Characteristic nanoscale deformation on a large-area coherent graphite moiré pattern

Highly oriented pyrolytic graphite may be the only known monatomic crystal with the ability to host naturally formed moiré patterns on its cleaved surfaces, which are coherent over micrometer scales and with discrete sets of twist angles of fixed periodicity. Such an aspect is in marked contrast to twisted bilayer graphene and other multilayered systems, where the long-range coherence of the moiré is not easily maintained due to twist angle disorder. We investigate the electronic and mechanical response of coherent graphite moiré patterns through inducing external strain from scanning tunneling microscopy tip-induced deformation. Consequently, unique anisotropic mechanical characteristics are revealed. For example, a lateral widening of one-dimensional domain walls (DWs) bridging Bernal (ABA) and rhombohedral (ABC) stacking domains (A, B, and C refer to the atomic layer positioning), was indicated. Further, in situ tunneling spectroscopy as a function of the deformation indicated a tendency towards increased electrical conductance, which may be associated with a higher density of electronic states, and the consequent flattening of the electronic energy band dispersion. Such features were probed across the DWs, with implications for strain-induced electronic modulation of the moiré characteristics.