Negative-U centers model for high-Tc superconductivity

The state with anomalous high conductivity is observed at temperature T, in the room temperature range for some low-coordinated semiconductors (chalcogenide glasses) and polymers. We propose a model to describe the phenomenon based on the theory of superconducting (SC) properties of the system of localized electron pairs. SC properties of the model are determined by transport along a band formed by the localized pairs of carriers belonging to negative-U centers, i.e., intrinsic defects with a negative effective correlation energy (U < 0). The negative-U centers superconducting model (NUCS model) also well describes the high-T-c superconducting state in metal oxides. (c) 2005 Elsevier B.V. All rights reserved.