The ferroelectricity emerging in non-polar graphene/hexagonal boron nitride (hBN) heterostructures has drawn considerable attention because of its fascinating properties and promising high-frequency electrical polarization switching. Yet, the underlying mechanism is still under debate. Here in twisted double bilayer graphene (TDBLG) aligned with its neighboring hBN, we observed two types of hysteresis - delayed hysteresis in top gate induced by the anomalous screening, and advanced hysteresis in back gate caused by the anomalous gate-tunable capacitance. To investigate the role played by moir\'e potential in the anomalous hysteresis, we studied a moir\'eless graphene heterostructure as control experiment. Unexpectedly, we observed exactly the same phenomena in this control device. Our findings suggest that the anomalous ferroelectricity in graphene/hBN heterostructures may originate from the dielectric material hBN, calling for further structural investigations on hBN. The observation of gate-tunable capacitance provides more insights in the mysterious ferroelectricity in graphene/hBN heterostructures, and should enable new design of memory devices such as memcapacitor based on tunable capacitance.
@article{arxiv.2405.03976,
title = {Anomalous Gate-tunable Capacitance in Van der Waals Heterostructures},
author = {Linshang Chen and Haoran Long and Heng Wu and Rui Mei and Zhengyu Su and Mengjie Feng and Jiang-Bin Wu and Kenji Watanabe and Takashi Taniguchi and Xuewei Cao and Zhongming Wei and Ping-Heng Tan and Yanmeng Shi},
journal= {arXiv preprint arXiv:2405.03976},
year = {2025}
}