Abstract
While the optical properties of the superconducting salt remain metallic down to 2 K, in the nonsuperconducting K analog a pseudogap develops at frequencies of about for temperatures . We show that the optical conductivity calculated with exact-diagonalization techniques on an extended Hubbard model at quarter filling is consistent with the observed low-frequency feature. We argue that the different optical responses observed are a consequence of the proximity of these compounds to a charge-ordering transition driven by the intermolecular Coulomb repulsion.
- Received 20 June 2002
DOI:https://doi.org/10.1103/PhysRevLett.90.167002
©2003 American Physical Society