Abstract
Hirsch's dynamic Hubbard model describes the effect of orbital expansion with occupancy by coupling the doublon operator to an auxiliary boson. In the Mott insulating phase, empty sites (holes) and doubly occupied orbitals (doublons) become charge carriers on top of the half-filled background. We use the nonequilibrium dynamical mean field method to study the properties of photo-doped doublons and holes in this model in the strongly correlated regime. In particular, we discuss how photodoping leads to doublon and hole populations with different effective temperatures, and we analyze the relaxation behavior as a function of the boson coupling and boson energy. In the polaronic regime, the nontrivial energy exchange between doublons, holes, and bosons can result in a negative temperature distribution for the holes.
Highlights
Correlated electron systems are often described in terms of the Hubbard model or its multiorbital extensions
Hirsch introduced the dynamic Hubbard model,1 which contains an additional coupling of the doublon operator to an auxiliary boson
We have discussed a dynamical mean field theory (DMFT) based method for the simulation of nonequilibrium phenomena in the dynamic Hubbard model.1. This class of models has originally been introduced to capture the fact that atomic orbitals expand if occupied by two-electrons, which results in particle-hole asymmetric correlations
Summary
Correlated electron systems are often described in terms of the Hubbard model or its multiorbital extensions. As was pointed out by Hirsch and co-workers in a series of papers, this model ignores the fact that doubly occupied atomic orbitals expand as a result of Coulomb interactions and electron correlations To capture this physics, Hirsch introduced the dynamic Hubbard model, which contains an additional coupling of the doublon operator to an auxiliary boson. A dynamic Hubbard model has been proposed to explain the behavior of organic charge-transfer salts in which molecular orbitals are periodically modulated via the selective excitation of an optical phonon mode with intense laser fields.7,8 In this context, the particle-hole asymmetric electron-boson coupling provides an experimental “knob” to tune the interaction effects in the solid, and raises the interesting prospect of dynamical control of material properties.
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