Toward structural control, uniformity, and reproducibility

In recent years there has been an increased interest in van-der Waals moire systems, systems obtained by rotating and layering van-der Waals materials with identical or nearly-identical crystal lattices. Since 2018, where the moire systems of interest consisted of primarily hexagonal boron nitride (hBN) layers + two graphene (Gr) layers, researchers have made progress in both in both complicating the van der Waals moire space by going beyond two Gr layers and diversifying it to include the transition-metal dichalcogenides (TMDs.) Within the current van-der Waals moire space many phenomena have been observed, including superconductivity (2+Gr, hetero-/homo-TMD bilayers), ferroelectricity (hBN/hBN, Gr/Gr), ferromagnetism (discovered by our group with aligned hBN/Gr/Gr), and the quantum anomalous Hall effect (aligned hBN/Gr/Gr.)

While many phenomena have been observed in the various moire systems, our understanding of why they occur is still in its infancy. Researchers around the world have measured different electronic properties for devices of nominally the same structure. This is because moire systems are not an equilibrium configuration and are highly sensitive to the parameters of the environment when they are assembled, which is not the same across the world. To understand the moire systems at a fundamental level the variations between devices must be eliminated. Equipped with a mechanical press for consistent van-der Waals exfoliation, an automated microscope for substrate imaging and flake identification, and a vacuum stacker with automated stacking routines and high environment control, the Goldhaber-Gordon group will explore the parameter space of moire assembly to enable reproducible study of moire systems.

We have collaborations with Professor Andy Mannix of Materials Science who pioneered techniques for vacuum stacking of two-dimensional materials as a postdoc.