Giant thermal Hall effect in Topological Magnon Insulator Cr3Se4 monolayer

Abstract

Thermal Hall effect, the thermal analogue of Hall effect, has emerged as a key probe of charge-neutral excitations in topological magnons. Therefore, achieving the giant thermal Hall effect in topological magnon insulator (TMI) is highly desirable, but the underlying origin has been under active debate. Here, through a Heisenberg–Dzyaloshinskii–Moriya (DM) model combined with first-principles calculations that explicitly include both nearest- and next-nearest-neighbor DM interactions, we show that the usually neglected next-nearest-neighbor DMI is crucial for the magnonic thermal Hall effect and can even induce a sign change of the magnonic Chern number. Remarkably, based on the Chern number and edge states analyses, the Cr₃Se₄ monolayer is identified as an experimentally feasible candidate of the TMI with a sign-changed magnonic Chern number and a giant thermal Hall effect, with thermal Hall conductivity reaching as much as |κ_TH^xy| = 3.82 ×10^-11 W/K. Moreover, the Cr₃Se₄ monolayer simultaneously realizes the Chern insulator with quantum anomalous Hall effect, giving rise to dual Chern-insulating behavior in which electronic and magnonic edge states emerged within a single ferromagnet. These findings identify a prototypical platform for intrinsic topological magnonic phenomena, offering strong prospects for experimental exploration.