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Appl. Sci. 2018, 8(5), 694; https://doi.org/10.3390/app8050694

Surface State Dynamics of Topological Insulators Investigated by Femtosecond Time- and Angle-Resolved Photoemission Spectroscopy

1
Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
2
National Lab for Superconductivity, Institute of Physics, Chinese Academy of Science, Beijing 100190, China
3
IFN-CNR c/o Dipartimento di Fisica, Politecnico di Milano, 20133 Milan, Italy
*
Author to whom correspondence should be addressed.
Received: 11 April 2018 / Revised: 26 April 2018 / Accepted: 27 April 2018 / Published: 30 April 2018
(This article belongs to the Special Issue Extreme Time Scale Photonics)
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Abstract

Topological insulators (TI) are known for striking quantum phenomena associated with their spin-polarized topological surface state (TSS). The latter in particular forms a Dirac cone that bridges the energy gap between valence and conduction bands, providing a unique opportunity for prospective device applications. In TI of the BixSb2−xTeySe3−y (BSTS) family, stoichiometry determines the morphology and position of the Dirac cone with respect to the Fermi level. In order to engineer specific transport properties, a careful tuning of the TSS is highly desired. Therefore, we have systematically explored BSTS samples with different stoichiometries by time- and angle-resolved photoemission spectroscopy (TARPES). This technique provides snapshots of the electronic structure and discloses the carrier dynamics in surface and bulk states, providing crucial information for the design of electro-spin current devices. Our results reveal the central role of doping level on the Dirac cone structure and its femtosecond dynamics. In particular, an extraordinarily long TSS lifetime is observed when the the vertex of the Dirac cone lies at the Fermi level. View Full-Text
Keywords: TARPES; topological insulator; electronic dynamics; topological surface state; BSTS; ultrafast spectroscopy; Dirac cone TARPES; topological insulator; electronic dynamics; topological surface state; BSTS; ultrafast spectroscopy; Dirac cone
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Hedayat, H.; Bugini, D.; Yi, H.; Chen, C.; Zhou, X.; Cerullo, G.; Dallera, C.; Carpene, E. Surface State Dynamics of Topological Insulators Investigated by Femtosecond Time- and Angle-Resolved Photoemission Spectroscopy. Appl. Sci. 2018, 8, 694.

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