We implemented the charge self-consistent combination of Density Functional Theory and Dynamical Mean Field Theory (DMFT) in two full-potential methods, the Augmented Plane Wave and the Linear Muffin-Tin Orbital methods. We categorize the commonly used projection methods in terms of the causality of the resulting DMFT equations and the amount of partial spectral weight retained. The detailed flow of the Dynamical Mean Field algorithm is described, including the computation of response functions such as transport coefficients. We discuss the implementation of the impurity solvers based on hybridization expansion and an analytic continuation method for self-energy. We also derive the formalism for the bold continuous time quantum Monte Carlo method. We test our method on a classic problem in strongly correlated physics, the isostructural transition in Ce metal. We apply our method to the class of heavy fermion materials CeIrIn_5, CeCoIn_5 and CeRhIn_5 and show that the Ce 4f electrons are more localized in CeRhIn_5 than in the other two, a result corroborated by experiment. We show that CeIrIn_5 is the most itinerant and has a very anisotropic hybridization, pointing mostly towards the out-of-plane In atoms. In CeRhIn_5 we stabilized the antiferromagnetic DMFT solution below 3K, in close agreement with the experimental Néel temperature.
The use of effective local Coulomb interactions that are dynamical, that is, frequency-dependent, is an efficient tool to describe the effect of long-range Coulomb interactions and screening thereof in solids. The dynamical character of the interaction introduces the coupling to screening degrees of freedom such as plasmons or particle-hole excitations into the many-body description. We summarize recent progress using these concepts, putting emphasis on dynamical mean field theory (DMFT) calculations with dynamical interactions ("doubly dynamical mean field theory"). We discuss the relation to…
Electronic structure of CeRu4Sn6: a density functional plus dynamical mean field theory study
近藤体系CeRu $_4$ Sn $_6$在电学、光学和磁学性质上表现出很强的各向异性。我们采用密度泛函理论和动力学平均场论，并表明占主导地位的$f$态具有总角动量$J=5/2$和$z$ -组件$m_J=\pm 1/2$与最近的X射线吸收实验。即使CeRu $_4$ Sn $_6$具有通过大部分布里渊区的近藤绝缘体的直接间隙，它仍然保持弱金属性。这是因为（i）在$z$方向上的带交叉和（ii）负的间接带隙。
Perovskite rhodates are characterized by intermediate strengths of both electronic correlation as well as spin-orbit coupling (SOC) and usually behave as moderately correlated metals. A recent publication (Phys. Rev. B 95, 245121(2017)) on epitaxial SrRhO$_3$ thin films unexpectedly reported a bad-metallic behavior and suggested the occurrence of antiferromagnetism below 100 K. We studied this SrRhO$_3$ thin film by hard x-ray photoemission spectroscopy and found a very small density of states (DOS) at Fermi level, which is consistent with the reported bad-metallic behavior. However, this negl…
We present a fully charge self-consistent implementation of dynamical mean field theory (DMFT) combined with density functional theory (DFT) for electronic structure calculations of materials with strong electronic correlations. The implementation uses the Quantum ESPRESSO package for the density functional theory calculations, the Wannier90 code for the up-/downfolding and the TRIQS software package for setting up and solving the DMFT equations. All components are available under open source licenses, are MPI-parallelized, fully integrated in the respective packages, and use an hdf5 archive i…
Using local density approximation plus dynamical mean-field theory (LDA+DMFT), we have computed the valence band photoelectron spectra of highly popular multiferroic BiFeO$_{3}$. Within DMFT, the local impurity problem is tackled by exact diagonalization (ED) solver. For comparison, we also present result from LDA+U approach, which is commonly used to compute physical properties of this compound. Our LDA+DMFT derived spectra match adequately with the experimental hard X-ray photoelectron spectroscopy (HAXPES) and resonant photoelectron spectroscopy (RPES) for Fe 3$d$ states, whereas the other …
Electronic Structure and Dynamical Correlations in Antiferromagnetic BiFeO$_3$
École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院）；National Center for Computational Design and Discovery of Novel Materials (MARVEL)（国家新材料计算设计与发现中心 (MARVEL)）；Institute of Physics, École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院物理研究所）；California Institute of Technology（加州理工学院）；Paul Scherrer Institute（保罗谢勒研究所）；University of Cambridge（剑桥大学）
We investigate the dynamical structure factor associated with lattice fluctuations in a model that approximates the manganites. It involves electrons strongly coupled to core spins, and to lattice distortions, in a weakly disordered background. This model is solved in the adiabatic limit in two dimensions via Monte Carlo, retaining all the thermal fluctuations. In the metallic phase near the polaronic crossover this approach captures the effect of thermally induced polaron formation, and their short range correlation, on the electronic spectral functions. The dynamical fluctuations of the opti…
Dynamical screening is a key property of charged many-particle systems. Its theoretical description is based on the $GW$ approximation that is extensively applied for ground-state and equilibrium situations but also for systems driven out of equilibrium. The main limitation of the $GW$ approximation is the neglect of strong electronic correlation effects that are important in many materials as well as in dense plasmas. Here we derive the dynamically screened ladder (DSL) approximation that selfconsistently includes, in addition to the $GW$ diagrams, also particle--particle and particle--hole $…
The reliable {\it ab-initio} description of strongly correlated materials is a long-sought capability in condensed matter physics. The $GW$+EDMFT method is a promising scheme, which provides a self-consistent description of correlations and screening, and does not require user-provided parameters. In order to test the reliability of this approach we apply it to the experimentally well characterized perovskite compound Ca$_2$RuO$_4$, in which a temperature-dependent structural deformation drives a paramagnetic metal-insulator transition. Our results demonstrate that the nonlocal polarization an…
We have employed one of the well-known many-body techniques, density functional theory plus dynamical mean-field theory (DFT + DMFT), to investigate the electronic structure of ferromagnetic monolayer CrI3 as a function of temperature and hole-doping concentration. The computed magnetic susceptibility follows the Curie's law, indicating that the ferromagnetism of monolayer CrI3 originates from localized magnetic moments of Cr atoms rather than Stoner-type itinerant ones. The DFT + DMFT calculations show a different coherent temperature for each spin component, demonstrating apparent strong spi…
Theoretically, various physical properties of AV$_{2}$O$_{4}$ (A=Zn, Cd and Mg) spinels have been extensively studied for last 15 years. Besides of this, no systematic comparative study has been done for these compounds, where the material specific parameters are used. Here, we report the comparative electronic behaviour of these spinels by using a combination of density functional theory and dynamical mean-field theory, where the self-consistent calculated Coulomb interaction $U$ and Hund's coupling $J$ (determined by Yukawa screening $λ$) are used. The main features, such as insulating band …
Recently discovered heavy fermion CeRh$_{2}$As$_{2}$ compound crystallizes in the nonsymmorphic $P4/nmm$ symmetry, which enables the occurrence of topological protection. Experimental results show that this material exhibits unusual behavior, which is manifested by the appearance of two superconducting phases. In this work, we uncover and discuss a role of Rh$_{2}$As$_{2}$ layers and their impact on the electronic and dynamical properties of the system. The location of Ce atoms between two non-equivalent layers allows for the realization of hidden orbital order. We point out that the electroni…
The noncentrosymmetric NbReSi superconductor with $T_{c} \simeq 6.5$ K is characterized by the relatively large upper critical magnetic field. Its multigap features were observed experimentally. Recent studies suggested realization of P$\bar{6}$2m or Ima2 symmetry. We discuss the dynamical properties of both symmetries (e.g., phonon spectra). In this paper, using the ab initio techniques, we clarify this ambiguity, and conclude that the Ima2 symmetry is unstable, and P$\bar{6}$2m should be realized. The P$\bar{6}$2m symmetry is also stable in the presence of external hydrostatic pressure. We s…
Electronic band structure of BaCo$_{2}$As$_2$: a fully-doped ferropnictide with reduced electronic correlations
本文报道了BaCo $_{2}$ As $_2$的费米面和电子能带结构的角分辨光电子能谱研究。虽然它的准嵌套自由费米面从它的Fe-磷属元素化物表兄弟，我们表明，BaCo $_{2}$作为$_2$系统可以被用来作为一个近似的裸未占用的能带结构的相关BaFe $_{2-x}$ Co $_x$作为$_2$和Ba $_{1-x}$ K $_x$ Fe $_2$作为$_2$化合物。然而，我们的实验结果，与动力学平均场理论计算一致，表明电子相关性在BaCo $_{2}$ As $_2$中比在铁磷族化合物中重要得多。我们的研究结果表明，这种效果是由于增加填充的电子3 $d$壳中存在显着的Hund的交换耦合。
In rare-earth semiconductors, wide ligand $p$ and rare-earth 5$d$ bands coexist with localized, partially filled 4$f$ shells. A simultaneous description for both extended and localized states represents a significant challenge for first-principles theories. Here, we combine an {\it ab initio} dynamical mean-field theory approach to strong local correlations with a perturbative application of the semi-local modified Becke-Johnson exchange potential to correct the semiconducting gap. We apply this method to calculate the electronic structure and optical response of the light rare-earth sesquioxi…
Electronic correlations and dynamical screening with ab initio quantum embedding
Center for Computational Quantum Physics, Flatiron Institute（Flatiron Institute 计算量子物理中心）；Department of Physics, University of Fribourg（弗里堡大学物理系）；Université Paris-Saclay, CNRS, CEA, Institut de Physique Théorique (IPhT)（巴黎萨克雷大学、法国国家科学研究中心、法国原子能和替代能源委员会、理论物理研究所）；Collège de France（法兰西公学院）；CPHT, CNRS, École Polytechnique, Institut Polytechnique de Paris（巴黎理工学院、法国国立高等矿业电信学校联盟、法国国家科学研究中心计算物理和理论化学中心）；Department of Quantum Matter Physics, University of Geneva（日内瓦大学量子物质物理系）
Alkali-doped fullerides exhibit a wealth of unusual phases that remain controversial by nature. Here we report a cryogenic scanning tunneling microscopy study of the sub-molecular structural and electronic properties of expanded fullerene C60 films with various cesium (Cs) doping. By varying the discrete charge states and film thicknesses, we reveal a large tunability of orientational ordering of C60 anions, yet the tunneling conductance spectra are all robustly characteristic of energy gaps, hallmarks of Jahn-Teller instability and electronic correlations. The Fermi level lies halfway within …
The modern semilocal exchange potential is an accurate and efficient approximation to the exact exchange potential of density functional theory. We tried to combine it with the dynamical mean-field theory to derive a new first-principles many-body approach for studying correlated electronic materials. As a paradigm, this approach was employed to investigate the electronic structures and optical properties of strongly correlated ionic insulator YbS. Compared to the standard density functional theory plus dynamical mean-field theory which surprisingly failed to give an insulating solution, the n…
