Abstract For a finite chain of strongly correlated electrons a nonlinear transport theory is treated. The time dependent behaviour of the expectation values for singly and doubly occupied states and the local and total current densities are calculated for oscillating boundary conditions in the asymptotic limit (t → ∞).
We study the ground-state phase diagram of the Anderson-Hubbard model with correlated hopping at half-filling in one dimension. The Hamiltonian has a local Coulomb repulsion U and a disorder potential with local energies randomly distributed in the interval $(\ensuremath{-}W,+W)$ with equal probability, acting on the singly occupied sites. The hopping process which modifies the number of doubly occupied sites is forbidden. The hopping between nearest-neighbor singly occupied and empty sites or between singly occupied and doubly occupied sites has the same amplitude t. We identify three different phases as functions of the disorder amplitude W and Coulomb interaction strength U>0. When U<4t the system shows a metallic phase: (i) only when no disorder is present W=0 or an Anderson-localized phase, (ii) when disorder is introduced $W\ensuremath{\ne}0$. When U>4t the Anderson-localized phase survives as long as disorder effects dominate on the interaction effects, otherwise a Mott-insulator phase (iii) arises. Phases (i) and (ii) are characterized by a finite density of doublons and a vanishing charge gap among the ground state and the excited states. Phase (iii) is characterized by the vanishing density of doublons and a finite gap for the charge excitations.
We discuss a nonequilibrium dynamical mean-field framework for simulating inhomogeneous Hubbard models with local disorders. Our approach treats electron interactions and disorders on equal footing, by considering only local dynamical fluctuations. The theory reduces to nonequilibrium dynamical mean-field theory in the presence of only electron-electron interactions and to the coherent potential approximation in noninteracting systems with disorders. Both time-dependent and steady-state problems are treated by implementing the theory on the three-branch Kadanoff-Baym contour and two-branch Schwinger-Keldysh contour, respectively. Benchmarks on a eight-site cube show that the method yields rather accurate spectral functions in both the weakly and strongly interacting regimes. In a cubic lattice, we demonstrate energy conservation after an interaction quench and thermalization after just a few hopping times in both clean and disordered systems. As an application, we study transport through a serial double quantum-dot sandwiched between two leads, focusing on the current and dot occupations after a voltage quench.
We investigate electron transport in disordered Hubbard chains contacted to macroscopic leads, via the nonequilibrium Green's function technique. We observe a crossover of currents and conductances at finite bias which depends on the relative strength of disorder and interactions. We provide a proof that the coherent potential approximation, a widely used method for treating disorder averages, fulfills particle conservation at finite bias with or without electron correlations. Finally, our results hint that the observed trends in conductance due to interactions and disorder also appear as signatures in the single-site entanglement entropy.
A diagrammatic technique that treats the kinetic energy as a perturbation on the Coulomb interaction term is used to show the correspondence between the Hubbard Hamiltonian and a disordered alloy of singly and doubly occupied atoms. The method generalizes the alloy-analogy approach. Infinite and finite chains, and finite clusters of the square lattice, are considered. Finite systems are handled by means of a method that includes, in a self-consistent manner, only those configurations with the same number of particles. Total energies and momentum distributions are calculated. The results for chains up to 14 sites and 4\ifmmode\times\else\texttimes\fi{}4 clusters of the square lattice compare satisfactorily with exact results.