In-depth Analysis of Anisotropic Magnetoconductance in Bi$_2$Se$_3$ thin films with electron-electron interaction corrections

TL;DR

This study systematically analyzes magnetoconductance in Bi$_2$Se$_3$ thin films, separating surface and bulk contributions, and highlights the importance of electron-electron interactions and anisotropic effects in topological insulators.

Contribution

It provides a comprehensive method to distinguish surface and bulk contributions in magnetoconductance, including electron-electron interactions, in topological insulator films.

Findings

Weak localization from bulk states coexists with weak anti-localization from surface states.

Electron-electron interactions significantly affect magnetoconductance measurements.

Bulk disorder influences the decoupling of top and bottom surface states.

Abstract

A combination of out-of-plane and in-plane magnetoconductance (MC) study in topological insulators (TI) is often used as an experimental technique to probe weak anti-localization (WAL) response of the topological surface states (TSSs). However, in addition to the above WAL response, weak localization (WL) contribution from conducting bulk states are also known to coexist and contribute to the overall MC; a study that has so far received limited attention. In this article, we accurately extract the above WL contribution by systematically analyzing the temperature and magnetic field dependency of conductivity in Bi$_2$Se$_3$ films. For accurate analysis, we quantify the contribution of electron-electron interactions to the measured MC which is often ignored in recent WAL studies. Moreover, we show that the WAL effect arising from the TSSs with finite penetration depth, for out-of-plane and in-plane magnetic field can together explain the anisotropic magnetoconductance (AMC) and, thus, the investigated AMC study can serve as a useful technique to probe the parameters like phase coherence length and penetration depth that characterise the TSSs in 3D TIs. We also demonstrate that increase in bulk-disorder, achieved by growing the films on amorphous SiO$_2$ substrate rather than on crystalline Al$_2$O$_3$(0001), can lead to stronger decoupling between the top and bottom surface states of the film.