Browsing by Author "Lai, Yi-Ping"

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Plasmonics in Topological Insulators
(2014-04-16)
Lai, Yi-Ping
;
Lin, I-Tan
;
Wu, Kuang-Hsiung
;
Liu, Jia-Ming
;
電子物理學系
With strong spin-orbit coupling, topological insulators have an insulating bulk state, characterized by a band gap, and a conducting surface state, characterized by a Dirac cone. Plasmons in topological insulators show high frequency-tunability in the mid-infrared and terahertz spectral regions with transverse spin oscillations, also called "spin-plasmons". This paper presents a discussion and review of the developments in this field from the fundamental theory of plasmons in bulk, thin-film, and surface-magnetized topological insulators to the techniques of plasmon excitation and future applications.
Temperature-dependent carrier-phonon coupling in topological insulator Bi2Se3
(2014-12-08)
Lai, Yi-Ping
;
Chen, Hsueh-Ju
;
Wu, Kuang-Hsiung
;
Liu, Jia-Ming
;
電子物理學系
Temperature-dependent (11.0K +/- 294.5 K) carrier-phonon coupling in Bi2Se3 is investigated by ultrafast pump-probe spectroscopy. The rise time of the differential reflectivity is interpreted by a combined effect of electron temperature relaxation and hot-phonon lifetime. The electron-phonon coupling constant of the bulk state (lambda = 0.63 +/- 0.05) is deduced from theoretical fitting. Increasing hot-phonon lifetime with decreasing temperature is attributed to a decreasing phonon-phonon collision rate. A complete analysis of the thermalization process is presented. Understanding carrier and phonon dynamics is essential for future optoelectronic and spintronic applications of topological insulators. (C) 2014 AIP Publishing LLC.
Terahertz Optoelectronic Property of Graphene: Substrate-Induced Effects on Plasmonic Characteristics
(2014-03-01)
Lin, I-Tan
;
Lai, Yi-Ping
;
Wu, Kuang-Hsiung
;
Liu, Jia-Ming
;
電子物理學系
The terahertz plasmon dispersion of a multilayer system consisting of graphene on dielectric and/or plasma thin layers is systematically investigated. We show that graphene plasmons can couple with other quasiparticles such as phonons and plasmons of the substrate; the characteristics of the plasmon dispersion of graphene are dramatically modified by the presence of the coupling effect. The resultant plasmon dispersion of the multilayer system is a strong function of the physical parameters of the spacer and the substrate, signifying the importance of the substrate selection in constructing graphene-based plasmonic devices.