Explanipedia

Superconductivity of Bad Fermions: Origin of Two Gaps in HTSC Cuprates Open

Е. А. Степанов, Sergei Iskakov, M. I. Katsnelson, A. I. Lichtenstein · 2025

We investigate the spectral properties of the doped ${t-t'}$ Hubbard model with parameters typical for high-temperature cuprate superconductors. Our approach is based on a novel strong-coupling Green's function expansion around a reference…

Pairing boost from enhanced spin-fermion coupling in the pseudogap regime Open

Yang Yu, Sergei Iskakov, Emanuel Gull, Karsten Held, Friedrich Krien · 2024

We perform a fluctuation analysis of the pairing interaction in the hole-doped Hubbard model within the dynamical cluster approximation. Our analysis reveals that spin-fluctuation-mediated pairing differs qualitatively in the over- and und…

TRIQS/Nevanlinna: Implementation of the Nevanlinna Analytic Continuation method for noise-free data Open

Sergei Iskakov, Alexander Hampel, Nils Wentzell, Emanuel Gull · 2024

Green/WeakCoupling: Implementation of fully self-consistent finite-temperature many-body perturbation theory for molecules and solids Open

Sergei Iskakov, Chia-Nan Yeh, Pavel Pokhilko, Yang Yu, Lei Zhang , et al. · 2024

The accurate ab initio simulation of molecules and periodic solids with diagrammatic perturbation theory is an important task in quantum chemistry, condensed matter physics, and materials science. In this article, we present the WeakCoupli…

Perturbative solution of fermionic sign problem in quantum Monte Carlo computations Open

Sergei Iskakov, M. I. Katsnelson, A. I. Lichtenstein · 2024

We have developed a strong-coupling perturbation scheme for a general doped Hubbard model around a particle-hole-symmetric reference system, which is free from the fermionic sign problem. Our approach is based on the lattice determinantal …

Data for "Perturbative Solution of Fermionic Sign Problem in Quantum Monte Carlo Computations" Open

Sergei Iskakov, A. I. Lichtenstein, M. I. Katsnelson · 2024

Datasets used to produce figures in the "Perturbative Solution of Fermionic Sign Problem in Quantum Monte Carlo Computations" manuscript. 8x8/U=8.0/G(w).txt contains data for Figs. 2, 3 and 4 8x8/U=8.0/G_dual.txt contains data for Figs. 5 …

Data for "Perturbative Solution of Fermionic Sign Problem in Quantum Monte Carlo Computations" Open

Sergei Iskakov, A. I. Lichtenstein, M. I. Katsnelson · 2024

Datasets used to produce figures in the "Perturbative Solution of Fermionic Sign Problem in Quantum Monte Carlo Computations" manuscript. 8x8/U=8.0/G(w).txt contains data for Figs. 2, 3 and 4 8x8/U=8.0/G_dual.txt contains data for Figs. 5 …

Unambiguous fluctuation decomposition of the self-energy: pseudogap physics beyond spin fluctuations Open

Yang Yu, Sergei Iskakov, Emanuel Gull, Karsten Held, Friedrich Krien · 2024

Correlated electron systems may give rise to multiple effective interactions whose combined impact on quasiparticle properties can be difficult to disentangle. We introduce an unambiguous decomposition of the electronic self-energy which a…

Tensor train continuous time solver for quantum impurity models Open

André Erpenbeck, Wei‐Ting Lin, Thomas Blommel, L. Zhang, Sergei Iskakov , et al. · 2023

The simulation of strongly correlated quantum impurity models is a significant challenge in modern condensed matter physics that has multiple important applications. Thus far, the most successful methods for approaching this challenge invo…

Overcoming Fermionic Sign Problem in Quantum Monte Carlo Computations: Reference System Method Open

Sergei Iskakov, M. I. Katsnelson, A. I. Lichtenstein · 2023

We have developed a novel strong-coupling perturbation scheme for a general doped Hubbard model around a particle-hole-symmetric reference system, which is free from the fermionic sign problem. Our approach is based on the lattice determin…

Heating and cooling in self-consistent many-body simulations Open

Yang Yu, Sergei Iskakov, Emanuel Gull · 2023

We present a temperature extrapolation technique for self-consistent many-body methods, which provides a causal starting point for converging to a solution at a target temperature. The technique employs the Carathéodory formalism for inter…

Perturbative solution of fermionic sign problem in lattice Quantum Monte Carlo Open

Sergei Iskakov, M. I. Katsnelson, A. I. Lichtenstein · 2023

We develop a strong-coupling perturbation scheme for a generic Hubbard model around a half-filled particle-hole-symmetric reference system, which is free from the fermionic sign problem. The approach is based on the lattice determinantal Q…

Single- and two-particle finite size effects in interacting lattice systems Open

Sergei Iskakov, Hanna Terletska, Emanuel Gull · 2022

Simulations of extended quantum systems are typically performed by extrapolating results of a sequence of finite-system-size simulations to the thermodynamic limit. In the quantum Monte Carlo community, twist-averaging was pioneered as an …

Fully self-consistent finite-temperature in Gaussian Bloch orbitals for solids Open

Chia-Nan Yeh, Sergei Iskakov, Dominika Zgid, Emanuel Gull · 2022

In this work, we present algorithmic and implementation details for the fully self-consistent finite-temperature $GW$ method in Gaussian Bloch orbitals for solids. Our implementation is based on the finite-temperature Green's function form…

Magnetic phases of the anisotropic triangular lattice Hubbard model Open

Y. Yu, Shaozhi Li, Sergei Iskakov, Emanuel Gull · 2022

The Hubbard model on an anisotropic triangular lattice in two dimensions, a fundamental model for frustrated electron physics, displays a wide variety of phases and phase transitions. This work investigates the model using the ladder dual …

Single- and two-particle finite size effects in interacting lattice systems Open

Sergei Iskakov, Hanna Terletska, Emanuel Gull · 2022

Simulations of extended quantum systems are typically performed by extrapolating results of a sequence of finite-system-size simulations to the thermodynamic limit. In the quantum Monte Carlo community, twist-averaging was pioneered as an …

Fully Self-Consistent Finite-Temperature $GW$ in Gaussian Bloch Orbitals for Solids Open

Chia-Nan Yeh, Sergei Iskakov, Dominika Zgid, Emanuel Gull · 2022

We present algorithmic and implementation details for the fully self-consistent finite-temperature $GW$ method in Gaussian Bloch orbitals for solids. Our implementation is based on the finite-temperature Green's function formalism in which…

Degenerate plaquette physics as key ingredient of high-temperature superconductivity in cuprates Open

Michael Danilov, Erik G. C. P. van Loon, Sergey Brener, Sergei Iskakov, M. I. Katsnelson , et al. · 2022

We study the physics of high-temperature cuprate superconductors starting from the highly degenerate four-site plaquette of the $$t-t^{\prime} -U$$ Hubbard model as a reference system. The degeneracy causes strong fluctuations w…

Phase transitions in partial summation methods: Results from the 3D Hubbard model Open

Sergei Iskakov, Emanuel Gull · 2021

The accurate determination of magnetic phase transitions in electronic systems is an important task of solid state theory. While numerically exact results are readily available for model systems such as the half-filled 3D Hubbard model, th…

Dynamical cluster approximation study of electron localization in the extended Hubbard model Open

Hanna Terletska, Sergei Iskakov, Thomas Maier, Emanuel Gull · 2021

We perform a detailed study of the phase transitions and mechanisms of electron localization in the extended Hubbard model using the dynamical cluster approximation on a $2\times 2$ cluster. We explore the interplay of charge order and Mot…

Evaluation of two-particle properties within finite-temperature self-consistent one-particle Green’s function methods: Theory and application to GW and GF2 Open

Pavel Pokhilko, Sergei Iskakov, Chia-Nan Yeh, Dominika Zgid · 2021

One-particle Green’s function methods can model molecular and solid spectra at zero or non-zero temperatures. One-particle Green’s functions directly provide electronic energies and one-particle properties, such as dipole moment. However, …

Dynamical Cluster Approximation Study of Electron Localization in the Extended Hubbard Model Open

Hanna Terletska, Sergei Iskakov, Thomas Maier, Emanuel Gull · 2021

We perform a detailed study of the phase transitions and mechanisms of electron localization in the extended Hubbard model using the dynamical cluster approximation on a $2\times 2$ cluster. We explore the interplay of charge order and Mot…

Testing the Green's function coupled cluster singles and doubles impurity solver on real materials within the framework of self-energy embedding theory Open

Chia-Nan Yeh, Avijit Shee, Sergei Iskakov, Dominika Zgid · 2021

We apply the Green's function coupled cluster singles and doubles (GFCCSD) impurity solver to realistic impurity problems arising for strongly correlated solids within the self-energy embedding theory (SEET) framework. We describe the deta…

<i>Ab initio</i> self-energy embedding for the photoemission spectra of NiO and MnO Open

Sergei Iskakov, Chia-Nan Yeh, Emanuel Gull, Dominika Zgid · 2020

The accurate ab-initio simulation of periodic solids with strong correlations\nis one of the grand challenges of condensed matter. While mature methods exist\nfor weakly correlated solids, the ab-initio description of strongly correlated\n…

Erratum: Momentum-space cluster dual-fermion method [Phys. Rev. B <b>97</b>, 125114 (2018)] Open

Urs R. Hähner, Sergei Iskakov, Hanna Terletska, Emanuel Gull · 2019

Received 15 August 2019DOI:https://doi.org/10.1103/PhysRevB.100.169906©2019 American Physical SocietyPhysics Subject Headings (PhySH)TechniquesApproximation methods for many-body systemsDynamical mean field theoryHubbard modelCondensed Mat…

Effect of propagator renormalization on the band gap of insulating solids Open

Sergei Iskakov, Alexander A. Rusakov, Dominika Zgid, Emanuel Gull · 2019

We present momentum-resolved spectral functions and band gaps from bare and\nself-consistent second-order perturbation theory for insulating periodic\nsolids. We establish that, for systems with large gap sizes, both bare and\nself-consist…

Charge order and antiferromagnetism in the extended Hubbard model Open

Joseph Paki, Hanna Terletska, Sergei Iskakov, Emanuel Gull · 2019

We study the extended Hubbard model on a two-dimensional half-filled square\nlattice using the dynamical cluster approximation. We present results on the\nphase boundaries between the paramagnetic metallic (normal) state and the\ninsulatin…

Effect of propagator renormalization on the band gap of solids. Open

Sergei Iskakov, Alexander A. Rusakov, Dominika Zgid, Emanuel Gull · 2018

We present momentum-resolved spectral functions and band gaps from bare and self-consistent second order perturbation theory for insulating periodic solids. We establish that, for systems with large gap sizes, both bare and self-consistent…

Self-Energy Embedding Theory (SEET) for Periodic Systems Open

Alexander A. Rusakov, Sergei Iskakov, Lan Nguyen Tran, Dominika Zgid · 2018

We present an implementation of the self-energy embedding theory (SEET) for periodic systems and provide a fully self-consistent embedding solution for a simple realistic periodic problem-one-dimensional (1D) crystalline hydrogen-that disp…

Updated Core Libraries of the ALPS Project Open

Markus Wallerberger, Sergei Iskakov, Alexander Gaenko, Joseph Kleinhenz, Igor Krivenko , et al. · 2018

The open source ALPS (Algorithms and Libraries for Physics Simulations) project provides a collection of physics libraries and applications, with a focus on simulations of lattice models and strongly correlated electron systems. The librar…

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