Spin splitting of subbands in quasi-one-dimensional electron quantum channels

Abstract

We report on self-consistent calculations of the electronic structure of quantum wires with an in-plane magnetic field parallel to the wire. The spin-polarized density-functional theory of Kohn and Sham is used. The self-consistent results show that exchange interactions cause a large subband splitting whenever the Fermi energy passes the subband threshold energies. Full spin polarization appears at low electron densities. The results are consistent with recent observations of a conductance anomaly in a quantum point contact and its interpretation in terms of spontaneous spin polarization of the lowest subband. On the basis of the present model we conjecture that similar conductance anomalies may appear also in the higher subbands at zero magnetic field. Finite magnetic fields tend to suppress the spin polarization induced by exchange interactions. A diamagnetic shift of the subbands is determined and is in qualitative agreement with observations. \textcopyright{} 1996 The American Physical Society.