Ultrafast Surface Carrier Dynamics in the Topological Insulator Bi2Te3

Mahdi Hajlaoui (1) , E. Papalazarou (1) , Julien Mauchain (1) , G. Lantz (1) , N. Moisan (2) , Davide Boschetto (2) , Z. Jiang (3) , I. Miotkowski (4) , P. Chen Y. (4) , Amina Taleb-Ibrahimi (5) , Luca Perfetti (6) , M. Marsi (1)

1 LPS - Laboratoire de Physique des Solides
2 LOA - Laboratoire d'optique appliquée
3 Sch Phys
4 Dept Phys
5 CASSIOPEE
6 LSI - Laboratoire des Solides Irradiés

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 non-equilibrium 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.

Keywords: Topological insulator; ultrafast spectroscopy; bismuth telluride; carrier dynamics; interband scattering; non-equilibrium Dirac cone

Domains: Engineering Sciences [physics]; Mechanics [physics.med-ph]

Mahdi Hajlaoui, E. Papalazarou, Julien Mauchain, G. Lantz, N. Moisan, et al.. Ultrafast Surface Carrier Dynamics in the Topological Insulator Bi2Te3. Nano Letters, 2012, 12 (7), pp.3532-3536. ⟨10.1021/nl301035x⟩. ⟨hal-01068621⟩