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In oxide heterostructures, different materials are integrated into a single artificial crystal, resulting in a breaking of inversion symmetry across the heterointerfaces. A notable example are interfaces between polar and nonpolar materials, where structural discontinuities lead to otherwise inaccessible charge and spin states. This approach enabled the discovery of numerous unconventional interfacial properties absent in the bulk constituents.

In this talk I would like to review recent research engaged in the engineering of quantum effects through the manipulation of the geometry of wave-functions. Quantum materials can display physical phenomena rooted in the geometric properties of their electronic wave-functions and governed by an effective field known as Berry curvature (BC). Large BCs typically arise when electronic states with different spin, atomic orbital or sublattice quantum numbers hybridize at finite crystal momentum. In this talk I will discuss the manipulation of BC sources in oxide heterostructures.

In the first part of the talk, we will focus on heterointerfaces with broken time reversal symmetry. These are composed of ultrathin SrRuO3, an itinerant ferromagnet hosting momentum-space sources of BC, and LaAlO3, a polar wide-band-gap insulator. We will discuss how real-space charge reconstructions drive a reorganization of topological charges in the band structure, thereby modifying the momentum-space BC in SrRuO3.

In the second part of the talk, we will discuss heterointerfaces with time reversal symmetry but very low crystalline symmetry. I will report the observation of the first material system having both spin and orbital-sourced BC: LaAlO3/SrTiO3 interfaces grown along the [111] direction. We detect independently these two sources and directly probe the BC associated to the spin degree of freedom through measurements of an anomalous planar Hall effect. The observation of a nonlinear Hall effect under time-reversal symmetric conditions signals instead a large orbital-mediated BC dipole.

You can download the slides of the presentation here (pdf).

Please make sure to register at this doodle before Thursday evening (15 December) so that we can order enough pizza!

Location: Stuckelberg, Ecole de Physique
Time: Friday 16 December 2022, 12:00 for pizza, 12:30 start discussion