Fermi-liquid versus Luttinger-liquid behavior and metal-insulator transition inN,N’-dicyanoquinonediimine-Cu salt studied by photoemission

We have made a high-resolution photoemission study of quasi-one-dimensional partially deuterated (DMe-DCNQI${)}_2$Cu, where DMe-DCNQI denotes dimethyl N,${\mathit{N}}^{\mathcal{’}}$-dicyanoquinonediimine. The spectra in the metallic phase exhibit a power-law dependence on the electron binding energy ‖ω‖ on a high-energy scale (0.3≳‖ω‖≳0.05 eV) or at high temperatures (T≳ 300 K) while a weak but finite intensity is found at the Fermi level at low temperatures, consistent with the existence of a Fermi edge. These results imply how a crossover occurs from a one-dimensional Luttinger liquid to a three-dimensional Fermi liquid as a function of excitation energy, temperature, and mass anisotropy.