Abstract Many experiments show that strong excitations of correlated quantum materials can cause non-thermal phases without equilibrium analogues. Understanding the origin and properties of these nonequilibrium states has been challenging due to the limitations of theoretical methods for nonequilibrium strongly correlated systems. In this work, we introduce a generalized Gibbs ensemble description that enables a systematic analysis of the long-time behavior of photo-doped states in Mott insulators based on equilibrium methods. We demonstrate the power of the method by mapping out the nonequilibrium phase diagram of the one-dimensional extended Hubbard model, which features η-pairing and charge density wave phases in a wide photo-doping range. We furthermore clarify that the peculiar kinematics of photo-doped carriers, and the interaction between them, play an essential role in the formation of these non-thermal phases. Our results establish a new path for the systematic analysis of nonequilibrium strongly correlated systems.
We study the nonequilibrium phase diagram of long-lived photo-doped states in the one-dimensional
U-
V Hubbard model, where
η-pairing, spin density wave and charge density wave (CDW) phases are found. The photo-doped states are studied using an effective model obtained by a Schrieffer-Wolff transformation combined with separate chemical potentials for the approximately conserved pseudoparticle excitations, leading to a generalized Gibbs ensemble type description. These photo-doped states are characterized by gapless (
η-paring) and gapped (CDW) features in the nonequilibrium spectra. For small
V, the
η-pairing correlations dominate over a wide doping range even when the SU
c(2) symmetry that protects
η-pairing in the pure Hubbard model is absent. With increasing
V, the CDW correlations take over in a wide doping range and are strong relative to the chemically doped case. We attribute the strong CDW correlations to the competition between intra- and inter-species repulsion and the one-dimensional configuration. Our results show that photo-doped strongly correlated systems exhibit different phases than conventional semiconductors.