Chirality-dependent shift current based on spotaneous rotation symmetry breaking

Shift current is an electric polarization current in a nonlinear optical response, in which the electron cloud is shifted in real space by optical excitation. The shift current is present in crystals with broken inversion symmetry. On the other hand, in nonmagnetic chiral crystals with no polarity, the shift current does not appear in general.

We consider a spin model on a 3D layered honeycomb lattice with interlayer interactions along a helical direction, which makes the crystal structure chiral. By including up to intralayer next-nearest neighbor exchange interactions, the spins become frustrated, and their configrations breaks rotational symmetry. We show that it induces a nonzero shift current, whose direction depends on the chirality of the crystal. We demonstrate that the the correction term linear in the wavenumber of light exists and it does not depend on the chirality of the crystal.