Spin electrodynamics in a mesoscopic ring

Abstract

The minimal-coupled Pauli equation is used to calculate the linear microscopic spin conductivity tensor of a circular mesoscopic free-electron ring possessing complete (single-level) transverse electron confinement. A detailed comparison of the structures (and magnitudes) of the spin and space conductivity tensors is made. When the incident electric field is polarized perpendicular to the plane of the ring only the spin conductivity is nonvanishing. The polarization selection rules for the spin conductivity always involve a transfer of orbital angular momentum between neighbouring running ring states. Numerical spectral results are presented for a nano-sized Al ring excited perpendicular to the ring plane for different temperatures. The frequency spectra of the relevant spin conductivity component are qualitatively different for rings holding even and uneven half number of electrons due to different state occupancy probabilities near the Fermi edge. Far-field electromagnetic scattering spectra related to the spin dynamics are calculated in the limit where the quantum ring behaves as an electric-dipole absorber and radiator.