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We present a new continuous time solver for quantum impurity models such as those relevant to dynamical mean field theory. It is based on a stochastic sampling of a perturbation expansion in the impurity-bath hybridization parameter.…

Strongly Correlated Electrons · Physics 2009-11-11 Philipp Werner , Armin Comanac , Luca De Medici , Matthias Troyer , Andrew J. Millis

We present a continuous-time Monte Carlo method for quantum impurity models, which combines a weak-coupling expansion with an auxiliary-field decomposition. The method is considerably more efficient than Hirsch-Fye and free of time…

Strongly Correlated Electrons · Physics 2008-06-02 Emanuel Gull , Philipp Werner , Olivier Parcollet , Matthias Troyer

Generalized quantum impurity models -- which feature a few localized and strongly-correlated degrees of freedom coupled to itinerant conduction electrons -- describe diverse physical systems, from magnetic moments in metals to…

Strongly Correlated Electrons · Physics 2024-10-23 Jonas B. Rigo , Andrew K. Mitchell

We present a diagrammatic Monte Carlo method for quantum impurity problems with general interactions and general hybridization functions. Our method uses a recursive determinant scheme to sample diagrams for the scattering amplitude. Unlike…

Strongly Correlated Electrons · Physics 2020-08-13 Jia Li , Markus Wallerberger , Emanuel Gull

An impurity solver based on a continuous-time quantum Monte Carlo method is developed for the Coqblin-Schrieffer model. The Monte Carlo simulation does not encounter a sign problem for antiferromagnetic interactions, and accurately…

Strongly Correlated Electrons · Physics 2007-10-25 J. Otsuki , H. Kusunose , P. Werner , Y. Kuramoto

A Monte Carlo sampling of diagrammatic corrections to the non-crossing approximation is shown to provide numerically exact estimates of the long-time dynamics and steady state properties of nonequilibrium quantum impurity models. This…

Strongly Correlated Electrons · Physics 2012-12-21 Emanuel Gull , David R. Reichman , Andrew J. Millis

We present a numerically exact steady-state inchworm Monte Carlo method for nonequilibrium quantum impurity models. Rather than propagating an initial state to long times, the method is directly formulated in the steady-state. This…

Strongly Correlated Electrons · Physics 2023-05-17 André Erpenbeck , Emanuel Gull , Guy Cohen

An acceleration of continuous time quantum Monte Carlo (CTQMC) methods is a potentially interesting branch of work as they are matchless as impurity solvers of a density functional theory in combination with a dynamical mean field theory…

Strongly Correlated Electrons · Physics 2019-08-07 Taegeun Song , Hunpyo Lee

Strongly correlated quantum impurity problems appear in a wide variety of contexts ranging from nanoscience and surface physics to material science and the theory of strongly correlated lattice models, where they appear as auxiliary systems…

Strongly Correlated Electrons · Physics 2013-02-19 Hartmut Hafermann , Philipp Werner , Emanuel Gull

Quantum Monte Carlo methods have proved very valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying…

The conductance of two Anderson impurity models, one with two-fold and another with four-fold degeneracy, representing two types of quantum dots, is calculated using a world-line quantum Monte Carlo (QMC) method. Extrapolation of the…

Mesoscale and Nanoscale Physics · Physics 2011-09-02 Dong E. Liu , Shailesh Chandrasekharan , Harold U. Baranger

We extend the recently developed real-time Diagrammatic Monte Carlo method, in its hybridization expansion formulation, to the full Kadanoff-Baym-Keldysh contour. This allows us to study real-time dynamics in correlated impurity models…

Strongly Correlated Electrons · Physics 2015-05-14 Marco Schiró

The quantum Monte Carlo methods represent a powerful and broadly applicable computational tool for finding very accurate solutions of the stationary Schroedinger equation for atoms, molecules, solids and a variety of model systems. The…

Computational Physics · Physics 2011-01-28 Jindrich Kolorenc , Lubos Mitas

We generalize the recently developed diagrammatic Monte Carlo techniques for quantum impurity models from an imaginary time to a Keldysh formalism suitable for real-time and nonequilibrium calculations. Both weak-coupling and…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 Philipp Werner , Takashi Oka , Andrew J. Millis

In order to investigate the effects of nonmagnetic impurities in strongly correlated systems, Quantum Monte Carlo (QMC) simulations have been carried out for the doped two-dimensional Hubbard model with one nonmagnetic impurity. Using a…

Strongly Correlated Electrons · Physics 2009-11-10 N. Bulut

Employing a classical density-functional description of liquid environments, we introduce a rigorous method for the diffusion quantum Monte Carlo calculation of free energies and thermodynamic averages of solvated systems that requires…

The coupling between localized magnetic moments and itinerant electrons presents a plethora of interesting physics. The low-energy physics of some quantum impurity systems can be described using conformal field theory (CFT). In this paper,…

High Energy Physics - Theory · Physics 2019-11-26 Ying-Hai Wu , Hong-Hao Tu

Quantum impurity solvers are the computational bottleneck of quantum embedding approaches to correlated materials, such as dynamical mean-field theory (DMFT). We show that neural networks trained on synthetic, material-agnostic data learn…

Strongly Correlated Electrons · Physics 2026-03-25 Agnes Valenti , Ina Park , Antoine Georges , Andrew J. Millis , Olivier Parcollet

A continuous-time path integral Quantum Monte Carlo method using the directed-loop algorithm is developed to simulate the Anderson single-impurity model in the occupation number basis. Although the method suffers from a sign problem at low…

Strongly Correlated Electrons · Physics 2009-11-10 Jaebeom Yoo , Shailesh Chandrasekharan , Harold U. Baranger

We develop a continuous-time quantum Monte Carlo method based on a strong-coupling expansion for Anderson impurity models with phonon-assisted hybridizations for arbitrary number of phonon modes. As a benchmark, we investigate the…

Strongly Correlated Electrons · Physics 2015-06-15 Kazumasa Hattori
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