Nuclear relaxation in one-dimensional Hubbard systems

Abstract

Measurements of the proton nuclear relaxation time $T_1$ have been performed at room temperature in two conductive tetracyanoquinodimethane (TCNQ) salts: $N-\mathrm{methylphenazinium}-\mathrm{TCNQ}$ and quinolinium-${\mathrm{}\left(\mathrm{TCNQ}\right)\mathrm{}}^2$. A frequency dependence of $T_1$ is reported, which provides evidence for a one-dimensional diffusive motion. In order to explain this result, the spin correlation function is calculated for the Hubbard chain model by explicitly taking into account the one-dimensional character of the system. A diffusive process is shown to arise from the scattering of the conduction electrons by the Coulomb repulsions.