Seminář ÚFKL: Libor Šmejkal

Ústav fyziky kondenzovaných látek vás zve na přednášku

Libor Šmejkal (Max Planck Institute, Dresden, Germany; Johannes Gutenberg Universität Mainz, Germany; Institute of Physics, CAS, Praha):
Introduction to Altermagnetism and Anti-Altermagnetism: From Spin Symmetries to Experiments

Symmetry plays a crucial role in physics, shaping how particles and forces interact. The concept of spontaneous symmetry breaking, where a system that initially follows certain symmetry rules naturally shifts into a state that no longer does, has proven useful in many areas of physics, from particle physics to superconductors.

In this talk, we introduce our recent classification of magnetic symmetry breakings using spin symmetries, which involve pairs of operations in spin and lattice space. This approach led us to discover two new types of magnetic quantum phases: altermagnets and anti-altermagnets. These expand on the well-known categories of ferromagnets (which have a net magnetization) and antiferromagnets (where atomic magnetic moments cancel each other out) [1-3]. What makes altermagnets and anti-altermagnets special is their unique spin arrangement. Unlike traditional magnets, they form compensated yet spin-polarized states, which break specific lattice symmetries while preserving certain combinations with spin rotations [1-3].

We will explain how these discoveries were motivated by our earlier prediction and observation of an unusual Hall effect[4], where an electric field generates a transverse Hall current in a compensated magnet. We will also discuss recent experiments confirming altermagnetism in materials like MnTe and CrSb, using photoemission techniques guided by our first-principles calculations [5]. Finally, we will explore how altermagnets could be used in spintronics, magnonics, topological materials, and multiferroics, paving the way for faster, smaller, and more energy-efficient nanoelectronics [1,6].

References:
[1] https://www.economist.com/science-and-technology/2024/01/24/scientists-have-found-a-new-kindof-magnetic-material, https://www.science.org/content/article/researchers-discover-new-kindmagnetism
[2] PRX 12, 031042 (2022).
[3] arXiv:2309.01607v3 (2024).
[4] Science Adv. 6, 23 (2020), PNAS 118 42 (2021), Nature Commun. 15, 4961 (2024).
[5] Nature 626, 517 (2024), Nature Commun. 15, 2116 (2024), Nature 636, 348 (2024).
[6] PRX 12, 011028 (2022), PRL 131, 256703 (2023), arXiv:2309.02355 (2023), arXiv:2411.19928 (2024).

This lecture was supported by the project QM4ST (Quantum materials for applications in sustainable technology), reg. no. CZ.02.01.01/00/22_008/0004572, cofunded by the ERDF from the Programme Johannes Amos Commenius, call Excellent Research.