Robust wavefront dislocations of Friedel oscillations in gapped graphene

TL;DR

This paper investigates Friedel oscillations in gapped graphene, revealing that wavefront dislocations persist despite broken pseudospin-momentum locking, linking topological invariants to observable wave phenomena.

Contribution

It demonstrates that wavefront dislocations in Friedel oscillations occur in gapped graphene, connecting topological pseudospin winding numbers to observable wavefront features even when pseudospin-momentum locking is broken.

Findings

Wavefront dislocations are present in gapped graphene Friedel oscillations.

The number of dislocations relates to the pseudospin winding number.

Potential for observing these effects in other 2D materials like transition metal dichalcogenides.

Abstract

Friedel oscillation is a well-known wave phenomenon, which represents the oscillatory response of electron waves to imperfection. By utilizing the pseudospin-momentum locking in gapless graphene, two recent experiments demonstrate the measurement of the topological Berry phase by corresponding to the unique number of wavefront dislocations in Friedel oscillations. Here, we study the Friedel oscillations in gapped graphene, in which the pseudospin-momentum locking is broken. Unusually, the wavefront dislocations do occur as that in gapless graphene, which expects the immediate verification in the current experimental condition. The number of wavefront dislocations is ascribed to the invariant pseudospin winding number in gaped and gapless graphene. This study deepens the understanding of correspondence between topological quantity and wavefront dislocations in Friedel oscillations, and implies the possibility to observe the wavefront dislocations of Friedel oscillations in intrinsic gapped two-dimensional materials, e.g., transition metal dichalcogenides.