Nonlinear optical responses in chiral magnetic metals*

Chiral magnetic metals breaking both spatial inversion and time reversal symmetries carry a potential for novel nonlinear optical responses. We theoretically study such nonlinear optical responses in a chiral conical magnetic state as a prototypical example. By using the second-order response theory, we show that electrons coupled to a chiral conical magnetic texture exhibit a photovoltaic effect and second harmonic generation. In particular, we find that the coefficient of the photovoltaic effect changes in not only the magnitude but also the sign depending on the external magnetic field and the frequency of light. Our results would pave the way for the next-generation optical electronic devices, such as an unconventional solar cell and optical sensor.