Signatures of coherent electronic quasiparticles in the paramagnetic   Mott insulator
  We show that the Mott insulating state of the half-filled paramagnetic Hubbard model in infinite dimensions contains electronic quasiparticles with very small quasiparticle weight at the inner edge of the Hubbard bands. We use a stochastic and non-perturbative quantum impurity solver based on calculating the impurity self energy as a sample average over a representative distribution of impurity models solved by exact diagonalization. Due to the natural parallelization of the method, millions of poles are readily generated for the self energy which allows to work with very small pole-broadening $\eta$. Solutions at small and large $\eta$ are qualitatively different, and only at $\eta\leq 0.001$ (in units of half bare band width) are quasiparticles found. Evaluated on the imaginary frequency axis we find that the small $\eta$ solutions agree within statistical error with results using continuous time quantum Monte Carlo. 
Mats Granath and Johan Sch\"ott
cond-mat.str-el