Ballistic transport through quantum point contacts of multi-orbital oxides

Abstract

Linear and non-linear transport properties through an atomic-size point contact based on oxides two-dimensional electron gas is examined using the tight-binding method and the $\mathbf{k}\cdot \mathbf{p}$ approach. The ballistic transport is analyzed in contacts realized at the (001) interface between band insulators $LaAl{O}_3$ and $SrTi{O}_3$ by using the Landauer-Büttiker method for many sub-bands derived from three Ti 3d orbitals ($d_{yz}$, $d_{zx}$ and $d_{xy}$) 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 pointing out three transport regimes: the first, at low energies, involving the first $d_{xy}$-like sub-bands, where the conductance quantization is robust; a second one, at intermediate energies, entailing further $d_{xy}$-like sub-bands, where the sub-band splitting induced by the magnetic field is quenched; the third one, where the mixing between light $d_{xy}$-like, heavy $d_{yz}$-like and $d_{zx}$-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.

11 pages, 9 figures

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• Probing Topological Superconductivity of oxide nanojunctions using fractional Shapiro steps
• Theory of charge-to-spin conversion under quantum confinement
• Spin Hall and Edelstein effects in a ballistic quantum dot with Rashba spin-orbit coupling
• Scanning gate microscopy probing of anisotropic electron flow in a two dimensional electron gas at the (110) ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ interface: A theoretical investigation