Daniel F. Agterberg

University of Wisconsin-Milwaukee

Microscopic Models for Altermagnetism

Altermagnetism has recently emerged as an important class of magnetic materials due to their vanishing net magnetization and large, strongly momentum dependent, energy splittings between opposite spin states.   Most existing theoretical research on this magnetic state stems from density functional theory (DFT). Here I present recent progress [1] on developing minimal, Hubbard-like, Hamiltonians for altermagnetism that faithfully reproduce important features found in DFT electronic bandstructures. These minimal models apply to a wide range of crystal classes and provide microscopic descriptions for d-wave, g-wave, and i-wave altermagnets. Then I turn to correlation driven altermagnetism in 2D, where we develop a patch renormalization group (RG) approach for interacting fermions near coincident Van Hove singularities [2]. Coincident Van Hove singularities are symmetry-required to be coincident in both energy and momentum. We show that, unlike in other Van Hove scenarios, coincident Van Hove singularities give rise to altermagnetism as a correlation-driven weak-coupling instability.  

[1] M. Roig, A. Kreisel, Y. Yu, B. M. Andersen, and D. F. Agterberg, arXiv: 2402.15616 (2024).

[2] Y. Yue, H.G. Suh, M. Roig, and D.F. Agterberg, arXiv: 2402.05180 (2024).