title: Probing Dirac fermion dynamics in topological insulator Bi2Se3 films with a scanning tunneling microscope.
abstract: Scanning tunneling microscopy and spectroscopy have been used to investigate the femtosecond dynamics of Dirac fermions in the topological insulator Bi2Se3 ultrathin films. At the two-dimensional limit, bulk electrons become quantized and the quantization can be controlled by the film thickness at a single quintuple layer level. By studying the spatial decay of standing waves (quasiparticle interference patterns) off steps, we measure directly the energy and film thickness dependence of the phase relaxation length lϕ and inelastic scattering lifetime τ of topological surface-state electrons. We find that τ exhibits a remarkable (E - EF)(-2) energy dependence and increases with film thickness. We show that the features revealed are typical for electron-electron scattering between surface and bulk states.
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Can-Li
authors.initials: CL
authors.lastname: Song
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Ke
authors.initials: K
authors.lastname: He
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Shuai-Hua
authors.initials: SH
authors.lastname: Ji
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Xu-Cun
authors.initials: XC
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100084, China.
authors.forename: Qi-Kun
authors.initials: QK
authors.lastname: Xue