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High-Harmonic Generation in a Correlated Electron System

High-harmonic generation (HHG) in crystalline solids have been examined so far on the basis of one-body energy-band structures arising from electron itineracy in a periodic potential. Here, we show emergence of HHG signals which are attributed to dynamics of many-body states in a low-dimensional correlated electron system. An interacting fermion model and its effective pseudo-spin model on a one-dimensional dimer-type lattice are analyzed. Observed HHG signals in a spontaneously symmetry-broken state, where charge densities are polarized inside of dimer units, show threshold behavior with respect to light amplitude and are interpreted in terms of tunneling and recombination of kink-antikink excitations in an electric field.