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Nat Commun. 2016 Apr 26;7:11421. doi: 10.1038/ncomms11421.

Strong nonlinear terahertz response induced by Dirac surface states in Bi2Se3 topological insulator.

Author information

1
INFN and Dipartimento di Fisica, Università di Roma 'La Sapienza', Piazzale A. Moro 2, I-00185 Roma, Italy.
2
Laboratori Nazionali di Frascati-INFN, Via E. Fermi, 40, I-00044 Frascati, Italy.
3
INSTM Udr Trieste-ST and Elettra-Sincrotrone Trieste S.C.p.A, Area Science Park, I-34012 Trieste, Italy.
4
INFN and Dipartimento di Fisica, Università di Roma 'Tor Vergata', viale della Ricerca Scientifica 1, I-00133 Roma, Italy.
5
INFN and Dipartimento S.B.A.I., Università di Roma 'La Sapienza', Piazzale A. Moro 2, I-00185 Roma, Italy.
6
Department of Physics and Astronomy Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854-8019, USA.

Abstract

Electrons with a linear energy/momentum dispersion are called massless Dirac electrons and represent the low-energy excitations in exotic materials such as graphene and topological insulators. Dirac electrons are characterized by notable properties such as a high mobility, a tunable density and, in topological insulators, a protection against backscattering through the spin-momentum locking mechanism. All those properties make graphene and topological insulators appealing for plasmonics applications. However, Dirac electrons are expected to present also a strong nonlinear optical behaviour. This should mirror in phenomena such as electromagnetic-induced transparency and harmonic generation. Here we demonstrate that in Bi2Se3 topological insulator, an electromagnetic-induced transparency is achieved under the application of a strong terahertz electric field. This effect, concomitantly determined by harmonic generation and charge-mobility reduction, is exclusively related to the presence of Dirac electron at the surface of Bi2Se3, and opens the road towards tunable terahertz nonlinear optical devices based on topological insulator materials.

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