Coupling of Quantum Valley Hall Edge States between CVD Bilayer Graphene Layer Stacking Domain Walls

Quantum valley Hall (QVH) edge states are topologically protected in the absence of valley mixing. In addition to the long mean free path from the protection, their inter-wall coupling enables novel properties such as current partition and valley filtering, when arranged in specific configurations. Stacking order alternation across a boundary in Bernal stacking bilayer graphene creates a layer stacking wall (LSW) where QVH edge states are bound. However, the uncontrollable strain of LSWs upon their creation places a big challenge to study their inter-wall coupling. Here we use different strain mechanisms during chemical vapor deposition (CVD) and subsequent transfer processess to create well-separated LSWs and close packing LSW bundles, and report inter-wall coupling of QVH edge states in the latter case through electron transport measurements.