Mott Transition Coupled to Molecular Motion in a Quasi-Two-Dimensional Organic Material

We performed resistivity and 1H-NMR measurements of a quasi-two-dimensional organic material, β-(BDA-TTP)2I3, to investigate its electronic and magnetic properties across the Mott transition. The NMR spectra and spin–lattice relaxation rate, \(T_{1}^{- 1}\), show a commensurate antiferromagnetic order in a Mott insulating phase at low pressures and a strongly discontinuous Mott transition around 8 kbar. In the metallic state, the resistivity shows Fermi liquid behavior at low temperatures, whereas (T1T)−1 is weakly temperature-dependent in the same temperature range. The temperature profile of \(T_{1}^{ - 1}\) indicates that the Mott transition is associated with a marked change in molecular dynamics, suggesting the strong coupling of the Mott transition to the intramolecular degrees of freedom, which is very probably associated with a structural transition.