Electronic transport studies of ultrathin bismuth grown inside van der Waals materials

Bismuth exhibits a wide variety of topological electronic phenomena depending on its dimensionality. 3D bismuth sits at a transition between different topological phases, while 2D bismuth is predicted to be a room temperature 2D topological insulator. Studies of 2D and ultrathin bismuth are limited by irregular surfaces and substrate interactions in MBE. We present a new synthesis approach where ultrathin bismuth crystals are molded from the melt phase inside vdW materials under compression. This method consistently produces 5-30 nm thick bismuth crystals with atomically flat surfaces and single crystal domains up to 10 um in size. Cryogenic transport studies of the vdW-molded ultrathin bismuth exhibit metallic temperature dependence, as a result of the SOC-induced surface states conducting in parallel with the gapped bulk bands due to confinement effect. The residual resistance ratio is 10x larger than epitaxial-grown bismuth of similar thicknesses. Furthermore, magnetotransport shows gate-tunable quantum oscillations originating from the multi-pocket surface states. In my talk, I will present up-to-date transport data analysis including thickness-dependence and field effects on various ultrathin bismuth devices. We anticipate that the vdW-molding technique will be generalized for other soft materials and our research can cast new light on ultrathin bismuth studies.