Numerical solution of the t-J model with random exchange couplings in   d=infinity dimensions
  To explore the nature of the metallic state near the transition to a Mott insulator we investigate the t-J model with random exchange interaction in d=infinity dimensions. A numerically exact solution is obtained by an extension of the continuous-time quantum Monte Carlo (CT-QMC) method to the case of a vector bosonic field coupled to a local spin. We show that the paramagnetic solution near the Mott insulator describes an incoherent metal with a residual moment, and that single-particle excitations produce an additional band, which is separated from the Mott-Hubbard band. 
Junya Otsuki, Dieter Vollhardt
cond-mat.str-el