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arXiv · 2207.09789

Dirac bands in the topological insulator Bi2Se3 mapped by time-resolved momentum microscopy

Stefano Ponzoni·Felix Paßlack·Matija Stupar·David Maximilian Janas·Giovanni Zamborlini·Mirko Cinchetti
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Abstract

We have studied the energy dispersion of the Dirac bands of the topological insulator Bi2Se3 at large parallel momenta using a setup for laser-based time-resolved momentum microscopy with 6 eV probe-photons. Using this setup, we can probe the manifold of unoccupied states up to higher intermediate-state energies in a wide momentum window. We observe a strongly momentum-dependent evolution of the topologically protected Dirac states into a conduction band resonance, highlighting the anisotropy dictated by the surface symmetry. Our results are in remarkable agreement with the theoretical surface spectrum obtained from a GW-corrected tight-binding model, suggesting the validity of the approach in the prediction of the quasiparticle excitation spectrum of large systems with non-trivial topology. After photoexcitation with 0.97 eV photons, assigned to a bulk valence band-conduction band transition, the out-of-equilibrium population of the surface state evolves on a multi-picosecond time scale, in agreement with a simple thermodynamical model with a fixed number of particles, suggesting a significant decoupling between bulk and surface states.

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Stefano Ponzoni, Felix Paßlack, Matija Stupar, David Maximilian Janas, Giovanni Zamborlini, Mirko Cinchetti. 2022-07-20. Dirac bands in the topological insulator Bi2Se3 mapped by time-resolved momentum microscopy. https://arxiv.org/abs/2207.09789

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