Nonlinear electrical transport effects in tetrathiafulvalene-tetracyanoquinodimethane as driven through charge-density-wave commensurability

Electric-field–dependent conductivity measurements in the organic two-chain conductor TTF-TCNQ are reported in the pressure (P) range 4≤P≤24 kbar. Deviations from Ohm’s law, with a threshold field ${\mathrm{E}}_{\mathrm{T}}$, are found at all P at temperatures below the upper Peierls transition. At low P, we find that the ${\mathrm{E}}_{\mathrm{T}}$ temperature dependence approaches that found for ${\mathrm{NbSe}}_3$. As TTF-TCNQ is driven through third-order commensurability at ∼19 kbar, we observe a peak in ${\mathrm{E}}_{\mathrm{T}}$ and a dip in the excess current at constant field. The results are discussed in terms of charge-density wave and/or discommensuration transport.