We are an Emmy Noether Research group at the University of Cologne, led by Urban Seifert. Our work is concerned with the theory of quantum materials, with a particular focus on quantum matter in van der Waals heterostructures and novel phenomena in optically driven systems.
For more, please see our > research page and get to know our team > here.
News
Jul/2026New preprint: vacancies in altermagnets
In > arXiv:2607.07789 we study how vacancies distort magnetic order in altermagnets. In work led by Ruben Burkard, we use microscopic simulations and low-energy field theory to show that a vacancy generically produces an anisotropic texture, encoding the symmetry of the altermagnetic state. In classical altermagnets, this can be observed in the presence of a transverse magnetic field. Including quantum fluctuations, longitudinal power-law distortions emerge already at zero field. We envision that this vacancy response may allow for real-space imaging of the symmetry of the altermagnetic order parameter.
May/2026New preprint: frustrated quadrupoles
In > arXiv:2605.02336 we study spin-1 moments on the honeycomb lattice coupled by frustrated bond-dependent quadrupolar interactions. Growing out of Partha's Master's thesis work, we uncover a degenerate manifold of classical mean-field states and an exact gauge structure in a Majorana parton construction, and find that a combined lattice-reflection and spin-rotation symmetry decides the character of a putative spin liquid state. Our work is relevant to higher-spin Kitaev materials and Rydberg atom array quantum simulators.
Feb/2026Scholarship for Ruben Burkard
Congratulations to Ruben Burkard who has obtained a prestigious PhD scholarship from the Studienstiftung des dt. Volkes (German Academic Scholarship Foundation)!
Nov/2025Congratulations to graduating students!
In September, Mark Hannappel successfully defended his Bachelor's thesis, and in November, Partha Sarker completed his Master's degree. Congratulations! Partha will continue research in our group as a PhD student.
Sep/2025New preprints: magnetism in Hubbard models for moiré bilayers and field-induced gauge fluxes in QED3
We investigated the fate of (2+1)-dim. quantum electrodynamics in a Zeeman field in > arXiv:2508.08528, a problem relevant to frustrated triangular lattice antiferromagnets in magnetic fields. We find that the gauge field generates a finite flux! This results in relativistic Landau levels for the fermions and a number of verifiable predictions for experiments. In > arXiv:2505.06339, we investigate Hubbard models with longer-ranged interactions at fractional fillings: we show that self-organised charge crystals are new platforms that can host quantum spin liquid states.
May/2025Welcoming new group members
A warm welcome to Ruben Burkard, who has recently started as a PhD student in our group, and Mark Hannappel, who is working on his Bachelor's research project!
Apr/2025New preprints: altermagnetism in spin liquids and topologically enabled superconductivity
We have recently finished two preprints: altermagnetism can be implemented projectively in fractionalized spin liquids > arXiv:2504.12298, and a topological mechanism for superconductivity with possible connections to recent experiments on rhombohedral graphene > arXiv:2504.13166.
Dec/2024Starting up and new website
We are excited that our Emmy Noether group at the University of Cologne officially started in Nov. 2024! Haoyang Tian has joined the group as a PhD student and Partha Sarker as Master's student.