Nonlinear optical response in one-dimensional Mott insulators Original Research Article

We theoretically study nonlinear optical susceptibility χ(3) and photo-excited states of the Mott insulators in one dimension (1D) by using effective models in the strong-coupling limit of a half-filled Hubbard model. The spin–charge separation and large on-site Coulomb interaction play a crucial role in obtaining degenerate odd- and even-parity states in the photo-excited states observed in recent experiments. χ(3)(−3ω;ω,ω,ω) contains information about both odd- and even-parity states via multi-photon resonance process. We find that the even-parity states can be detected in the |χ(3)(−3ω;ω,ω,ω)| spectrum as a hump structure.