Journal Article

Spatial aspects of spin polarization of structurally split surface states in thin films with magnetic exchange and spin–orbit interaction

Nechaev, I A, Krasovskii, E E

2022

Overview

A theoretical study is presented of the effect of an in-plane magnetic exchange field on the band structure of centrosymmetric films of noble metals and topological insulators. Based on an ab initio relativistic k ⋅ p theory, a minimal effective model is developed that describes two coupled copies of a Rashba or Dirac electronic system residing at the opposite surfaces of the film. The coupling leads to a structural gap at Γ ¯ and causes an exotic redistribution of the spin density in the film when the exchange field is introduced. We apply the model to a nineteen-layer Au(111) film and to a five-quintuple-layer Sb 2 Te 3 film. We demonstrate that at each film surface the exchange field induces spectrum distortions similar to those known for Rashba or Dirac surface states with an important difference due to the coupling: at some energies, one branch of the state loses its counterpart with the oppositely directed group velocity. This suggests that a large-angle electron scattering between the film surfaces through the interior of the film is dominant or even the only possible for such energies. The spin-density redistribution accompanying the loss of the counterpart favors this scattering channel.

• Publisher: IOP Publishing
• Subject: Coupling / Density / Electromagnetism / Electronic systems / Exchanging / Group velocity / k ⋅ p method / magnetic exchange interaction / method / Noble metals / Polarization (spin alignment) / Relativistic theory / Scattering / spin-momentum locking / Spin-orbit interactions / spin–orbit interaction / Thin films / Topological insulators