Topological 'Luttinger' invariants protected by non-symmorphic symmetry in semimetals

Understand

Luttinger's theorem is a fundamental result in the theory of interacting Fermi systems: it states that the volume inside the Fermi surface is left invariant by interactions, if the number of particles is held fixed.

• Although this is traditionally justified using perturbation theory, it can be viewed as arising from a momentum balance argument that examines the response of the ground state to the insertion of a single flux quantum [M.
• Oshikawa, Phys.
• Rev.