Absence of the Rashba Splitting of Au(111) Surface Bands

I N Yakovkin

doi:10.1155/2018/6919031

Abstract

The electronic structure of Au(111) films is studied by means of relativistic DFT calculations. It is found that the twinning of the surface bands, observed in photoemission experiment, does not necessarily correspond to the spin-splitting of the surface states caused by the break of the inversion symmetry at the surface. The twinning of the bands of clean Au(111) films can be obtained within nonrelativistic or scalar-relativistic approximation, so that it is not a result of spin-orbit coupling. However, the spin-orbit coupling does not lead to the spin-splitting of the surface bands. This result is explained by Kramers’ degeneracy, which means that the existence of a surface itself does not destroy the inversion symmetry of the system. The inversion symmetry of the Au(111) film can be broken, for example, by means of adsorption, and a hydrogen monolayer deposited on one face of the film indeed leads to the appearance of the spin-splitting of the bands.

Highlights

The twin surface bands of Au(111) with a parabolic dispersion, pertinent to nearly free electrons, were found in angle-resolved photoemission study by LaShell et al [1] and explained as a result of the spin-splitting caused by spinorbit coupling (SOC)
The theory of the Rashba effect [6] is based on the model of a 2D electron gas, which might be applicable for true surface states in semiconductor heterostructures, but obviously not for surface resonances in metals
Results of present calculations of the band structures of Au(111) films lead to conclusion that the twinning of the surface bands, observed in photoemission experiment, does not necessarily correspond to the spin-splitting of the surface states caused by the break of the inversion symmetry at the surface

Summary

Introduction

The twin surface bands of Au(111) with a parabolic dispersion, pertinent to nearly free electrons, were found in angle-resolved photoemission study by LaShell et al [1] and explained as a result of the spin-splitting caused by spinorbit coupling (SOC). The surface bands (marked red in Figure 1) appear in a doublet form already in scalar calculations, which means that the splitting seen in Figure 1(a) stems not from spin-orbit coupling but is a result of possible interaction of electrons in the surface states of the terminating surfaces, as it was suggested in [14].

Results

Conclusion