title: Pseudospin Vortex Ring with a Nodal Line in Three Dimensions.
abstract: We present a model of a topological semimetal in three dimensions whose energy spectrum exhibits a nodal line acting as a vortex ring; this in turn is linked by a pseudospin structure akin to that of a smoke ring. Contrary to a Weyl point node spectrum, the vortex ring gives rise to Skyrmionic pseudospin patterns in cuts on both sides of the nodal ring plane; this pattern covers the full Brillouin zone, thus leading to a fully extended chiral Fermi arc and a new, "maximal," anomalous Hall effect in a 3D semimetal. Tuning a model parameter shrinks the vortex ring until it vanishes, giving way to a pair of Weyl nodes of opposite chirality. This establishes a connection between two distinct momentum-space topologies-that of a vortex ring (a circle of singularity) and a monopole-antimonopole pair (two point singularities). We present the model both as a low-energy continuum and a two-band tight-binding lattice model. Its simplicity permits an analytical computation of its Landau level spectrum.
authors.affiliation: Institute for Advanced Study, Tsinghua University, Beijing 100084, People's Republic of China.|Max-Planck-Institut für Physik komplexer Systeme, D-01187 Dresden, Germany.
authors.forename: Lih-King
authors.initials: LK
authors.lastname: Lim
authors.affiliation: Max-Planck-Institut für Physik komplexer Systeme, D-01187 Dresden, Germany.
authors.forename: Roderich
authors.initials: R
authors.lastname: Moessner