Composite Weyl loops in magnetic topological semimetals

The discovery of magnetic Weyl semimetals has propelled the investigation of electronic topology in correlated systems. Many topological correlated and magnetic materials exhibit complex electronic structures at the Fermi level, which are essential in driving anomalous response and exhibit rich interplay with correlated order parameters. However, systematic characterization of the complete topological properties near the Fermi level in complex semimetals remains limited. Here I disentangle the rich topological structure of Co₂MnGa through bulk-sensitive soft X-ray angle-resolved photoemission spectroscopy combined with ab initio calculations [1,2]. I experimentally examine the system on multiple cleaving planes and identify three distinct families of Weyl loops, demonstrating a rich composite Weyl loop structure at the Fermi level. I discuss the implications of our findings for exotic transport in Co₂MnGa and related magnetic Weyl systems [3,4].