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Phase Separation Induced by Symmetric Monocycle Optical Pulse in Extended Hubbard Models

Many-electron dynamics induced by a symmetric monocycle electric-field pulse of large amplitude is theoretically investigated in one- and two-dimensional half-filled extended Hubbard models on regular lattices (i.e., without dimerization) using the exact diagonalization method for small systems and the Hartree-Fock approximation for large systems. The formation of a negative-temperature state and the change from repulsive interactions to effective attractive interactions are shown to be realized for a wide region of the field amplitude and the excitation energy. For a nonnegligible intersite repulsive interaction, the numerical results are consistent with the fact that the phase separation between charge-rich and charge-poor regions is caused by the corresponding effective attraction.