Cover: Linearly dispersive surface state of topological insulator Bi₂Te₃ measured by angle resolved photoemission spectroscopy, forming a single Dirac fermion. The crystal structure of Bi₂Te₃ is illustrated below. Topological insulators represent a new state of quantum matter with a bulk insulting gap and odd number of relativistic Dirac fermions on the surface. In the simplest case, the surface state consists of a single Dirac cone, with one quarter the degrees of freedom of graphene. The mathematical structure of a topological insulator is relevant to important issues under investigation by the quantum information processing community. It has the novelty of dissipationless edge state transport of reminiscent of quantum hall system but without external magnetic field. Moreover, with a surface magnetic layer the electrodynamics of the topological insulator is described by an additional topological term in Maxwell’s equation, leading to striking quantum phenomena such as an image magnetic monopole induced by an electric charge. More details could be found in the article “Studies on the electronic structures of three-dimensional topological insulators by angle resolved photoemission spectroscopy” by Yulin Chen, pp 175-192. [Photo credits: Yulin Chen at University of Oxford, UK]