Anomalous Hysteresis in Graphite/Boron Nitride Transistors

Field-effect devices constructed from van der Waals (vdW) materials with hexagonal boron nitride (hBN) as gate dielectrics usually exhibit negligible hysteresis, enabling exquisitely detailed studies of diverse gate-voltage-tuned phenomena. Recently, a dramatic hysteresis effect, sometimes called the "gate doesn't work" or "electron ratchet" effect, has been observed sporadically in otherwise typical vdW devices. Its lack of reproducibility has hindered clear identification of its origin, which has been postulated to rely on the combination of bilayer graphene with moiré patterns from rotationally aligned hBN. Here, we report observing this effect in devices with thicker graphite channels, associating it with a single graphite surface. Remarkably, the hysteresis persists at room temperature, without intentional hBN alignment, and even with a WSe₂ monolayer inserted between the graphite and hBN. Furthermore, it exhibits continuous relaxation over long time scales. These observations impose strong constraints on the origin of this puzzling phenomenon, which has exciting potential applications if it can be mastered.