Mott-Hubbard metal-insulator transition at noninteger filling

Correlated electrons in a binary alloy A(x)B(1-x) are investigated within the Hubbard model and dynamical mean-field theory (DMFT). The random energies epsilon(i) have a bimodal probability distribution and an energy separation Delta. We solve the DMFT equations by the numerical renormalization-group method at zero temperature and calculate the spectral density as a function of disorder strength Delta and interaction U at different fillings. For filling factors nu=x or 1+x the lower or upper alloy subband is half filled and the system becomes a Mott insulator at strong interactions, with a correlation gap at the Fermi level. At the metal-insulator transition hysteresis is observed. We also analyze the effective theory in the Delta-->infinity limit and find good agreement between analytical and numerical results for the critical interaction U-c at which the metal-insulator transition occurs.