Aharonov–Bohm interference in topological insulator nanoribbons

Abstract

Topological insulators represent unusual phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional topological insulator phase was predicted in HgTe quantum wells¹ and confirmed by transport measurements². Recently, Bi₂Se₃ and related materials have been proposed as three-dimensional topological insulators with a single Dirac cone on the surface^3,4, protected by time-reversal symmetry^5,6,7. The topological surface states have been observed by angle-resolved photoemission spectroscopy experiments^4,8. However, few transport measurements⁹ in this context have been reported, presumably owing to the predominance of bulk carriers from crystal defects or thermal excitations¹⁰. Here we show unambiguous transport evidence of topological surface states through periodic quantum interference effects in layered single-crystalline Bi₂Se₃ nanoribbons, which have larger surface-to-volume ratios than bulk materials and can therefore manifest surface effects. Pronounced Aharonov–Bohm oscillations¹¹ in the magnetoresistance clearly demonstrate the coherent propagation of two-dimensional electrons around the perimeter of the nanoribbon surface, as expected from the topological nature of the surface states. The dominance of the primary h/e oscillation, where h is Planck’s constant and e is the electron charge, and its temperature dependence demonstrate the robustness of these states. Our results suggest that topological insulator nanoribbons afford promising materials for future spintronic devices at room temperature ^{(2009)." href="/articles/nmat2609#ref12" aria-label="Reference 12" data-track="click" data-track-action="reference anchor" data-track-label="link">12}.