Pseudogap universality in the doping-driven metal to Mott-insulator transition

A pseudogap was observed in the doping-driven metal to Mott-insulator transition using Cluster Dynamical Mean-Field Theory (CDMFT) for the Hubbard model on small 2×2 square clusters¹. Here, we show that this pseudogap displays some universal behavior under the change of temperature T, hopping terms t' and double occupancy cost U. We use three different approaches : the one band model for a 2×2 square cluster using CDMFT, the three band model for a 2×2 square cluster using CDMFT, and the one-band model for a 3×2 cluster using the Dynamical Cluster Approximation (DCA). We find that, if there is a first order transition, the filling as a function of shifted chemical potential μ does not depend on either U, T nor t' for t' in the interval [0.4,1]. The electron-doped and hole-doped cases however are different. Defining μ_PG as the chemical potential that we considered to be the beginning of the pseudogap phase (n=0.995), we also find that μ_PG does not vary with U as long as one is in the strong interaction regime.

1. G. Sordi, K. Haule, and A.-M. S. Tremblay. Phys. Rev. B, 84(7):075161, Aug 2011.