# Transport in topological insulators with bulk-surface coupling: Interference corrections and conductance fluctuations

## TL;DR

This paper investigates how bulk-surface coupling in topological insulator thin films affects low-temperature transport, focusing on interference effects and conductance fluctuations to better understand their combined influence.

## Contribution

It provides a theoretical analysis of bulk-surface coupling effects on interference corrections and conductance fluctuations in topological insulators using diagrammatic perturbation theory.

## Key findings

- Bulk-surface coupling modifies interference corrections and conductance fluctuations.
- Simultaneous measurement of WL/WAL and CFs can reveal underlying transport physics.
- Predictions depend on different parameter regimes of the coupled system.

## Abstract

Motivated by the experimental difficulty to produce topological insulators (TIs) of the Bi$_2$Se$_3$ family with pure surface-state conduction, we study the effect that the bulk can have on the low-temperature transport properties of gated thin TI films. In particular, we focus on interference corrections, namely weak localization (WL) or weak-antilocalization (WAL), and conductance fluctuations (CFs) based on an effective low-energy Hamiltonian. Utilizing diagrammatic perturbation theory we first analyze the bulk and the surface separately and subsequently discuss WL/WAL and CFs when a tunneling-coupling is introduced. We identify the relevant soft diffusion modes of the coupled system and use this insight to make simultaneous predictions for both interference corrections and conductance fluctuations in various parameter regimes. The results strongly suggest that the combined measurement of both quantities can provide an improved understanding of the physics underlying the low-temperature transport processes in thin TI films with bulk-surface coupling.