The plain and simple parquet approximation: single-and multi-boson exchange in the two-dimensional Hubbard model

The European Physical Journal B, Journal Year: 2022, Volume and Issue: 95(4)

Published: April 1, 2022

Abstract The parquet approach to vertex corrections is unbiased but computationally demanding. Most applications are therefore restricted small cluster sizes or rely on various simplifying approximations. We have recently shown that the bosonization of diagrams provides interpretative and algorithmic advantages over original purely fermionic formulation. Here, we present first results numerical implementation this method by applying it half-filled Hubbard model square lattice at weak coupling. improved performance allows us evaluate approximation for a $$16\times 16$$ 16 × lattice, retaining full momentum frequency structure functions. discuss their symmetries consider parametrizations dependence using truncated-unity approximation. Graphical abstract

Language: Английский

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Assessment of the Second-Order Statically Screened Exchange Correction to the Random Phase Approximation for Correlation Energies

Journal of Chemical Theory and Computation, Journal Year: 2022, Volume and Issue: 18(10), P. 5948 - 5965

Published: Sept. 23, 2022

With increasing interelectronic distance, the screening of electron–electron interaction by presence other electrons becomes dominant source electron correlation. This effect is described random phase approximation (RPA) which therefore a promising method for calculation weak interactions. The success RPA relies on cancellation errors, can be traced back to violation crossing symmetry 4-point vertex, leading strongly overestimated total correlation energies. By addition second-order screened exchange (SOSEX) energy, this issue substantially reduced. In adiabatic connection (AC) SOSEX formalism, one two lines in term dynamically (SOSEX(W, vc)). A related expression both are statically (SOSEX(W(0), W(0))) obtained from G3W2 contribution electronic self-energy. contrast SOSEX(W, vc), evaluation energy does not require an expensive numerical frequency integration and advantageous computational perspective. We compare accuracy variant RPA+SOSEX(W, vc) wide range chemical reactions. While methods fail barrier heights, SOSEX(W(0), W(0)) agrees very well with charged excitations noncovalent interactions where they lead major improvements over RPA.

Language: Английский

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Two-site reduced density matrix from one- and two-particle Green's functions

Physical review. B./Physical review. B, Journal Year: 2024, Volume and Issue: 110(7)

Published: Aug. 8, 2024

Strongly correlated electron systems are challenging to calculate, and entanglement in such is not widely analyzed. We present an approach that can be used as a postprocessing step for calculating the two-site reduced density matrix from it measures mutual information negativity. Input only one- two-particle Green's function, which output of numerous many-body methods. As illustration, we results toy model, Hubbard model on $2\ifmmode\times\else\texttimes\fi{}2$ cluster six-site ring.

Language: Английский

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Strongly correlated superconductivity with long-range spatial fluctuations

Journal of Physics Materials, Journal Year: 2022, Volume and Issue: 5(3), P. 034005 - 034005

Published: July 1, 2022

Abstract We review recent studies for superconductivity using diagrammatic extensions of dynamical mean field theory. These approaches take into account simultaneously both, the local correlation effect and spatial long-range fluctuations, which are essential to describe unconventional in a quasi-two-dimensional plane. The results reproduce predict experimental phase diagrams strongly correlated system such as cuprates nickelates. Further reveal that screening pairing interaction vertex has dramatic consequences transition temperature may even support exotic mechanisms like odd-frequency pairing. also discuss dimensionality layered materials how interpret numerical two dimensions.

Language: Английский

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Spectral representation of Matsubara n-point functions: Exact kernel functions and applications

SciPost Physics, Journal Year: 2023, Volume and Issue: 15(5)

Published: Nov. 1, 2023

In the field of quantum many-body physics, spectral (or Lehmann) representation simplifies calculation Matsubara n n -point correlation functions if eigensystem a Hamiltonian is known. It expressed via universal kernel function and system- correlator-specific product matrix elements. Here we provide in full generality, for arbitrary , combinations bosonic or fermionic operators an number anomalous terms. As application, consider 3- 4-point Hubbard atom free spin length S display="inline">S respectively.

Language: Английский

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