Topological valley currents via ballistic edge modes in graphene superlattices near the primary Dirac point

Abstract

Graphene on hexagonal boron nitride (hBN) can exhibit a topological phase via mutual crystallographic alignment. Recent measurements of nonlocal resistance ($R_{nl}$) near the secondary Dirac point (SDP) in ballistic graphene/hBN superlattices have been interpreted as arising due to the quantum valley Hall state. We report hBN/graphene/hBN superlattices in which $R_{nl}$ at SDP is negligible, but below 60 K approaches the value of $h/2e^2$ in zero magnetic field at the primary Dirac point with a characteristic decay length of 2 $\mu$m. Furthermore, nonlocal transport transmission probabilities based on the Landauer-Büttiker formalism show evidence for spin-degenerate ballistic valley-helical edge modes, which are key for the development of valleytronics

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Cited by in corpus (9)

• Non-identical moiré twins in bilayer graphene
• Universal subdiffusive behavior at band edges from transfer matrix exceptional points
• Valley current generation using biased bilayer graphene dots
• Kagomé network of chiral miniband-edge states in double-aligned graphene-hexagonal boron nitride structures
• Environment assisted superballistic scaling of conductance
• Generation and control of non-local chiral currents in graphene superlattices by orbital Hall effect
• Tunable atomically enhanced moiré Berry curvatures in twisted triple bilayer graphene
• Berry curvature induced valley Hall effect in non-encapsulated hBN/Bilayer graphene heterostructure aligned with near-zero twist angle
• Composite fermions and parton wavefunctions in twisted graphene on hexagonal boron nitride