Fabian Kugler

I am a Flatiron Research Fellow in the Center for Computational Quantum Physics at the Flatiron Institute. My research is focused on strongly correlated electrons in model systems as well as in quantum materials. I am also interested in method development, particularly in renormalization group based approaches with real-frequency resolution.

In 2019, I obtained my PhD from LMU Munich, Germany, in Jan von Delft's group. Thereafter, I was a postdoctoral fellow at Rutgers University, hosted by Gabriel Kotliar and funded by the Humboldt foundation. I have been named as a recipient of the Arnold Sommerfeld PhD Prize of LMU Munich, and the Otto Hahn Medal of the Max Planck Society.

Starting March 2025, I will build a research group at the Institute for Theoretical Physics of the University of Cologne, focused on Theoretical Spectroscopy of Quantum Materials. Please contact me if you are interested in a PhD or postdoc position.

Publications

  1. M. Gievers, R. Schmidt, J. von Delft, F. B. Kugler, Subleading logarithmic behavior in the parquet formalism, Phys. Rev. B 111, 085151 (2025). DOI
  2. D. Oh, A. Hampel, J. P. Wakefield, P. Moen, S. Smit, X. Luo, M. Zonno, S. Gorovikov, M. Leandersson, C. Polley, A. K. Kundu, A. Rajapitamahuni, E. Vescovo, C. Jozwiak, A. Bostwick, E. Rotenberg, M. Isobe, M. Verma, M. Crispino, M. Grundner, F. B. Kugler, O. Parcollet, U. Schollwöck, H. Takagi, A. Damascelli, G. Sangiovanni, J. G. Checkelsky, A. Georges, R. Comin, Hund flat band in a frustrated spinel, arXiv:2502.07234 (2025). arXiv
  3. J. Lee-Hand, H. LaBollita, F. B. Kugler, L. Van Muñoz, J. Kaye, S. Beck, A. Hampel, A. Georges, C. E. Dreyer, Fermi-Liquid T2 Resistivity: Dynamical Mean-Field Theory Meets Experiment, arXiv:2412.16363 (2024). arXiv
  4. M. Straub, F. Petocchi, C. Witteveen, F. B. Kugler, A. Hunter, Y. Alexanian, G. Gatti, S. Mandloi, C. Polley, G. Carbone, J. Osiecki, F. O. von Rohr, A. Georges, F. Baumberger, A. Tamai, Nature of metallic and insulating domains in the CDW system 1T-TaSe2, arXiv:2411.18205 (2024). arXiv
  5. M. Grundner, F. B. Kugler, O. Parcollet, U. Schollwöck, A. Georges, A. Hampel, LiV2O4: Hund-Assisted Orbital-Selective Mottness, arXiv:2409.17268 (2024). arXiv
  6. S. Dirnböck, S.-S. B. Lee, F. B. Kugler, S. Huber, J. von Delft, K. Held, M. Wallerberger, Overcomplete intermediate representation of two-particle Green's functions and its relation to partial spectral functions, Phys. Rev. Research 6, 043228 (2024). DOI
  7. F. B. Kugler, C.-J. Kang, G. Kotliar, Low-energy perspective on two-orbital Hund metals and the case of LaNiO2, Phys. Rev. B 110, 155101 (2024). DOI
  8. Y. Chang, J. Yi, A.-K. Wu, F. B. Kugler, E. Andrei, D. Vanderbilt, G. Kotliar, J. H. Pixley, Vacancy-induced tunable Kondo effect in twisted bilayer graphene, Phys. Rev. Lett. 133, 126503 (2024). DOI
  9. N. Ritz, A. Ge, E. Walter, S. Aguirre, J. von Delft, F. B. Kugler, KeldyshQFT: A C++ codebase for real-frequency multiloop functional renormalization group and parquet computations of the single-impurity Anderson model, J. Chem. Phys. 161, 054118 (2024). DOI
  10. A. Ge, J. Halbinger, S.-S. B. Lee, J. von Delft, F. B. Kugler, Analytic continuation of multipoint correlation functions, Ann. Phys. (Berlin) 536, 2300504 (2024). DOI
  11. M. Grundner, P. Westhoff, F. B. Kugler, O. Parcollet, U. Schollwöck, Complex Time Evolution in Tensor Networks, Phys. Rev. B 109, 155124 (2024). DOI
  12. J.-M. Lihm, J. Halbinger, J. Shim, J. von Delft, F. B. Kugler, S.-S. B. Lee, Symmetric improved estimators for multipoint vertex functions, Phys. Rev. B 109, 125138 (2024), Editors' Suggestion. DOI
  13. A. Ge, N. Ritz, E. Walter, S. Aguirre, J. von Delft, F. B. Kugler, Real-frequency quantum field theory applied to the single-impurity Anderson model, Phys. Rev. B 109, 115128 (2024). DOI
  14. F. B. Kugler, G. Kotliar, Is the orbital-selective Mott phase stable against interorbital hopping?, Phys. Rev. Lett. 129, 096403 (2022). DOI
  15. M. Gievers, E. Walter, A. Ge, J. von Delft, F. B. Kugler, Multiloop flow equations for single-boson exchange fRG, Eur. Phys. J. B 95, 108 (2022). DOI
  16. M. K. Ritter, D. Kiese, T. Müller, F. B. Kugler, R. Thomale, S. Trebst, J. von Delft, Benchmark Calculations of Multiloop Pseudofermion fRG, Eur. Phys. J. B 95, 102 (2022). DOI
  17. F. B. Kugler, Improved estimator for numerical renormalization group calculations of the self-energy, Phys. Rev. B 105, 245132 (2022), Editor's Suggestion. DOI
  18. P. Chalupa-Gantner, F. B. Kugler, C. Hille, J. von Delft, S. Andergassen, A. Toschi, Fulfillment of sum rules and Ward identities in the multiloop functional renormalization group solution of the Anderson impurity model, Phys. Rev. Research 4, 023050 (2022). DOI
  19. S.-S. B. Lee, F. B. Kugler, J. von Delft, Computing local multipoint correlators using the numerical renormalization group, Phys. Rev. X 11, 041007 (2021). DOI
  20. F. B. Kugler, S.-S. B. Lee, J. von Delft, Multipoint correlation functions: spectral representation and numerical evaluation, Phys. Rev. X 11, 041006 (2021). DOI
  21. J. Thoenniss, M. K. Ritter, F. B. Kugler, J. von Delft, M. Punk, Multiloop pseudofermion functional renormalization for quantum spin systems: Application to the spin-1/2 kagome Heisenberg model, arXiv:2011.01268 (2020). arXiv
  22. C. Hille, F. B. Kugler, C. J. Eckhardt, Y.-Y. He, A. Kauch, C. Honerkamp, A. Toschi, S. Andergassen, Quantitative functional renormalization group description of the two-dimensional Hubbard model, Phys. Rev. Research 2, 033372 (2020). DOI
  23. F. B. Kugler, M. Zingl, H. U. R. Strand, S.-S. B. Lee, J. von Delft, A. Georges, Strongly Correlated Materials from a Numerical Renormalization Group Perspective: How the Fermi-Liquid State of Sr2RuO4 Emerges, Phys. Rev. Lett. 124, 016401 (2020). DOI
  24. F. B. Kugler, S.-S. B. Lee, A. Weichselbaum, G. Kotliar, J. von Delft, Orbital differentiation in Hund metals, Phys. Rev. B 100, 115159 (2019). DOI
  25. C. J. Lindner, F. B. Kugler, V. Meden, H. Schoeller, Renormalization group transport theory for open quantum systems: Charge fluctuations in multilevel quantum dots in and out of equilibrium, Phys. Rev. B 99, 205142 (2019). DOI
  26. A. Tagliavini, C. Hille, F. B. Kugler, S. Andergassen, A. Toschi, C. Honerkamp, Multiloop functional renormalization group for the two-dimensional Hubbard model: Loop convergence of the response functions, SciPost Phys. 6, 009 (2019). DOI
  27. F. B. Kugler, J. von Delft, Derivation of exact flow equations from the self-consistent parquet relations, New. J. Phys. 20, 123029 (2018). DOI
  28. F. B. Kugler, Counting Feynman diagrams via many-body relations, Phys. Rev. E 98, 023303 (2018). DOI
  29. C. J. Lindner, F. B. Kugler, H. Schoeller, J. von Delft, Flavor fluctuations in 3-level quantum dots: Generic SU(3)-Kondo fixed point in equilibrium and non-Kondo fixed points in nonequilibrium, Phys. Rev. B 97, 235450 (2018). DOI
  30. F. B. Kugler, J. von Delft, Fermi-edge singularity and the functional renormalization group, J. Phys.: Condens. Matter 30, 195501 (2018). DOI
  31. F. B. Kugler, J. von Delft, Multiloop functional renormalization group for general models, Phys. Rev. B 97, 035162 (2018). DOI
  32. F. B. Kugler, J. von Delft, Multiloop functional renormalization group that sums up all parquet diagrams, Phys. Rev. Lett. 120, 057403 (2018). DOI
Dissertation: Renormalization group approaches to strongly correlated electron systems (LMU Munich, Germany, Advisor: Jan von Delft)


Contact

logo