Unoccupied topological surface state in Bi$_{2}$Te$_{2}$Se

TL;DR

This study reveals that the topological surface state in Bi$_{2}$Te$_{2}$Se persists at high energies beyond the Dirac point, exhibiting spin-selective scattering due to warping effects, which is crucial for spintronic applications.

Contribution

It demonstrates the persistence of topological surface states at high unoccupied energies and their spin-selective scattering, advancing understanding of spin and charge dynamics in topological insulators.

Findings

Topological surface state persists beyond the Dirac point into unoccupied energies.

Strong warping causes spin-selective scattering of surface states.

Implications for designing opto-spintronic devices.

Abstract

Bias voltage dependent scattering of the topological surface state is studied by scanning tunneling microscopy/spectroscopy for a clean surface of the topological insulator Bi$_2$Te$_2$Se. A strong warping of constant energy contours in the unoccupied part of the spectrum is found to lead to a spin-selective scattering. The topological surface state persists to higher energies in the unoccupied range far beyond the Dirac point, where it coexists with the bulk conduction band. This finding sheds light on the spin and charge dynamics over the wide energy range and opens a way to designing opto-spintronic devices.