Oral: Exploration of the magnetic proximity effect in a Dirac semimetal

The coexistence of time-reversal and inversion symmetry in Dirac semimetals (DSMs) is responsible for topologically protected, spin-degenerate bulk states with Dirac dispersion. Breaking either of these symmetries results in a Weyl semimetal with broken Kramers degeneracy. This motivates the development of materials platforms wherein an external parameter (such as a gate voltage) is used to break a relevant symmetry (such as time-reversal) in a DSM. We explore this concept by using molecular beam epitaxy to interface a canonical DSM, with a ferromagnetic semiconductor, with perpendicular magnetic anisotropy. Measurements of the anomalous Hall effect (AHE) in top-gated devices show that the ferromagnetic Curie temperature is highly gate-tunable. We map out the AHE in these heterostructures as a function of sample structure and chemical potential. To gain additional insights into the exchange interactions at the heterointerface, we carry out polarized neutron reflectometry (PNR) measurements down to cryogenic temperatures. Preliminary analysis of the PNR data indicates a complex magnetic profile, with potential for a net magnetization within the Cd₃As₂.