Exceptional Electronic Transport and Quantum Oscillations in Thin Bismuth Crystal Grown inside Van der Waals Materials

Most materials are challenging to produce as uniform and thin crystals with large grain size. Varying the thickness of a material alters its electronic behaviors and enables new devices. We have developed a new synthesis technique to grow crystals in a nanoscale mold defined by atomically-flat van der Waals (vdW) materials. We heat and compress bismuth in a vdW-mold made of hexagonal boron nitride (hBN), resulting in controlled thickness such as ultraflat 10 nm to 100 nm thick bismuth. The vdW-molded bismuth at different thickness all shows exceptional electronic transport, enabling the observation of Shubnikov–de Haas quantum oscillations originating from the (111) surface state Landau levels, which have eluded previous studies. Our vdW-mold growth technique establishes a platform for electronic studies and control of bismuth’s Rashba surface states and topological boundary modes. Other than molding bismuth, we have also successfully molded tin and gold. Beyond confining in thickness, we also molded bismuth into vdW-molds with predefined shapes. This vdW-molding approach provides a low-cost way to synthesize ultrathin crystals and directly integrate them into a vdW heterostructure.