A charge model as an effective model of one-dimensional Hubbard and extended Hubbard systems: its application to linear optical spectrum calculations in large systems based upon many-body Wannier functions
We propose an effective model called the "charge model", for the half-filled one-dimensional Hubbard and extended Hubbard models. In this model, spin-charge separation, which has been justified from an infinite on-site repulsion ($U$) in the strict sense, is compatible with charge fluctuations. Our analyses based on the many-body Wannier functions succeeded in determining the optical conductivity spectra in large systems. The obtained spectra reproduce the spectra for the original models well even in the intermediate $U$ region of $U=5-10T$, with $T$ being the nearest-neighbor electron hopping energy. These results indicate that the spin-charge separation works fairly well in this intermediate $U$ region against the usual expectation and that the charge model is an effective model that applies to actual quasi-one-dimensional materials classified as strongly correlated electron systems.
We present first-principles calculations of optimally localized Wannier functions for Cu and use these for an ab-initio determination of Hubbard (Coulomb) matrix elements. We use a standard linearized muffin-tin orbital calculation in the atomic-sphere approximation (LMTO-ASA) to calculate Bloch functions, and from these determine maximally localized Wannier functions using a method proposed by Marzari and Vanderbilt. The resulting functions were highly localized, with greater than 89% of the norm of the function within the central site for the occupied Wannier states. Two methods for calculat…
We show that one can properly take into account of the interaction effects and construct a set of orthonormal Wannier functions for a Bose-Einstein condensate in an optical lattice. These interaction-dependent Wannier functions are used to compute the tunneling rate $J$ and the on-site repulsion $U$ in the Bose-Hubbard model. Both parameters are found to be substantially different from ones calculated with the single-particle Wannier functions. Our numerical results of $U$ are found in good agreement with the measured on-site energy in a recent experiment [Campbell {\it et al.} Science {\bf 31…
We derive a "Wannier-Hubbard" model consisting of an array of overlapping atomic orbitals interacting via a local Coulomb interaction. Transforming to an orthogonal Wannier basis set, the resulting Hamiltonian displays long range hopping and interactions, with new terms such as correlated hopping and ferromagnetic direct exchange, among others. We numerically study the one-dimensional version of the model at half-filling using the density matrix renormalization group (DMRG) method, unveiling a rich phase diagram as a function of the interaction $U$ and the overlap $s$ with metallic, and ferrom…
We present a model example of a quantum critical behavior of renormalized single-particle Wannier function composed of Slater s-orbitals and represented in an adjustable Gaussian STO-7G basis, which is calculated for cubic lattices in the Gutzwiller correlated state near the metal-insulator transition (MIT). The discussion is carried out within the extended Hubbard model and the method of approach proposed earlier [cf. Eur. Phys. J. B {\bf 66}, 385 (2008)]. The component atomic-wave-function size, the Wannier function maximum, as well as the system energy, all scale with the increasing lattice…
We use maximally localized Wannier functions to construct tight-binding (TB) parameterizations for the e_g bands of LaMnO_3 based on first principles electronic structure calculations. We compare two different ways to represent the relevant bands around the Fermi level: i) a d-p model that includes atomic-like orbitals corresponding to both Mn(d) and O(p) states in the TB basis, and ii) an effective e_g model that includes only two e_g-like Wannier functions per Mn site. We first establish the effect of the Jahn-Teller distortion within the d-p model, and then compare the TB representations fo…
We refer to our recent calculations (Eur. Phys. J. B, \textbf{86}, 252 (2013)) of metallization pressure of the three-dimensional simple-cubic crystal of atomic hydrogen and study the effect on the crucial results concocting from approximating the $1s$ Slater-type orbital function with a series of $p$ Gaussians. As a result, we find the critical metallization pressure $p_C = 102\ GPa$. The latter part is a discussion of the influence of zero-point motion on the stabilizing pressure. We show that in our model the estimate magnitude of zero-point motion carries a little effect on the critical me…
We extend our previous approach (Eur. Phys. J. B, \textbf{74}, 63(2010)) to modeling correlated electronic states and the metal-insulator transition by applying the so-called \emph{statistically consistent Gutzwiller approximation} (SGA) to carry out self-consistent calculations of the renormalized single-particle Wannier functions in the correlated state. The transition to the Mott-Hubbard insulating state at temperature T=0 is of weak first order even if antiferromagnetism is disregarded. The magnitude of the introduced self-consistent magnetic correlation field is calculated and shown to le…
For the one-dimensional, extended Peierls--Hubbard model we calculate analytically the ground-state energy and the single-particle gap to second order in the Coulomb interaction for a given lattice dimerization. The comparison with numerically exact data from the Density-Matrix Renormalization Group shows that the ground-state energy is quantitatively reliable for Coulomb parameters as large as the band width. The single-particle gap can almost triple from its bare Peierls value before substantial deviations appear. For the calculation of the dominant optical excitations, we follow two approac…
The method used earlier for analysis of correlated nanoscopic systems is extended to infinite (periodic) s-band like systems described by the Hubbard model and its extensions. The optimized single-particle wave functions contained in the parameters of the Hubbard model (the hopping \textit{t} and the magnitude of the intraatomic interaction \textit{U}) are determined explicitly in the correlated state for the electronic systems of various symmetries and dimensions: Hubbard chain, square and triangular planar lattices, and the three cubic lattices (SC, BCC, FCC). In effect, the evolution of the…
The most general way to describe localized atomic-like electronic states in strongly correlated compounds is to utilize Wannier functions. In the present paper we continue the development of widely-spread DFT+U method onto Wannier function basis set and propose the technique to calculate the Hubbard contribution to the forces. The technique was implemented as a part of plane-waves pseudopotential code Quantum-ESPRESSO and successfully tested on a charge transfer insulator NiO.
We study the electronic transport in an infinite one-dimensional Hubbard chain, driven by a homogeneous electric field. The physical chain is coupled to fermion bath chains, in order to account for dissipation and to prevent the occurrence of Bloch Oscillations. The steady state current is computed in the frame of Keldysh Green's functions in Cluster Perturbation Theory. The current characteristics are dominated by resonant-tunneling-like structures, which can be traced back to Wannier-Stark resonances due to anti-ferromagnetic correlations. The same current characteristic occurs in a non-inte…
Sliced-basis DMRG(sb-DMRG) is used to simulate a chain of hydrogen atoms and to construct low-energy effective Hubbard-like models. The downfolding procedure first involves a change of basis to a set of atom-centered Wannier functions constructed from the natural orbitals of the exact DMRG one-particle density matrix. The Wannier function model is then reduced to a fewer-parameter Hubbard-like model, whose parameters are determined by minimizing the expectation value of the Wannier Hamiltonian in the ground state of the Hubbard Hamiltonian. This indirect variational procedure not only yields c…
When the first four spectral moments are considered, spectral features missing in standard Kohn-Sham (KS) density-functional theory (DFT), such as upper and lower Hubbard bands, as well as spectral satellite peaks, can be described, and the bandwidths can be corrected. Therefore, we have devised a \textit{moment-functional based spectral density functional theory} (MFbSDFT) recently. However, many computational tools in theoretical solid state physics, such as the construction of maximally localized Wannier functions (MLWFs), have been developed for KS-DFT and require modifications if they are…
Maximally localized Wannier functions are the key tool for a variety of physical applications of Bloch states. Here we develop a simple and exact procedure to construct maximally localized Wannier functions for one dimensional periodic potentials of arbitrary form. As opposed to relatively complex numerical minimization approaches that may return somewhat different results depending on implementation and running conditions, this computationally straightforward method guarantees a unique (and optimal) result on each run. These features make it a useful vehicle for evaluation of Hubbard interact…
We derive ab initio local Hubbard models for several optical lattice potentials of current interest, including the honeycomb and Kagomé lattices, verifying their accuracy on each occasion by comparing the interpolated band structures against the originals. To achieve this, we calculate the maximally-localized generalized Wannier basis by implementing the steepest-descent algorithm of Marzari and Vanderbilt [N. Marzari and D. Vanderbilt, Phys. Rev. B 56, 12847 (1997)] directly in one and two dimensions. To avoid local minima we develop an initialization procedure that is both robust and require…
Starting from a single band Hubbard model in the Wannier function basis, we revisit the problem of the ligand contribution to exchange and derive explicit formulae for the exchange integrals in metal oxide compounds in terms of atomic parameters that can be calculated with constrained LDA and LDA+U. The analysis is applied to the investigation of the isotropic exchange interactions of LiCu$_{2}$O$_{2}$, a compound where the Cu-O-Cu angle of the dominant exchange path is close to 90$^{\circ}$. Our results show that the magnetic moments are localized in Wannier orbitals which have strong contrib…
We present a quantum critical behavior of the renormalized single-particle Wannier function, calculated in the Gutzwiller correlated state near the insulator-metal transition (IMT) for cubic lattices. The wave function size and its maximum, as well as the system energy scale with increasing lattice parameter $R$ as $R^{n}$. Such scaling is interpreted as the evidence of a dominant role of the Coulomb repulsion. Relation of the insulator-metal transition lattice-parameter value $R=R_{C}$ to the original {\em Mott criterion\} is obtained. The method is tested by comparing our results with the ex…
We define Wannier functions for interacting systems, and show that the results on the localization of the Wannier functions for non-interacting systems carry over to the Wannier functions for interacting systems. In addition we demonstrate that the characterization of metals and insulators by the decay properties of their respective density matrices does not only apply to non-interacting, but also to interacting systems. As a prototypical example of a correlated system we investigate the one-dimensional Hubbard model. We propose an expression for the density matrix of that model, and derive a …
We study effects of charge self-consistency within the combination of density functional theory (DFT; Wien2k) with dynamical mean field theory (DMFT; w2dynamics) in a basis of maximally localized Wannier orbitals. Using the example of two cuprates, we demonstrate that even if there is only a single Wannier orbital with fixed filling, a noteworthy charge redistribution can occur. This effect stems from a reoccupation of the Wannier orbital in k-space when going from the single, metallic DFT band to the split, insulating Hubbard bands of DMFT. We analyze another charge self-consistency effect be…
Parameterizing DFT+U+V from Hybrid Functionals: A Wannier-Function-Based Approach for Strongly Correlated Materials
M.N. Mikheev Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences（俄罗斯科学院乌拉尔分支 M.N. 米凯耶夫金属物理研究所）；Department of Theoretical Physics and Applied Mathematics, Ural Federal University（乌拉尔联邦大学理论物理与应用数学系）
We have applied a many-body Wannier functions method to theoretically calculate an excitonic optical conductivity spectrum and energy structure in a one-dimensional (1D) Mott insulator at absolute zero temperature with large system size. Focusing on full charge fluctuations associated with pairs of a holon and doublon, we employ a charge model, which is interpreted as a good effective model to investigate photoexcitations of a 1D extended Hubbard model at half-filling in the spin-charge separation picture. As a result, the theoretical spectra with appropriate broadenings qualitatively reproduc…
Using the newly developed VASP2WANNIER90 interface we have constructed maximally localized Wannier functions (MLWFs) for the e_g states of the prototypical Jahn-Teller magnetic perovskite LaMnO3 at different levels of approximation for the exchange-correlation kernel. These include conventional density functional theory (DFT) with and without additional on-site Hubbard U term, hybrid-DFT, and partially self-consistent GW. By suitably mapping the MLWFs onto an effective e_g tight-binding (TB) Hamiltonian we have computed a complete set of TB parameters which should serve as guidance for more el…
An effective low-energy model describing magnetic properties of alkali-cluster-loaded sodalites is derived by {\em ab initio} downfolding. We start with constructing an extended Hubbard model for maximally localized Wannier functions. {\em Ab initio} screened Coulomb and exchange interactions are calculated by constrained random phase approximation. We find that the system resides in the strong coupling regime and thus the Heisenberg model is derived as a low-energy model of the extended Hubbard model. We obtain antiferromagnetic couplings $\sim$ $O$(10 K), being consistent with the experiment…
We study the complete extended Hubbard-Holstein Hamiltonian on a four-site chain with equally spaced sites, with spacing-dependent electronic interaction parameters evaluated in terms of Wannier functions built from Gaussian atomic orbitals. By successive application of generalized displacement and squeezing transformations, an effective polaronic Hamiltonian is obtained, containing a purely phonon-induced, long-range intersite charge interaction. The phase diagrams for N=1,2,3,4 electrons have been determined by variational minimization of the sum of the electronic and the phononic energy, pa…
The mean field Green function solution of the two-band singlet-hole Hubbard model for high-$T\sb{c}$ superconductivity in cuprates (Plakida, N.M. et al., Phys. Rev. B51, 16599 (1995), JETP 97, 331 (2003)) involves expressions of higher order correlation functions describing respectively the singlet hopping and the superconducting pairing. Rigorous derivation of their values is reported based on the finding that specific invariant classes of polynomial Green functions in terms of the Wannier overlap coefficients $ν\sb{ij}$ exist.
We propose an improved scheme to construct many-body trial wave functions for fractional Chern insulators (FCI), using one-dimensional localized Wannier basis. The procedure borrows from the original scheme on a continuum cylinder, but is adapted to finite-size lattice systems with periodic boundaries. It fixes several issues of the continuum description that made the overlap with the exact ground states insignificant. The constructed lattice states are translationally invariant, and have the correct degeneracy as well as the correct relative and total momenta. Our prescription preserves the (…
We study Bose-Hubbard models on tight-binding, non-Bravais lattices, with a filling of one boson per unit cell -- and thus fractional site filling. At integer filling of a unit cell neither symmetry breaking nor topological order is required, and in principle a trivial and featureless (i.e., symmetry-unbroken) insulator is allowed. We demonstrate by explicit construction of a family of wavefunctions that such a featureless Mott insulating state exists at 1/3 filling on the kagome lattice, and construct Hamiltonians for which these wavefunctions are exact ground states. We briefly comment on th…
We consider a model Hamiltonian for a dimer including all the electronic one- and two-body terms consistent with a single orbital per site, a free Einstein phonon term, and an electron-phonon coupling of the Holstein type. The bare electronic interaction parameters were evaluated in terms of Wannier functions built from Gaussian atomic orbitals. An effective polaronic Hamiltonian was obtained by an unrestricted displaced-oscillator transformation, followed by evaluation of the phononic terms over a squeezed-phonon variational wave function. For the cases of quarter-filled and half-filled orbit…
In the series of 3d1 t2g perovskites, SrVO3--CaVO3--LaTiO3--YTiO3 the transition-metal d electron becomes increasingly localized and undergoes a Mott transition between CaVO3 and LaTiO3. By defining a low-energy Hubbard Hamiltonian in the basis of Wannier functions for the t2g LDA band and solving it in the single-site DMFT approximation, it was recently shown[1] that simultaneously with the Mott transition there occurs a strong suppression of orbital fluctuations due to splitting of the t2g levels. The present paper reviews and expands this work, in particular in the direction of exposing the…
For a simple-cubic optical lattice with lattice spacing d, occupied by two species of fermionic atoms of mass m that interact repulsively, we ask what conditions maximize the Neel temperature in the Mott insulating phase at density one atom per site, with equal numbers of the two species. This maximum occurs near the edge of the regime where the system is well-approximated by the usual Hubbard model. The correction to the Hubbard-model approximation that produces a "direct" ferromagnetic interaction between atoms in nearest-neighbor Wannier orbitals is the leading term that limits how high the…
Correlated materials are extremely sensitive to external stimuli, such as temperature or pressure. Describing the electronic properties of such systems often requires applying many-body techniques to effective low energy problems in the spirit of the Hubbard model, or extensions thereof. While the effect of pressure on structures and bands has been investigated extensively within density-functional based methods, the pressure dependence of electron-electron interactions has so far received little attention. As a step toward ab initio pressure studies for realistic systems within a setup of max…
In materials like transition metals oxides where electronic Coulomb correlations impede a description in terms of standard band-theories, the application of genuine many-body techniques is inevitable. Interfacing the realism of density-functional based methods with the virtues of Hubbard-like Hamiltonians, requires the joint ab initio construction of transfer integrals and interaction matrix elements (like the Hubbard U) in a localized basis set. In this work, we employ the scheme of maximally localized Wannier functions and the constrained random phase approximation to create effective low-en…
We study the electronic state of the doped Mott-Hubbard insulator within Dynamical Mean Field Theory. The evolution of the finite temperature spectral functions as a function of doping show large redistributions of spectral weight in both antiferromagnetic and paramagnetic phases. In particular, a metallic antiferromagnetic state is obtained with a low frequency Slater-splitted quasiparticle peak coexisting with Hubbard bands. In the high temperature paramagnetic metallic phase, upon reducing doping, the system has a crossover through a ``bad metal'' state characterized by an anomalous shift o…
The spectral weight evolution of the low-dimensional Mott insulator TiOCl upon alkali-metal dosing has been studied by photoelectron spectroscopy. We observe a spectral weight transfer between the lower Hubbard band and an additional peak upon electron-doping, in line with quantitative expectations in the atomic limit for changing the number of singly and doubly occupied sites. This observation is an unconditional hallmark of correlated bands and has not been reported before. In contrast, the absence of a metallic quasiparticle peak can be traced back to a simple one-particle effect.
We clarify some aspects of the calculation of the thermal transport coefficients. For a tight-binding Hamiltonian we discuss the approximate nature of the charge current and the thermal current obtained by Peierls substitution which is also identical to the equation of motion technique. We address the issue of choosing an appropriate basis for making the Peierls construction for transport calculations. We propose a criteria for finding an optimum Wannier basis where the difference between the exact current and the approximate one is minimum. Using the equations of motion we derive the thermal …
The physics of the Mott transition in the anodic region of NiO Resistance Random Access Memory (RRAM) is discussed from the Hubbard model. The Hubbard approximation is examined in details and it is shown that the Wannier functions in the definition of Hubbard U should not be replaced by atomic s-functions when it comes to the metallic side of the transition. The corresponding effective Hubbard U is subject to variations, which may also be understood by introducing an effective permittivity of the solid as an ansatz. Furthermore, the transition could be demonstrated in the Brinkman-Rice picture…
In a partially filled flat Bloch band electrons do not have a well defined Fermi surface and hence the low-energy theory is not a Fermi liquid. Neverethless, under the influence of an attractive interaction, a superconductor well described by the Bardeen-Cooper-Schrieffer (BCS) wave function can arise. Here we study the low-energy effective Hamiltonian of a generic Hubbard model with a flat band. We obtain an effective Hamiltonian for the flat band physics by eliminating higher lying bands via perturbative Schrieffer-Wolff transformation. At first order in the interaction energy we recover the…
We present key issues of related phenomenons of the Ferroelectricity and the Charge Disproportionation in organic metals. In (TMTTF_2X the dielectric susceptibility demonstrates clear cases of the ferroelectric and anti-ferroelectric phase transitions. Both the susceptibility and the conductivity prove independence and occasional coexistence of "structurless" ferroelectric transitions and usual "anionic" ones. Their sequence gives access to physics of three types of solitons emerging upon cooling via several steps of symmetry breaking. The theory invokes a concept of the Combined Mott-Hubbard …
In this work, we explore the possibility of emergent nonequilibrium steady states arising from the electric-field-driven Mott insulator via the Keldysh-Floquet dynamical mean field theory (DMFT), which can determine the fully-interacting, nonequilibrium steady-state Green's functions with the noninteracting counterparts as an input to the DMFT self-consistency loop. Unlike the retarded component, obtaining the lesser Green's function for the noninteracting system presents an important obstacle since the thermalization of the noninteracting system still requires a precise understanding of the d…
We explore magnetic behavior of kagome francisites Cu3Bi(SeO3)2O2X (X = Cl and Br) using first-principles calculations. To this end, we propose an approach based on the Hubbard model in the Wannier functions basis constructed on the level of local-density approximation (LDA). The ground-state spin configuration is determined by a Hartree-Fock solution of the Hubbard model both in zero magnetic field and in applied magnetic fields. Additionally, parameters of an effective spin Hamiltonian are obtained by taking into account the hybridization effects and spin-orbit coupling. We show that only th…
We show numerically that the nature of the doping induced metal-insulator transition in the two-dimensional Hubbard model is radically altered by the inclusion of a term, $W$, which depends upon a square of a single-particle nearest-neighbor hopping. This result is reached by computing the localization length, $ξ_l$, in the insulating state. At finite values of $W$ we find results consistent with $ξ_l \sim | μ- μ_c|^{- 1/2} $ where $μ_c$ is the critical chemical potential. In contrast, $ξ_l \sim | μ- μ_c|^{-1/4}$ for the Hubbard model. At finite values of $W$, the presented numerical results i…
We introduce a new type of Gutzwiller variational wavefunction for correlated electrons coupled to phonons, able to treat on equal footing electronic and lattice degrees of freedom. We benchmark the wavefunction in the infinite-$U$ Hubbard-Holstein model away from half-filling on a Bethe lattice, where we can directly compare with exact results by Dynamical Mean-Field Theory. For this model, we find that variational results agree perfectly well with the exact ones. In particular the wavefunction correctly describes the crossover to a heavy polaron gas upon increasing the electron-phonon coupli…
We employ the dynamical mean field approximation to study the effects of ionic potential ($Δ$) on the square lattice Hubbard model. At half-filling when the staggered potential ($Δ$) dominates the on-site Hubbard interaction ($U$), the system is in the band insulator phase. We find that competition between $U$ and $Δ$ can suppress the gap to zero and leading to an intermediate metallic region. At the large-$U$ limit, we identify a Mott insulator phase where the gap opens again and increases upon increasing the Hubbard interaction U. For $U\leq 9t$ and $Δ\approx 0$ the phase of the system is me…
An expression is derived for angle-resolved photocurrent from a semi-infinite correlated system. Within the sudden approximation, the photocurrent is proportional to the spectral function of a one-particle two-time retarded Green's function $\mathcal{G}$ of an operator that creates an electron in a special quantum state $χ$ localized at the surface. For a system described by a many-body single-band model we present an analytical expression that relates the Green's function $\mathcal{G}$ with the Green's function of an infinite crystal $G_{b,\mathbf{k}}(ω)$ in Wannier representation. The role o…
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University（斯坦福材料能源科学研究所、SLAC国家加速器实验室和斯坦福大学）；Department of Physics and Astronomy, California State University, Northridge（加州州立大学北岭分校物理与天文学系）
We have performed large-scale density-matrix renormalization group studies of the lightly doped Hubbard model on the honeycomb lattice on long three and four-leg cylinders. We find that the ground state of the system upon lightly doping is consistent with that of a superconducting state with coexisting quasi-long-range superconducting and charge density wave orders. Both the superconducting and charge density wave correlations decay as a power law at long distances with corresponding exponents $K_{sc}<2$ and $K_c<2$. On the contrary, the spin-spin and single-particle correlations decay exponen…
The interactions between holes in the Hubbard model, in the low density, intermediate to strong coupling limit, are investigated by systematically improving mean field calculations. The Configuration Interaction basis set is constructed by applying to local Unrestricted Hartree-Fock configurations all lattice translations and rotations. It is shown that this technique reproduces, correctly, the properties of the Heisenberg model, in the limit of large U. Upon doping, dressed spin polarons in neighboring sites have an increased kinetic energy and an enhanced hopping rate. Both effects are of th…
We study the anisotropic two-dimensional Hubbard model at and near half filling within a functional renormalization group method, focusing on the structure of momentum-dependent correlations which grow strongly upon approaching a critical temperature from above. We find that a finite nearest-neighbor interchain hopping is not sufficient to introduce a substantial momentum dependence of single-particle properties along the Fermi surface. However, when a sufficiently large second-nearest neighbor inter-chain hopping is introduced, the system is frustrated and we observe the appearance of so-call…
Using recent advances in auxiliary-field quantum Monte Carlo techniques and the phaseless approximation to control the sign/phase problem, we determine the equation of state in the ground state of the two-dimensional repulsive single-band Hubbard model at intermediate interactions. Shell effects are eliminated and finite-size effects are greatly reduced by boundary condition integration. Spin-spin correlation functions and structure factors are also calculated. In lattice sizes up to $16\times 16$, the results show signal for phase-separation. Upon doping, the system separates into one phase o…
To explore conditions underlying the superconductivity in electron-doped TiNCl where T$_c$ = 16 K, we calculate the electronic structure, Wannier functions and spin and charge susceptibilities using first-principles density functional theory. TiNCl is the first high-temperature superconductor discovered in the $α$-structure of the layered transition-metal nitride family MNCl (M=Ti, Zr, Hf). We construct a tight-binding model based on Wannier functions derived from the band structure, and consider explicit electronic interactions in a multi-band Hubbard Hamiltonian, where the interactions are t…
We reformulate the time-dependent Gutzwiller approximation by M. Schiró and M. Fabrizio [Phys. Rev. Lett. 105, 076401 (2010)] in the framework of slave-boson mean-field theory, which is used to investigate the dynamical Mott transition of the generic two-band Hubbard model at half filling upon an interaction quench. Interorbital fluctuations lead to notable changes with respect to the single-band case. The singular dynamical transition is replaced by a broad regime of long-lived fluctuations between metallic and insulating states, accompanied by intriguing precursor behavior. A mapping to a sp…
A novel hybrid scheme is proposed. The {\it ab initio} LDA calculation is used to construct the Wannier functions and obtain single electron and Coulomb parameters of the multiband Hubbard-type model. In strong correlation regime the electronic structure within multiband Hubbard model is calculated by the Generalized Tight-Binding (GTB) method, that combines the exact diagonalization of the model Hamiltonian for a small cluster (unit cell) with perturbation treatment of the intercluster hopping and interactions. For undoped La$_2$CuO$_4$ and Nd$_2$CuO$_4$ this scheme results in charge transfer…
