Signature of surface state coupling in thin films of the topological Kondo insulator SmB$_6$ from anisotropic magnetoresistance

TL;DR

This study investigates how the anisotropic magnetoresistance in SmB$_6$ thin films varies with temperature and thickness, revealing a sign change linked to surface and bulk state interactions in topological Kondo insulators.

Contribution

It provides the first detailed analysis of AMR sign change in SmB$_6$ thin films, highlighting surface-bulk coupling effects in topological Kondo insulators.

Findings

AMR sign changes from negative to positive with decreasing temperature

The sign change temperature T$_s$ decreases with increasing film thickness

T$_s$ vanishes for films thicker than 30 nm

Abstract

The temperature and thickness dependencies of the in-plane anisotropic magnetoresistance (AMR) of SmB$_6$ thin films are reported. We find that the AMR changes sign from negative ($\rho_{||}<\rho_{\perp}$) at high temperatures to positive ($\rho_{||}>\rho_{\perp}$) at low temperatures. The temperature, T$_s$, at which this sign change occurs, decreases with increasing film thickness $t$ and T$_s$ vanishes for $t$ $>$ 30 nm. We interpret our results in the framework of a competition between two components: a negative bulk contribution and a positive surface AMR.