Spin-Polarized Surface Resonances Accompanying Topological Surface State Formation

TL;DR

This study reveals a previously unidentified spin-polarized surface resonance in Bi2Se3, linked to topological surface states, and demonstrates how these states evolve through a topological phase transition using advanced spectroscopy.

Contribution

It uncovers a new surface resonance associated with topological surface states and shows how trivial Rashba-like states transform into topological states via spin-orbit-induced band inversion.

Findings

Identification of a distinct spin-polarized surface resonance

Evidence of the connection between trivial and topological states

Direct measurement of unoccupied spin-polarized band structure

Abstract

Topological insulators host spin-polarized surface states born out of the energetic inversion of bulk bands driven by the spin-orbit interaction. Here we discover previously unidentified consequences of band-inversion on the surface electronic structure of the topological insulator Bi$_2$Se$_3$. By performing simultaneous spin, time, and angle-resolved photoemission spectroscopy, we map the spin-polarized unoccupied electronic structure and identify a surface resonance which is distinct from the topological surface state, yet shares a similar spin- orbital texture with opposite orientation. Its momentum- dependence and spin texture imply an intimate connection with the topological surface state. Calculations show these two distinct states can emerge from trivial Rashba-like states that change topology through the spin-orbit-induced band inversion. This work thus provides a compelling view of the coevolution of surface states through a topological phase transition, enabled by the unique capability of directly measuring the spin-polarized unoccupied band structure.