Ballistic transport through quantum point contacts of multiorbital oxides

Linear and nonlinear transport properties through a quantum point contact based on oxides two-dimensional electron gas is examined using the tight-binding method and the k·p approach. The ballistic transport is analyzed in contacts realized at the (001) interface between band insulators LaAlO3 and SrTiO3 by using the Landauer-Büttiker method for many sub-bands derived from three Ti 3d orbitals (dyz, dzx, and dxy) in the presence of an out-of-plane magnetic field. We focus especially on the role played by the atomic spin-orbit coupling and the inversion-symmetry-breaking term. Three different transport regimes stem out: The first, at low energies, involving the first dxy-like sub-bands, where the conductance quantization is clearly observed; a second one, at intermediate energies, entailing further dxy-like sub-bands, where the sub-band splitting induced by the magnetic field is quenched; the third one, where the mixing between light dxy-like, heavy dyz-like, and dzx-like sub-bands is so strong that the conductance plateaus turn out to be very narrow. Very good agreement is found with recent experiments exploring the transport properties at low energies.