Observation of Planar Hall Effect in Topological Insulator -- Bi$_2$Te$_3$

TL;DR

This study demonstrates that bulk conduction significantly influences the planar Hall effect in topological insulators, with PHE amplitude increasing with film thickness and temperature, highlighting the importance of bulk states alongside surface states.

Contribution

It reveals the role of bulk conduction in PHE in topological insulators and shows that increasing film thickness enhances PHE amplitude, which was previously underestimated.

Findings

PHE amplitude triples with doubled film thickness.

PHE amplitude increases with temperature in Bi2Te3 films.

Bulk states contribute significantly to PHE in TIs.

Abstract

Planar Hall effect (PHE) in topological insulators (TIs) is discussed as an effect that stems mostly from conduction due to topologically protected surface states. Although surfaces states play a critical role and are of utmost importance in TIs, our present study reflects the need for considering the bulk conduction in understanding PHE in TIs. Here, we demonstrate an enhancement in PHE amplitude by three times by doubling the thickness of Bi$_2$Te$_3$ film on Si (111). The PHE amplitude reaches $\approx$~6 n$\Omega$m in 30 quintuple layer (QL) device as compared to $\approx$~2 n$\Omega$m in 14 QL. We find that the PHE amplitude increases with temperature in the 30 QL Bi$_2$Te$_3$ films grown on Si (111) and Al$_2$O$_3$ (0001). Our experiments indicate that the contribution of bulk states to PHE in TIs could be significant.