Engineering Electronic Structure of a Two-Dimensional Topological Insulator Bi(111) Bilayer on Sb Nanofilms by Quantum Confinement Effect

Abstract

We report on fabrication of a two-dimensional topological insulator-Bi(111) bilayer on Sb nanofilms via a sequential molecular beam epitaxy (MBE) growth technique. Our angle-resolved photoemission measurements demonstrate the evolution of the electronic band structure of the heterostructure as a function of the film thickness and reveal the existence of a two-dimensional spinful massless electron gas within the top Bi bilayer. Interestingly, Our first-principles calculation extrapolating the observed band structure shows that, by tuning down the thickness of the supporting Sb films into the quantum dimension regime, a pair of isolated topological edge states emerges in a partial energy gap at 0.32 eV above the Fermi level as a consequence of quantum confinement effect. Our results and methodology of fabricating nanoscale heterostructures establish the Bi bilayer/Sb heterostructure as a platform of great potential for both ultralow-energy-cost electronics and surface-based spintronics.

Centimeter‐scale growth of two‐dimensional layered high‐mobility bismuth films by pulsed laser deposition

“…Meanwhile, the epitaxially grown Bi thin films can be directly dry transferred to a secondary substrate, which could maintain the structural, optical, and electrical properties quite similar to the as‐grown Bi films . It is worth noting that the orientation of ultrathin Bi films significantly determines their properties . More recently, the direct growth of Bi thin films with different orientations has been demonstrated .…”

Controlling the growth of Bi(110) and Bi(111) films on an insulating substrate

“…Especially the spin-momentum locked surface states of topological insulating Bi films [13][14][15][16], make them very attractive candidates for spintronic devices. To develop and optimize topological insulators (TIs) towards applications, thin films of high quality are a necessity, as otherwise the exotic electronic properties are hampered by bulk conduction [7,17,18].…”

Large gap two dimensional topological insulators: the bilayer triangular lattice TlM (M = N, P, As, Sb)

“…Although large number of 2D TIs were theoretically predicated, unfortunately, the topological edge states only detected in few 2D materials, including HgTe/CdTe 14 and InAs/GaSb 15 quantum well, bilayer Bi [20][21][22][23] , and 2D ZrTe 5 24,25 . Moreover, the conditions to synthesis these 2D TIs are very rigours including extremely low temperature, ultrahigh vacuum, and high- accuracy molecular beam epitaxy growth.…”