Ultrathin crystals of bismuth grown inside atomically-smooth van der Waals materials

Confining materials to 2D forms changes the behavior of electrons and enables new devices. However, most materials are challenging to produce as uniform thin crystals. We present a new synthesis approach where crystals are grown in a nanoscale mold defined by atomically-flat van der Waals (vdW) materials. By heating and compressing bismuth in a vdW mold made of hexagonal boron nitride, we produce ultrathin crystals less than 10 nm thick with flat surfaces. Cryogenic measurements of the ultrathin bismuth demonstrate high quality electronic transport exhibiting quantum oscillations and a 10x larger residual resistance ratio compared to thin films grown by molecular beam epitaxy. In this talk, I will be focusing on our recent transport data on ultrathin bismuth and applying the vdW-molding technique to other soft metals.