Electric polarization and nonlinear optical effects in noncentrosymmetric magnets

Magnetic excitations in multiferroic materials accompany electric polarization, known as electromagnons. The authors develop here a general framework to study polarization and nonlinear optical responses of noncentrosymmetric magnets based on spin models. They theoretically demonstrate the excitation electromagnon-induced dc current generation (i.e., photovoltaic effect) from so-called shift mechanism.