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SYES: Symposium Electronic Structure Theory for Quantum Technology: From Complex Magnetism to Topological Superconductors and Spintronics

SYES 1: Electronic Structure Theory for Quantum Technology

SYES 1.4: Invited Talk

Friday, March 21, 2025, 11:15–11:45, H1

Non-collinear magnetism in 2D materials from first principles: Multiferroic order and magnetoelectric effects. — •Thomas Olsen — Department of Physics, Technical University of Denmark

We present a systematic classification of the magnetic ground states in hundreds of two-dimensional (2D) materials. Non-collinear order is shown to be abundant and may typically be represented by planar spin spiral ground states. We discuss a range of physical effects associated with non-collinear order and take specific materials as examples. The Ni(Cl,Br,I)₂ compounds exhibit type II multiferroic order where the spontaneous polarization is induced by spiral order and we discuss the subtleties associated with the calculation of the polarization from first principles. The breathing Kagomé compounds Nb₃(Cl,Br,I)₈ are pyroelectric and have spiral ground states with ordering vectors that couple strongly to out-of-plane external electric fields. Finally we discuss a set of 2D altermagnets and analyse the important role of spin-orbit coupling with respect to the band structure, magnons and non-collinearity.

Keywords: Two-dimensional materials; Magnetism; Magnons; Multiferroic; Density Functional Theory