Seminarium Fizyki Materii Skondensowanej

Altermagnetism represents a type of collinear magnetism, that is in some aspects distinct from ferromagnetism and conventional antiferromagnetism. In contrast to standard ferro- and antiferromagnets, altermagnets exhibit extra even-parity wave spin order parameters resulting in a spin splitting of electronic bands in momentum space. I will start with a pedagogical introduction to the altermagnetic symmetry requirements, by studying a simple toy model, which can be realized with ultracold fermionic atoms in optical lattices. However, this and all other current models featuring altermagnetic instabilities, rely on specific lattices with crystallographic sublattice anisotropy. I will show that altermagnetism can also form as an interaction-induced electronic instability in a lattice without such strong symmetry requirements. As proof of principle I will introduce a microscopic example of a two-orbital model demonstrating that the coexistence of antiferromagnetic and staggered orbital order can realize robust altermagnetism. Finally, I will discuss a mechanism for spontaneous altermagnetism in cuprate compounds based on the formation of oxygen moments.