Photogenerated holon-doublon cluster states in strongly correlated low-dimensional electron systems

Abstract

We theoretically investigate the properties of multiphoton excited states in strongly correlated one-dimensional (1D) and two-dimensional (2D) electron systems at half filling using the extended Hubbard model. In the 2D case, we find the photoexcited states where two or more than two holons and doublons are strongly bound, and the cluster of bound holons and doublons coexists with the surrounding antiferromagnetic (AF) spin order, for the realistic Coulomb interaction parameters. The holon-doublon cluster (HDC) states have a unique charge aggregation mechanism originating from the spin-spin interaction in the AF spin background as well as from the direct Coulomb interaction. In the 1D case, the HDC states are destabilized by the spin-spin interaction in contrast to the 2D case. These charge aggregation mechanisms are the outcomes of exotic natures of holons and doublons, and the difference in the mechanism between the 1D and 2D cases is due to the difference in the coupling between spin and charge degrees of freedom. We also calculate the light-induced absorption that enables us to experimentally observe the predicted HDC states.