The interplay between long-range and local Coulomb repulsions in strongly interacting electron systems is explored through a two-dimensional Hubbard-Wigner model. An unconventional metallic state is found in which collective low-energy excitations characteristic of the Wigner crystal induce a flow of electrical current despite the absence of one-electron spectral weight at the Fermi surface. Photoemission experiments on certain quarter-filled layered molecular crystals should observe a gap in the excitation spectrum whereas optical spectroscopy should find a finite Drude weight indicating metallic behavior.

• Received 20 July 2009

DOI:https://doi.org/10.1103/PhysRevB.80.165110