Dimer gas model for tetracyanoquinodimethane (TCNQ)

Abstract

By assuming the dominance of electrostatic terms in the Hamiltonian, Hubbard has recently formulated a "dimer gas" model for tetracyanoquinodimethane which is closely related to a strongly anisotropic Heisenberg-Ising spin chain. We show here that in the anisotropic limit, the exact Bethe-ansatz equations describing the spin chain are very simple, and a full analysis of the lowest-state energy and elementary excitation spectrum for any magnetization is given. We also find the excitation spectrum for the anisotropy and electron density throught to be correct for tetrathiafulvalene-tetracyanoquinodimethane, and the results are very similar to the limiting case.