Infrared Absorption in High-Tc Superconductors Using the Spin Polaron Formulation

In this paper optical absorption of high-T-c superconductors in the infrared region is investigated within the framework of the spin polaron theory. The approach uses a representation where holes are spinless fermions while spins are normal bosons. Thus, we explored infrared absorption in high-T-c superconductors at finite temperature in a completely analytical way. This task is done through the use of the Matsubara Green's function method in the spin polaron formulation. Infrared absorption is then analyzed in terms of the conductivity which is a function of the energy gap and the frequency of the infrared energy. Our main result is consistent with the conductivity of superconductors in the clean limit.