Impurity Pinning and Microwave Conductivity of Incommensurate Spin Density Waves

Abstract

We calculate the microwave conductivity due to the phase mode in an incommensurate SDW taking into account nonmagnetic impurity effects and long-range Coulomb interaction between the phason and quasi-particles. It is shown that the conductivity is represented in a scaled form by a pinning frequency. The pinning frequency of SDW is shown to be comparable to that of CDW because the dynamics of phason through the phason self-energy gives important contributions on the pinning frequency and the small parameter µ -1/2 which exists in the CDW systems remarkably suppresses the pinning frequency of CDW. The long-range Coulomb effect on the conductivity is seen as the deviation of the frequency dependence of the conductivity from ω 2 to ω α with 1/2<α<3/2 at low frequencies.