Disorder-induced gap in the normal density of states of the organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br

摘要

The local density of states (DOS) of the organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)] Br, measured by scanning tunneling spectroscopy on in situ cleaved surfaces, reveals a logarithmic suppression near the Fermi edge persisting above the critical temperature T-c. The experimentally observed suppression of the DOS is in excellent agreement with a soft Hubbard gap as predicted by the Anderson-Hubbard model for systems with disorder. The electronic disorder also explains the diminished coherence peaks of the quasi-particle DOS below T-c.