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Erik van Loon

Contact details

E-mailerik.van_loon AT teorfys.lu.se
Office

B310
Division of Mathematical Physics
Professorsgatan 1
Lund

Post

Division of Mathematical Physics
Department of Physics
Lund University
Box 118
SE - 221 00 Lund
Sweden

About me

I have been working as an Associate Senior University Lecturer at Lund University since March 2021 and became docent in November 2022. My main research interest is the study of strongly correlated electrons and their collective excitations. This line of research is supported by the Crafoord Foundation, the Krapperup foundation, the Royal Physiographic Society of Lund, the Swedish Research Council (Vetenskapsrådet) and eSSENCE. I am also involved in teaching at the bachelor and master/PhD level. More information about my teaching, research and publications can be found below.

Previously, I was working with Professor Wehling at the University of Bremen (2018-2021). I did my PhD with Professor Katsnelson at Radboud University (2013-2018, thesis Collective phenomena in strongly correlated systems). Radboud University is also where I studied Physics, with a research stay with Professor Alexander Lichtenstein in Hamburg for my MSc. thesis.

MSc. and BSc. Thesis projects

Thesis projects on topics in condensed matter theory are available, with a focus on the quantum mechanics of correlated systems. Most projects will involve a combination of theoretical and computational studies. For MSc. thesis project, prior knowledge of advanced quantum mechanics and solid state physics are beneficial. If you are interested in doing a thesis project with me, please contact me via e-mail (see above) so that we can find a suitable project for you.

Teaching

I am currently responsible for the courses FYSB23 and FYST68 (formerly FYST25). More information about the courses can be found on their respective Canvas pages. Please contact me by e-mail if you encounter problems in the registration process or if you have questions about the course.

Basic Statistical Physics and Quantum Statistics (FYSB 23, VT1)

Solid State Theory (FYST68/EXTP90/NAFY017, VT2)

Research

Many interesting and useful properties of materials, such as their color, conductivity and magnetism, are determined by the electrons and their ability to move. Electrons are charged particles, so there is a repulsive Coulomb interaction that tries to keep them apart. Because of this, electrons do not move independently, their motion is correlated. An illustrative example of the role of correlations is the metal-insulator transition: sufficiently strong electronic repulsion can create a traffic jam of electrons, immobilizing them completely, making the electrical conductivity zero.

My main interest is the study of systems where these correlations are very strong or close to phase transitions, with particular attention to the collective, many-particle excitations of the system: compressibility, magnetic susceptibility, dielectric function, charge-density waves, etc. Both spatial and temporal correlations are important for these collective properties. For temporal correlations, an efficient method exists in the form of dynamical mean-field theory (DMFT). I have been working on so-called diagrammatic extensions of DMFT to be able to address spatial correlations as well. Several diagrammatic extensions of DMFT exist, my work has focussed on two of them which are called the dual fermion and dual boson approach. During my PhD, I implemented the dual boson approach for single-orbital systems and used it to study plasmons and charge-density waves, among other things. I currently maintain an open source code for multi-orbital dual fermion calculations, which can be found here: github.com/egcpvanloon/dualfermion.

In the spring of 2022, we had an online workshop on two-particle correlations. In the summer of 2024, we will have the conference Trends in Magnetism, which brings together Swedish magnetism researchers. More information can be found on the dedicated web pages.

Publications

  1. Second-order phase transitions and divergent linear response in dynamical mean-field theory
    Erik G. C. P. van Loon
    [arXiv:2401.04042]
  2. Downfolding from Ab Initio to Interacting Model Hamiltonians: Comprehensive Analysis and Benchmarking
    Yueqing Chang, Erik G. C. P. van Loon, Brandon Eskridge, Brian Busemeyer, Miguel A. Morales, Cyrus E. Dreyer, Andrew J. Millis, Shiwei Zhang, Tim O. Wehling, Lucas K. Wagner, Malte Rösner
    [arXiv:2311.05987]
  3. Unconventional charge-density-wave gap in monolayer NbS2
    Timo Knispel, Jan Berges, Arne Schobert, Erik G. C. P. van Loon, Wouter Jolie, Tim Wehling, Thomas Michely, Jeison Fischer
    NanoLetters 24, 1045–1051 (2024) [arXiv:2307.13791]
  4. Dual Bethe-Salpeter equation for the multi-orbital lattice susceptibility within dynamical mean-field theory
    Erik G. C. P. van Loon, Hugo U. R. Strand
    [arXiv:2306.05157]
  5. Nb3Cl8: A Prototypical Layered Mott-Hubbard Insulator
    Sergii Grytsiuk, Mikhail I. Katsnelson, Erik G.C.P. van Loon, Malte Rösner
    npj Quantum Mater. 9, 8 (2024) [arXiv:2305.04854]
  6. Ab initio electron-lattice downfolding: potential energy landscapes, anharmonicity, and molecular dynamics in charge density wave materials
    Arne Schobert, Jan Berges, Erik G. C. P. van Loon, Michael A. Sentef, Sergey Brener, Mariana Rossi, Tim O. Wehling
    SciPost Phys. 16, 046 (2024) [arXiv:2303.07261]
  7. Larmor precession in strongly correlated itinerant electron systems
    Erik G. C. P. van Loon and Hugo U. R. Strand
    Communications Physics 6, 289 (2023) [arXiv:2303.03468]
  8. Two-particle correlations and the metal-insulator transition: Iterated Perturbation Theory revisited
    Erik G. C. P. van Loon
    Phys. Rev. B 105, 245104 (2022) [arXiv:2110.11116]
  9. Degenerate plaquette physics as key ingredient of high-temperature superconductivity in cuprates
    M. Danilov, E.G.C.P. van Loon, S. Brener, S. Iskakov, M.I. Katsnelson, A.I. Lichtenstein
    npj Quantum Materials 7, 50 (2022) [arXiv:2107.11344]
  10. Downfolding the Su-Schrieffer-Heeger model
    Arne Schobert, Jan Berges, Tim Wehling and Erik van Loon
    SciPost Phys. 11, 079 (2021) [arXiv:2104.09207]
  11. Random Phase Approximation for gapped systems: role of vertex corrections and applicability of the constrained random phase approximation
    Erik G. C. P. van Loon, Malte Rösner, Mikhail I. Katsnelson, Tim O. Wehling
    Phys. Rev. B 104, 045134 (2021)  [arXiv:2103.04419]
  12. Downfolding approaches to electron-ion coupling: Constrained density-functional perturbation theory for molecules
    Erik G. C. P. van Loon, Jan Berges, Tim O. Wehling
    Phys. Rev. B 103, 205103 (2021) [arXiv:2102.10072]
  13. A full gap above the Fermi level: the charge density wave of monolayer VS2
    Camiel van Efferen, Jan Berges, Joshua Hall, Erik van Loon, Stefan Kraus, Arne Schobert, Tobias Wekking, Felix Huttmann, Eline Plaar, Nico Rothenbach, Katharina Ollefs, Lucas Machado Arruda, Nick Brookes, Gunnar Schoenhoff, Kurt Kummer, Heiko Wende, Tim Wehling, Thomas Michely
    Nature Comms 12, 6837 (2021) [arXiv:2101.01140]
  14. An efficient fluctuation exchange approach to low-temperature spin fluctuations and superconductivity: from the Hubbard model to NaxCoO2⋅yH2O
    Niklas Witt, Erik G. C. P. van Loon, Takuya Nomoto, Ryotaro Arita, Tim Wehling
    Phys. Rev. B 103, 205148 (2021) [arXiv:2012.04562]
  15. Second-order dual fermion for multi-orbital systems
    Erik G. C. P. van Loon
    J. Phys.: Condens. Matter 33 135601 (2021)[arXiv:2011.08780]
  16. The Bethe-Salpeter equation at the critical end-point of the Mott transition
    Erik G. C. P. van Loon, Friedrich Krien and Andrey Katanin
    Phys. Rev. Lett. 125, 136402 (2020)[arXiv:2002.12745]
  17. Coulomb Engineering of two-dimensional Mott materials
    Erik G. C. P. van Loon, Malte Schüler, Daniel Springer, Giorgio Sangiovanni, Jan M. Tomczak, Tim O. Wehling
    npj 2D Materials and Applications 7, 47 (2023) [arXiv:2001.01735]
  18. Turbulent hydrodynamics in strongly correlated Kagome metals
    Domenico Di Sante, Johanna Erdmenger, Martin Greiter, Ioannis Matthaiakakis, Rene Meyer, David Rodriguez Fernandez, Ronny Thomale, Erik van Loon, Tim Wehling
    Nature Communications 11, 3997 (2020)[arXiv:1911.06810]
  19. Ab-initio phonon self-energies and fluctuation diagnostics of phonon anomalies: lattice instabilities from Dirac pseudospin physics in transition-metal dichalcogenides
    Jan Berges, Erik G. C. P. van Loon, Arne Schobert, Malte Rösner, Tim O. Wehling
    Phys. Rev. B 101, 155107 (2020)[arXiv:1911.02450]
  20. Environmental control of charge density wave order in monolayer 2H-TaS2
    Joshua Hall, Niels Ehlen, Jan Berges, Erik van Loon, Camiel van Efferen, Clifford Murray, Malte Rösner, Jun Li, Boris V. Senkovskiy, Martin Hell, Matthias Rolf, Tristan Heider, María C. Asensio, José Avila, Lukasz Plucinski, Tim Wehling, Alexander Grüneis and Thomas Michely
    ACS Nano 13, 10210 (2019)
  21. Thermodynamics of the metal-insulator transition in the extended Hubbard model
    M. Schüler, E. G. C. P. van Loon, M. I. Katsnelson, T. O. Wehling
    SciPost Phys. 6, 067 (2019)[arXiv:1903.09947]
  22. Dual Boson approach with instantaneous interaction
    L. Peters, E. G. C. P. van Loon, A. N. Rubtsov, A. I. Lichtenstein, M. I. Katsnelson, E. A. Stepanov
    Phys. Rev. B 100, 165128 (2019)[arXiv:1902.06604]
  23. Bandwidth renormalization due to the intersite Coulomb interaction
    Yann in ‘t Veld, Malte Schüler, Tim Wehling, Mikhail I. Katsnelson, Erik G. C. P. van Loon
    J. Phys.: Condens. Matter 31, 465603 (2019)[arXiv:1901.11257]
  24. Two-particle Fermi liquid parameters at the Mott transition: Vertex divergences, Landau parameters, and incoherent response in dynamical mean-field theory
    Friedrich Krien, Erik G. C. P. van Loon, Mikhail I. Katsnelson, Alexander I. Lichtenstein, Massimo Capone
    Phys. Rev. B 99, 245128 (2019)[arXiv:1811.00362]
  25. Fermion-boson vertex within Dynamical Mean-Field Theory
    Erik G. C. P. van Loon, Friedrich Krien, Hartmut Hafermann, Alexander I. Lichtenstein and Mikhail I. Katsnelson
    Phys. Rev. B 98, 205148 (2018)[arXiv:1806.10415]
  26. Second-order dual fermion approach to the Mott transition in the two-dimensional Hubbard model
    Erik G. C. P. van Loon, Mikhail I. Katsnelson and Hartmut Hafermann
    Phys. Rev. B 98, 155117 (2018)[arXiv:1805.08572]
  27. Confining graphene plasmons to the ultimate limit
    Alessandro Principi, Erik van Loon, Marco Polini and Mikhail I. Katsnelson
    Phys. Rev. B 98, 035427 (2018)[arXiv:1802.06797]
  28. First-order metal-insulator transitions in the extended Hubbard model due to self-consistent screening of the effective interaction
    M. Schüler, E. G. C. P. van Loon, M. I. Katsnelson, T. O. Wehling
    Phys. Rev. B 97, 165135 (2018)[arXiv:1706.09644]
  29. Precursors of the insulating state in the square-lattice Hubbard model
    E. G. C. P. van Loon, Hartmut Hafermann and M. I. Katsnelson
    Phys. Rev. B 97, 085125 (2018)[arXiv:1712.08379]
  30. The extended Hubbard model with attractive interactions
    E. G. C. P. van Loon and M. I. Katsnelson
    J. Phys.: Conf. Ser., 1136, 012006 (2018)[arXiv:1709.06379]
  31. Competing Coulomb and electron–phonon interactions in NbS2
    E. G. C. P. van Loon, M. Rösner, G. Schönhoff, M. I. Katsnelson, T. O. Wehling
    npj Quantum Materials 3, 32 (2018)[arXiv:1707.05640]
  32. Conservation in two-particle self-consistent extensions of dynamical-mean-field-theory
    F. Krien, E. G. C. P. van Loon, H. Hafermann, J. Otsuki, M. I. Katsnelson, A. I. Lichtenstein
    Phys. Rev. B 96, 075155 (2017)[arXiv:1706.10233]
  33. A comparison between methods of analytical continuation for bosonic functions
    Johan Schött, Erik G. C. P. van Loon, Inka L. M. Locht, Mikhail Katsnelson, Igor Di Marco
    Phys. Rev. B 94, 245140 (2016)[arXiv:1607.04212]
  34. From local to nonlocal correlations: The Dual Boson perspective
    E. A. Stepanov, A. Huber, E. G. C. P. van Loon, A. I. Lichtenstein, M. I. Katsnelson
    Phys. Rev. B 94, 205110 (2016)[arXiv:1604.07734]
  35. Capturing non-local interaction effects in the Hubbard model: optimal mappings and limits of applicability
    E. G. C. P. van Loon, M. Schüler, M. I. Katsnelson, T. O. Wehling
    Phys. Rev. B 94, 165141 (2016)[arXiv:1605.09140]
  36. Interaction-driven Lifshitz transition with dipolar fermions in optical lattices
    E. G. C. P. van Loon, M. I. Katsnelson, L. Chomaz, M. Lemeshko
    Phys. Rev. B 93, 195145 (2016)[arXiv:1603.09358]
  37. Double occupancy in dynamical mean-field theory and the Dual Boson approach
    Erik G. C. P. van Loon, Friedrich Krien, Hartmut Hafermann, Evgeny A. Stepanov, Alexander I. Lichtenstein, Mikhail I. Katsnelson
    Phys. Rev. B 93, 155162 (2016)[arXiv:1602.09129]
  38. Self-consistent Dual Boson approach to single-particle and collective excitations in correlated systems
    E. A. Stepanov, E. G. C. P. van Loon, A. A. Katanin, A. I. Lichtenstein, M. I. Katsnelson, A. N. Rubtsov
    Phys. Rev. B 93, 045107 (2016)[arXiv:1508.07237]
  39. Ultralong-range order in the Fermi-Hubbard model with long-range interactions
    Erik G. C. P. van Loon, Mikhail I. Katsnelson and Mikhail Lemeshko
    Phys. Rev. B 92, 081106(R) (2015)[arXiv:1506.06007]
  40. Thermodynamic consistency of the charge response in dynamical mean-field based approaches
    Erik G. C. P. van Loon, Hartmut Hafermann, Alexander I. Lichtenstein, and Mikhail I. Katsnelson
    Phys. Rev. B 92, 085106 (2015)[arXiv:1505.05305]
  41. Beyond extended dynamical mean-field theory: Dual boson approach to the two-dimensional extended Hubbard model
    Erik G. C. P. van Loon, Alexander I. Lichtenstein, Mikhail I. Katsnelson, Olivier Parcollet, and Hartmut Hafermann
    Phys. Rev. B 90, 235135 (2014)[arXiv:1408.2150]
  42. Plasmons in Strongly Correlated Systems: Spectral Weight Transfer and Renormalized Dispersion
    E. G. C. P. van Loon, H. Hafermann, A. I. Lichtenstein, A. N. Rubtsov, and M. I. Katsnelson
    Phys. Rev. Lett. 113, 246407 (2014)[arXiv:1406.6188]
  43. Collective charge excitations of strongly correlated electrons, vertex corrections, and gauge invariance
    Hartmut Hafermann, Erik G. C. P. van Loon, Mikhail I. Katsnelson, Alexander I. Lichtenstein, and Olivier Parcollet
    Phys. Rev. B 90, 235105 (2014)[arXiv:1406.6515]

Popular Publications

  1. Faseovergangen door quantumonzekerheid
    Jins de Jong, Lennert van Tilburg en Erik van Loon
    Nederland Tijdschrift voor Natuurkunde, november 2012
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