THE OPTICAL CONDUCTIVITY OF GAUGE FIELD MODEL

The thermal Green's function method has been used to calculate the rea l part of the optical conductivity in the gauge-held model. The gauge invariant response functions were considered to the second order of th e gauge field. We found that there is a structure in the frequency ran ge of a fraction of the Fermi energy. It is due to the excitation of p article-hole pair and a gauge field by a photon. In the small-frequenc y region, the optical conductivity is sensitive to temperature because of boson excitations. In the intermediate and high frequency region i t is not sensitive because fermion excitations dominates.