Mixed-dimensional moir\'e systems of graphitic thin films with a twisted interface

Moir\'e patterns formed by stacking atomically-thin van der Waals crystals with a relative twist angle can give rise to dramatic new physical properties. The study of moir\'e materials has so far been limited to structures comprising no more than a few vdW sheets, since a moir\'e pattern localized to a single two-dimensional interface is generally assumed to be incapable of appreciably modifying the properties of a bulk three-dimensional crystal. Layered semimetals such as graphite offer a unique platform to challenge this paradigm, owing to distinctive properties arising from their nearly-compensated electron and hole bulk doping. Here, we perform transport measurements of dual-gated devices constructed by slightly rotating a monolayer graphene sheet atop a thin bulk graphite crystal. We find that the moir\'e potential transforms the electronic properties of the entire bulk graphitic thin film. At zero and small magnetic fields, transport is mediated by a combination of gate-tunable moir\'e and graphite surface states, as well as coexisting semimetallic bulk states that do not respond to gating. At high field, the moir\'e potential hybridizes with the graphitic bulk states owing to the unique properties of the two lowest Landau bands of graphite. These Landau bands facilitate the formation of a single quasi-two-dimensional hybrid structure in which the moir\'e and bulk graphite states are inextricably mixed. Our results establish twisted graphene-graphite as the first in a new class of mixed-dimensional moir\'e materials.