One-dimensional Asymmetric Hubbard Model Research Articles

Phase separation and pairing regimes in the one-dimensional asymmetric Hubbard model

We address some open questions regarding the phase diagram of the one-dimensional Hubbard model with asymmetric hopping coefficients and balanced species. In the attractive regime we present a numerical study of the passage from on-site pairing dominant correlations at small asymmetries to charge-density waves in the region with markedly different hopping coefficients. In the repulsive regime we exploit two analytical treatments in the strong- and weak-coupling regimes in order to locate the onset of phase separation at small and large asymmetries, respectively.

Fidelity susceptibility, scaling, and universality in quantum critical phenomena

We study fidelity susceptibility in the one-dimensional asymmetric Hubbard model and show that the fidelity susceptibility can be used to identify the universality class of the quantum phase transitions in this model. The Kosterlitz--Thouless-type transition occurred at half-filling and the Landau transition away from half-filling can be discriminated from distinct critical exponents of the fidelity susceptibility.

The asymmetric Hubbard model with a confining potential: The partial filling case

We investigate the one-dimensional asymmetric Hubbard model with a confining potential, which may describe the ground state of two species of fermionic atoms trapped in a one-dimensional optical lattice. We use White's density matrix renormalization group and the global electronic density considered is n = 0.8 . The fermion density profiles and their variance were computed. We observe coexistence of insulating and metallic regions in the system. The effective confinement region is different for each kind of fermionic atom.

The one-dimensional asymmetric Hubbard model at partial band filling

We study the one-dimensional asymmetric Hubbard model (AHM) through the White's density matrix renormalization group technique at the density n = 0.8 . The AHM describes a correlated system where the hopping of electrons depend on their spin. The spin structure factor and the charge structure factor of heavy electrons were calculated as a function of the hopping and the repulsive on-site interaction. We found that the ground state displays phase separation for strong coupling, and a non-universal critical hopping separates the states of density wave and the phase separation. This outcome generalizes the result found one in the Falicov–Kimball model, which is a particular case of the AHM.

Bosonization study of quantum phase transitions in the one-dimensional asymmetric Hubbard model

The quantum phase transitions in the one-dimensional asymmetric Hubbard model are investigated with the bosonization approach. The conditions for the phase transition from density wave to phase separation, the correlation functions, and their exponents are obtained analytically. Our results show that the difference between the hopping integrals for up- and down-spin electrons is crucial for the occurrence of the phase separation. When the difference is large enough, the phase separation will appear even if the on-site interaction is small.

Breakdown of the Mott insulator: Exact solution of an asymmetric Hubbard model

The breakdown of the Mott insulator is studied when the dissipative tunneling into the environment is introduced to the system. By exactly solving the one-dimensional asymmetric Hubbard model, we show how such a breakdown of the Mott insulator occurs. As the effect of the tunneling is increased, the Hubbard gap is monotonically decreased and finally disappears, resulting in the insulator-metal transition. We discuss the origin of this quantum phase transition in comparison with other non-Hermitian systems recently studied.

Asymmetric Hubbard chain at half-filling.

The ground-state phase diagram of the one-dimensional asymmetric Hubbard model at half-filling is studied by means of a perturbation expansion in the large-U limit and White's density matrix renormalization-group method for various values of the couplings. We argue that the introduction of asymmetry in the hopping parameters is a relevant perturbation for any repulsive U and drives the system into an ordered N\'eel antiferromagnet. The transition belongs to the Kosterlitz-Thouless universality class.