Ultralong Single-Crystal α-Bi₄Br₄Nanobelts with a High Current-Carrying Capacity by Mechanical Exfoliation

Mechanical exfoliation is of great potential in the preparation of two-dimensional (2D) materials such as graphene and transition metal dichalcogenides, offering new opportunities for exploring extraordinary electronic, optic, optoelectronic, and spintronic properties of low-dimensional materials. However, the extension of the exfoliation method from 2D van der Waals materials to one-dimensional (1D) materials has rarely been reported. Here, we show that the 1D α-Bi₄Br₄nanobelts can be prepared by direct exfoliation of single crystals, as characterized by optical microscopy, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and Raman spectroscopy. Electrical transportation measurements indicate that the nanobelts maintain the intrinsic semiconducting properties of the bulk. Remarkably, the nanobelts can bear a very high current density up to 10⁶Acm^-2at room temperature, much higher than that of most semiconducting nanowires reported so far and comparable with that of Cu or Ag. This behavior is attributed to their 1D topological edge states. Our work demonstrates that mechanical exfoliation is an effective way to prepare high-quality α-Bi₄Br₄nanobelts for the investigation of fundamental topological physics and the development of high-performance electronic devices.