Lei Shiming, Allen Kevin, Huang Jianwei, Moya Jaime M, Wu Tsz Chun, Casas Brian, Zhang Yichen, Oh Ji Seop, Hashimoto Makoto, Lu Donghui, Denlinger Jonathan, Jozwiak Chris, Bostwick Aaron, Rotenberg Eli, Balicas Luis, Birgeneau Robert, Foster Matthew S, Yi Ming, Sun Yan, Morosan Emilia
Department of Physics and Astronomy, Rice University, Houston, TX, 77005, USA.
Rice Center for Quantum Materials, Rice University, Houston, TX, 77005, USA.
Nat Commun. 2023 Sep 19;14(1):5812. doi: 10.1038/s41467-023-40767-z.
Magnetic topological semimetals allow for an effective control of the topological electronic states by tuning the spin configuration. Among them, Weyl nodal line semimetals are thought to have the greatest tunability, yet they are the least studied experimentally due to the scarcity of material candidates. Here, using a combination of angle-resolved photoemission spectroscopy and quantum oscillation measurements, together with density functional theory calculations, we identify the square-net compound EuGa as a magnetic Weyl nodal ring semimetal, in which the line nodes form closed rings near the Fermi level. The Weyl nodal ring states show distinct Landau quantization with clear spin splitting upon application of a magnetic field. At 2 K in a field of 14 T, the transverse magnetoresistance of EuGa exceeds 200,000%, which is more than two orders of magnitude larger than that of other known magnetic topological semimetals. Our theoretical model suggests that the non-saturating magnetoresistance up to 40 T arises as a consequence of the nodal ring state.
磁性拓扑半金属能够通过调节自旋构型来有效控制拓扑电子态。其中，外尔节线半金属被认为具有最大的可调性，但由于候选材料稀缺，它们在实验上的研究最少。在此，我们结合角分辨光电子能谱和量子振荡测量，以及密度泛函理论计算，确定正方网化合物EuGa为一种磁性外尔节环半金属，其中节线在费米能级附近形成闭环。外尔节环态在施加磁场时表现出明显的朗道量子化，具有清晰的自旋分裂。在14 T磁场中于2 K时，EuGa的横向磁电阻超过200000%，比其他已知磁性拓扑半金属大两个多数量级。我们的理论模型表明，高达40 T的非饱和磁电阻是节环态的结果。
