title: Interplay of Surface and Dirac Plasmons in Topological Insulators: The Case of Bi_{2}Se_{3}.
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.
authors.affiliation: Department of Physics, University of Calabria, 87036 Rende (CS), Italy.
authors.forename: A
authors.initials: A
authors.lastname: Politano
authors.affiliation: Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal 4, 20018 San Sebastián/Donostia, Spain.|Departamento de Física de Materiales, Universidad del País Vasco, Apartado 1072, 20080 San Sebastián/Donostia, Spain.|IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain.
authors.forename: V M
authors.initials: VM
authors.lastname: Silkin
authors.affiliation: Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal 4, 20018 San Sebastián/Donostia, Spain.|Tomsk State University, 634050 Tomsk, Russian Federation.|Saint Petersburg State University, 198504 Saint Petersburg, Russian Federation.
authors.forename: I A
authors.initials: IA
authors.lastname: Nechaev
authors.affiliation: NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy.
authors.forename: M S
authors.initials: MS
authors.lastname: Vitiello
authors.affiliation: NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Viti
authors.affiliation: Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal 4, 20018 San Sebastián/Donostia, Spain.|Institute of Catalysis and Inorganic Chemistry, ANAS, AZ1143 Baku, Azerbaijian.|Institute of Physics, ANAS, AZ1143 Baku, Azerbaijian.
authors.forename: Z S
authors.initials: ZS
authors.lastname: Aliev
authors.affiliation: Institute of Catalysis and Inorganic Chemistry, ANAS, AZ1143 Baku, Azerbaijian.
authors.forename: M B
authors.initials: MB
authors.lastname: Babanly
authors.affiliation: Department of Physics, University of Calabria, 87036 Rende (CS), Italy.|CNISM, Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Via della Vasca Navale, 84, 00146 Roma, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Chiarello
authors.affiliation: Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal 4, 20018 San Sebastián/Donostia, Spain.|Departamento de Física de Materiales, Universidad del País Vasco, Apartado 1072, 20080 San Sebastián/Donostia, Spain.|Centro de Física de Materiales CFM-Materials Physics Center MPC, Centro Mixto CSIC-UPV/EHU, Paseo de Manuel Lardizabal 5, 20018 San Sebastián/Donostia, Spain.
authors.forename: P M
authors.initials: PM
authors.lastname: Echenique
authors.affiliation: Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal 4, 20018 San Sebastián/Donostia, Spain.|Departamento de Física de Materiales, Universidad del País Vasco, Apartado 1072, 20080 San Sebastián/Donostia, Spain.|Tomsk State University, 634050 Tomsk, Russian Federation.|Saint Petersburg State University, 198504 Saint Petersburg, Russian Federation.|Centro de Física de Materiales CFM-Materials Physics Center MPC, Centro Mixto CSIC-UPV/EHU, Paseo de Manuel Lardizabal 5, 20018 San Sebastián/Donostia, Spain.
authors.forename: E V
authors.initials: EV
authors.lastname: Chulkov