Twist-Angle-Controlled Anomalous Gating in Bilayer Graphene/BN Heterostructures

Anomalous gating effects—such as ineffective electrostatic control and strong hysteresis in resistance-have been observed in graphene-based systems encapsulated in boron nitride (BN) and linked to a possible ferroelectric state. However, their origin, stability, and reproducibility remain under debate. Here we show, using dual-gated, dynamically rotatable van der Waals heterostructures based on bilayer graphene encapsulated in BN, that the angular alignment between the two BN layers—not the presence of a moir\'e superlattice with graphene—is the key parameter governing these effects. The relevant alignment between the two BN layers, to observe the anomalous gating effect at room temperature, lies between $\approx$ 15$^{\circ}$ and 45$^{\circ}$, with no evidence of the expected 60$^{\circ}$ periodicity. Both gate ineffectiveness and hysteresis are highly sensitive to small angular changes, which we classify into three distinct regimes. Our results clarify the conditions necessary to reproduce these phenomena and pave the way for theoretical investigation of their microscopic origins.