Three-Dimensional Spin Rotations at the Fermi Surface of a Strongly Spin-Orbit Coupled Surface System

TL;DR

This study uncovers complex three-dimensional spin textures on a strongly spin-orbit coupled surface, revealing spin rotations and anisotropies that challenge conventional models and highlight the interplay of Rashba and Dresselhaus effects.

Contribution

It provides the first detailed experimental and theoretical analysis of three-dimensional spin textures on a (root3 x root3)-Au/Ge(111) surface, demonstrating effects beyond the Rashba model.

Findings

Significant spin splitting due to spin-orbit interactions.

Observation of out-of-plane and in-plane spin components with complex patterns.

Revelation of spin textures influenced by crystalline anisotropies.

Abstract

The spin texture of the metallic two-dimensional electron system (root3 x root3)-Au/Ge(111) is revealed by fully three-dimensional spin-resolved photoemission, as well as by density functional calculations. The large hexagonal Fermi surface, generated by the Au atoms, shows a significant splitting due to spin-orbit interactions. The planar components of the spin exhibit helical character, accompanied by a strong out-of-plane spin component with alternating signs along the six Fermi surface sections. Moreover, in-plane spin rotations towards a radial direction are observed close to the hexagon corners. Such a threefold-symmetric spin pattern is not described by the conventional Rashba model. Instead, it reveals an interplay with Dresselhaus-like spin-orbit effects as a result of the crystalline anisotropies.