Theory Of Magnetoresistance In Tellurene And Related Mini-Gap Systems

The weak-field magnetoresistance is calculated in tellurene and related two-dimensional systems, characterized by interacting two bands having parabolic dispersion with their centers displaced from each other. Scatterers with short-range potential are assumed. In a Boltzmann theory, positive magnetoresistance appears in the direction of the band displacement near the bottom of the band gap with saddle-point dispersion and below the bottom of the second band. The magnetoresistance in the perpendicular direction remains small except within the gap. In a self-consistent Born approximation, the positive magnetoresistance is enhanced near the saddle point due to effects of magnetic breakdown. The change in the density of states due to diamagnetic shift of the energy bands, responsible to the diamagnetic susceptibility, causes a sharp drop of the magnetoresistance at the bottom of the second band and a broad dip at the saddle-point energy in both directions.