Observation of planar Hall effect in topological insulator—Bi2Te3

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 surface states play a critical role and are of utmost importance in TIs, our present study in Bi2Te3 thin films reflects the need for considering the bulk conduction in understanding the origin of PHE in TIs. This necessity emerges from our observation of an unconventional increase in the PHE signal with TI thickness and temperature where the bulk effect takes over. Here, we find an enhancement in the PHE amplitude by doubling the Bi2Te3 film-thickness on the Si (111) substrate—from ≈ 1.9 nΩ m in 14 quintuple layer (QL) to ≈ 3.1 nΩ m in 30 QL devices at B = 5 T. Also, the PHE amplitude in the 30 QL Bi2Te3 films grown on two different substrates, viz., Si (111) and Al2O3 (0001), shows an increase with temperature. Our experiments indicate that the contribution of bulk states to PHE in TIs could be significant.