Exotic Doublon-Holon Pairing State in Photodoped Mott Insulators

Abstract: We demonstrate the existence of a unique pairing state in photodoped Mott insulators on ladder geometries, characterized by quasi-long-ranged doublon-holon correlations, using the density matrix renormalization group method. This phase exhibits doublon-holon pairing correlations with opposite signs along the rung and chain directions, reminiscent of d-wave pairing in chemically doped ladder systems. By constructing the phase diagram, we reveal that the doublon-holon pairing state emerges between the spin-singlet phase and the charge-density-wave/$\eta$-pairing phase. Our study suggests that the interplay of charge, spin, and $\eta$-spin degrees of freedom can give rise to exotic quantum many-body states in photodoped Mott insulators.