Abstract
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 antiunitary symmetries. Surface states and Nielsen-Ninomiya doubling of nodal surfaces are also investigated.
- Received 2 November 2017
DOI:https://doi.org/10.1103/PhysRevB.97.075120
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