Bulk-Free Topological Insulator Bi2Se3 nanoribbons with Magnetotransport Signatures of Dirac Surface States

TL;DR

This study demonstrates that Bi2Se3 nanoribbons with reduced thickness exhibit suppressed bulk conduction, allowing the clear observation of high-mobility topological surface states through magnetotransport measurements.

Contribution

The paper reports the growth of Bi2Se3 nanoribbons with inherently low bulk carriers and shows that size confinement below 30nm fully suppresses bulk transport, revealing topological surface states.

Findings

Bulk transport is suppressed below 30nm thickness.

Magnetotransport measurements confirm the presence of Dirac surface states.

Size confinement enhances the visibility of topological surface states.

Abstract

Many applications for topological insulators (TIs) as well as new phenomena require devices with reduced dimensions. While much progress has been made to realize thin films of TIs with low bulk carrier density, nanostructures have not yet been reported with similar properties, despite the fact that size confinement should help reduce contributions from bulk carriers. Here we demonstrate that Bi2Se3 nanoribbons, grown by a simple catalyst-free physical-vapour deposition, have inherently low bulk carrier densities, and can be further made bulk-free by size confinement, thus revealing the high mobility topological surface states. Magneto transport and Hall conductance measurements, in single nanoribbons, show that at thicknesses below 30nm the bulk transport is completely suppressed which is supported by self-consistent band-bending calculations. The results highlight the importance of material growth and geometrical confinement to properly exploit the unique properties of the topological surface states.