Dynamical screening in correlated electron systems—from lattice models to realistic materials

Werner, Philipp; Casula, Michele

doi:10.1088/0953-8984/28/38/383001

Cited by 61 publications

(56 citation statements)

References 173 publications

(492 reference statements)

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“…This suggests the possibility of studying complex multiband materials, where a full GW +EDMFT computation would be too costly, using techniques in the spirit of the recent screened exchange + dynamical DMFT (SEx+DDMFT) method [26,27,59]. In realistic materials, the simple single-band description is not sufficient, and substantial screening effects resulting from the presence of higher-energy degrees of freedom must be taken into account [60][61][62].…”

Section: Discussionmentioning

confidence: 99%

Influence of Fock exchange in combined many-body perturbation and dynamical mean field theory

et al. 2017

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In electronic systems with long-range Coulomb interaction, the nonlocal Fock-exchange term has a bandwidening effect. While this effect is included in combined many-body perturbation theory and dynamical mean field theory (DMFT) schemes, it is not taken into account in standard extended DMFT (EDMFT) calculations. Here, we include this instantaneous term in both approaches and investigate its effect on the phase diagram and dynamically screened interaction. We show that the largest deviations between previously presented EDMFT and GW +EDMFT results originate from the nonlocal Fock term, and that the quantitative differences are especially large in the strong-coupling limit. Furthermore, we show that the charge-ordering phase diagram obtained in GW +EDMFT methods for moderate interaction values is very similar to the one predicted by dual-boson methods that include the fermion-boson or four-point vertex. DOI: 10.1103/PhysRevB.95.245130 Dynamical mean field theory (DMFT) [1] self-consistently maps a correlated Hubbard lattice problem with local interactions onto an effective impurity problem consisting of a correlated orbital hybridized with a noninteracting fermionic bath. If the bath is integrated out, one obtains an impurity action with retarded hoppings. Extended dynamical mean field theory [2-10] (EDMFT) extends the DMFT idea to systems with long-range interactions. It does so by mapping a lattice problem with long-range interactions onto an effective impurity model with self-consistently determined fermionic and bosonic baths, or, in the action formulation, an impurity model with retarded hoppings and retarded interactions.While EDMFT captures dynamical screening effects and charge-order instabilities, it has been found to suffer from qualitative shortcomings in finite dimensions. For example, the charge susceptibility computed in EDMFT does not coincide with the derivative of the average charge with respect to a small applied field [11], nor does it obey local charge conservation rules [12] essential for an adequate description of collective modes such as plasmons.The EDMFT formalism has an even more basic deficiency: since it is based on a local approximation to the self-energy, it does not include even the first-order nonlocal interaction term, the Fock term. The combined GW +EDMFT [13][14][15] scheme corrects this by supplementing the local self-energy from EDMFT with the nonlocal part of the GW diagram, where G is the interacting Green's function and W the fully screened interaction. Indeed, the nonlocal Fock term [Gv] nonloc is included in the nonlocal [GW ] nonloc diagram. As described in more detail in Ref. [15] (see also the appendix of Ref.[16]), the GW +EDMFT method is formally obtained by constructing an energy functional of G and W , the Almbladh [17] functional , and by approximating as a sum of two terms, one containing all local diagrams (corresponding to EDMFT) and the other containing the simplest nonlocal correction (corresponding to the GW approximation [18]). This functional construct...

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Section: Discussionmentioning

confidence: 99%

Influence of Fock exchange in combined many-body perturbation and dynamical mean field theory

et al. 2017

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“…[53][54][55][56] for longer reviews). The workflow of the approach is depicted in Figure 5: On the left -in blue -is the DMFT [49,118,119] cycle with an additional self-consistency for the two-particle interaction: It is required that the local screened interaction W loc equals the screened impurity interaction W imp = U + UP imp W imp = U − UχU, where χ = T n(τ )n(0) is the impurity density-density correlation function and U the local interaction (containing, e.g., Hubbard and Hund terms).…”

Section: Methodsmentioning

confidence: 99%

“…We discuss the GW+DMFT approach and present results in Section 3; for a more detailed introduction we refer the reader to references [53][54][55][56]. One should note, however, that the treatment of non-local correlations is very limited in GW+DMFT as only charge fluctuations and only the particle-hole channel are included in GW.…”

Section: Introductionmentioning

confidence: 99%

Merging GW with DMFT and non-local correlations beyond

Tomczak¹,

Liu²,

Toschi³

et al. 2017

Eur. Phys. J. Spec. Top.

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Abstract. We review recent developments in electronic structure calculations that go beyond state-of-the-art methods such as density functional theory (DFT) and dynamical mean field theory (DMFT). Specifically, we discuss the following methods: GW as implemented in the Vienna ab initio simulation package (VASP) with the self energy on the imaginary frequency axis, GW+DMFT, and ab initio dynamical vertex approximation (DΓA). The latter includes the physics of GW, DMFT and non-local correlations beyond, and allows for calculating (quantum) critical exponents. We present results obtained by the three methods with a focus on the benchmark material SrVO 3.

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“…A low-energy model with an energy-dependent Hubbard U as opposed to a static one poses a new theoretical challenge for solving the impurity problem. A breakthrough was made with the development of the continuous-time quantum Monte Carlo (CT-QMC) technique that offers a natural means of solving a model with an effective action containing a retarded or frequency-dependent interaction [65][66][67][68][69]. The frequency-dependent U gives a new insight into the role of non-local self-energy neglected in the LDA+DMFT scheme.…”

Section: Lda+dmftmentioning

confidence: 99%

Recent Progress in First-Principles Methods for Computing the Electronic Structure of Correlated Materials

Nilsson

Aryasetiawan

2018

Computation

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Substantial progress has been achieved in the last couple of decades in computing the electronic structure of correlated materials from first principles. This progress has been driven by parallel development in theory and numerical algorithms. Theoretical development in combining ab initio approaches and many-body methods is particularly promising. A crucial role is also played by a systematic method for deriving a low-energy model, which bridges the gap between real and model systems. In this article, an overview is given tracing the development from the LDA+U to the latest progress in combining the GW method and (extended) dynamical mean-field theory (GW+EDMFT). The emphasis is on conceptual and theoretical aspects rather than technical ones.

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Dynamical screening in correlated electron systems—from lattice models to realistic materials

Cited by 61 publications

References 173 publications

Influence of Fock exchange in combined many-body perturbation and dynamical mean field theory

Influence of Fock exchange in combined many-body perturbation and dynamical mean field theory

Merging GW with DMFT and non-local correlations beyond

Recent Progress in First-Principles Methods for Computing the Electronic Structure of Correlated Materials

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