We develop a Non-Crossing Approximation (NCA) for the effective cluster problem of the recently developed Dynamical Cluster Approximation (DCA). The DCA technique includes short-ranged correlations by mapping the lattice problem onto a self-consistently embedded periodic cluster of size Nc. It is a fully causal and systematic approximation to the full lattice problem, with corrections O(1/Nc) i...

X-ray absorption spectra on the overdoped high-temperature superconductors Tl2Ba2CuO(6+delta) and La(2-x)SrxCuO(4+/-delta) reveal a striking departure in the electronic structure from that of the underdoped regime. The upper Hubbard band, identified with strong correlation effects, is not observed on the oxygen K edge, while the lowest-energy prepeak gains less intensity than expected above p a...

To study digital Mott insulator LaTiO3 and band insulator SrTiO3 interfaces, we apply correlated band theory within the local density approximation including a Hubbard U to (n, m) multilayers, 1<or=n, m<or=9 using unit cells with larger lateral periodicity. If the on-site repulsion on Ti is big enough to model the Mott insulating behavior of undistorted LaTiO3, the charge imbalance at the inter...

The effective on-site Coulomb interaction (Hubbard U) between localized electrons at crystal surfaces is expected to be enhanced due to the reduced coordination number and reduced subsequent screening. By means of first principles calculations employing the constrained random-phase approximation we show that this is indeed the case for simple metals and insulators but not necessarily for transi...

We describe the evolution of the spectral density as we dope a Mott insulator within a dynamical mean field method. After giving an intuitive description of this Local Impurity Self-Consistent Approximation (LISA) for a model with several orbitals per unit cell, we illustrate its implementation in the context of the Hubbard model in infinite dimensions. For this purpose a new iterative perturba...

In this paper we explore the use of an equation of motion decoupling method as an impurity solver to be used in conjunction with the dynamical mean field self-consistency condition for the solution of lattice models. We benchmark the impurity solver against exact diagonalization, and apply the method to study the infinite U Hubbard model, the periodic Anderson model and the pd model. This simpl...

The Kitaev-Hubbard model of interacting fermions is defined on the honeycomb lattice and, at strong coupling, interpolates between the Heisenberg model and the Kitaev model. It is basically a Hubbard model with ordinary hopping t and spin-dependent hopping t ′. We study this model in the weak to intermediate coupling regime, at half filling, using the cellular dynamical impurity approximation (...

Even at weak to intermediate coupling, the Hubbard model poses a formidable challenge. In two dimensions in particular, standard methods such as the Random Phase Approximation are no longer valid since they predict a finite temperature antiferromagnetic phase transition prohibited by the Mermin-Wagner theorem. The Two-Particle-Self-Consistent (TPSC) approach satisfies that theorem as well as pa...

We propose a fast impurity solver for the general quantum impurity model based on the perturbation theory around the atomic limit, which can be used in combination with the local density approximation LDA and the dynamical mean-field theory DMFT . We benchmark the solver in the two-band Hubbard model within DMFT against quantum Monte Carlo QMC and numerical renormalization-group NRG results. We...

We propose a fast multi-orbital impurity solver for dynamical mean field theory (DMFT). Our DMFT solver is based on the equations of motion (EOMs) for local Green's functions and is constructed by generalizing from the single-orbital case to the multi-orbital case with the inclusion of the inter-orbital hybridizations and applying a mean field approximation to the inter-orbital Coulomb interact...