dr. Erik G. C. P. van Loon | |
evloon at itp dot uni-bremen dot de | |
Room | NW1 O3040 |
Otto-Hahn-Allee 1 | |
University of Bremen | |
28359, Bremen, Germany | |
Telephone | +49 421 218 62041 |
Since January 2020, I hold an independent postdoc position supported by the Central Research Development Fund of the University of Bremen, working on the Theory of plasmonic and optical excitations in correlated electron materials. I have been working in the group of prof. dr. Wehling at the University of Bremen since October 2018. From December 2013 until September 2018, I was in the Theory of Condensed Matter group of prof. dr. Katsnelson, part of the Institute for Molecules and Materials of the Radboud University Nijmegen. On March 20 2018, I defended my PhD thesis Collective Phenomena in Strongly Correlated Systems. I finished my Master in the same group, having spent a year as an exchange student doing research in the group of prof. dr. Alexander Lichtenstein in Hamburg.
Research
My main interest is the study of collective excitations in strongly correlated systems.
Over the last three decades, Dynamical Mean-Field Theory (DMFT) has emerged as the best tool to describe the electronic structure of strongly correlated materials. It relies the assumption that most correlations occur locally and can be captured in a single-site reference model. This approach has been hugely successful at describing the one-particle properties of correlated models (Hubbard model) and materials: for example, the density of states, self-energy and spectral function. As a non-perturbative technique, DMFT can be used at arbitrary interaction strength and can follow the evolution from weakly interacting metal via strongly correlated metal to Mott insulator.
My work has focused on the collective properties of this kind of systems: compressibility, magnetic susceptibility, dielectric function, charge-density waves, etc. These used to be too difficult to accurately determine computationally, due to a difference in length scales. The DMFT approach knows about on-site correlations, but not about momentum dependence and long wavelengths. These aspect are necessary for determining the dispersion of collective modes (plasmons, magnons and zero-sound modes) as well as for investigating charge-density waves.
Diagrammatic extensions of DMFT address this deficiency, by adding spatial correlations to the DMFT solution. I have been working on one of these extensions, the Dual Boson approach. An important aspect in these investigations is the issue of consistency: Approximate solutions can violate known exact properties of the system. For the case of the charge susceptibility, we have shown that the Dual Boson approach gives results satisfying the charge conservation law, by taking into account vertex corrections to all orders via the so-called ladder equation. With this machinery, we were able to study the renormalization of the plasmon dispersion due to correlation. In addition to this, we have investigated charge ordering in the extended Hubbard model, with applications to dipolar fermions in optical lattices, and the competition of electron-electron and electron-phonon interaction in NbS2.
Publications
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2101.01140
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A full gap above the Fermi level: the charge density wave of monolayer VS2
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An efficient fluctuation exchange approach to low-temperature spin fluctuations and superconductivity: from the Hubbard model to NaxCoO2⋅yH2O
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Second-order dual fermion for multi-orbital systems
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The Bethe-Salpeter equation at the critical end-point of the Mott transition
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Coulomb Engineering of two-dimensional Mott materials
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Turbulent hydrodynamics in strongly correlated Kagome metals
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Ab-initio phonon self-energies and fluctuation diagnostics of phonon anomalies: lattice instabilities from Dirac pseudospin physics in transition-metal dichalcogenides
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Environmental control of charge density wave order in monolayer 2H-TaS2
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Thermodynamics of the metal-insulator transition in the extended Hubbard model
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Dual Boson approach with instantaneous interaction
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Bandwidth renormalization due to the intersite Coulomb interaction
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Two-particle Fermi liquid parameters at the Mott transition: Vertex divergences, Landau parameters, and incoherent response in dynamical mean-field theory
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Fermion-boson vertex within Dynamical Mean-Field Theory
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Second-order dual fermion approach to the Mott transition in the two-dimensional Hubbard model
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Confining graphene plasmons to the ultimate limit
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First-order metal-insulator transitions in the extended Hubbard model due to self-consistent screening of the effective interaction
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Precursors of the insulating state in the square-lattice Hubbard model
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The extended Hubbard model with attractive interactions
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Competing Coulomb and electron–phonon interactions in NbS2
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Conservation in two-particle self-consistent extensions of dynamical-mean-field-theory
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A comparison between methods of analytical continuation for bosonic functions
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From local to nonlocal correlations: The Dual Boson perspective
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Capturing non-local interaction effects in the Hubbard model: optimal mappings and limits of applicability
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Interaction-driven Lifshitz transition with dipolar fermions in optical lattices
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Double occupancy in dynamical mean-field theory and the Dual Boson approach
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Self-consistent Dual Boson approach to single-particle and collective excitations in correlated systems
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Ultralong-range order in the Fermi-Hubbard model with long-range interactions
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Thermodynamic consistency of the charge response in dynamical mean-field based approaches
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Beyond extended dynamical mean-field theory: Dual boson approach to the two-dimensional extended Hubbard model
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Plasmons in Strongly Correlated Systems: Spectral Weight Transfer and Renormalized Dispersion
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Collective charge excitations of strongly correlated electrons, vertex corrections, and gauge invariance
Popular Publications
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