Laser-Irradiated CrI$_3$: When Chiral Photons Meet Topological Magnons

Abstract

Insulating honeycomb ferromagnet CrI 3 has recently attracted considerable attention due to its potential use for dissipationless spintronics applications. Recently, topological spin excitations have been observed experimentally in bulk CrI 3 by L. Chen, et al. Phys. Rev. X 8, 041028 (2018) using inelastic neutron scattering. This suggest that bulk CrI 3 has strong spin-orbit coupling and its spin Hamiltonian should include a next-nearest neighbour Dzyaloshinskii-Moriya (DM) interaction.Inspired by this experiment, we study non-equilibrium emergent photon-dressed topological spin and thermal Hall transports in laser-irradiated CrI 3 with and without the DM interaction. We show that the spin excitations can be manipulated into different topological phases with different Chern numbers. Most importantly, we show that the emergent photon-dressed spin and thermal Hall response can be switched to different signs. Hence, the generated magnon spin photocurrents can be manipulated by the laser field, which is of great interest in ultrafast spin current generation and could pave the way for future applications of CrI 3 to topological opto-spintronics and optomagnonics.

Ultrafast control of spin interactions in honeycomb antiferromagnetic insulators

“…In magnetic systems with broken inversion symmetry, there is also an antisymmetric exchange interaction between spins that breaks the chiral symmetry, namely, the Dzyaloshinskii-Moriya interaction (DMI) [19][20][21][22]. Although this interaction is considerably weaker than the exchange interaction, it is essential in magnetic materials for enabling weak ferromagnetism in AFM materials [19 and 20], topological objects such as chiral skyrmions [23][24][25][26] and chiral domain walls [27][28][29], and exotic phases of topological magnon insulators [30][31][32][33][34][35]. The ratio between the exchange interaction and the DMI controls the tilt angle of the canted spins.…”