Orbital selective crossover and Mott transitions in an asymmetric Hubbard model of cold atoms in optical lattices

TL;DR

This paper investigates the phase diagram of an asymmetric Hubbard model for cold atoms in optical lattices, revealing orbital-selective crossover and Mott transitions using Dynamical Mean Field Theory.

Contribution

It provides the first detailed phase diagram of the asymmetric Hubbard model at half-filling, highlighting orbital-selective crossover and coexistence of solutions.

Findings

Identification of a Mott transition with coexisting solutions for all nonzero asymmetries.

Discovery of an orbital-selective crossover leading to a bad metallic state.

Calculation of observables like double occupation, specific heat, and entropy across phases.

Abstract

We study the asymmetric Hubbard model at half-filling as a generic model to describe the physics of two species of repulsively interacting fermionic cold atoms in optical lattices. We use Dynamical Mean Field Theory to obtain the paramagnetic phase diagram of the model as function of temperature, interaction strength and hopping asymmetry. A Mott transition with a region of two coexistent solutions is found for all nonzero values of the hopping asymmetry. At low temperatures the metallic phase is a heavy Fermi-liquid, qualitatively analogous to the Fermi liquid state of the symmetric Hubbard model. Above a coherence temperature, an orbital-selective crossover takes place, wherein one fermionic species effectively localizes, and the resulting bad metallic state resembles the non-Fermi liquid state of the Falicov-Kimball model. We compute observables relevant to cold atom systems such as the double occupation, the specific heat and entropy and characterize their behavior in the different phases.