Abstract: Symmetry is a key to unlocking exotic phenomena in condensed matter physics. Particularly in magnetic systems, symmetry analysis enables deep understanding of magnetic ordering and electron transports. In this talk, I will give two examples showing how symmetry analysis can help understand and design magnetic materials of interest.
First, I will show the prediction of a giant perpendicular magnetic anisotropy (PMA) in an iron monolayer on top of a III-V nitride substrate. The magnitude of the PMA is up to 50 meV, in contrast to 1 meV in conventional iron-based thin films. A paradigm shift from a second-order to a first-order perturbation of the spin-orbit coupling is the origin of such a large PMA.
In the second topic, the electron transport in MnTe thin films will be discussed. A zero-field planar Hall effect was experimentally observed in antiferromagnetic MnTe. I will show how time reversal and its combined symmetries are broken in this material and how an effective Hamiltonian constructed by a theory of invariants successfully describes all transport signatures.