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29 March 2024 |
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Observation of Dirac plasmons in a topological insulator | P. Di Pietro
; M. Ortolani
; O. Limaj
; A. Di Gaspare
; V. Giliberti
; F. Giorgianni
; M. Brahlek
; N. Bansal
; N. Koirala
; S. Oh
; P. Calvani
; S. Lupi
; | Date: |
23 Jul 2013 | Abstract: | Plasmons are the quantized collective oscillations of electrons in metals and
doped semiconductors. The plasmons of ordinary, massive electrons are since a
long time basic ingredients of research in plasmonics and in optical
metamaterials. Plasmons of massless Dirac electrons were instead recently
observed in a purely two-dimensional electron system (2DEG)like graphene, and
their properties are promising for new tunable plasmonic metamaterials in the
terahertz and the mid-infrared frequency range. Dirac quasi-particles are known
to exist also in the two-dimensional electron gas which forms at the surface of
topological insulators due to a strong spin-orbit interaction. Therefore,one
may look for their collective excitations by using infrared spectroscopy. Here
we first report evidence of plasmonic excitations in a topological insulator
(Bi2Se3), that was engineered in thin micro-ribbon arrays of different width W
and period 2W to select suitable values of the plasmon wavevector k. Their
lineshape was found to be extremely robust vs. temperature between 6 and 300 K,
as one may expect for the excitations of topological carriers. Moreover, by
changing W and measuring in the terahertz range the plasmonic frequency vP vs.
k we could show, without using any fitting parameter, that the dispersion curve
is in quantitative agreement with that predicted for Dirac plasmons. | Source: | arXiv, 1307.5974 | Services: | Forum | Review | PDF | Favorites |
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