Junya Otsuki, University of Augsburg
To explore the nature of the metallic state near the transition to a Mott insulator, the t-J model with random exchange interaction is considered. This model at half-filling has been discussed in the context of the spin glass. In infinte dimensions, the model is mapped to an Anderson impurity model, where the local spin is coupled to a vector bosonic field. A numerically exact solution is obtained by an extension of the continuous-time quantum Monte Carlo (CT-QMC) method. It is shown that the paramagnetic solution near the Mott insulator is an incoherent metal with a residual moment. The single-particle excitation in this regime shows an energy dispersion consisting of the Hubbard band and an additional band, which is qualitatively different from that of the Fermi-liquid regime. The appearance of the additional band is discussed in terms of a one-hole excitation in the Mott insulator.