent scattering induced by surface states in spin-degenerate nodal-line semimetal

拓扑节线半金属指的是电子的导带和价带在倒空间相交于一维的环或者线,其体能带拓扑体现在节线携带π的贝里相位.根据体边对应原理,在系统边界存在色散较弱的表面态,由节线在表面布里渊区的投影所包围,称为鼓面态.大部分节线半金属中,自旋-轨道耦合效应较弱,因此在单粒子图像下表面态不存在自旋构型.与此同时,鼓面态特有的弱散射也使得其中的电子间相互作用效应变得显著,并诱发铁磁失稳使得自旋简并的表面态发生自旋劈裂.本文考虑自旋简并的节线半金属中铁磁表面态导致的自旋相关散射,发现自旋劈裂的两个鼓面态均会导致共振的自旋翻转反射,该物理过程体现为自旋电导谱中的双峰结构.具体地,分别用散射矩阵和格林函数理论处理了普通金属和节线半金属异质结中表面态导致的散射问题,得到一致的结论.本文的工作指出了自旋简并节线半金属表面态依旧可以导致自旋相关输运,这为其输运探测和在自旋电子中的应用提供了新的思路.

The topological nodal-line semimetal is characterized by the conduction band and valence band of electrons crossing along a one-dimensional line or closed loop in reciprocal space,with each nodal line carrying P Berry phase.According to bulk-boundary correspondence,there exist drumheadlike surface states with weak dispersion at the boundary of system,surrounded by the projection of nodal loops onto the surface Brillouin zone.In most of nodal-line semimetals,the spin orbit coupling effect is weak,leading to the absence of a spin configuration for surface states under the single-particle picture.However,the featured weak dispersion of drumheadlike surface states enhances the electron-electron interaction effect,which triggers out ferromagnetic instability and causes spin splitting in the surface state.In this work,spin-dependent scattering caused by ferromagnetic surface states in spin-degenerate nodal-line semimetals is considered.It is found that both spinsplitting drumheadlike surface states can lead to resonant spin-flipped reflection.This physical process is reflected in a double-peak structure in the spin conductance spectrum.Specifically,we deal with the scattering problem induced by surface states in normal metal and nodal-line semimetal heterojunctions by using the scattering matrix and the Green’s functions theory,respectively,and obtain consistent conclusions.The result points out that spin-degenerate nodal-line semimetal surface states can still lead to spin-dependent transport,which provides a new perspective for the detection and potential application of spintronics in nodal-line semimetals.