Optical conductivity of nodal superconductors

Recently a number of nodal superconductors have been identified. These include high Tc cuprate superconductors, the ones in Sr2RuO4, CeCoIn5, κ-(ET)2Cu(NCS)2, UPd2Al3, etc. The optical conductivity for E parallel to the conducting plane is the same for these nodal superconductors. Limiting our study to T = 0 K, we compute σ1(ω) and ωσ2(ω) in the presence of impurities. When the impurity scattering is in the unitary limit, σ1(ω) has a peak for ω/Δ ∼ 0.1–0.5. This may account for the peak seen by Basov et al. [D.N. Basov, B. Dabrowski, T. Timusk, Phys. Rev. Lett. 81 (1998) 2132] in Zn-substituted YBCO.