Ab plane ac conductivity in the cuprates: pseudogap effects below Tc.

Abstract

Building on our understanding of the superfluid density rho(s)(T), we show how the pseudogap enters the in-plane optical conductivity sigma(omega,T) for temperatures T</=T(c). Signatures in sigma(omega,T) associated with competing proposals of a "hidden order" and "superconducting" origin for the pseudogap differ in their qualitative omega,T dependences. For the latter case, as T increases from 0, Re sigma(omega) is enhanced at high and low frequencies. We discuss these theories in light of current experiments.