Topological insulator materials for advanced optoelectronic devices

Topological insulators are quantum materials that have an insulating bulk state

and a topologically protected metallic surface state with spin and momentum

helical locking and a Dirac-like band structure [1–3]. Two-dimensional (2D)

topological insulators are associated with gapless edge states, and three-dimensional

(3D) topological insulators with gapless surface states [4]. A variety of

compounds have been identified as 2D or 3D topological insulators, including

HgTe/CdTe, Bi2Se3, Bi2Te3, Sb2Te3, BiTeCl, Bi1.5Sb0.5Te1.8Se1.2, SmB6 and so on

[5–8]. The topological surface (edge) states in these materials have been mainly

investigated by first-principle theoretical calculation, electronic transport,

angle-resolved photoemission spectroscopy (ARPES), and scanning tunneling

microscopy (STM) [6]. Unique and fascinating electronic properties, such as

the quantum spin Hall effect, quantum anomalous Hall effect, topological magnetoelectric

effect, magnetic monopole image, and Majorana fermions, have

been observed in the topological insulator materials [9, 10]. With these unique

properties, topological insulator materials have great potential applications in

spintronics and quantum information processing, as well as magnetoelectric

devices with higher efficiency and lower energy consumption [11, 12].