Quantum mechanics

Fermi level

Spin (aerodynamics)

Surface states

Electronic band structure

Dirac (video compression format)

Neutrino

Mirror symmetry

Band gap

Surface (topology)

Thermodynamics

Physics

Fermi surface

Mathematics

Topological insulator

Semimetal

Superconductivity

Point reflection

Condensed matter physics

Geometry

Combinatorics

Symmetry (geometry)

Electron

Topology (electrical circuits)

Fermi Gamma-ray Space Telescope

Density of states

Nature Communications

Band inversions are key to stabilising a variety of novel electronic states in solids, from topological surface states to the formation of symmetry-protected three-dimensional Dirac and Weyl points and nodal-line semimetals. Here, we create a band inversion not of bulk states, but rather between manifolds of surface states. We realise this by aliovalent substitution of Nb for Zr and Sb for S in the ZrSiS family of nonsymmorphic semimetals. Using angle-resolved photoemission and density-functional theory, we show how two pairs of surface states, known from ZrSiS, are driven to intersect each other near the Fermi level in NbGeSb, and to develop pronounced spin splittings. We demonstrate how mirror symmetry leads to protected crossing points in the resulting spin-orbital entangled surface band structure, thereby stabilising surface state analogues of three-dimensional Weyl points. More generally, our observations suggest new opportunities for engineering topologically and symmetry-protected states via band inversions of surface states.

Weyl-like points from band inversions of spin-polarised surface states in NbGeSb