Designing spin and orbital sources of Berry curvature at oxide interfaces

Abstract

Quantum materials can display physical phenomena rooted in the geometry of electronic wavefunctions. The corresponding geometric tensor is characterized by an emergent field known as Berry curvature (BC). Large BCs typically arise when electronic states with different spin, orbital or sublattice quantum numbers hybridize at finite crystal momentum. In all materials known to date, the BC is triggered by the hybridization of a single type of quantum number. Here, we report the discovery of the first material system having both spin and orbital-sourced BC: LaAlO$_3$/SrTiO$_3$ interfaces grown along the [111] direction. We detect independently these two sources and directly probe the BC associated to the spin quantum number through measurements of an anomalous planar Hall effect. The observation of a nonlinear Hall effect with time-reversal symmetry signals large orbital-mediated BC dipoles. The coexistence of different forms of BC enables the combination of spintronic and optoelectronic functionalities in a single material.