The moving electrons can become very special in solid more than our imagination. The energy of the mobile electrons has been found to be linearly proportional to the momentum which gives massless electrons -- Dirac Fermion in Dirac Cone-like band structures. Such kind of photon-like electrons in solid is realized in some very special systems: Graphene and Topological Insulator. In topological insulator, the Dirac Cone has less symmetry. It does not have spin degeneracy which results in Helical Dirac Fermions. In this talk, I will introduce our spectroscopic studies on the helical Dirac Cone on the surface/interface of the Topological Insulators and some other related artificial structures. The studies of the two dimensional helical Dirac Fermions will bring many new opportunities both in fundamental and applied researches in condensed matter physics.

钱冬，1998年本科毕业于复旦大学物理系。2003年在复旦大学物理系获得博士学。毕业后在美国普林斯顿大学从事博士后和研究学者工作。2009年加入上海交通大学物理与天文系。主要利用角分辨光电子能谱研究低维量子系，电子强关联系统的电子结构。近年来，和合作者一起在实验上发现了第一种强拓扑绝缘体。发表学术论文40余篇，其中包括Nature（3篇），Science（1篇），Nature physics（1篇），Phys. Rev. Lett.（12篇）等。