Using the dynamical mean-field theory (DMFT) we study the paramagnetic phase of the Hubbard model with the density of states (DOS) corresponding to the three-dimensional cubic lattice and the two-dimensional square lattice, as well as a DOS with inverse square root singularity. We show that the electron correlations rapidly smooth out the square-root van Hove singularities (kinks) in the spectral function for the 3D lattice and that the Mott metal-insulator transition (MIT) as well as the magnetic-field-induced MIT differ only little from the well-known results for the Bethe lattice. The consequences of the logarithmic singularity in the DOS for the 2D lattice are more dramatic. At half filling, the divergence pinned at the Fermi level is not washed out, only its integrated weight decreases as the interaction is increased. While the Mott transition is still of the usual kind, the magnetic-field-induced MIT falls into a different universality class as there is no field-induced localization of quasiparticles. In the case of a power-law singularity in the DOS at the Fermi level, the power-law singularity persists in the presence of interaction, albeit with a different exponent, and the effective impurity model in the DMFT turns out to be a pseudo-gap Anderson impurity model with a hybridization function which vanishes at the Fermi level. The system is then a generalized Fermi liquid. At finite doping, regular Fermi liquid behavior is recovered.
The electronic properties of paramagnetic V_2O_3 are investigated by the ab-initio computational scheme LDA+DMFT(QMC). This approach merges the local density approximation (LDA) with dynamical mean-field theory (DMFT) and uses numerically exact quantum Monte Carlo simulations (QMC) to solve the effective Anderson impurity model of DMFT. Starting with the crystal structure of metallic V_2O_3 and insulating (V_{0.962}Cr_{0.038})_2O_3 we find a Mott-Hubbard metal-insulator-like transition at a Coulomb interaction U\approx 5eV. The calculated spectrum is in very good agreement with experiment. Fur…
A comparative study of the magnetocaloric effect (MCE) in metals within the single-band Hubbard model on the face-centered cubic (fcc) lattice using both mean-field (Stoner) approximation (MFA) and dynamical mean-field theory (DMFT) is done. The MCE is investigated in the case of second order magnetic phase transition from ferromagnet to paramagnet. To ensure presence of itinerant ferromagnetism in the Hubbard model the special case of spectrum parameters generating giant van Hove singularity at the bottom of the band is considered, while the Fermi level $E_{\rm f}$ is in the vinicity of the b…
The electronic spectrum, energy gap and local magnetic moment of paramagnetic NiO are computed by using the local density approximation plus dynamical mean-field theory (LDA+DMFT). To this end the noninteracting Hamiltonian obtained within the local density approximation (LDA) is expressed in Wannier functions basis, with only the five anti-bonding bands with mainly Ni 3d character taken into account. Complementing it by local Coulomb interactions one arrives at a material-specific many-body Hamiltonian which is solved by DMFT together with quantum Monte-Carlo (QMC) simulations. The large insu…
Density of states, dynamic (optical) conductivity and phase diagram of paramagnetic two-dimensional Anderson-Hubbard model with strong correlations and disorder are analyzed within the generalized dynamical mean-field theory (DMFT+Sigma approximation). Strong correlations are accounted by DMFT, while disorder is taken into account via the appropriate generalization of the self-consistent theory of localization. We consider the two-dimensional system with the rectangular "bare" density of states (DOS). The DMFT effective single impurity problem is solved by numerical renormalization group (NRG)…
The first-order metal-insulator transition (MIT) in paramagnetic $V_{2}O_{3}$ is studied within the ab-initio scheme LDA+DMFT, which merges the local density approximation (LDA) with dynamical mean field theory (DMFT). With a fixed value of the Coulomb $U=6.0 eV$, we show how the abrupt pressure driven MIT is understood in a new picture: pressure-induced decrease of the trigonal distortion within the strong correlation scenario (which is not obtained within LDA). We find good quantitative agreement with $(i)$ switch of the orbital occupation of $(a_{1g},e_{g1}^π, e_{g2}^π)$ and the spin state …
LDA+DMFT, the computation scheme merging the local density approximation and the dynamical mean-field theory, is employed to calculate spectra both below and above the Fermi energy and spin and orbital occupations in the correlated paramagnetic metallic and Mott insulating phase of V_2O_3. The self-consistent DMFT equations are solved by quantum Monte Carlo simulations. Room temperature calculations provide direct comparison with experiment. They show a significant increase of the quasiparticle height in comparison with the results at 1160 K. We also obtain new insights into the nature of the …
We study the antiferromagnetic and the paramagnetic Kondo insulator phases of the Kondo lattice model on the cubic lattice at half-filling using the cellular dynamical mean-field theory (CDMFT) with numerical renormalization group (NRG) as the impurity solver, focusing on the fine details of the spectral function and self-energy. We find that the non-local correlations increase the gap in both the antiferromagnetic and the Kondo insulator phase and shrink the extent of the antiferromagnetic phase in the phase diagram but do not alter any properties qualitatively. The agreement between the nume…
We address the nature of the Mott transition in the Hubbard model at half-filling using cluster Dynamical Mean Field Theory (DMFT). We compare cluster DMFT results with those of single site DMFT. We show that inclusion of the short range correlations on top of the on-site correlations, already treated exactly in single site DMFT, do not change the nature of the transition between the paramagnetic metal and the paramagnetic Mott insulator, which remains first order. However, the short range correlations reduce substantially the critical $U$ and modify the shape of transition lines. Moreover, th…
The interplay of magnetic and superconducting fluctuations in two dimensional systems with van Hove singularities in the electronic spectrum is considered within the functional renormalization group (fRG) approach. While the fRG flow has to be stoped at a certain minimal temperature T_RG^min, we study temperature dependence of magnetic and superconducting susceptibilities both, above and below T_RG^min, which allows to obtain the resulting ground state phase diagram. Close to half filling the fRG approach yields two quantum phase transitions: from commensurate antiferromagnetic to incommensura…
We investigate the origin of the orbital ordering in the paramagnetic phase of KCrF$_3$. All previous studies described structural parameters of the paramagnetic phase using a magnetic ordering in the compound. Our simulations of real paramagnetic KCrF$_3$ were performed within an approach combining density functional theory and dynamical mean field theory (DFT+DMFT). As a result, it was found that the experimentally observed cooperative Jahn-Teller effect is successfully described in a lattice relaxation calculation for structure without any long-range magnetic ordering. It is established tha…
We study the magnetic excitation spectra in the paramagnetic state of BaFe$_{2}$As$_{2}$ from the \textit{ab initio} perspective. The one-particle excitation spectrum is determined within the combination of the density functional theory and the dynamical mean-field theory method. The two-particle response function is extracted from the local two-particle vertex function, also computed by the dynamical mean field theory, and the polarization function. This method reproduces all the experimentally observed features in inelastic neutron scattering (INS), and relates them to both the one particle …
Dynamical mean-field theory is used to study the three orbital model of the $d^3$ compound SrRu$_2$O$_6$ both with and without explicitly including the O-$p$ states. Depending on the size of the Hund's coupling $J$, at low to intermediate temperatures we find solutions corresponding to Mott or correlated covalent insulator. The latter can explain the experimentally observed absence of Curie susceptibility in the paramagnetic phase. At high temperatures a single phase with smoothly varying properties is observed. SrRu$_2$O$_6$ provides an ideal system to study the competition between the local …
Square-octagon lattice underlies the description of a family of two-dimensional materials such as tetragraphene. In the present paper we show that the tight-binding model of square-octagon lattice contains both conventional and high-order van Hove points. In particular, the spectrum of the model contains flat lines along some directions composed of high-order saddle points. Their role is analyzed by calculating orbital susceptibility of electrons. We find that the presence of van Hove singularities of different kinds in the density of states leads to strong responses: paramagnetic for ordinary…
We present a cluster dynamical mean-field treatment of the Hubbard model on a square lattice to study the evolution of magnetism and quasiparticle properties as the electron filling and interaction strength are varied. Our approach for solving the dynamical mean-field equations is an extension of Potthoff's "two-site" method [Phys. Rev. B. 64, 165114 (2001)] where the self-consistent bath is represented by a highly restricted set of states. As well as the expected antiferromagnetism close to half filling, we observe distortions of the Fermi surface. The proximity of a van Hove point and the in…
We present a correlated {\it ab initio} description of the paramagnetic phase of Tl$_2$Mn$_2$O$_7$, employing a combined local density approximation (LDA) with multiorbital dynamical mean field theory (DMFT) treatment. We show that the insulating state observed in this colossal magnetoresistance (CMR) pyrochlore is determined by strong Mn intra- and inter-orbital local electron-electron interactions. Hybridization effects are reinforced by the correlation-induced spectral weight transfer. Our result coincides with optical conductivity measurements, whose low energy features are remarkably acco…
Strong correlations and local self-energies from on-site ensembles
Paul Scherrer Institute（保罗谢尔研究所）；Örebro University（厄勒布鲁大学）；University of Fribourg（弗里堡大学）；École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院）；Universität Bremen（不来梅大学）；University of Cambridge（剑桥大学）
We report a density functional theory plus dynamical mean field theory (DFT+DMFT) study of an oxide heterostructure of LaNiO$_3$ (LNO) bilayers in [111] direction interleaved with four atomic monolayers of LaAlO$_3$. DFT+$U$ optimizations yield two stable solutions: a uniform structure with equivalent NiO$_6$ octahedra, as well as a bond-disproportionated (BD) structure featuring a breathing distortion. For both structures, we construct the low-energy models describing the Ni $e_g$ states by means of Wannier projections supplemented by the Kanamori interaction, and solve them by DMFT. Using th…
The metal-insulator transition (MIT) in paramagnetic VO2 is studied within LDA+DMFT(IPT), which merges the local density approximation (LDA) with dynamical mean field theory (DMFT). With a fixed value of the Coulomb U=5.0eV, we show how the MIT is understood in a new picture: spectral weight transfer accompanying the increase in the displacement of V ion ($\perp c$) within the strong correlation scenario. Within this new scenario, we find good quantitative agreement with (i) switch of the orbital occupation of (xy,yz+zx,yz-zx), (ii) thermodynamics, and (iii) the one-electron spectral function …
We have studied a disordered $N_{\rm c} \times N_{\rm c}$ plaquette Hubbard model on a two-dimensional square lattice at half-filling using a coherent potential approximation (CPA) in combination with a single-site dynamical mean field theory (DMFT) approach with a paramagnetic bath. Such a model conveniently interpolates between the ionic Hubbard model at $N_{\rm c}=\sqrt{2}$ and the Anderson model at $N_{\rm c} = \infty$ and enables the analysis of the various limiting properties. We confirmed that within the CPA approach a band insulator behavior appears for non-interacting strongly disorde…
We present a computational scheme for total energy calculations of disordered alloys with strong electronic correlations. It employs the coherent potential approximation combined with the dynamical mean-field theory and allows one to study the structural transformations. The material-specific Hamiltonians in the Wannier function basis are obtained by density functional theory. The proposed computational scheme is applied to study the ${γ\textrm{-}\varepsilon}$ structural transition in paramagnetic Fe-Mn alloys for Mn content from 10 to 20 at. %. The electronic correlations are found to play a …
We revisit Nagaoka ferromagnetism in the U=oo Hubbard model within the dynamical mean-field theory (DMFT) using the recently developed continuous time quantum Monte Carlo method as the impurity solver. The stability of Nagaoka ferromagnetism is studied as a function of the temperature, the doping level, and the next-nearest-neighbor lattice hopping t'. We found that the nature of the phase transition as well as the stability of the ferromagnetic state is very sensitive to the t' hopping. Negative t'=-0.1t stabilizes ferromagnetism up to higher doping levels. The paramagnetic state is reached t…
Delafossite PdCrO$_2$ is an intriguing material which displays nearly-free electron and Mott insulating behaviour in different layers. Both angle-resolved photoemission spectroscopy (ARPES) and Compton scattering measurements have established a hexagonal Fermi surface in the material's paramagnetic phase. However, the Compton experiment detected an additional structure in the projected occupancy which was originally interpreted as an additional Fermi surface feature not seen by ARPES. Here, we revisit this interpretation of the Compton data. State-of-the-art density functional theory (DFT) wit…
We study the Anderson lattice model with one f-orbital per lattice site as the simplest model which describes generic features of heavy fermion materials. The resistivity and magnetic susceptibility results obtained within dynamical mean field theory (DMFT) for a nearly half-filled conduction band show the existence of a single energy scale $T^*$ which is similar to the single ion Kondo temperature $T_K^o$. To determine the importance of inter-site correlations, we have also solved the model within cellular DMFT (CDMFT) with two sites in a unit cell. The antiferromagnetic region on the phase d…
We investigate the possibility of ferromagnetic ordering in the non-degenerate Hubbard model on the face-centered cubic lattice within the functional renormalization group technique using temperature as a scale parameter. We assume the relations between nearest, next-nearest, and next-next-nearest hopping parameters providing higher order (giant) van Hove singularity of the density of states. The ferromagnetic instability formation with lowering temperature is described consistently in the one-loop approximation for a one-particle irreducible vertex of two-particle electron interaction. The ch…
We study the magnetic field driven metal-to-insulator transition in half-filled Hubbard model on the Bethe lattice, using the dynamical mean-field theory by solving the quantum impurity problem with density-matrix renormalization group algorithm. The method enables us to obtain a high-resolution spectral densities in the presence of a magnetic field. It is found that the Kondo resonance at the Fermi level splits at relatively high magnetic field: the spin-up and spin-down components move away from the Fermi level and finally form a spin polarized band insulator. By calculating the magnetizatio…
Observation of an anomalous temperature dependence of the spin susceptibility, along with a spin gap in NMR, in the quantum paramagnetic normal state of Iron Pnictides is a signature of an unusual metallic state. We argue that both these anomalous features are associated with a wide fluctuational regime dominated by dynamical, short-ranged and frustrated spin correlations in a strongly correlated metal. Using LDA+DMFT, we show that both these features can be quantitatively undertstood in the doped Fe-pnictides. We argue that such spin correlations naturally arise in a Mottness scenario, where …
The paramagnetic phase of the one-band Hubbard model is studied at zero-temperature, within the framework of dynamical mean-field theory, and for general particle-hole asymmetry where a doping-induced Mott transition occurs. Our primary focus is the Mott insulator (MI) phase, and our main aim to establish what can be shown exactly about it. To handle the locally doubly-degenerate MI requires two distinct self-energies, which reflect the broken symmetry nature of the phase and together determine the standard single self-energy. Exact results are obtained for the local charge, local magnetic mom…
A brief account of the zero temperature magnetic response of a system of strongly correlated electrons in strong magnetic field is given in terms of its quasiparticle properties. The scenario is based on the paramagnetic phase of the half-filled Hubbard model, and the calculations are carried out with the dynamical mean field theory (DMFT) together with the numerical renormalization group (NRG). As well known, in a certain parameter regime one finds a magnetic susceptibility which increases with the field strength. Here, we analyze this metamagnetic response based on Fermi liquid parameters, w…
The Fermi surface topology plays an important role in the macroscopic properties of metals. It can be particularly sensitive to electron correlation, which appears to be especially significant for the weak itinerant ferromagnet ZrZn$_{2}$. Here, we look at the differences in the predicted Fermi surface sheets of this metallic compound in its paramagnetic phase for both density functional theory (DFT) and the combination of DFT with dynamical mean field theory (DFT+DMFT). The theoretical spectral functions evaluated at the Fermi level were used along with calculations of the electron-positron m…
We study the phase diagram of the ionic Hubbard model (IHM) at half-filling using dynamical mean field theory (DMFT), with two impurity solvers, namely, iterated perturbation theory (IPT) and continuous time quantum Monte Carlo (CTQMC). The physics of the IHM is governed by the competition between the staggered potential $Δ$ and the on-site Hubbard U. In both the methods we find that for a finite $Δ$ and at zero temperature, anti-ferromagnetic (AFM) order sets in beyond a threshold $U=U_{AF}$ via a first order phase transition below which the system is a paramagnetic band insulator. Both the m…
We apply a recently introduced hybridization-flow functional renormalization group scheme for Anderson-like impurity models as an impurity solver in a dynamical mean-field theory (DMFT) approach to lattice Hubbard models. We present how this scheme is capable of reproducing metallic and insulating solutions of the lattice model. Our setup also offers a numerically rather inexpensive method to calculate two-particle correlation functions. For the paramagnetic Hubbard-model on the Bethe lattice in infinite dimensions we calculate the local two-particle-vertex for the metallic and the insulating …
We study the Hubbard model at half band-filling on a Bethe lattice with infinite coordination number in the paramagnetic insulating phase at zero temperature. We use the dynamical mean-field theory (DMFT) mapping to a single-impurity Anderson model with a bath whose properties have to be determined self-consistently. For a controlled and systematic implementation of the self-consistency scheme we use the fixed-energy (FE) approach to the DMFT. In FE-DMFT the onset and the width of the Hubbard bands are adjusted self-consistently but the energies of the bath levels are kept fixed relatively to …
The local-density approximation combined with the dynamical mean-field theory (LDA+DMFT) is applied to the paramagnetic phase of light actinide dioxides: UO2, NpO2, and PuO2. The calculated band gaps and the valence-band electronic structure are in a very good agreement with the optical absorption experiments as well as with the photoemission spectra. The hybridization of the actinide 5f shell with the 2p states of oxygen is found to be relatively large, it increases the filling of the 5f orbitals from the nominal ionic configurations with two, three, and four electrons to nearly half-integer …
Density of states, dynamic (optical) conductivity and phase diagram of strongly correlated and strongly disordered paramagnetic Anderson-Hubbard model are analyzed within the generalized dynamical mean field theory (DMFT+Σapproximation). Strong correlations are accounted by DMFT, while disorder is taken into account via the appropriate generalization of self-consistent theory of localization. The DMFT effective single impurity problem is solved by numerical renormalization group (NRG) and we consider the three-dimensional system with semi-elliptic density of states. Correlated metal, Mott insu…
We introduce DMET, a new quantum embedding theory for predicting ground-state properties of infinite systems. Like dynamical mean-field theory (DMFT), DMET maps the the bulk interacting system to a simpler impurity model and is exact in the non-interacting and atomic limits. Unlike DMFT, DMET is formulated in terms of the frequency-independent local density matrix, rather than the local Green's function. In addition, it features a finite, algebraically constructible bath of only one bath site per impurity site, which exactly embeds ground-states at a mean-field level with no bath discretizatio…
Applying the local density approximation (LDA) and dynamical mean field theory (DMFT) to paramagnetic $α$-iron, we revisit a problem of theoretical description of its magnetic properties. The analysis of local magnetic susceptibility shows that at sufficiently low temperatures $T<1500K$, both, $e_{g}$ and $t_{2g}$ states equally contribute to the formation of the effective magnetic moment with spin S=1. The self-energy of t_{2g} states shows sizable deviations from Fermi-liquid form, which accompanies earlier found non-quasiparticle form of e_{g} states. By considering the non-uniform magnetic…
LiV_2 O_4 is one of the most puzzling compounds among transition metal oxides because of its heavy fermion like behavior at low temperatures. In this paper we present results for the orbital state and magnetic properties of LiV_2 O_4 obtained from a combination of density functional theory within the local density approximation and dynamical mean-field theory (DMFT). The DMFT equations are solved by quantum Monte Carlo simulations. The trigonal crystal field splits the V 3d orbitals such that the a_{1g} and e_{g}^{pi} orbitals cross the Fermi level, with the former being slightly lower in ener…
Splitting of electronic spectrum in paramagnetic phase of itinerant ferromagnets and altermagnets
Moscow Institute of Physics and Technology（莫斯科物理技术学院）；M. N. Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences（俄罗斯科学院乌拉尔分校 M.N. 米凯耶夫金属物理研究所）
We calculate the renormalized parameters for the quasiparticles and their interactions for the Hubbard model in the paramagnetic phase as deduced from the low energy Fermi liquid fixed point using the results of a numerical renormalization group calculation (NRG) and dynamical mean-field theory (DMFT). Even in the low density limit there is significant renormalization of the local quasiparticle interaction $\tilde U$, in agreement with estimates based on the two-particle scattering theory of Kanamori (1963). On the approach to the Mott transition we find a finite ratio for $\tilde U/\tilde D$,…
Incoherent Spectral Weight Emerging from a Van Hove Singularity in a Kagome Metal
Donostia International Physics Center (DIPC)（多诺斯蒂亚国际物理中心）；University of the Basque Country (UPV/EHU)（巴斯克大学）；Aalto University School of Science（阿尔托大学理学院）；Department of Physics, University of Science and Technology of China（中国科学技术大学物理系）；CIC nanoGUNE（nanoGUNE创新中心）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Diamond Light Source Ltd（钻石光源有限公司）
Interplay of Pomeranchuk instability (spontaneous symmetry breaking of the Fermi surface) and d-wave superconductivity is studied for the repulsive Hubbard model on the square lattice with the dynamical mean field theory combined with the fluctuation exchange approximation (FLEX+DMFT). We show that the four-fold symmetric Fermi surface becomes unstable against a spontaneous distortion into two-fold near the van Hove filling, where the symmetry of superconductivity coexisting with the Pomeranchuk distorted Fermi surface is modified from the d-wave pairing to (d+s)-wave. By systematically shifti…
A metal-insulator transition (MIT) in BiFeO$_3$ under pressure was investigated by a method combining Generalized Gradient Corrected Local Density Approximation with Dynamical Mean-Field Theory (GGA+DMFT). Our paramagnetic calculations are found to be in agreement with experimental phase diagram: Magnetic and spectral properties of BiFeO3 at ambient and high pressures were calculated for three experimental crystal structures $R3c$, $Pbnm$ and $Pm\bar{3}m$. At ambient pressure in the $R3c$ phase, an insulating gap of 1.2 eV was obtained in good agreement with its experimental value. Both $R3c$ …
We study the effects of anisotropic hopping amplitudes on quantum phases of ultracold fermions in optical lattices described by the repulsive Fermi-Hubbard model. In particular, using dynamical mean-field theory (DMFT) we investigate the dimensional crossover between the isotropic square and the isotropic cubic lattice. We analyze the phase transition from the antiferromagnetic to the paramagnetic state and observe a significant change in the critical temperature: Depending on the interaction strength, the anisotropy can lead to both a suppression or increase. We also investigate the localizat…
Magnetic phases of the anisotropic triangular Hubbard model from the ghost-Gutzwiller approximation in the rotating spin-frame
Université de Montréal（蒙特利尔大学）；Flatiron Institute（平顿研究所）；National Chung Cheng University（国立中正大学）；Université de Sherbrooke（舍布鲁克大学）；Rochester Institute of Technology（罗切斯特理工学院）；Université Paris-Saclay（巴黎萨克雷大学）
We review recent progress in our theoretical understanding of strongly correlated fermion systems in the presence of disorder. Results were obtained by the application of a powerful nonperturbative approach, the Dynamical Mean-Field Theory (DMFT), to interacting disordered lattice fermions. In particular, we demonstrate that DMFT combined with geometric averaging over disorder can capture Anderson localization and Mott insulating phases on the level of one-particle correlation functions. Results are presented for the ground-state phase diagram of the Anderson-Hubbard model at half filling, bot…
Revealing Short- and Long-range Li-ion diffusion in Li$_2$MnO$_3$ from finite-temperature dynamical mean field theory
University of Illinois at Chicago（芝加哥伊利诺伊大学）；Argonne National Laboratory（阿贡国家实验室）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；University of California Berkeley（加州大学伯克利分校）
We develop a cluster dynamical mean field theory of the periodic Anderson model in three dimensions, taking a cluster of two sites as a basic reference frame. The mean field theory displays the basic features of the Doniach phase diagram: a paramagnetic Fermi liquid state, an antiferromagnetic state and a transition between them. In contrast with spin density wave theories, the transition is accompanied by a large increase of the effective mass everywhere on the Fermi surface and a substantial change of the Fermi surface shape across the transition. To understand the nature and the origin of t…
We present results of a detailed theoretical study of the electronic, magnetic, and structural properties of the chalcogenide parent system FeSe using a fully charge self-consistent implementation of the density functional theory plus dynamical mean-field theory (DFT+DMFT) method. In particular, we predict a remarkable change of the electronic structure of FeSe which is accompanied by a complete reconstruction of the Fermi surface topology (Lifshitz transition) upon a moderate expansion of the lattice volume. The phase transition results in a change of the in-plane magnetic nesting wave vector…
We study the Kondo alloy model on a square lattice using dynamical mean-field theory (DMFT) for Kondo substitution and disorder effects, together with static mean-field approximations. We computed and analyzed photoemission properties as a function of electronic filling $n_c$, Kondo impurity concentration $x$, and strength of Kondo temperature $T_K$. We provide a complete description of the Angle Resolved Photoemission Spectroscopy (ARPES) signals expected in the paramagnetic Kondo phases. By analyzing the Fermi surface, we observe the Lifshitz-like transition predicted previously for strong $…
We study the prototype 5d pyrochlore iridate Y2Ir2O7 from first principles using the local density approximation and dynamical mean-field theory (LDA+DMFT). We map out the phase diagram in the space of temperature, onsite Coulomb repulsion U, and filling. Consistent with experiments, we find that an all-in-all-out ordered insulating phase is stable for realistic values of U. The trigonal crystal field enhances the magnetic moments of the jeff=1/2 doublet, and strong inter-band correlations are induced by the Coulomb interaction, which indicates that a three-band description is important. We de…
In this paper, we investigate how nonlocal correlations affect, selectively, the physics of correlated electrons over different energy scales, from the Fermi level to the band-edges. This goal is achieved by applying a diagrammatic extension of dynamical mean field theory (DMFT), the dynamical vertex approximation (D$Γ$A), to study several spectral and thermodynamic properties of the unfrustrated Hubbard model in two and three dimensions. Specifically, we focus first on the low-energy regime by computing the electronic scattering rate and the quasiparticle mass renormalization for decreasing t…
We study the one-band Hubbard model on the honeycomb lattice using a combination of quantum Monte Carlo (QMC) simulations and static as well as dynamical mean-field theory (DMFT). This model is known to show a quantum phase transition between a Dirac semi-metal and the antiferromagnetic insulator. The aim of this article is to provide a detailed comparison between these approaches by computing static properties, notably ground-state energy, single-particle gap, double occupancy, and staggered magnetization, as well as dynamical quantities such as the single-particle spectral function. At the s…
