Abstract
We have investigated plasmonic excitations at the surface of Bi_{2}Se_{3}(0001) via high-resolution electron energy loss spectroscopy. For low parallel momentum transfer q_{∥}, the loss spectrum shows a distinctive feature peaked at 104 meV. This mode varies weakly with q_{∥}. The behavior of its intensity as a function of primary energy and scattering angle indicates that it is a surface plasmon. At larger momenta (q_{∥}~0.04 Å^{-1}), an additional peak, attributed to the Dirac plasmon, becomes clearly defined in the loss spectrum. Momentum-resolved loss spectra provide evidence of the mutual interaction between the surface plasmon and the Dirac plasmon of Bi_{2}Se_{3}. The proposed theoretical model accounting for the coexistence of three-dimensional doping electrons and two-dimensional Dirac fermions accurately represents the experimental observations. The results reveal novel routes for engineering plasmonic devices based on topological insulators.
Highlights
We have investigated plasmonic excitations at the surface of Bi2Se3ð0001Þ via high-resolution electron energy loss spectroscopy
In most cases, the Fermi level is shifted from the bulk band gap and pinned by the bulk states occupied by doping electrons or holes. These bulk carriers give rise to their own three-dimensional electron gas (3DEG), which is well known to have plasmonic excitations characterized by the bulk plasmon energy ωp
The frequency of the surface plasmon ωsp is related to the bulk pplaffiffisffiffimffiffiffiffioffiffinffiffi energy ωp [9]
Summary
We have investigated plasmonic excitations at the surface of Bi2Se3ð0001Þ via high-resolution electron energy loss spectroscopy. The behavior of its intensity as a function of primary energy and scattering angle indicates that it is a surface plasmon.
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