Anisotropic transport properties in prismatic topological insulator nanowires

TL;DR

This paper explores how the shape of topological insulator nanowires affects their electronic transport properties under magnetic fields, proposing conductance measurements as a method to identify cross-sectional shapes.

Contribution

It introduces a method to differentiate polygonal nanowire shapes via conductance measurements under magnetic field rotation, considering effects of impurities.

Findings

Distinct energy spectra for different polygonal shapes.

Conductance steps reveal sub-band structures.

Shape differentiation remains robust with impurities.

Abstract

The surface of a three dimensional topological insulator (TI) hosts surface states whose properties are determined by a Dirac-like equation. The electronic system on the surface of TI nanowires with polygonal cross-sectional shape adopts the corresponding polygonal shape. In a constant transverse magnetic field, such an electronic system exhibits rich properties as different facets of the polygon experience different values of the magnetic field due to the changing magnetic field projection between facets. We investigate the energy spectrum and transport properties of nanowires where we consider three different polygonal shapes, all showing distinct properties visible in the energy spectrum and transport properties. Here we propose that the wire conductance can be used to differentiate between cross-sectional shapes of the nanowire by rotating the magnetic field around the wire. Distinguishing between the different shapes also works in the presence of impurities as long as conductance steps are discernible, thus revealing the sub-band structure.