title: Resonance effects in thickness-dependent ultrafast carrier and phonon dynamics of topological insulator Bi2Se3.
abstract: Resonance effects in the thickness-dependent ultrafast carrier and phonon dynamics of topological insulator Bi2Se3 are found irrespective of the kind of substrate by measuring thickness-dependent abrupt changes of pump-probe differential-reflectivity signals (ΔR/R) from Bi2Se3 thin films on four different substrates of poly- and single-crystalline (sc-) ZnO, sc-GaN and SiO2. The absolute peak intensity of the ΔR/R is maximized at ∼t C (6 ∼ 9 quintuple layers), which is not directly related to but is very close to the critical thickness below which the energy gap opens. The intensities of the two phonon modes deduced from the oscillatory behaviors superimposed on the ΔR/R profiles are also peaked at ∼t C for the four kinds of substrates, consistent with the thickness-dependent Raman-scattering behaviors. These resonant effects and others are discussed based on possible physical mechanisms including the effects of three-dimensional carrier depletion and intersurface coupling.
authors.affiliation: Department of Applied Physics and Institute of Natural Sciences, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Sung
authors.initials: S
authors.lastname: Kim
authors.forename: Dong Hee
authors.initials: DH
authors.lastname: Shin
authors.forename: Ju Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Chan Wook
authors.initials: CW
authors.lastname: Jang
authors.forename: Jun Woo
authors.initials: JW
authors.lastname: Park
authors.forename: Hosun
authors.initials: H
authors.lastname: Lee
authors.forename: Suk-Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Ki-Ju
authors.initials: KJ
authors.lastname: Yee
authors.forename: Namrata
authors.initials: N
authors.lastname: Bansal
authors.forename: Seongshik
authors.initials: S
authors.lastname: Oh