title: Experimental demonstration of topological surface states protected by time-reversal symmetry.
abstract: We report direct imaging of standing waves of the nontrivial surface states of topological insulator Bi2Te3 using a scanning tunneling microscope. The interference fringes are caused by the scattering of the topological states off Ag impurities and step edges on the Bi2Te3(111) surface. By studying the voltage-dependent standing wave patterns, we determine the energy dispersion E(k), which confirms the Dirac cone structure of the topological states. We further show that, very different from the conventional surface states, backscattering of the topological states by nonmagnetic impurities is completely suppressed. The absence of backscattering is a spectacular manifestation of the time-reversal symmetry, which offers a direct proof of the topological nature of the surface states.
authors.affiliation: Department of Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhang
authors.forename: Peng
authors.initials: P
authors.lastname: Cheng
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.forename: Jin-Feng
authors.initials: JF
authors.lastname: Jia
authors.forename: Xucun
authors.initials: X
authors.lastname: Ma
authors.forename: Ke
authors.initials: K
authors.lastname: He
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.forename: Haijun
authors.initials: H
authors.lastname: Zhang
authors.forename: Xi
authors.initials: X
authors.lastname: Dai
authors.forename: Zhong
authors.initials: Z
authors.lastname: Fang
authors.forename: Xincheng
authors.initials: X
authors.lastname: Xie
authors.forename: Qi-Kun
authors.initials: QK
authors.lastname: Xue