Wavefront dislocations in graphene systems revealed by transport measurement

TL;DR

This paper introduces a novel transport measurement approach to detect wavefront dislocations in graphene, revealing phase singularities in transmission coefficients linked to topological properties, with robustness in bilayer systems.

Contribution

It proposes a new transport-based method to observe wavefront dislocations in graphene, connecting phase singularities to topological characteristics through analytical and numerical analysis.

Findings

Phase singularities appear in transmission coefficients due to intervalley interference.

Wavefront dislocations are robust in bilayer graphene despite multiple sublattice coupling.

The method enables exploration of valley-related topological properties in materials.

Abstract

The wavefront dislocation is an important and ubiquitous phenomenon in wave fields. It is closely related to the phase singularity in a wave function. Some recent studies have verified that the wavefront dislocations in the local density of states (LDOS) map can well manifest the intrinsic topological characteristics in graphene and some topological systems. Different from these previous schemes, we raise a transport method to measure such wavefront dislocations in monolayer and Bernal-stacked bilayer graphene. Combining analytical analysis and numerical calculation, we find phase singularities naturally appear in the transmission coefficients between different sublattices, due to the intervalley interference on the electron propagating paths. These phase singularities could contribute wavefront dislocations in the conductance map. Additionally, in bilayer graphene, the wavefront dislocations are found to remain robust even though the tip is coupled to multiple sublattices. Biased bilayer graphene is also explored. Our scheme provides a new transport routine to explore valley-related topological properties of materials.