Spin and charge transport of electron on a mesoscopic ring of topological insulator thin film in uniform magnetic field

Abstract

Spin dynamics and persistent spin and charge currents of an electron on a mesoscopic ring of topological insulator (TI) thin film in a uniform magnetic field are investigated. We find that the circular symmetry of TI in the magnetic field leads to a shift of the valence band maxima and conduction band minima in the energy spectrum from the charge neutrality point depending on the strength of the magnetic field, in addition to the bandgap induced by the hybridization and Zeeman energies. The numerical analysis of the dynamical equations obtained from the Heisenberg equation of motion shows that the tangential, radial, and longitudinal components of the electron’s spin exhibit periodic oscillations. Interestingly, the longitudinal component of spin polarized current vanishes due to the inversion symmetry along the cylindrical axis, whereas its x- and y-components oscillate with a finite phase shift. The persistent charge current on the ring of the TI thin film changes sign from positive to negative approaching maximal saturated values at large magnetic fluxes. Moreover, we investigate the effect of dephasing on persistent currents when the ring is coupled to an electron reservoir. Strikingly, both charge and spin persistent currents dissipate significantly with increasing the coupling parameter.