Theoretical study of X-ray absorption of three-dimensional topological insulator $\mathrm{Bi}_2\mathrm{Se}_3$

TL;DR

This paper theoretically investigates the X-ray absorption edge singularity in the topological insulator Bi2Se3, deriving and solving a generalized integral equation that accounts for spin texture effects on the singularity.

Contribution

It introduces a generalized integral equation for X-ray edge singularity in topological insulators, incorporating spin texture effects, which is a novel theoretical development.

Findings

Spin texture influences the singularity component.

A component without excitonic singularity is identified.

The integral equation is successfully derived and solved.

Abstract

X-ray absorption edge singularity which is usually relevant for metals is studied for the prototype topological insulator $\mathrm{Bi}_2\mathrm{Se}_3$. The generalized integral equation of Nozi\`eres and Dominicis type for X-ray edge singularity is derived and solved. The spin texture of surfaces states causes a component of singularity dependent on the helicity of the spin texture. It also yields another component for which the singularity from excitonic processes is absent.