Weak Localization Effects as Evidence for Bulk Quantization in Thin Films Bi2Se3

TL;DR

This study demonstrates that in ultra-thin Bi2Se3 films, the emergence of negative magnetoresistance due to weak localization confirms bulk quantization in the 2D quantum limit, revealing distinct scattering mechanisms.

Contribution

It provides experimental evidence for bulk quantization in thin topological insulator films through weak localization effects in magnetoresistance measurements.

Findings

Negative magnetoresistance feature appears in ultra-thin Bi2Se3 films.

Weak localization observed in quantized bulk channels.

Different scattering mechanisms identified in bulk vs surface states.

Abstract

Strong spin-orbit coupling in topological insulators results in the ubiquitously observed weak antilocalization feature in their magnetoresistance. Here we present magnetoresistance measurements in ultra thin films of the topological insulator Bi_2Se_3, and show that in the 2D quantum limit, in which the topological insulator bulk becomes quantized, an additional negative magnetoresistance feature appears. Detailed analysis associates this feature with weak localization of the quantized bulk channels, providing thus evidence for this quantization. Examination of the dephasing fields at different temperatures indicates different scattering mechanism in the bulk vs the surface states.