Emanuel Gull
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View article: Inchworm tensor train hybridization expansion quantum impurity solver
Inchworm tensor train hybridization expansion quantum impurity solver Open
The investigation of quantum impurity models plays a crucial role in condensed matter physics because of their wide-ranging applications, such as embedding theories and transport problems. Traditional methods often fall short of producing …
View article: Compact representation and long-time extrapolation of real-time data for quantum systems
Compact representation and long-time extrapolation of real-time data for quantum systems Open
Representing real-time data as a sum of complex exponentials provides a compact form that enables both denoising and extrapolation. As a fully data-driven method, the Estimation of Signal Parameters via Rotational Invariance Techniques (ES…
View article: Minimal pole representation for spectral functions
Minimal pole representation for spectral functions Open
Representing spectral densities, real-frequency, and real-time Green’s functions of continuous systems by a small discrete set of complex poles is a ubiquitous problem in condensed matter physics, with applications ranging from quantum tra…
View article: Large exciton binding energy in a bulk van der Waals magnet from quasi-1D electronic localization
Large exciton binding energy in a bulk van der Waals magnet from quasi-1D electronic localization Open
Excitons, bound electron-hole pairs, influence the optical properties in strongly interacting solid-state systems and are typically most stable and pronounced in monolayer materials. Bulk systems with large exciton binding energies, on the…
View article: Adaptive time stepping for the two-time integro-differential Kadanoff-Baym equations
Adaptive time stepping for the two-time integro-differential Kadanoff-Baym equations Open
The nonequilibrium Green's function gives access to one-body observables for quantum systems. Of particular interest are quantities such as density, currents, and absorption spectra which are important for interpreting experimental results…
View article: Nonequilibrium steady state full counting statistics in the noncrossing approximation
Nonequilibrium steady state full counting statistics in the noncrossing approximation Open
Quantum transport is often characterized not just by mean observables like the particle or energy current but by their fluctuations and higher moments, which can act as detailed probes of the physical mechanisms at play. However, relativel…
View article: Minimal pole representation and analytic continuation of matrix-valued correlation functions
Minimal pole representation and analytic continuation of matrix-valued correlation functions Open
We present a minimal pole method for analytically continuing matrix-valued imaginary frequency correlation functions to the real axis, enabling precise access to off-diagonal elements and thus improving the interpretation of self-energies …
View article: Pairing boost from enhanced spin-fermion coupling in the pseudogap regime
Pairing boost from enhanced spin-fermion coupling in the pseudogap regime Open
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…
View article: Denoising of imaginary time response functions with Hankel projections
Denoising of imaginary time response functions with Hankel projections Open
Imaginary-time response functions of finite-temperature quantum systems are often obtained with methods that exhibit stochastic or systematic errors. Reducing these errors comes at a large computational cost—in quantum Monte Carlo simulati…
View article: Nonequilibrium Steady State Full Counting Statistics in the Noncrossing Approximation
Nonequilibrium Steady State Full Counting Statistics in the Noncrossing Approximation Open
Quantum transport is often characterized not just by mean observables like the particle or energy current, but by their fluctuations and higher moments, which can act as detailed probes of the physical mechanisms at play. However, relative…
View article: Feynman diagrammatics based on discrete pole representations: A path to renormalized perturbation theories
Feynman diagrammatics based on discrete pole representations: A path to renormalized perturbation theories Open
By merging algorithmic Matsubara integration with discrete pole representations we present a procedure to generate fully analytic closed form results for impurity problems at fixed perturbation order. To demonstrate the utility of this app…
View article: Steady-state properties of multi-orbital systems using quantum Monte Carlo
Steady-state properties of multi-orbital systems using quantum Monte Carlo Open
A precise dynamical characterization of quantum impurity models with multiple interacting orbitals is challenging. In quantum Monte Carlo methods, this is embodied by sign problems. A dynamical sign problem makes it exponentially difficult…
View article: Green/WeakCoupling: Implementation of fully self-consistent finite-temperature many-body perturbation theory for molecules and solids
Green/WeakCoupling: Implementation of fully self-consistent finite-temperature many-body perturbation theory for molecules and solids Open
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…
View article: Symmetry adaptation for self-consistent many-body calculations
Symmetry adaptation for self-consistent many-body calculations Open
The exploitation of space group symmetries in numerical calculations of periodic crystalline solids accelerates calculations and provides physical insight. We present results for a space-group symmetry adaptation of electronic structure ca…
View article: Adaptive Time Stepping for the Two-Time Integro-Differential Kadanoff-Baym Equations
Adaptive Time Stepping for the Two-Time Integro-Differential Kadanoff-Baym Equations Open
The non-equilibrium Green's function gives access to one-body observables for quantum systems. Of particular interest are quantities such as density, currents, and absorption spectra which are important for interpreting experimental result…
View article: Numerically Exact Simulation of Photodoped Mott Insulators
Numerically Exact Simulation of Photodoped Mott Insulators Open
A description of long-lived photodoped states in Mott insulators is challenging, as it needs to address exponentially separated timescales. We demonstrate how properties of such states can be computed using numerically exact steady state t…
View article: Stark Many-Body Localization in Interacting Infinite Dimensional Systems
Stark Many-Body Localization in Interacting Infinite Dimensional Systems Open
We study bulk particle transport in a Fermi-Hubbard model on an infinite-dimensional Bethe lattice, driven by a constant electric field. Previous numerical studies showed that one dimensional analogs of this system exhibit a breakdown of d…
View article: Denoising and Extension of Response Functions in the Time Domain
Denoising and Extension of Response Functions in the Time Domain Open
Response functions of quantum systems, such as electron Green's functions, magnetic, or charge susceptibilities, describe the response of a system to an external perturbation. They are the central objects of interest in field theories and …
View article: Large Exciton Binding Energy in the Bulk van der Waals Magnet CrSBr
Large Exciton Binding Energy in the Bulk van der Waals Magnet CrSBr Open
Excitons, bound electron-hole pairs, influence the optical properties in strongly interacting solid state systems. Excitons and their associated many-body physics are typically most stable and pronounced in monolayer materials. Bulk system…
View article: Denoising of Imaginary Time Response Functions with Hankel projections
Denoising of Imaginary Time Response Functions with Hankel projections Open
Imaginary-time response functions of finite-temperature quantum systems are often obtained with methods that exhibit stochastic or systematic errors. Reducing these errors comes at a large computational cost -- in quantum Monte Carlo simul…
View article: Chirped amplitude mode in photo-excited superconductors
Chirped amplitude mode in photo-excited superconductors Open
Using a state-of-the-art numerical scheme, we show that the Higgs mode under excitation exhibits chirped oscillations and exponential decay when fluctuations are included. This is in stark contrast to conventional BCS collisionless dynamic…
View article: Dynamical mean field theory of the bilayer Hubbard model with inchworm Monte Carlo
Dynamical mean field theory of the bilayer Hubbard model with inchworm Monte Carlo Open
Dynamical mean field theory allows access to the physics of strongly correlated materials with nontrivial orbital structure, but relies on the ability to solve auxiliary multiorbital impurity problems. The most successful approaches to dat…
View article: Unambiguous fluctuation decomposition of the self-energy: pseudogap physics beyond spin fluctuations
Unambiguous fluctuation decomposition of the self-energy: pseudogap physics beyond spin fluctuations Open
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…
View article: Equivariant neural network for Green's functions of molecules and materials
Equivariant neural network for Green's functions of molecules and materials Open
The many-body Green's function provides access to electronic properties beyond density functional theory level in ab inito calculations. In this manuscript, we propose a deep learning framework for predicting the finite-temperature Green's…
View article: Minimal Pole Representation and Controlled Analytic Continuation of Matsubara Response Functions
Minimal Pole Representation and Controlled Analytic Continuation of Matsubara Response Functions Open
Analytical continuation is a central step in the simulation of finite-temperature field theories in which numerically obtained Matsubara data is continued to the real frequency axis for physical interpretation. Numerical analytic continuat…
View article: Quantum-centric Supercomputing for Materials Science: A Perspective on Challenges and Future Directions
Quantum-centric Supercomputing for Materials Science: A Perspective on Challenges and Future Directions Open
Computational models are an essential tool for the design, characterization, and discovery of novel materials. Hard computational tasks in materials science stretch the limits of existing high-performance supercomputing centers, consuming …
View article: Dynamical Mean Field Theory of the Bilayer Hubbard Model with Inchworm Monte Carlo
Dynamical Mean Field Theory of the Bilayer Hubbard Model with Inchworm Monte Carlo Open
Dynamical mean-field theory allows access to the physics of strongly correlated materials with nontrivial orbital structure, but relies on the ability to solve auxiliary multi-orbital impurity problems. The most successful approaches to da…
View article: Numerically exact simulation of photo-doped Mott insulators
Numerically exact simulation of photo-doped Mott insulators Open
A description of long-lived photo-doped states in Mott insulators is challenging, as it needs to address exponentially separated timescales. We demonstrate how properties of such states can be computed using numerically exact steady state …