Photoinduced superconducting-like properties: η-pairing and charge stiffness in optically driven Mott-Hubbard systems

We theoretically investigate the electron-electron (superconducting) pairing correlations and charge stiffness in the one-dimensional Hubbard model subjected to a pump electric field. By employing unbiased numerical methods, we show that irradiation of the Mott insulating state of the Hubbard model induces strong pair density-wave-like correlations. The pair density-wave correlations induced here are due to η-pairing states, which are preferentially generated by photoexcitation and possess staggered off-diagonal long-range correlations in the excited states of the Hubbard model. We show that the optically induced η-pairing states give rise to the nonzero charge stiffness, in contrast to the Mott insulating state, where the charge stiffness vanishes. We also discuss the system size dependence associated with the η-pairing state and show that the pairing correlations decay very slowly with system size.