Weyl nodal surfaces

Understand

We consider three-dimensional fermionic band theories that exhibit Weyl nodal surfaces defined as two-band degeneracies that form closed surfaces in the Brillouin zone.

• We demonstrate that topology ensures robustness of these objects under small perturbations of a Hamiltonian.
• This topological robustness is illustrated in several four-band models that exhibit nodal surfaces protected by unitary or anti-unitary symmetries.
• Surface states and Nielsen-Ninomiya doubling of nodal surfaces are also investigated.