Shaping crystals into confined geometries with low disorder is an outstanding challenge. We have developed an approach to growing thin crystals of predefined geometry between atomically flat van der Waals (vdW) materials. This is achieved by injecting molten material into silica molds lined by vdW materials. Following this approach, we can directly produce ultraflat single crystals of bismuth, tin, indium, lead, and tellurium in various geometries, including hall bars and nanowires, that are fully encapsulated within a vdW material. The combination of geometric control, confinement, low disorder, and oxidation protection unlocks a new regime for single-crystal quantum devices. This approach provides a path to unlocking the transport physics of two-dimensional bismuth, a predicted room-temperature topological insulator. I will also discuss how this approach can be extended to realize unique heterostructures of vdW and non-vdW materials, such as superconducting junctions, or to trap molecules and atoms for quantum sensing.
Time permitting, I will also discuss how driven electrons in graphene can be used to generate and detect terahertz sound waves via an acoustic analog of Cerenkov radiation.
Exceptional electronic transport and quantum oscillations in thin bismuth crystals grown inside van der Waals materials
Chen et. al. Nature Materials 2024
Van der Waals injection-molded crystals
Tran et. al. npj 2D Materials and Applications 2025
Electrically driven amplification of terahertz acoustic waves in graphene
Barajas-Aguilar et. al. Nature Communications 2024