Cryogenic shock exfoliation for ultrahigh mobility rhombohedral graphite nanoelectronics

Rhombohedral multilayer graphene offers a tunable platform for correlated electron physics, featuring field-effect control of magnetic, superconducting and topological phases. The promise of these materials has been held back by the limited abundance of rhombohedral stacking in natural graphite, which constrains both sample yield and useful area. Here we introduce cryogenic shock exfoliation to produce large-area rhombohedral graphene flakes. This exfoliation, combined with a low-pressure van der Waals assembly technique that preserves stacking order, enables highly uniform devices exceeding 1,300 μm² in area with fabrication yields of ∼90%. Using scanning nanoSQUID-on-tip imaging, we demonstrate uniform spin magnetism over the full central 10 × 10 μm² area of our devices. Transverse magnetic focusing reveals a disorder mean free path exceeding 200 μm at low temperatures. Within the flat surface bands of rhombohedral multilayer graphene, we observe a size-driven crossover from Poiseuille to porous electron flow in the intermediate-temperature regime of strong electron-electron hydrodynamics, providing a further signature of ultrahigh device quality. Our approach overcomes a key materials bottleneck in the fabrication of mesoscopic rhombohedral graphene devices, paving the way for incorporating strongly correlated phases into two-dimensional nanoelectronics.