Fluctuation conductivity near a Peierls lattice distortion

There have been a number of recent theories for the fluctuation conductivity due to phonon softening near a one-dimensional Peierls lattice distortion. In these, the conductivity is evaluated for one or more Feynman response diagrams, with a resulting fluctuation conductivity which is positive, negative, or negligible. We calculate the conductivity using a conserving response theory which derives all of the response diagrams for any particular approximation to the electron propagator for the solid in thermodynamic equilibrium. Using this method in the mean-field theories to date, valid in principle for sufficiently high temperatures, the fluctuation conductivity due to phonon softening is positive and proportional to ($\text{T - T}{}_{\mathrm{p}}\text{)}{}^{\mathrm{<mtext>-</mtext><mtext>3</mtext><mtext>2</mtext>}}$, where T_p is the mean-field temperature scale in the one-dimensional Peierls system. This conductivity contribution is not due to the Fröhlich sliding mode.