Fluctuation-induced pseudogap in high-temperature superconductors

We study the effect of fluctuations on the ac conductivity of a layered superconductor for c-axis electromagnetic wave polarization. The fluctuation contributions of different physical nature and sign (paraconductivity, Maki-Thompson anomalous contribution, one-electron density-of-states renormalization) are found to be suppressed by the external field at different characteristic frequencies (omega(AL)similar to T-T-c, omega(MT)similar to max{T-T-c,tau(phi)(-1)}, omega(DOS)similar to min{T,tau(-1)}). As a result, the appearance of a nonmonotonic frequency dependence (pseudogap) in the infrared optical conductivity of high-temperature superconductor is predicted. (C) 1996 American Institute of Physics.