Photoinduced insulator-metal transition in one-dimensional Mott insulators

We theoretically investigate the dynamics of insulator-metal transition induced by light-pulse excitation in one-dimensional Mott insulators. We adopt the Pariser-Parr-Pople model and the pump-probe signal is obtained by numerically calculating the time development of the state excited by light pulse. When the photo-excitation density is below about 10%, an extremely small portion of the energy eigenstates dominates the optical process and the spin-charge separation holds in these dominant energy eigenstates. As a result, the Mott gap and the short-range antiferromagnetic (AF) spin order are preserved and spin relaxation does not occur. When the density is above the value, a metallic state without the Mott gap is photogenerated and the magnitude of the short-range AF spin order is significantly reduced by photoexcitation. This is consistent with the experimentally observed photoinduced Mott transition. Furthermore, spin relaxation occurs in the metallic state. This photoinduced Mott transition is a manifestation of the spin-charge coupling in the intensely photoexcited states.