Browsing by Author "Wang, Haibo"

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Confined breather-type excitation in a quinoidal thiophene after sub-5 fs pulse excitation
(2006-07-28)
Kobayashi, Takayoshi
;
Wang, Haibo
;
Wang, Zhuan
;
Otsubo, Tetsuo
;
電子物理學系
A quinoidal thiophene molecule which is a prototype of the repeated unit of s-trans-cis-polyacetylene was studied by sub-5 fs spectroscopy. A breatherlike mode modulation of both the amplitude and frequency of the C = C stretching was observed for the first time. It generates two sidebands of 2238 and 700 cm(-1) with a separation of 769 cm(-1) corresponding to the modulation frequency. The latter mode is very close to the C-S-C ring deformation, which indicate that this mode mediates coupling between the breather mode and the C-beta-C-beta stretching mode. It was also found that the breather-type excitation has a longer lifetime (2-3 ps) than in all-trans-polyacetylene (50 fs) due to its confinement. (c) 2006 American Institute of Physics.
Periodic elastic nanodomains in ultrathin tetragonal-like BiFeO3 films
(2013-08-26)
Luo, Zhenlin
;
Chen, Zuhuang
;
Yang, Yuanjun
;
Liu, Heng-Jui
;
Huang, Chuanwei
We present a synchrotron grazing incidence x-ray diffraction analysis of the domain structure and polar symmetry of highly strained BiFeO3 (BFO) thin films grown on LaAlO3 substrate. We reveal the existence of periodic elastic nanodomains in the pure tetragonal-like BFO ultrathin films down to a thickness of 6 nm. A unique shear strain-accommodation mechanism is disclosed. We further demonstrate that the periodicity of the nanodomains increases with film thickness but deviates from the classical square root law in the ultrathin thickness regime (6-30 nm). Temperature-dependent experiments further reveal the disappearance of periodic modulation above similar to 90 degrees C due to a M-C-M-A structural phase transition.
Sub-5-fs spectroscopy of a thiophene derivative with a quinoid structure
(2006-07-26)
Kobayashi, Takayoshi
;
Wang, Haibo
;
Wang, Zhuan
;
Otsubo, Tetsuo
;
電子物理學系
Sub-5-fs spectroscopy of a thiophene derivative with an electron donative and an acceptive moieties and quinoid structure provided the experimental evidence of dynamic mode coupling. It was shown that two out-of-plane bending modes mediate the dynamic mode coupling between 1469 and 1379 cm(-1) and between 1603 and 1469 cm(-1). These couplings are considered to be associated with geometrical relaxation relevant to the neutral bipolaron formation in all-s-trans polyacetylene. (c) 2006 Elsevier B.V. All rights reserved.