One-dimensional Kronig-Penney superlattices at the LaAlO3/SrTiO3 interface

Abstract

Semiconductor heterostructures(1) and ultracold neutral atomic lattices(2) capture many of the essential properties of one-dimensional electronic systems. However, fully one-dimensional superlattices are highly challenging to fabricate in the solid state due to the inherently small length scales involved. Conductive atomic force microscope lithography applied to an oxide interface can create ballistic few-mode electron waveguides with highly quantized conductance and strongly attractive electron-electron interactions(3). Here we show that artificial Kronig-Penney-like superlattice potentials can be imposed on such waveguides, introducing a new superlattice spacing that can be made comparable to the mean separation between electrons. The imposed superlattice potential fractures the electronic subbands into a manifold of new subbands with magnetically tunable fractional conductance. The lowest plateau, associated with ballistic transport of spin-singlet electron pairs(3), shows enhanced electron pairing, in some cases up to the highest magnetic fields explored. A one-dimensional model of the system suggests that an engineered spin-orbit interaction in the superlattice contributes to the enhanced pairing observed in the devices. These findings are an advance in the ability to design new families of quantum materials with emergent properties and the development of solid-state one-dimensional quantum simulation platforms.