Giant Anisotropy of Spin-Orbit Splitting at the Bismuth Surface

TL;DR

This study reveals a giant anisotropy in spin-orbit splitting at the bismuth (111) surface, driven by out-of-plane buckling, challenging simple Rashba models and confirmed by first-principles calculations.

Contribution

It demonstrates the significant anisotropy of spin-orbit splitting on bismuth surfaces and highlights the limitations of Rashba-like models, supported by experimental and theoretical analysis.

Findings

Giant anisotropy of spin-orbit splitting observed

Deviations from Rashba-like coupling identified

First-principles calculations match experimental dispersion

Abstract

We investigate the bismuth (111) surface by means of time and angle resolved photoelectron spectroscopy. The parallel detection of the surface states below and above the Fermi level reveals a giant anisotropy of the Spin-Orbit (SO) spitting. These strong deviations from the Rashba-like coupling cannot be treated in $\textbf{k}\cdot \textbf{p}$ perturbation theory. Instead, first principle calculations could accurately reproduce the experimental dispersion of the electronic states. Our analysis shows that the giant anisotropy of the SO splitting is due to a large out-of plane buckling of the spin and orbital texture.