Andreas Schnyder

Max Planck Institute for Solid State Research, Stuttgart

Symmetry-enforced topological nodal planes at the Fermi surface of a chiral magnet

Topological semimetals and metals may contain nodal points or lines, i.e., zero- or one-dimensional crossings in the energy bands. In the present work we discuss an extension to two-dimensional nodal features. These nodal planes are enforced in systems described by certain nonsymmorphic space groups. We give criteria to predict nodal planes and consider in the process paramagnetic as well as magnetic space groups. Based on an analysis of symmetry eigenvalues we identify space groups with a necessarily non-zero Chern number associated to the nodal planes. The arguments are supported by generic models and explicit calculations of the topological invariants and band structures. We have identified a number of materials with topological nodal planes, among them MnSi in its ferromagnetic phase.

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