Enhanced electron dephasing in three-dimensional topological insulators

TL;DR

This study investigates electron dephasing mechanisms in 3D topological insulators, revealing a transition from electron-electron interaction-dominated dephasing to enhanced dephasing due to coupling with bulk charge puddles.

Contribution

It provides new insights into the dephasing mechanisms in 3D TIs, especially the role of surface-bulk coupling, using weak antilocalization measurements.

Findings

Dephasing rate shifts from linear to sublinear temperature dependence.

Enhanced low-temperature dephasing linked to surface-bulk coupling.

Dephasing mechanisms differ between bulk and surface-dominant regimes.

Abstract

Study of the dephasing in electronic systems is not only important for probing the nature of their ground states, but also crucial to harnessing the quantum coherence for information processing. In contrast to well-studied conventional metals and semiconductors, it remains unclear which mechanism is mainly responsible for electron dephasing in three-dimensional (3D) topological insulators (TIs). Here, we report on using weak antilocalization effect to measure the dephasing rates in highly tunable (Bi,Sb)$_2$Te$_3$ thin films. As the transport is varied from a bulk-conducting regime to surface-dominant transport, the dephasing rate is observed to evolve from a linear temperature dependence to a sublinear power-law dependence. While the former is consistent with the Nyquist electron-electron interactions commonly seen in ordinary 2D systems, the latter leads to enhanced electron dephasing at low temperatures and is attributed to the coupling between the surface states and the localized charge puddles in the bulk of 3D TIs.