Photogalvanic spin current of magnons in magnetic insulators

Photogalvanic responses in noncentrosymmetric semiconductors are a powerful tool for studying various aspects of low-energy electronic properties, including topological electronic states. In recent years, several different mechanisms for the spin current analog of the photogalvanic effect has been theoretically proposed. However, neither candidate materials nor a general formula for calculating the photogalvanic spin current is known. In this work, we develop a generic theory for the photogalvanic spin current through a magnetic resonance process.

 

Using a nonlinear response formalism [1,2], we find the nonlinear conductivity consists of two contributions: contribution involving one magnon band, and that involving two bands. The former is related to those studied recently, whereas the latter is a contribution unknown to date. We argue that the two-band process produces a large photogalvanic spin current in the antiferromagnetic phase of bilayer CrI3, whose resonance frequency can be tuned between GHz-THz range by an external magnetic field. Our finding opens a route to studies on the photogalvanic effect of spin-angular momentum in realistic setups.

 

[1] H. Ishizuka and M. Sato, Phys. Rev. Lett. 122, 197702 (2019).

[2] H. Ishizuka and M. Sato, Phys. Rev. B 100, 224411 (2019).