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Modern Physics Letters B

Metal–insulator transitions of fermionic mixtures with mass imbalance in disordered optical lattice

Anh-Tuan Hoang, Thi-Hai-Yen Nguyen, Duc‐Anh Le

Published Jun 9, 2021• 4 citations
Publisher

Abstract

We study the metal–insulator transitions in the half-filled Anderson–Hubbard model with mass imbalance by the typical medium theory using the equation of motion method as an impurity solver. The nonmagnetic ground state phase diagram of the system with mass imbalance is constructed numerically. In addition to the three phases showed up in the balanced case, the phase diagram of the mass imbalanced case contains a spin-selective localized phase, where one spin component is metallic while the other spin component is insulating. We find that if one increases the mass imbalance the metal region in the phase diagram is reduced, while both Anderson and Mott insulator regions are enlarged.

DOI
10.1142/s0217984921503577

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We study the metal–insulator transitions in the half-filled Anderson–Hubbard model with mass imbalance by the typical medium theory using the equation of motion method as an impurity solver. The nonmagnetic ground state phase diagram of the system with mass imbalance is constructed numerically. In addition to the three phases showed up in the balanced case, the phase diagram of the mass imbalanced case contains a spin-selective localized phase, where one spin component is metallic while the other spin component is insulating. We find that if one increases the mass imbalance the metal region in the phase diagram is reduced, while both Anderson and Mott insulator regions are enlarged.
We investigated the effects of mass imbalance on the metal-insulator phase diagram in the half-filled ionic Hubbard model using dynamical mean field theory (DMFT) and the equations of motion (EOM) method to solve the impurity problem. Our results show that the band insulator region changes less significantly compared to the Mott insulator region, while the metallic region shrinks as the mass imbalance increases. Additionally, the staggered charge density was calculated and analyzed for various values of mass imbalance, providing further insight into the critical Coulomb interaction values that govern phase transitions.
We investigate two-component mass-imbalanced fermions in an optical lattice with spatially modulated interactions by using two-site dynamical mean field theory. At half-filling and zero temperature, the phase diagram of the system is analytically obtained, in which the metallic region is reduced with increasing the mass imbalance. The ground-state properties of the fermionic system are discussed from the behaviors of both the spin-dependent quasi-particle weight at the Fermi level and the double occupancy for each sublattice as functions of the local interaction strengths for various values of the mass imbalance.
Abstract We study metal-insulator phase diagram in the half-filled disordered Hubbard model at finite temperature. We calculate the averaged local density of states at the Fermi level and the site occupation as a function of the on-site energy at finite temperature by using typical medium theory with an impurity solver of equation of motion method. Although the metallicity in the correlated metallic region changes with temperature change, the phase diagram is almost temperature independent. We find fairly good agreement between our site occupation and those obtained by the typical medium method with other impurity solver.
Abstract We consider Anderson localization in the half-filled Anderson–Hubbard model in the presence of either random on-site interactions or spatially alternating interactions in the lattice. By using dynamical mean field theory with the equation of motion method as an impurity solver, we calculate the arithmetically and geometrically averaged local density of states and derive the equations determining the critical value for the phase transition between metallic, Anderson and Mott insulating phases. The nonmagnetic ground state phase diagrams are constructed numerically. We figure out that the presence of Coulomb disorder drives the system toward the Anderson localized phase that can occur even in the absence of Anderson structural disorder. For the spatially alternating interactions, we find that the metallic region is reduced and the Anderson insulator one is enlarged with increasing interaction modulation. Our obtained results are relevant to current research in ultracold atoms in disordered optical lattices where metal–insulator transition can be observed experimentally by using ultracold atom techniques.
The effects of mass imbalance in a three-component Hubbard model are studied by the dynamical mean-field theory combined with exact diagonalization. The model describes a fermion-fermion mixture of two different particle species with a mass imbalance. One species is two-component fermion particles, and the other is single-component ones. The local interaction between particle species is considered isotropically. It is found that the mass imbalance can drive the mixture from insulator to metal. The insulator-metal transition is a species-selective-like transition of lighter mass particles and occurs only at commensurate particle densities and moderate local interactions. For weak and strong local interactions the mass imbalance does not change the ground state of the mixture.
Ground-state properties of fermionic mixtures confined in a one-dimensional optical lattice are studied numerically within the spinless Falicov-Kimball model with a harmonic trap. A number of remarkable results are found. i) At low particle filling the system exhibits phase separation with heavy atoms in the center of the trap and light atoms in the surrounding regions. ii) Insulating phases always coexist with metallic phases. iii) Atomic-density waves are observed in the insulating regions for all particle fillings near the half-filled lattice case. iv) The variance of the local density exhibits universal behavior (independent of the particle filling, the Coulomb interaction and the strength of a confining potential) over the whole region of the local density values.