Theory of anisotropic Rashba splitting of surface states

TL;DR

This paper develops a theoretical framework and performs ab initio calculations to demonstrate that Rashba surface state splitting is anisotropic due to bulk state admixture, especially on Au(110) surfaces.

Contribution

It introduces a k.p perturbation theory revealing anisotropic Rashba splitting caused by bulk state mixing, supported by relativistic ab initio calculations.

Findings

Rashba splitting is anisotropic on surfaces with reduced in-plane symmetry.

Bulk state admixture causes the anisotropic Rashba effect.

Large Rashba anisotropy observed on Au(110) surface.

Abstract

We investigate the surface Rashba effect for a surface of reduced in-plane symmetry. Formulating a k.p perturbation theory, we show that the Rashba splitting is anisotropic, in agreement with symmetry-based considerations. We show that the anisotropic Rashba splitting is due to the admixture of bulk states of different symmetry to the surface state, and it cannot be explained within the standard theoretical picture supposing just a normal-to-surface variation of the crystal potential. Performing relativistic ab initio calculations we find a remarkably large Rashba anisotropy for an unreconstructed Au(110) surface that is in the experimentally accessible range.