Role of acoustic phonons in Bi2Se3 topological insulator slabs: A quantum transport investigation

We present a model for quantum transport in a Bi2Se3 slab, which is based on using a nonequilibrium Green's function approach in which bulk and surface states are modeled realistically, and the effects of phonon scatterings are included. Resistivity is computed for different temperatures and strengths of the electron-phonon coupling at various doping levels. Temperature dependence of resistivity is found to display an insulating trend when the slab is biased at the Dirac point even in the presence of strong electron-phonon coupling. In sharp contrast, for carrier doping, the material displays a metallic behavior induced by acoustic scattering effects, even though purely ballistic transport yields an insulating trend, explaining contradictory trends reported in transport experiments on Bi2Se3. Our analysis, furthermore, suggests an experimental strategy for obtaining a handle on the strength of electron-phonon coupling in topological insulators via temperature-dependent transport measurements.