Wavefront-Dislocation Evolution via Quadratic Band Touching Annihilation

TL;DR

This paper shows that wavefront dislocation evolution in graphene systems is driven by pseudospin texture changes, not topological charge, challenging previous interpretations of WDs as topological signatures.

Contribution

It demonstrates that wavefront dislocation evolution is governed by pseudospin winding changes, not topological charge, in bilayer and magneto-spin-orbit graphene systems.

Findings

WD evolution is governed by pseudospin winding changes.

WD measures wavefunction pseudospin texture, not topological charge.

Solid-state platforms for engineering and observing WD evolution.

Abstract

Wavefront dislocations (WDs) -- phase singularities observed in quasiparticle interference (QPI) experiments -- have been widely interpreted as the definitive real-space signatures of Berry phases in graphene-family systems. Here, we disentangle the roles of topological charge and pseudospin texture in WD experiments. By investigating various way of the annihilation of quadratic band touchings (QBTs) in bilayer graphene and magneto-spin-orbit graphene systems, we demonstrate that WD evolution is governed exclusively by changes in the underlying pseudospin winding, while remaining insensitive to the topological charge (i.e., vorticity) of the band touching itself. Our results imply that WD measures wavefunction pseudospin texture rather than a diagnostic of topological charge and provide solid-state platforms in which WD evolution can be engineered and observed.