Finn Lasse Buessen

Hi, I am a computational physicist working on condensed matter systems. Currently, I am a postdoctoral fellow associated with the group of Arun Paramekanti at the University of Toronto.

You can find me on LinkedIn, on Github, on Google Scholar, or in person at

Department of Physics

University of Toronto

60 St. George Street

Toronto, Ontario M5S 1A7


Office: MP1023

Email: fbuessen (at)

About me

I am passionate about the development of elegant code which pushes the limits of modern computational physics, drawing on my strong background in software development and high-performance computing. I firmly believe that scientific software should outlive the context it has originally been created in and should be made available to the community for future use, thereby serving as a catalyst to accelerate research in a time where state-of-the-art computational algorithms can sometimes be intimidatingly complex to implement.

A successful publication of scientific code requires extra steps to be taken in order to ensure good usability and documentation — steps which I was happy to take in my SpinParser project [see also the associated publication arXiv:2109.13317] for highly efficient (pseudo-fermionic) functional renormalization group calculations in quantum magnetism, written in modern C++ and capable of leveraging high-performance computing platforms with thousands of compute cores. Similarly, I have developed a flexible Monte Carlo implementation, SpinMC.jl, in the Julia programming language, which has been applied in numerous research projects on classical frustrated magnetism.

On the application side, I am interested in the theory of strongly correlated systems, frustrated quantum magnetism, and the formation of quantum spin liquids.

Brief CV

since 10/2019
Postdoctoral fellow at University of Toronto
Ph.D. at University of Cologne (working with Simon Trebst)
M.Sc. at University of Cologne



Jackson Pitts, Finn Lasse Buessen, Roderich Moessner, Simon Trebst, and Kirill Shtengel

Order by disorder in classical kagome antiferromagnets with chiral interactions


Emily Z. Zhang, Finn Lasse Buessen, and Yong Baek Kim

Dynamical Signatures of Rank-2 U(1) Spin Liquids


Finn Lasse Buessen

The SpinParser software for pseudofermion functional renormalization group calculations on quantum magnets


Finn Lasse Buessen and Yong Baek Kim

Functional renormalization group study of the Kitaev-Gamma model on the honeycomb lattice and emergent incommensurate magnetic correlations

Physical Review B 103, 184407 (2021)

Finn Lasse Buessen, Sopheak Sorn, Ivar Martin, and Arun Paramekanti

Nematic order driven by superconducting correlations

Annals of Physics (in press), 168494 (2021) [arXiv:2101.03174]

Nazim Boudjada, Finn Lasse Buessen, and Arun Paramekanti

Molecular dipoles in designer honeycomb lattices

Physical Review B 103, 165408 (2021)

Li Ern Chern, Finn Lasse Buessen, and Yong Baek Kim

Classical magnetic vortex liquid and large thermal Hall conductivity in frustrated magnets with bond-dependent interactions

npj Quantum Materials 6, 33 (2021)


P. Padmanabhan, F.L. Buessen, R. Tutchton, K.W.C. Kwock, S. Gilinsky, M.C. Lee, M.A. McGuire, S.R. Singamaneni, D.A. Yarotski, A. Paramekanti, J.-X. Zhu, R.P. Prasankumar

Coherent Helicity-Dependent Spin-Phonon Oscillations in the Ferromagnetic van der Waals Crystal CrI3


A. Revelli, M. Moretti Sala, G. Monaco, C. Hickey, P. Becker, F. Freund, A. Jesche, P. Gegenwart, T. Eschmann, F.L. Buessen, S. Trebst, P.H.M. van Loosdrecht, J. van den Brink, and M. Grüninger

Fingerprints of Kitaev physics in the magnetic excitations of honeycomb iridates

Physical Review Research 2, 043094 (2020)

Nazim Boudjada, Finn Lasse Buessen, and Arun Paramekanti

Domes of Tc in superconductors with finite-range attractive interactions

Physical Review B 102, 054504 (2020)

Dominik Kiese, Finn Lasse Buessen, Ciarán Hickey, Simon Trebst, and Michael M. Scherer

Emergence and stability of spin-valley entangled quantum liquids in moiré heterostructures

Physical Review Research 2, 013370 (2020)


Finn Lasse Buessen

A Functional Renormalization Group Perspective on Quantum Spin Liquids in Three-Dimensional Frustrated Magnets

Ph.D. thesis, University of Cologne (2019)

Finn Lasse Buessen, Vincent Noculak, Simon Trebst, and Johannes Reuther

Functional renormalization group for frustrated magnets with nondiagonal spin interactions

Physical Review B 100, 125164 (2019)

A. Revelli, C.C. Loo, D. Kiese, P. Becker, T. Fröhlich, T. Lorenz, M. Moretti Sala, G. Monaco, F.L. Buessen, J. Attig, M. Hermanns, S.V. Streltsov, D.I. Khomskii, J. van den Brink, M. Braden, P.H.M. van Loosdrecht, S. Trebst, A. Paramekanti, and M. Grüninger

Spin-orbit entangled j=1/2 moments in Ba2CeIrO6: A frustrated fcc quantum magnet

Physical Review B 100, 085139 (2019)


Finn Lasse Buessen, Max Hering, Johannes Reuther, and Simon Trebst

Quantum spin liquids in frustrated spin-1 diamond antiferromagnets

Physical Review Letters 120, 057201 (2018)

Finn Lasse Buessen, Dietrich Roscher, Sebastian Diehl, and Simon Trebst

Functional renormalization group approach to SU(N) Heisenberg models: Real-space RG at arbitrary N

Physical Review B 97, 064415 (2018)

Dietrich Roscher, Finn Lasse Buessen, Michael M. Scherer, Simon Trebst, and Sebastian Diehl

Functional renormalization group approach to SU(N) Heisenberg models: Momentum-space RG for the large-N limit

Physical Review B 97, 064416 (2018)


Finn Lasse Buessen and Simon Trebst

Competing magnetic orders and spin liquids in two- and three-dimensional kagome systems: Pseudo-fermion functional renormalization group perspective

Physical Review B 94, 235138 (2016)

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