Influence of helical spin structure on the magnetoresistance of an ideal topological insulator

In an ideal topological insulator, the helical spin structure of surface electrons suppresses backscattering and thus can enhance surface conductivity. In this study, we investigate the effect of perpendicular magnetic field on the spin structure of electrons at the Fermi energy and define a magnetic-field dependent topological enhancement factor using Boltzmann transport and calculate this factor for different disorder potentials, ranging from short-range disorder to screened Coulomb potential. Within the Boltzmann approximation, the topological enhancement factor reaches its maximum value of 4 for a short-range disorder at zero magnetic field and approaches a value of 1 at high magnetic fields. The topological enhancement factor becomes independent of the nature of the disorder potential at high magnetic fields.