Disentangling the magnetoelectric and thermoelectric transport in topological insulator thin films

TL;DR

This study investigates transport phenomena in topological insulator thin films, revealing a sign anomaly between Hall and Seebeck coefficients caused by different contributions of bulk and surface states, with implications for thermoelectric device design.

Contribution

It uncovers the distinct roles of bulk and surface states in transport properties, demonstrating a sign anomaly in Hall and Seebeck coefficients in topological insulator films.

Findings

Surface Dirac fermions dominate magnetoelectric transport.

Bulk states primarily influence thermoelectric effects.

Sign anomaly between Hall and Seebeck coefficients observed.

Abstract

We report transport studies on (Bi,Sb)2Te3 topological insulator thin films with tunable electronic band structure. We find a doping and temperature regime in which the Hall coefficient is negative indicative of electron-type carriers, whereas the Seebeck coefficient is positive indicative of hole-type carriers. This sign anomaly is due to the distinct transport behaviors of the bulk and surface states: the surface Dirac fermions dominate magnetoelectric transport while the thermoelectric effect is mainly determined by the bulk states. These findings may inspire new ideas for designing topological insulator-based high efficiency thermoelectric devices.