Charge ordering patterns and their excitation spectra in two-dimensional charge-transfer compounds

Abstract

We calculate optical conductivity spectra for various charge ordering (CO) states in the two-dimensional extended Hubbard model at quarter filling with the random phase approximation. The results are examined from a viewpoint of the atomic limit. We compare our results with the measured spectra for the θ-(ET) 2 X salts and discuss the CO patterns and their charge excitations realized in these compounds.