Nuclear relaxation in one-dimensional Hubbard systems

Measurements of the proton nuclear relaxation time T₁ have been performed at room temperature in two conductive tetracyanoquinodimethane (TCNQ) salts: N-methylphenazinium-TCNQ and quinolinium-(TCNQ)². A frequency dependence of T₁ 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.