Abstract
The exceptional tunability of van der Waals heterostructures provides a powerful platform for exploring electron interactions, disorder, and emergent quantum phenomena in two-dimensional systems. In this talk, I will discuss our recent experiments demonstrating how electrostatic control and heterostructure design can be used to engineer the electronic properties of graphene-based
devices.
First, I will show how ultraclean graphene can be used as a sensitive charge sensor to probe defect states in high-quality hBN. We find that an applied displacement field induces charge transfer between graphene and hBN, resulting in additional electron doping and increased carrier-density inhomogeneity. These effects are consistent with displacement-field-induced ionization of defect states within the hBN bandgap, showing that even high-quality hBN can actively modify the electronic response of van der Waals heterostructures.
Next, I will discuss an approach to suppress disorder in graphene arising from those charged defects in hBN crystals. To this end, we use graphene devices encapsulated by additional graphene layers, which provide tunable Coulomb screening. By suppressing long-range disorder and charge inhomogeneity, this approach enables quantum Hall quantization at magnetic fields of only a few millitesla.
Finally, I will present a new class of moiré systems in which twisted graphene layers are separated by an atomically thin spacer. Despite the absence of direct atomic contact, these structures develop well-defined moiré minibands, while the strength of interlayer hybridization can be continuously tuned by an applied displacement field. This architecture provides a unique platform for disentangling the roles of moiré periodicity and interlayer coupling.
Together, these results illustrate how defects, screening, and moiré hybridization can be probed and controlled independently, establishing new routes for designing high-quality and highly tunable quantum electronic systems.
Anyone interested is welcome to attend.