Photoexcited States in Dimer Mott Insulators κ-(BEDT-TTF)2X

Abstract

We theoretically investigate the physical properties of photoexcited states in dimer Mott insulators of the form κ-(BEDT-TTF) 2 X. We adopt the quarter-filled extended Hubbard Hamiltonian on a two-dimensional anisotropic triangular lattice. The energy eigenstates responsible for the major peaks in the light absorption spectrum are numerically calculated, and their physical properties are investigated. Inter dimer charge transfer excited states form quite a broad band, and the large bandwidth mainly arises from the distribution of the kinetic energy of the photogenerated doublon and holon. The band of intra dimer photoexcited states is much narrower because of the isolated nature of the excitation. As a result, the main optical components in the lower-energy region in the light absorption spectrum are due to inter dimer charge transfer excitations, and those in the higher-energy region are due to excitations to the energy eigenstates where inter dimer charge transfer and intra dimer excited states are hybr...