Preprint online: Observation of Berry Curvature Quadrupole Induced Nonlinear Anomalous Hall Effect

We couldn’t be prouder to see our very first ‘homegrown’ scientific article appearing as a preprint on the arXiv. We report on the observation of a 3rd order nonlinear anomalous Hall effect (NLAHE) in the kagome antiferromagnet FeSn at room temperature. Combining nonlinear Hall measurements on FeSn thin films with a symmetry analysis, toy model and ab-initio calculations, and magnetic Monte-Carlo simulations, we demonstrate a new type of Hall effect that is induced by the Berry curvature quadrupole in the spin-canted state of FeSn. We further develop a scaling law analysis in terms of the charge carrier scattering time and show that the 3rd Hall response at room temperature is of almost purely topological origin consistent with the presence of the Berry curvature quadrupole moment in this material.

Because NLAHE based on Berry curvature multipoles are predicted to exist for up to 90 magnetic point groups, our work opens a new area of research in which nonlinear Hall effects can be used to study a variety of magnetic topological materials. Owing to the sensitivity of the nonlinear Hall effects on the underlying magnetic point group symmetries, our work further demonstrates the suitability of nonlinear Hall measurements to study antiferromagnetic phase transitions in electric transport measurements. Moreover, our work showcases that epitaxially grown kagome magnets are a suitable venue to study nonlinear Hall effects in optimised material and device geometries toward their future application as frequency multiplication and rectification elements.

This work is the result of a fruitful collaboration with our colleagues Kam Tuen Law and Qiming Shao at HKUST, and Zi Yang Meng at HKU. Also Kudos to all students and postdocs involved in this work.

Have a look at our preprint and enjoy! Link