Ultrafast photodoping and effective Fermi-Dirac distribution of the Dirac particles in Bi2Se3

Abstract

We exploit time- and angle- resolved photoemission spectroscopy to determine the evolution of the out-of-equilibrium electronic structure of the topological insulator Bi2Se. The response of the Fermi-Dirac distribution to ultrashort IR laser pulses has been studied by modelling the dynamics of the hot electrons after optical excitation. We disentangle a large increase of the effective temperature T* from a shift of the chemical potential mu*, which is consequence of the ultrafast photodoping of the conduction band. The relaxation dynamics of T* and mu* are k-independent and these two quantities uniquely define the evolution of the excited charge population. We observe that the energy dependence of the non-equilibrium charge population is solely determined by the analytical form of the effective Fermi-Dirac distribution.

5 Pages, 3 Figures

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• Topological Insulators with Inversion Symmetry
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• A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
• 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
• Ultrafast Optical Excitation of a Persistent Surface-State Population in the Topological Insulator Bi2Se3
• Ultrafast surface carrier dynamics in the topological insulator Bi2Te3

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