Planar Hall effect from the surface of topological insulators

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Topological insulators (TIs) exhibit unique surface states with Dirac fermions.
• Controlling Fermi levels in TI thin films is crucial for studying surface transport.
• Previous research has not fully explored the effects of in-plane magnetic fields on TI surface properties.

Purpose of the Study:

• To investigate a novel planar Hall effect (PHE) in topological insulator thin films.
• To understand the origin of resistivity anisotropy induced by in-plane magnetic fields.
• To explore the dependence of this effect on gate voltage and its relation to the Dirac point.

Main Methods:

• Fabrication of dual-gated devices using bulk-insulating Bi₂₋ₓSbₓTe₃ thin films.
• Measurement of transport properties under varying gate voltages and in-plane magnetic fields.
• Analysis of resistivity anisotropy and its correlation with the Dirac point.

Main Results:

• Discovery of a novel planar Hall effect (PHE) originating from the TI surface.
• Observed strong gate voltage dependence of the field-induced anisotropy, with a two-peak structure near the Dirac point.
• Demonstrated that the PHE arises from time-reversal symmetry breaking by the in-plane magnetic field, affecting surface Dirac fermion backscattering.

Conclusions:

• The novel PHE in TI thin films is a consequence of anisotropic lifting of protection against backscattering for surface Dirac fermions.
• This PHE serves as a valuable tool for analyzing and manipulating the topological protection of TI surfaces.
• The findings contribute to a deeper understanding of quantum transport phenomena in topological materials.