Weyl nodal ring states and Landau quantization with very large magnetoresistance in square-net magnet EuGa4

Abstract

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 EuGa4 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 EuGa4 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.

Revealing the EuCd2As2 Semiconducting Band Gap via n-Type La-Doping

“…However, efficient utilization of these transport phenomena requires materials in which the Fermi level is coincident with the nodal band crossings and that there are no other topologically trivial bands at this energy. Almost all magnetic Weyl semimetal candidates have either trivial or nontrivial bands near the topologically nontrivial nodal crossing, as is the case for materials such as Co 2 MnGa, Mn 3 Sn, and EuGa 4 . − Alternatively, MnBi 2 Te 4 is a well-known magnetic Weyl semimetal candidate that has the ideal electronic structure but is hindered by the challenge in growing single crystals with experimentally relevant thickness in the cross-plane direction due to it being a peritectic phase with a <10 °C window of synthetic accessibility. , The identification and development of magnetic Weyl semimetals remain an important frontier in materials research.…”