Multi-channel conduction in electron transport dynamics of three dimensional topological insulators

Three-dimensional topological insulators (3D TIs) have been the subject of extensive research, primarily emphasizing their surface and bulk properties. Surface state transport is highly sought after due to its spin-momentum locking; however, in real systems, mixing between surface and bulk states often occurs because of defect states present in the bulk band gap. In this study, we provide a detailed electronic characterization of the 3D TI BiSbTeSe₂(BSTS), which exhibits pronounced surface transport effects. We observe a connection between the nonlinear Hall (NLH) effect at first order and quantum coherent transport, as evidenced by weak anti-localization. Our results show that NLH is a more sensitive technique to multi-channel transport in 3D TIs, thereby clearly distinguishing the temperature regime over which bulk and surface states dominate the transport dynamics. Additionally, we investigate the influence of magnetic impurities within the crystal structure on this phenomenon. Our study systematically elucidates the significance of multichannel transport, which is essential to understand the transport properties in presence of an external magnetic field.