One-dimensional spin texture of Bi(441); Quantum Spin Hall properties without a topological insulator

TL;DR

This study investigates the Bi(441) surface revealing one-dimensional spin textures with Quantum Spin Hall-like properties, achieved without a topological insulator, through STM and spin-resolved ARPES measurements.

Contribution

It demonstrates that Bi(441) exhibits topological insulator-like surface states with spin-momentum locking, despite not being a topological insulator.

Findings

Observation of linearly dispersing surface states with Dirac-like crossings

Strong in-plane and out-of-plane spin polarization detected

Surface states support spin-charge transport with suppressed backscattering

Abstract

The high index (441) surface of bismuth has been studied using Scanning Tunnelling Microscopy (STM), Angle Resolved Photoemission Spectroscopy (APRES) and spin-resolved ARPES. The surface is strongly corrugated, exposing a regular array of (110)-like terraces. Two surface localised states are observed, both of which are linearly dispersing in one in-plane direction ($k_x$), and dispersionless in the orthogonal in-plane direction ($k_y$), and both of which have a Dirac-like crossing at $k_x$=0. Spin ARPES reveals a strong in-plane polarisation, consistent with Rashba-like spin-orbit coupling. One state has a strong out-of-plane spin component, which matches with the miscut angle, suggesting its {possible} origin as an edge-state. The electronic structure of Bi(441) has significant similarities with topological insulator surface states and is expected to support one dimensional Quantum Spin Hall-like coupled spin-charge transport properties with inhibited backscattering, without requiring a topological insulator bulk.