Interlayer electron flow and field shielding in twisted trilayer graphene quantum dots

While multilayer graphene (MLG) possesses excellent intralayer electron mobility, its interlayer electrical conductance exhibits great diversity that results in exotic phenomena and various applications in electronic devices. Driven by a vertical electric field, electron flow occurs across the layers, and its current is tunable by controlling the interlayer stacking and distance, disc size and field strength. The electron rearrangement induced by the external field is appropriately described by the polarizability that measures the electronic response against the applied field. Based on the field-induced electron density variations computed with a first-principles approach, a polarizability decomposition scheme is developed in this work to isolate the inter- and intra-layer contributions from the total polarizability of twisted trilayer graphene (TTG) quantum dots. The inter- and intra-layer counterparts reflect the charge transfer (CT) and field shielding effects among the layers, respectively. Shielded by the top and bottom layers, the middle layer is particularly effective in bridging, switching and promoting the interlayer electron flow. Large CT and shielding effects occur not only in the strongly coupled Bernal stacking, but also in the structures misorientating from the full-AAA stacking by a small twist angle. Moreover, both effects vary with the twist angle and disc size, indicating a controllable conductive/dielectric conversion in the vertical direction. In light of inter- and intralayer polarizability, our study addresses the precise modulation of interlayer conductance for TTG quantum dots, which is required in the microstructure design and performance manipulation of MLG-based electronic devices.