Bulk-surface coupling in dual topological insulator Bi₁Te₁ and Sb-doped Bi₁Te₁ single crystals via electron-phonon interaction

Abstract

Recently, Bi1Te1 has been proved to be a dual topological insulator (TI), a new subclass of symmetry protected topological phases and predicted to be higher order topological insulator (HOTI). Being a dual TI, Bi1Te1is said to host quasi-1D surface states (SS) due to weak TI phase and topological crystalline insulating (TCI) surface states at the same time. On the other hand, HOTI supports topologically protected hinge states. So, Bi1Te1 is a unique platform to study the electrical signature of topological SS of fundamentally different origins. Though there is report of magneto-transport measurements on large scale Bi1Te1thin film, the Bi1Te1 single crystal is not studied experimentally till date. Even doping effect in a dual TI Bi1Te1 is missing in literature. In this regard, we performed the perpendicular and parallel field magneto-transport measurement on the exfoliated microflake of Bi1Te1 and Sb-doped Bi1Te1 single crystals, grown by modified Bridgmann method. Our metallic sample shows the weak anti-localization behavior analyzed by multi-channel Hikami-Larkin-Nagaoka equation. We observed the presence of a pair of decoupled topological surface states. Further, we extracted the dephasing index (β) from temperature (T)-dependence of phase coherence length (Lφ), following the power law equation (Lφ / ∝T−β). The thickness dependent value of p indicates the transition in dephasing mechanism from electron-electron to electron-phonon interaction with increase in thickness, indicating the enhancement in the strength of bulk-surface coupling.

Inversion Symmetry Breaking in the Probability Density by Surface‐Bulk Hybridization in Topological Insulators

“…In contrast, we are here focusing on its possible consequences on the resulting probability density distribution. We found that under certain configurations, when the surface and bulk spin polarizations in the hybrid state are parallel, it may display an asymmetric probability density distribution, a theoretical result not previously reported in the literature, [ 10–13,22,30 ] even though the importance of spin polarization for the emergence of the surface state was already recognized by first‐principles calculations in slab geometries. [ 25 ]…”

“…In this study, we are not delving into the detailed microscopic mechanism leading to the surface-bulk hybridization, which has been argued to be triggered, for instance, by disorder effects, [10][11][12][13]30] or analyzed by means of a Fano model with a phenomenological coupling constant [22] in previous works. In contrast, we are here focusing on its possible consequences on the resulting probability density distribution.…”

“…[8,9] Furthermore, there is evidence suggesting the existence of residual bulk carriers that couple with surface states through disorder. [10][11][12][13] On the other hand, it has been observed that charge carriers in TI nanostructures consist of both surface and bulk electronic states. [14][15][16][17][18] These studies point to the hybridization and interaction between topologically trivial and DOI: 10.1002/andp.202300398 non-trivial states.…”