# Reversible Modification of Rashba States in Topological Insulators at Room Temperature by Edge Functionalization

## TL;DR

This paper shows how to reversibly control spin textures in topological insulators at room temperature by modifying their edges with Se atoms.

## Contribution

A reversible method to control Rashba states in topological insulators via edge functionalization is demonstrated.

## Key findings

- Se functionalization alters the strength of spin-orbit coupling and Rashba edge states in Bi2Se3.
- Rashba edge states can be switched on and off repeatedly at room temperature through Se functionalization.
- Density functional theory confirms that edge termination changes the electronic structure.

## Abstract

Quantum materials with novel spin textures from strong spin‐orbit coupling (SOC) are essential components for a wide array of proposed spintronic devices. Topological insulators have a necessary strong SOC that imposes a unique spin texture on topological states and Rashba states that arise on the boundary, but there is no established methodology to control the spin texture reversibly. Here, it is demonstrated that functionalizing Bi2Se3 films by altering the step‐edge termination directly changes the strength of SOC and thereby modifies the Rashba strength of 1D edge states. Scanning tunneling microscopy/spectroscopy shows that these Rashba edge states arise and subsequently vanish through the Se functionalization and reduction process of the step edges. The observations are corroborated by density functional theory calculations, which show that a subtle chemical change of edge termination fundamentally alters the underlying electronic structure. Importantly, fully reversible and repeatable switching of Rashba edge states across multiple cycles at room temperature is experimentally demonstrated. The results imply Se functionalization as a practical method to control SOC and spin texture of quantum states in topological insulators.

The Rashba edge states at the step edges of Bi2Se3 display switching behavior, according to the functionalization and defunctionalization of step edges with Se atoms that are achieved by annealing in UHV and Se flux conditions, respectively.