Metal-insulator transition induced by mass imbalance in a three-component Hubbard model

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.

Figure 1

The total particle density $n$, calculated by DMFT+ED (lines) and by DMFT+QMC (symbols), as a function of the chemical potential $\mu$ for different values of interaction $U$ in the balanced mass case $\Delta t=0 \left(T=0.025t\right)$. The DMFT+QMC results are reproduced from Ref. [7].

Figure 2

The double occupancy as a function of the chemical potential $\mu$, calculated by DMFT+ED (lines) and by DMFT+QMC (symbols) for different values of interaction $U$ in the balanced mass case $\Delta t=0 \left(T=0.025t\right)$. The DMFT+QMC results are reproduced from Ref. [7].

Figure 3

The density of states (DOS), calculated by DMFT+ED (lines) and by DMFT+QMC (symbols) for different chemical potentials $\mu$ in the balanced mass case $\Delta t=0 (U=3t,T=0.05t)$. The DMFT+QMC results are reproduced from Ref. [7].

Figure 4

The total particle density $n$ as a function of the chemical potential $\mu$ for positive mass imbalances $\left(\Delta t>0\right)$ at fixed interaction $U=4t \left(T=0.02t\right)$.

Figure 5

The total particle density $n$ as a function of the chemical potential $\mu$ for negative mass imbalances $\left(\Delta t<0\right)$ at fixed interaction $U=2.5t \left(T=0.02t\right)$.

Figure 6

The density of states (DOS) of the two-component particles (blue solid lines) and of single-component particles (red dotted lines) for positive mass imbalances $(\Delta t>0)$ at fixed total particle density $n=1$ and interaction $U=4t \left(T=0.02t\right)$.

Figure 7

The density of states (DOS) of the two-component particles (blue solid lines) and of single-component particles (red dotted lines) for negative mass imbalances $(\Delta t<0)$ at fixed total particle density $n=1$ and interaction $U=2.5t \left(T=0.02t\right)$.

Figure 8

The intraspecies double occupancy $D_{\mathrm{intra}}$ (red filled circles) and the interspecies double occupancy $D_{\mathrm{inter}}$ (blue filled squares) at fixed total density $n=1 \left(T=0.02t\right)$. The left panel plots the region of $\Delta t<0 (U=2.5t)$, while the right panel plots the region of $\Delta t>0 \left(U=4t\right)$.

Figure 9

The intraspecies double occupancy $D_{\mathrm{intra}}$ (red filled circles) and the interspecies double occupancy $D_{\mathrm{inter}}$ (blue filled squares) at fixed total density $n=1$ and different mass imbalances $\left(T=0.02t\right)$.

Figure 10

Phase diagram at total particle density $n=1 \left(T=0.02\right)$.