  Recent experiments performed on cuprates and alkali-doped fullerides have
demonstated that key signatures of superconductivity can be induced above the
equilibrium critical temperature by optical modulation. These observations in
disparate physical systems may indicate a general underlying mechanism.
Multiple theories have been proposed, but these either consider specific
features, such as competing instabilities, or focus on conventional BCS-type
superconductivity. Here we show that periodic driving can enhance electron
pairing in strongly-correlated systems. Focusing on the strongly-repulsive
limit of the doped Hubbard model, we investigate in-gap, spatially
inhomogeneous, on-site modulations. We demonstrate that such modulations
substantially reduce electronic hopping, while simultaneously sustaining
super-exchange interactions and pair hopping via driving-induced virtual charge
excitations. We calculate real-time dynamics for the one-dimensional case,
starting from zero and finite temperature initial states, and show that
enhanced singlet--pair correlations emerge quickly and robustly in the
out-of-equilibrium many-body state. Our results reveal a fundamental pairing
mechanism that might underpin optically induced superconductivity in some
strongly correlated quantum materials.
