Probing Dirac Fermion Dynamics in Topological Insulator Bi${}_2$Se${}_3$ Films with Scanning Tunneling Microscope

Abstract

Scanning tunneling microscopy and spectroscopy have been used to investigate the femtosecond dynamics of Dirac fermions in the topological insulator Bi${}_2$Se${}_3$ ultrathin films. At two-dimensional limit, bulk electrons becomes quantized and the quantization can be controlled by film thickness at 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 phase relaxation length $l_{\varphi }$ and inelastic scattering lifetime $\tau$ of topological surface-state electrons. We find that $\tau$ exhibits a remarkable $(E-E_F{)}^{-2}$ energy dependence and increases with film thickness. We show that the features revealed are typical for electron-electron scattering between surface and bulk states.

5 pages, 4 figures, to be published in Physical Review Letters

References in corpus (6)

• Topological Surface States Protected From Backscattering by Chiral Spin Texture
• Coexistence of the topological state and a two-dimensional electron gas on the surface of Bi2Se3
• Emergent quantum confinement at topological insulator surfaces
• Momentum-Resolved Landau-Level Spectroscopy of Dirac Surface State in Bi2Se3
• Transmission of topological surface states through surface barriers
• Stationary phase approximation approach to the quasiparticle interference on the surface of a strong topological insulator