Planar Hall effect from the surface of topological insulators

Abstract

A prominent feature of topological insulators (TIs) is the surface states comprising of spin-nondegenerate massless Dirac fermions. Recent technical advances have made it possible to address the surface transport properties of TI thin films by tuning the Fermi levels of both top and bottom surfaces. Here we report our discovery of a novel planar Hall effect (PHE) from the TI surface, which results from a hitherto-unknown resistivity anisotropy induced by an in-plane magnetic field. This effect is observed in dual-gated devices of bulk-insulating Bi2−xSbxTe3 thin films, where the field-induced anisotropy presents a strong dependence on the gate voltage with a characteristic two-peak structure near the Dirac point. The origin of PHE is the peculiar time-reversal-breaking effect of an in-plane magnetic field, which anisotropically lifts the protection of surface Dirac fermions from backscattering. The observed PHE provides a useful tool to analyze and manipulate the topological protection of the TI surface.

Tunable Coupling between Surface States of a Three-Dimensional Topological Insulator in the Quantum Hall Regime

“…The diagonal feature of the Rxx maximum is a result of the strong capacitive coupling between the top and bottom surfaces, as observed in similar compounds [18,19].…”

“…Fine control of chemical potentials of the top and bottom surface states has been central to research in 3D TIs [6][7][8][9][10][11][12][13][14]. Dual electrostatic gating is an effective method as it provides an additional degree of tuning on both surfaces than a single-gate configuration [15][16][17][18][19]. Independent gate control of the decoupled top and bottom surface states in the quantum Hall regimes has been reported [15,16].…”

“…However, the study of the QHE in capacitively-coupled surface states, which serves as the starting point for intriguing quantum states such as topological exciton condensates [20,21], is still lacking. Several groups have demonstrated dual-gate control of the bulk insulating Bi2-xSbxTe3-ySey-based 3D TI in weak and moderate surface-state coupling [17][18][19]; however, the quality of those devices prevented the observation of QH states.…”

Ferromagnetic phase transition in topological crystalline insulator thin films: Interplay of anomalous Hall angle and magnetic anisotropy

“…As evidenced in Fig. 4(a), for the H ⊥ orientation, ∆σ of the reference SnTe layer presents around zero magnetic field an upward cusp: a fingerprint of weak antilocalization (WAL) due to the topological surface states (TSS) stabilized by the M symmetry in rocksalt SnTe(111) [48,50,75]. The WAL in the pristine SnTe layer points at the presence of massless DFs in the TSS at the (111) surface.…”

Tuning Insulator-Semimetal Transitions in 3D Topological Insulator thin Films by Intersurface Hybridization and In-Plane Magnetic Fields

“…Such a crossover of 3D TIs to the two-dimensional (2D) limit, as well as their response to magnetic fields, is little explored by electronic transport measurements in 3D TI materials with no bulk conduction and surface-dominant transport (such as BSTS). Previous in-plane magneto-transport studies in 3D TIs often suffer from their residual bulk conduction [16,17] and few have been reported in the hybridization regime [18][19][20].Our experiment is based on a 3D TI crystal BSTS (BiSbTeSe 2 ) that has no detectable bulk conducting carriers at low temperature, with DPs of the topological SS exposed in the bulk band gap [21,22], thus ideal for the study of low energy excitations in the vicinity of the surface DPs. The dual-gated BSTS devices [22] were fabricated into Hall-bar structures (with channel length l, width w, thickness t) on highly p-doped Si substrates (with 300 nm-thick SiO 2 coating).…”