Weak antilocalization in (111) thin films of a topological crystalline insulator SnTe

TL;DR

This study investigates weak antilocalization effects in (111) thin films of SnTe, a topological crystalline insulator, revealing surface state contributions and coupling to bulk states through magnetoresistance measurements.

Contribution

First observation of weak antilocalization in SnTe (111) thin films, demonstrating surface state effects and coupling to bulk states via magnetoresistance analysis.

Findings

Positive magnetoresistance indicates surface state weak antilocalization.

Negative magnetoresistance suggests bulk state weak localization.

Coupling between surface and bulk states inferred from prefactor analysis.

Abstract

We grew single-crystal thin films of a topological crystalline insulator (TCI) SnTe with a smooth surface at the atomic scale by molecular beam epitaxy (MBE). In the magnetoresistance (MR) measurement, we observed both positive and negative components near zero magnetic field at lowest temperatures of 2 - 3 K, while we observed only a negative MR at elevated temperatures of 6 - 10 K. The positive MR is attributed to the weak antilocalization (WAL) in the transport through the topological surface state (SS), demonstrating $\pi$ berry phase which is essential to the topological SS, while the negative MR to the weak localization (WL) in the transport through the bulk state (two-dimensional bulk subbbands). The absolute value of the prefactor $ \alpha $ deduced from the fitting of the observed positive MR to the Hikami-Larkin-Nagaoka equation was much smaller than expected from the number of transport channel of the SS, suggesting the coupling of the SS to the bulk state.