Tunable topological magnon-polaron states and anomalous Hall phenomena in two-dimensional ferromagnetic insulators

Abstract: We study magnon-polaron hybrid states, mediated by Dzyaloshinskii-Moriya and magnetoelastic interactions, in a two-dimensional ferromagnetic insulator. The magnetic system consists of both in-plane and flexural acoustic and optical phonon bands, as well as acoustic and optical magnon bands. Through manipulation of the ground-state magnetization direction using a magnetic field, we demonstrate the tunability of Chern numbers and (spin) Berry curvatures of magnon-polaron hybrid bands. This adjustment subsequently modifies two anomalous Hall responses of the system, namely, thermal Hall and spin Nernset signals. Notably, we find that by changing the magnetic field direction in particular directions, it is possible to completely suppress the thermal Hall signal while maintaining a finite spin Nernst signal. Our finding reveals the intricate interplay between topological and quantum geometrical phenomena and magnetic ordering, offering compelling avenues for on-demand control over emergent quantum states in condensed matter systems.