Laser-induced persistent photovoltage on the surface of a ternary topological insulator at room temperature

Using time- and angle-resolved photoemission, we investigate the ultrafast response of excited electrons in the ternary topological insulator (Bi1- x Sb x )2Te3 to fs-infrared pulses. We demonstrate that at the critical concentration x = 0.55, where the system becomes bulk insulating, a surface volt...

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Bibliographic Details
Published in:Applied physics letters 2017-04, Vol.110 (14)
Main Authors: Sánchez-Barriga, J., Battiato, M., Golias, E., Varykhalov, A., Yashina, L. V., Kornilov, O., Rader, O.
Format: Article
Language:English
Subjects:
Applied physics
Photoelectric emission
Room temperature
Topological insulators
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Summary:Using time- and angle-resolved photoemission, we investigate the ultrafast response of excited electrons in the ternary topological insulator (Bi1- x Sb x )2Te3 to fs-infrared pulses. We demonstrate that at the critical concentration x = 0.55, where the system becomes bulk insulating, a surface voltage can be driven at room temperature through the topological surface state solely by optical means. We further show that such a photovoltage persists over a time scale that exceeds ∼6 μs, i.e, much longer than the characteristic relaxation times of bulk states. We attribute the origin of the photovoltage to a laser-induced band-bending effect which emerges near the surface region on ultrafast time scales. The photovoltage is also accompanied by a remarkable increase in the relaxation times of excited states as compared to undoped topological insulators. Our findings are relevant in the context of applications of topological surface states in future optical devices.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4979596