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

TL;DR

This paper introduces a novel vdW-molding synthesis method to produce ultrathin bismuth crystals, revealing exceptional electronic transport and quantum oscillations from surface states, advancing studies of 2D topological materials.

Contribution

The study demonstrates a new growth technique for ultrathin bismuth crystals within vdW molds, enabling detailed transport studies of surface states and quantum oscillations.

Findings

Observation of Shubnikov-de Haas oscillations from bismuth surface states

Detection of Landau level splitting and multi-carrier quantum oscillations

Successful synthesis of uniform, ultraflat bismuth crystals less than 10 nm thick

Abstract

Confining materials to two-dimensional forms changes the behavior of electrons and enables new devices. However, most materials are challenging to produce as uniform thin crystals. Here, 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 (hBN), we grow ultraflat bismuth crystals less than 10 nanometers thick. Due to quantum confinement, the bismuth bulk states are gapped, isolating intrinsic Rashba surface states for transport studies. 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, which have eluded previous studies. 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 ultrathin crystals and directly integrate them into a vdW heterostructure.