Impurity scattering in unconventional density waves
  We have investigated the effect of nonmagnetic impurities on the quasi-one-dimensional unconventional density wave (UDW) ground state. The thermodynamics were found to be close to those of a d-wave superconductor in the Born limit. Four different optical conductivity curves were found depending on the direction of the applied electric field and on the wavevector dependence of the gap. 
Bal\'azs D\'ora, Attila Virosztek, Kazumi Maki