Spin waves, scattering at4kF, and spin-Peierls fluctuations in an organic metal: tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ)

An interpretation is given for recent diffuse x-ray and neutron scattering experiments on tetrathiafulvalene-tetracyanoquinodimethane using a model of strong Coulomb interactions. The diffuse x-ray scattering observed at $q=0.59\mathrm{}{b}^{*}\left(4\mathrm{}{k}_F\right)$ is identified as quasielastic scattering from a charge-density wave which is driven by long-range Coulomb interactions, while the scattering at $q=0.295\mathrm{}{b}^{*}\left(2\mathrm{}{k}_F\right)$ is due to a Kohn anomaly caused by spin-Peierls fluctuations. Three experiments are proposed in order to verify this interpretation, including a search for spin waves which are predicted to be observable by inelastic neutron scattering near $q=0.295\mathrm{}{b}^{*}$.