Electron-phonon Coupling on the Surface of the Topological Insulator Bi2Se3: Determined from Surface Phonon Dispersion Measurements

TL;DR

This study measures the electron-phonon coupling on the surface of Bi2Se3 topological insulator using inelastic helium atom scattering, revealing a stronger coupling constant than previous ARPES-based estimates.

Contribution

It introduces a novel phonon-based approach to quantify electron-phonon coupling on topological insulator surfaces, complementing existing ARPES methods.

Findings

Electron-phonon coupling constant of 0.43 for Bi2Se3 surface phonons.

First phonon perspective measurement of this coupling in topological insulators.

Stronger coupling observed compared to ARPES-based estimates.

Abstract

In this letter we report measurements of the coupling between Dirac fermion quasiparticles (DFQs) and phonons on the (001) surface of the strong topological insulator Bi2Se3. While most contemporary investigations of this coupling have involved examining the temperature dependence of the DFQ self-energy via angle-resolved photoemission spectroscopy (ARPES) measurements, we employ inelastic helium atom scattering to explore, for the first time, this coupling from the phonon perspective. Using a Hilbert transform, we are able to obtain the imaginary part of the phonon self-energy associated with a dispersive surface phonon branch identified in our previous work [1] as having strong interactions with the DFQs. From this imaginary part of the self-energy we obtain a branch-specific electron-phonon coupling constant of 0.43, which is stronger than the values reported form the ARPES measurements.