# Low temperature saturation of phase coherence length in topological insulators

## TL;DR

This study investigates the saturation of phase coherence length in topological insulators at low temperatures, revealing the need to identify new dephasing mechanisms affecting quantum coherence in these materials.

## Contribution

It systematically rules out known factors affecting phase coherence, highlighting the necessity to find alternative dephasing sources in topological insulators.

## Key findings

- Phase breaking length saturates below certain temperatures.
- Saturation is consistent across different measurement methods.
- Known dephasing factors are ruled out as causes.

## Abstract

Implementing topological insulators as elementary units in quantum technologies requires a comprehensive understanding of the dephasing mechanisms governing the surface carriers in these materials, which impose a practical limit to the applicability of these materials in such technologies requiring phase coherent transport. To investigate this, we have performed magneto-resistance (MR) and conductance fluctuations\ (CF) measurements in both exfoliated and molecular beam epitaxy grown samples. The phase breaking length ($l_{\phi}$) obtained from MR shows a saturation below sample dependent characteristic temperatures, consistent with that obtained from CF measurements. We have systematically eliminated several factors that may lead to such behavior of $l_{\phi}$ in the context of TIs, such as finite size effect, thermalization, spin-orbit coupling length, spin-flip scattering, and surface-bulk coupling. Our work indicates the need to identify an alternative source of dephasing that dominates at low $T$ in topological insulators, causing saturation in the phase breaking length and time.