Public Research Seminar by Advanced Materials Thrust, Function Hub, HKUST(GZ) - Novel properties due to crystal symmetry in topological superconductor and altermagnet

In this talk, I will present works about the novel properties due to crystal symmetry in spin-splitting antiferromagnets (AFMs) [Nat. Commun. 12, 2846 (2021)] (also named altermagnet) and in topological superconductor [Nature 633, 71 (2024)].

In spin-splitting AFMs, we propose the crystal-symmetry-paired spin-valley/momentum locking (CSVL), which is enabled by a crystal symmetry and intrinsically exists in AFMs (e.g., V2Se2O, V2Te2O, MnTe and RuO2) [Nat. Commun. 12, 2846 (2021)]. Moreover, CSVL enables feasible controls of both spin and valley in AFMs by simply manipulating the corresponding crystal symmetry. Typically, one can use a strain field to induce a large net valley polarization/magnetization and use an electric field to generate a large noncollinear spin current even without spin-orbit coupling. All these predictions have been confirmed in various experiments. We have extended CSVL to all magnetic systems and predicted another 140 experimentally verified AFMs that can realize CSVL [arXiv:2407.02319 (2024)]. These properties have helped us realize the electric readout and 180o deterministic switching of the Néel order in our recent experimental work [Sci. Adv. 10, eadn0479 (2024)]. Due to these unique properties, these materials were proposed to belong to a third type of collinear magnets and were named as altermagnet [Phys. Rev. X 12, 040501 (2022)].

In topological superconductors, magnetic mirror symmetry can project multiple Majorana zero modes (MZMs) in a single vortex, which allows feasible controls of hybridization of MZMs simply using an external field. This has been realized in our recent collaborative experimental works with Prof Jin-Feng Jia’s group [Nature 633, 71 (2024)].