The pseudogap in the c-axis optical conductivity in high T-c-cuprates

The pseudogap phenomenon is most remarkable in the underdoped region of hig h-T-c cuprates. Since the superconducting state in the optimally doped high -T-c cuprates is well described by the BCS-like d-wave superconductors, it is natural to assume that the pseudogap arises from the standard supercondu cting fluctuation. In particular in the layered compunds like high-T-c cupr ates Varlamov and his coworkers pointed out the density of states (DOS) cor rection to the superconducting fluctuation will play the crucial role. Howe ver, unfortunately in their analysis d-wave nature of the high-T-c cuprates is ignored. Perhaps more seriously some unnecessary approximations were in troduced in their analysis. The present theory gives somewhat different exp ressions of quasi-particle density of states for B = 0 and B not equal 0, w hich can be tested experimentally.