Seminars Archive
Strong Correlations and Orbital Fluctuactions in Disordered Doped Mott Insulators
Dipartimento di Fisica “E.R. Caianiello”, Università degli Studi di Salerno, Fisciano (SA), Italy
Abstract
We elucidate the effects of defect disorder and e-e interaction on the spectral density of the defect states emerging in the Mott-Hubbard gap of doped transition-metal oxides, such as Y1−xCaxVO3. A soft gap of kinetic origin develops in the defect band and survives defect disorder for e-e interaction strengths comparable to the defect potential and hopping integral values above a doping dependent threshold; otherwise only a pseudogap persists. These two regimes naturally emerge in the statistical distribution of gaps among different defect realizations, which turns out to be of Weibull type. Its shape parameter k determines the exponent of the power-law dependence of the density of states (k − 1) and hence distinguishes between the soft gap regime (k ≥ 2) and the pseudogap one (k < 2). Both k and the effective gap scale with the hopping integral and the e-e interaction in a wide doping range. The motion of doped holes is confined by the closest defect potential and the overall spin-orbital structure. Such a generic behavior leads to complex non-hydrogen-like defect states that tend to preserve the underlying C-type spin and G-type orbital order and can be detected and analyzed via scanning tunneling microscopy.