Prof Yulin Chen

Abstract:

Three-dimensional (3D) topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. The unusual surface states of topological insulators rise from the nontrivial topology of their electronic structures as a result of strong spin-orbital coupling. In this review, we will briefly introduce the concept of topological insulators and the experimental method that can directly probe their unique electronic structure: angle resolved photoemission spectroscopy (ARPES). A few examples are then presented to demonstrate the unique band structures of different families of topological insulators and the unusual properties of the topological surface states. Finally, we will briefly discuss the future development of topological quantum materials. © 2012 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Abstract:

Topological insulators are an intriguing class of materials with an insulating bulk state and gapless Dirac-type edge/surface states. Recent theoretical work predicts that few-layer topological insulators are promising candidates for broadband and high-performance optoelectronic devices due to their spin-momentum-locked massless Dirac edge/surface states, which are topologically protected against all time-reversal-invariant perturbations. Here, we present the first experimental demonstration of near-infrared transparent flexible electrodes based on few-layer topological-insulator Bi 2Se 3 nanostructures epitaxially grown on mica substrates by means of van der Waals epitaxy. The large, continuous, Bi 2Se 3-nanosheet transparent electrodes have single Dirac cone surface states, and exhibit sheet resistances as low as ∼330 per square, with a transparency of more than 70% over a wide range of wavelengths. Furthermore, Bi 2Se 3-nanosheet transparent electrodes show high chemical and thermal stabilities as well as excellent mechanical durability, which may lead to novel optoelectronic devices with unique properties. © 2012 Macmillan Publishers Limited. All rights reserved.