We calculate the spectral weight of one- and two-dimensional Hubbard models by performing exact diagonalizations finite clusters treating intercluster hopping with perturbation theory. Even relatively modest (e.g., 12 sites), spectra thus obtained give an accurate description results. Spin-charge separation (i.e., extended bounded singularities dispersing wave vector) is clearly recognized in one-dimensional model, so model.

We study the evolution of a Mott-Hubbard insulator into correlated metal upon doping in two-dimensional Hubbard model using cellular dynamical mean-field theory. Short-range spin correlations create two additional bands apart from familiar spectral function. Even tiny this causes jump Fermi energy to one these and an immediate momentum-dependent suppression weight at energy. The pseudogap is closely tied existence bands. This suggests strong-coupling mechanism that arises short-range large...

Cluster perturbation theory is a technique for calculating the spectral weight of Hubbard models strongly correlated electrons, which combines exact diagonalizations on small clusters with strong-coupling at leading order. It in both strong- and weak-coupling limits provides good approximation to function any wavevector. Following paper by Sénéchal et al. (Phys. Rev. Lett. {\bf 84}, 522 (2000)), we provide more complete description derivation method. We illustrate some its capabilities,...

Using cluster perturbation theory, it is shown that the spectral weight and pseudogap observed at Fermi energy in recent Angle Resolved Photoemission Spectroscopy (ARPES) of both electron hole-doped high-temperature superconductors find their natural explanation within t-t'-t''-U Hubbard model two dimensions. The value interaction U needed to explain experiments for electron-doped systems optimal doping weak intermediate coupling regime where t-J inappropriate. At strong coupling,...

Using variational cluster perturbation theory we study the competition between $d$-wave superconductivity ($d\mathrm{SC}$) and antiferromagnetism (AF) in $t\mathrm{\text{\ensuremath{-}}}{t}^{\ensuremath{'}}\mathrm{\text{\ensuremath{-}}}{t}^{\ensuremath{'}\ensuremath{'}}\mathrm{\text{\ensuremath{-}}}U$ Hubbard model. Large scale computer calculations reproduce overall ground-state phase diagram of high-temperature superconductors as well one-particle excitation spectra for both hole electron...

Proximity to a Mott insulating phase is likely be an important physical ingredient of theory that aims describe high-temperature superconductivity in the cuprates. Quantum cluster methods are well suited phase. Hence, as step towards quantitative competition between antiferromagnetism (AFM) and d-wave (SC) cuprates, we use Cellular Dynamical Mean Field Theory compute zero temperature properties two-dimensional square lattice Hubbard model. The order parameter found scale like superexchange...

We investigate the half-filled Hubbard model on an isotropic triangular lattice with variational cluster approximation. By decreasing on-site repulsion $U$ (or equivalently increasing pressure) we go from a phase long-range, three-sublattice, spiral magnetic order, to nonmagnetic Mott insulating phase---a spin liquid---and then, for $U\ensuremath{\lesssim}6.7t$, metallic phase. Clusters of sizes 3, 6, and 15 open boundary conditions are used in these calculations, extrapolation infinite size...

Experiments have shown that the families of cuprate superconductors largest transition temperature at optimal doping also oxygen hole content [D. Rybicki et al., Nat. Commun. 7, 1-6 (2016)]. They a large charge-transfer gap [W. Ruan Sci. Bull. (Beijing) 61, 1826-1832 (2016)], quantity accessible in normal state, is detrimental to superconductivity. We solve three-band Hubbard model with cellular dynamical mean-field theory and show both these observations follow from model. Cuprates play...

The nature of the metal-insulator Mott transition at zero temperature has been discussed for a number years. Whether it occurs through quantum critical point or first-order is expected to profoundly influence finite-temperature phase diagram. In this paper, we study in two-dimensional Hubbard model on square lattice with variational cluster approximation. This takes into account antiferromagnetic short-range correlations. By contrast single-site dynamical mean-field theory, turns out be...

Motivated by the possibility of superconductivity in doped graphene sheets, we investigate superconducting order extended Hubbard model on two-dimensional lattice using variational cluster approximation (VCA) and cellular dynamical mean-field theory (CDMFT) with an exact diagonalization solver at zero temperature. The nearest-neighbor interaction is treated a decoupling between clusters. We compare different pairing symmetries, singlet triplet, based short-range pairing. VCA simulations show...

Antiferromagnetism and $d$-wave superconductivity are the most important competing ground-state phases of cuprate superconductors. Using cellular dynamical mean-field theory (CDMFT) for Hubbard model, we revisit question coexistence competition these in one-band model with realistic band parameters interaction strengths. With an exact diagonalization solver, improve on previous works a more complete bath parametrization which is carefully chosen to grant maximal possible freedom...

We study the twisted Hubbard model of a cuprate bilayer at fixed twist angle $\ensuremath{\theta}=53.{13}^{\ensuremath{\circ}}$ and as function doping, using variational cluster approximation, method that treats short-range dynamical correlations exactly. At intermediate interlayer tunneling, we observe sudden change relative sign $d$-wave order parameters two layers between underdoped overdoped regimes. strong clear time-reversal symmetry breaking phase near optimal in which changes...

We study a one-band Hubbard model for twisted cuprate bilayer with twist angle of $43.{6}^{\ensuremath{\circ}}$ and moir\'e cell containing 58 sites. use the variational cluster approximation (VCA), which treats short-range correlations exactly leads, in single layers, to dome $d$-wave superconductivity away from half filling strong on-site repulsion alone. find time-reversal-symmetry (TRS) breaking phase small doping interval overdoped region when interlayer tunneling is enough. Contrary...

We examine the phase diagram of extended Hubbard model on a square lattice, for both attractive and repulsive nearest-neighbor interactions, using CDMFT+HFD, combination Cluster Dynamical Mean Field theory (CDMFT) Hartree-Fock mean-field decoupling inter-cluster interaction. For non-local this exhibits region separation near half-filling, in vicinity which we find islands d-wave superconductivity, decaying rapidly as function doping, with disconnected regions s-wave order at smaller (higher)...

This is a short review of the theoretical work on two-dimensional Hubbard model performed in Sherbrooke last few years. It written occasion twentieth anniversary discovery high-temperature superconductivity. We discuss several approaches, how they were benchmarked and agree sufficiently with each other that we can trust results are accurate solutions model. Then comparisons made experiment. show does exhibit d-wave superconductivity antiferromagnetism essentially where observed for both...

Confirmation of the phononic origin Cooper pair formation in superconductors came with demonstration that interaction was retarded and corresponding energy scales were associated phonons. Using cellular dynamical mean-field theory for two-dimensional Hubbard model, we identify such retardation effects d-wave pairing associate short-range spin fluctuations. We find which frequencies are relevant as a function strength doping show disappearance superconductivity on overdoped side coincides low...

Very large anisotropies in transport quantities have been observed the presence of very small in-plane structural anisotropy many strongly correlated electron materials. By studying two-dimensional Hubbard model with dynamical-mean-field theory for clusters, we show that such can be induced without static stripe order if interaction is enough to yield a Mott transition. Anisotropy decreases at frequency. The maximum effect on conductivity occurs underdoped regime, as high-temperature superconductors.

Many theoretical approaches find $d$-wave superconductivity in the prototypical one-band Hubbard model for high-temperature superconductors. At strong coupling ($U\ensuremath{\ge}W$, where $U$ is on-site repulsion and $W=8t$ bandwidth) pairing controlled by exchange energy $J=4{t}^{2}/U$. One may then surmise, ignoring retardation effects, that near-neighbor Coulomb $V$ will destroy when it becomes larger than $J$, a condition easily satisfied cuprates, example. Using cellular dynamical...

The question of the existence a spin liquid state in half-filled Hubbard model on honeycomb (also known as graphene) lattice is revisited. variational cluster approximation, dynamical mean field theory, and impurity approximation are applied to various systems. Assuming that phase coincides with Mott insulating this nonfrustrated system, we find transition preempted by magnetic occurring at lower value interaction U, therefore does not occur. This conclusion obtained using clusters two bath...

The possible superconducting states of strontium ruthenate $({\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4})$ are organized into irreducible representations the point group ${D}_{4h}$, with a special emphasis on nodes occurring within gap. Our analysis covers cases and without spin-orbit coupling takes account possibility interorbital pairing three-band, tight-binding description ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$. No dynamical treatment if performed: We confining ourselves to group-theoretical...