Ultrafast Surface Carrier Dynamics in the Topological Insulator Bi2Te3

• Published in: Nano letters 2012-07, Vol.12 (7), p.3532-3536
• Main Authors: Hajlaoui, M, Papalazarou, E, Mauchain, J, Lantz, G, Moisan, N, Boschetto, D, Jiang, Z, Miotkowski, I, Chen, Y. P, Taleb-Ibrahimi, A, Perfetti, L, Marsi, M
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron and ion emission by liquids and solids; impact phenomena; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals; Engineering Sciences; Exact sciences and technology; Interfaces, heterostructures, nanostructures; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Mechanics; Photoemission and photoelectron spectra; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl301035x

We discuss the ultrafast evolution of the surface electronic structure of the topological insulator Bi2Te3 following a femtosecond laser excitation. Using time and angle-resolved photoelectron spectroscopy, we provide a direct real-time visualization of the transient carrier population of both the surface states and the bulk conduction band. We find that the thermalization of the surface states is initially determined by interband scattering from the bulk conduction band, lasting for about 0.5 ps; subsequently, few picoseconds are necessary for the Dirac cone nonequilibrium electrons to recover a Fermi-Dirac distribution, while their relaxation extends over more than 10 ps. The surface sensitivity of our measurements makes it possible to estimate the range of the bulk-surface interband scattering channel, indicating that the process is effective over a distance of 5 nm or less. This establishes a correlation between the nanoscale thickness of the bulk charge reservoir and the evolution of the ultrafast carrier dynamics in the surface Dirac cone.