Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi 2 Se 3

Abstract : Three-dimensional topological insulators are fascinating materials with insulating bulk yet metallic surfaces that host highly mobile charge carriers with locked spin and momentum. Remarkably, surface currents with tunable direction and magnitude can be launched with tailored light beams. To better understand the underlying mechanisms, the current dynamics need to be resolved on the timescale of elementary scattering events (B10 fs). Here, we excite and measure photocurrents in the model topological insulator Bi 2 Se 3 with a time resolution of 20 fs by sampling the concomitantly emitted broadband terahertz (THz) electromagnetic field from 0.3 to 40 THz. Strikingly, the surface current response is dominated by an ultrafast charge transfer along the Se–Bi bonds. In contrast, photon-helicity-dependent photocurrents are found to be orders of magnitude smaller than expected from generation scenarios based on asymmetric depopulation of the Dirac cone. Our findings are of direct relevance for broadband optoelectronic devices based on topological-insulator surface currents.
Document type :
Journal articles
Complete list of metadatas

Cited literature [50 references]  Display  Hide  Download

https://hal-polytechnique.archives-ouvertes.fr/hal-01445495
Contributor : Marcin Konczykowski <>
Submitted on : Tuesday, January 24, 2017 - 11:03:10 PM
Last modification on : Monday, July 8, 2019 - 10:29:17 AM
Long-term archiving on : Tuesday, April 25, 2017 - 6:21:51 PM

File

ncomms13259.pdf
Publisher files allowed on an open archive

Identifiers

Citation

Lukas Braun, Gregor Mussler, Andrzej Hruban, Marcin Konczykowski, Thomas Schumann, et al.. Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi 2 Se 3. Nature Communications, Nature Publishing Group, 2016, 7, pp.13259. ⟨10.1038/ncomms13259⟩. ⟨hal-01445495⟩

Share

Metrics

Record views

330

Files downloads

328