利用第一原理計算模擬研究在巨大Rashba半導體溴碲化鉍上的準粒子干涉

Abstract

碲鉍⻧化物 (bismuth tellurohalides) 是擁有巨大 Rashba 效應的半導體,存在於 其帶有相反極性的兩端面中,帶有的自旋-動量垂直關係 (spin-momentum locked) 的載子,有應用在自旋電子學裝置的潛力。我們使用密度泛函方法,研究溴碲化 鉍的碲端面的晶格結構、表面電子組態。並且,藉由討論在倒空間等能量電子 組態分佈 (constant energy contours) 所有可能的態轉換,我們模擬出準粒子干涉 (quasiparticle interference) 條紋。結合狀態密度 (joint density of states) 和自旋散 射機率 (spin scattering probability) 分別是沒有考慮、有考慮自旋版本的準粒子干 涉。最後,比較模擬和實驗的準粒子干涉條紋,發現自旋不守恆的反向散射,不 存在於溴碲化鉍的碲端面上。

Bismuth Tellurohalides are semiconductors with a giant Rashba e ect. They have two oppositely polarised surfaces with two-dimensional spin-momentum locked he- lical charge carriers, which are good candidates to achieve the goal of spin control in novel spintronic devices. Within the framework of density functional theory, we study the band structure of the Te-termination of ordered phase bismuth telluro- bromide, BiTeBr. Considering all the possible parings of initial and nal states in the constant energy contours (CEC), we further simulate the quasiparticle interfer- ence (QPI) patterns. By excluding or including the helical spin texture, there are actually two versions of simulated QPI patterns, joint density of states (JDOS) and spin scattering probability (SSP). Finally, we compare the simulated phenomena with measured tunnelling spectro-microscopy maps. We show that backscattering with opposite spin is absent in this system.