Real-Space Imaging of Band Topology via Wavefunction Zeros

We prove that the wavefunction of a crystal at a high-symmetry momentum, $\Psi_{\boldsymbol{k}_*}(\boldsymbol{r})$, has symmetry-enforced zeros at certain positions in the unit cell, using a new invariant fixed uniquely by the symmorphic symmetry representation of the wavefunction. This allows one to infer the topology of an electronic band by probing zeros of the charge density, and in turn to connect scanning tunnelling microscopy to the group representation theory of bandstructure. We apply the theorem to 1H transition metal dichalcogenides, where it detects the obstructed atomic limit of WSe$_2$, the Haldane model, where it detects the Chern number modulo three, and the Bernevig-Hughes-Zhang model, where it detects the $\mathbb{Z}_2$ index. In addition, the zeros have important consequences for interaction effects: in kagome metals, they fix the sublattice structure of Van Hove wavefunctions, and in twisted bilayer graphene, they explain the qualitative interaction-induced reshaping of the flat bands.