Topological Winding Numbers from Wavefront Dislocations in Local Electronic Density

Abstract

Topological materials are characterized by integer invariants that underpin robust quantized electronic properties, as exemplified by the Chern number in the integer quantum Hall effect. Yet, for most candidate systems, the observable linked to the topological invariant remains unknown, precluding direct verification of their topological nature. We present a general method to identify topological materials by connecting the local electronic density~$\delta\rho(\bm{r})$ to Atiyah-Singer index theorems. This method offers a concrete protocol for determining the winding number, the topological invariant associated with chiral-symmetric Hamiltonians. It also identifies a contour-independent wavefront dislocation pattern in $\delta\rho(\bm{r})$ arising from interference induced by topological defects and demonstrates its application to numerical simulations and to existing STM data. The method clearly distinguishes topological states from non-topological ones through a unified, standardized filtering step, offering a definitive approach for identifying and characterizing quantum topological states and opening the door to their use as robust, entangleable building blocks in quantum technologies.