89 citations · 788 across the 32 of their papers we have counts for
32 papers
Linear response functions from inhomogeneous dynamical mean-field theory
Don Rolih, Fabian B. Kugler
We present a method for calculating static lattice susceptibilities with inhomogeneous dynamical mean-field theory. The method utilizes the response of the system to an external fi…
Revealing Hund superdispersion with tunneling spectroscopy
Luke C. Rhodes, Fabian B. Kugler, Olivier Gingras +5
In cuprate superconductors, electron-electron repulsion results in characteristic spectroscopic features known as `waterfalls', where the sharp quasiparticle dispersion transitions…
Symmetric estimator for discrete self-energy of discrete many-body systems
Aleksandrs Zacinskis, Frank T. Ebel, Mathias Pelz +5
We derive a discrete spectral representation of the single-particle self-energy using a discrete evaluation of Kugler's symmetric improved estimator. Our construction can be used o…
Unconventional plasmon dynamics due to strong correlations in SrRuO
Juraj Krsnik, Dino Novko, Fabian B. Kugler +2
Plasmon modes, their dispersion, and the onset of damping when approaching the electron-hole continuum are well understood when electron correlations are weak. However, we know lit…
The finite-difference parquet method: Enhanced electron-paramagnon scattering opens a pseudogap
Jae-Mo Lihm, Dominik Kiese, Seung-Sup B. Lee +1
We present the finite-difference parquet method that greatly improves the applicability and accuracy of two-particle correlation approaches to interacting electron systems. This me…
Testing the parquet equations and the U(1) Ward identity for real-frequency correlation functions from the multipoint numerical renormalization group
Nepomuk Ritz, Anxiang Ge, Markus Frankenbach +3
Recently, it has become possible to compute real-frequency four-point correlation functions of quantum impurity models using a multipoint extension of the numerical renormalization…
Subleading logarithmic behavior in the parquet formalism
Marcel Gievers, Richard Schmidt, Jan von Delft +1
The Fermi-edge singularity in x-ray absorption spectra of metals is a paradigmatic case of a logarithmically divergent perturbation series. Prior work has thoroughly analyzed the l…
KeldyshQFT: A C++ codebase for real-frequency multiloop functional renormalization group and parquet computations of the single-impurity Anderson model
Nepomuk Ritz, Anxiang Ge, Elias Walter +3
We provide a detailed exposition of our computational framework designed for the accurate calculation of real-frequency dynamical correlation functions of the single-impurity Ander…
Overcomplete intermediate representation of two-particle Green's functions and its relation to partial spectral functions
Selina Dirnböck, Seung-Sup B. Lee, Fabian B. Kugler +4
Two-particle response functions are a centerpiece of both experimental and theoretical quantum many-body physics. Yet, due to their size and discontinuity structure, they are chall…
Complex Time Evolution in Tensor Networks
M. Grundner, P. Westhoff, F. B. Kugler +2
Real-time calculations in tensor networks are strongly limited in time by entanglement growth, restricting the achievable frequency resolution of Green's functions, spectral functi…
Analytic continuation of multipoint correlation functions
Anxiang Ge, Johannes Halbinger, Seung-Sup B. Lee +2
Conceptually, the Matsubara formalism (MF), using imaginary frequencies, and the Keldysh formalism (KF), formulated in real frequencies, give equivalent results for systems in ther…
Symmetric improved estimators for multipoint vertex functions
Jae-Mo Lihm, Johannes Halbinger, Jeongmin Shim +3
Multipoint vertex functions, and the four-point vertex in particular, are crucial ingredients in many-body theory. Recent years have seen significant algorithmic progress toward nu…
Real-frequency quantum field theory applied to the single-impurity Anderson model
Anxiang Ge, Nepomuk Ritz, Elias Walter +3
A major challenge in the field of correlated electrons is the computation of dynamical correlation functions. For comparisons with experiment, one is interested in their real-frequ…
Benchmark Calculations of Multiloop Pseudofermion fRG
Marc K. Ritter, Dominik Kiese, Tobias Müller +4
The pseudofermion functional renormalization group (pffRG) is a computational method for determining zero-temperature phase diagrams of frustrated quantum magnets. In a recent meth…
Improved estimator for numerical renormalization group calculations of the self-energy
Fabian B. Kugler
We present a new estimator for the self-energy based on a combination of two equations of motion and discuss its benefits for numerical renormalization group (NRG) calculations. In…
Multiloop flow equations for single-boson exchange fRG
Marcel Gievers, Elias Walter, Anxiang Ge +2
The recently introduced single-boson exchange (SBE) decomposition of the four-point vertex of interacting fermionic many-body systems is a conceptually and computationally appealin…
Is the orbital-selective Mott phase stable against interorbital hopping?
Fabian B. Kugler, Gabriel Kotliar
The localization-delocalization transition is at the heart of strong correlation physics. Recently, there is great interest in multiorbital systems where this transition can be res…
Fulfillment of sum rules and Ward identities in the multiloop functional renormalization group solution of the Anderson impurity model
Patrick Chalupa-Gantner, Fabian B. Kugler, Cornelia Hille +3
We investigate several fundamental characteristics of the multiloop functional renormalization group (mfRG) flow by hands of its application to a prototypical many-electron system:…
Computing local multipoint correlators using the numerical renormalization group
Seung-Sup B. Lee, Fabian B. Kugler, Jan von Delft
Local three- and four-point correlators yield important insight into strongly correlated systems and have many applications. However, the nonperturbative, accurate computation of m…
Multipoint correlation functions: spectral representation and numerical evaluation
Fabian B. Kugler, Seung-Sup B. Lee, Jan von Delft
The many-body problem is usually approached from one of two perspectives: the first originates from an action and is based on Feynman diagrams, the second is centered around a Hami…
Multiloop pseudofermion functional renormalization for quantum spin systems: Application to the spin- kagome Heisenberg model
Julian Thoenniss, Marc K. Ritter, Fabian B. Kugler +2
We present a multiloop pseudofermion functional renormalization group (pffRG) approach to quantum spin systems. As a test case, we study the spin- Heisenberg model on…
Quantitative functional renormalization-group description of the two-dimensional Hubbard model
Cornelia Hille, Fabian B. Kugler, Christian J. Eckhardt +5
Using a leading algorithmic implementation of the functional renormalization group (fRG) for interacting fermions on two-dimensional lattices, we provide a detailed analysis of its…
Strongly correlated materials from a numerical renormalization group perspective: How the Fermi-liquid state of SrRuO emerges
Fabian B. Kugler, Manuel Zingl, Hugo U. R. Strand +3
The crossover from fluctuating atomic constituents to a collective state as one lowers temperature or energy is at the heart of the dynamical mean-field theory description of the s…
Orbital differentiation in Hund metals
Fabian B. Kugler, Seung-Sup B. Lee, Andreas Weichselbaum +2
Orbital differentiation is a common theme in multiorbital systems, yet a complete understanding of it is still missing. Here, we consider a minimal model for orbital differentiatio…