Magnon spin photogalvanic effect induced by Aharonov-Casher phase

Magnons are electrically neutral bosonic quasiparticles emerging as collective spin excitations of magnetically ordered materials, and they play a central role in next-generation spintronics due to its obviating Joule heating. A difficult obstacle for quantum magnonics is that the magnons do not couple to the external electric field directly so that a direct electric manipulation via bias or gate voltage as in conventional charge-based devices seems not to be applicable. In this work, we propose a mechanism in which magnons can be excited and controlled by an electric field of light directly. Since the electric field of light can be tuned in a wide and easy way, the proposal should be of great interest in realistic applications. We call it the magnon spin photogalvanic effect (SPGE), which comes from five contributions: Drude, Berry curvature dipole (BCD), injection, shift, and rectification, with distinct geometric origins. We further show that the responses to linearly polarized or circularly polarized light are determined by a band-resolved quantum metric or Berry curvature, both of which, when combined, comprise a quantum geometric tensor. The proposed magnon SPGE can be measured by a characterized topological phase transition. We also discuss a breathing kagome-lattice model of ferromagnets, and we suggest possible candidate materials to implement it.