Non-Ohmic conductivity in the fluctuation regime of charge- and spin-density-wave systems

Abstract

We extend an earlier analysis of the fluctuation contribution to the electric conductivity in quasi-one-dimensional charge (quasi-1D)- (CDW) and spin-density-wave (SDW) systems to the non-Ohmic regime and to nonvanishing frequencies. We find that the electric conductivity increases quadratically with E, when E is sufficiently small, and this increase is given by σ(E)-σ(0)=A${\mathrm{\sigma }}_{\mathit{a}}$(0)[7ζ(3)evE/ 8(πT${)}^2$τ${]}^2$, where ${\mathrm{\sigma }}_{\mathit{a}}$(0), v, and T are the anomalous contribution in the absence of E, the Fermi velocity in the chain direction, and the temperature, respectively, and τ=ln(T/${\mathit{T}}_{\mathit{c}}$) and ζ(3)=1.202 . . . . Here A takes on values of 3/8,3/16,1, and 1/2 for a 3D CDW, a 3D SDW, a 2D CDW, and a 2D SDW, respectively. The effect of the nonvanishing frequency scales exactly with the effect of E in the case of 2D fluctuation, while this scaling is approximate for 3D fluctuation. For 2D fluctuation the scaling is expressed by E=ω(Γ+Γ̃)/ev, where Γ and Γ̃ are the inverse of the pair-breaking lifetime and the quasiparticle lifetime, respectively.