Exceptional electronic transport and quantum oscillations in thin bismuth crystals grown inside van der Waals materials

The boundaries of bismuth have attracted increasing recent attention due to the spin-momentum locking in 2D Rashba surface states and 1D helical edge mode. However, the transport characterization and the approaches to application were limited due to the restrictions of conventional grown bismuth thin films. We have developed a new synthesis approach where ultrathin bismuth crystals are molded from the melt phase inside vdW materials under compression. This method consistently produces bismuth thin crystals with micron-scale atomically flat surfaces and single crystal domains up to 10 um in size. We are also able to implement injection molding in the growth process, which opens new avenues for the direct growth of nanostructured crystals. The vdW-molded bismuth shows exceptional electronic transport, enabling the observation of Shubnikov–de Haas quantum oscillations originating from the (111) surface state Landau levels. By measuring the gate-dependent magnetoresistance, we observe multi-carrier quantum oscillations and Landau level splitting, with features originating from both the top and bottom surfaces. Our vdW-mold growth technique establishes a platform for electronic studies and control of bismuth’s Rashba surface states and topological boundary modes. Beyond bismuth, the vdW-molding approach provides a low-cost way to synthesize ultraflat crystals and directly integrate them into a vdW heterostructure.