Intervalley scattering in monolayer graphene on hexagonal-boron nitride

Hexagonal boron nitride (hBN) is an ideal substrate for graphene-based devices because it minimally perturbs graphene’s intrinsic electronic properties. Nevertheless, it electronically imprints a periodic “moiré potential” onto graphene—a spatially varying energy modulation determined by the moiré superlattice. Since this potential has a much longer wavelength than the atomic lattice of graphene, it is generally not expected to couple the two inequivalent valleys, K and K′. Therefore, such a moiré potential is not expected to induce intervalley scattering (IVS), which typically arises only from atomically sharp defects and leads to constructive interference between time-reversed electron trajectories at zero magnetic field, producing weak localization. In this work, we use scanning tunneling microscopy and spectroscopy (STM/S) to reveal that even in long-wavelength graphene/hBN moiré superlattices, substantial IVS can occur. We find that both the amplitude and phase of the real-space IVS pattern are modulated by the moiré lattice. Our analysis further shows that IVS is strongest at the carbon–boron (C–B) site, where the moiré potential reaches its maximum. These findings call for a re-examination of how hBN substrates influence the electronic behavior of graphene devices.