Low-energy structure and topology of the two-band Hubbard-Kanamori model

Abstract: We investigate the Mott transition in a two-band Hubbard-Kanamori model using Dynamical Mean-Field Theory (DMFT) with the Density Matrix Renormalization Group (DMRG) and the Numerical Renormalization Group (NRG) as impurity solvers. Our study focuses on the case where the intraorbital and interorbital Coulomb interactions are equal (U = U2) and the Hund's coupling is absent (J = 0). Spectral analysis confirms the absence of an orbital-selective Mott transition (OSMT), even in systems with significantly different bandwidths (t1 and t2 for the wide and narrow bands, respectively), indicating a simultaneous Mott transition in both bands. Notably, the NRG results reveal the emergence of a pseudo-gap-like feature and a central peak in the narrow band, whose characteristics depend on the hopping parameter t2. These spectral features may serve as precursors to OSMT in more realistic systems with finite Hund's coupling (J > 0). Furthermore, in the Mott insulating phase, the self-energies of both bands diverge, suggesting that the Mott transition represents a topological phase transition. Our results highlight the crucial role of accurate impurity solvers in capturing the density of states and detailed spectral structures.