Higher-order contributions to the Rashba-Bychkov effect with application to Bi/Ag(111) surface alloy

TL;DR

This paper develops a theoretical framework using k.p perturbation theory to explain the anisotropic Rashba-Bychkov effect in metallic surface states, supported by ab initio calculations on Bi/Ag(111).

Contribution

It introduces third-order effective Rashba Hamiltonians and provides a group-theoretical analysis to explain anisotropic spin splitting in surface alloys.

Findings

Evidence of third-order Rashba terms in Bi/Ag(111) surface alloy

Derived expressions for third-order Rashba parameters

Qualitative explanation for differences between Au(111) and Bi/Ag(111) surface states

Abstract

In order to explain the anisotropic Rashba-Bychkov effect observed in several metallic surface-state systems, we use k.p perturbation theory with a simple group-theoretical analysis and construct effective Rashba Hamiltonians for different point groups up to third order in the wavenumber. We perform relativistic ab initio calculations for the Bi/Ag(111) ordered surface alloy and from the calculated splitting of the band dispersion we find evidence of the predicted third-order terms. Furthermore, we derive expressions for the corresponding third-order Rashba parameters to provide a simple explanation to the qualitative difference concerning the Rashba-Bychkov splitting of the surface states at Au(111) and Bi/Ag(111).