open access

https://doi.org/10.14943/doctoral.k11372

https://hdl.handle.net/2115/58183

ポリアセン及びその複素環式類似体における光誘起相転移

英語

2014-03-25

Hokkaido University

ⅳ, 61p

Photoinduced structure phase transitions in polyacene, paracyanogen and boron-nitride acene are studied. In each compound, there exist two degenerate lattice-distorted structure: double bonds in a cis pattern and those in a trans pattern. In polyacene and paracyanogen, cis patterned lattice configurations have the mirror symmetry while the trans ones have the C2z rotation invariance. In boron-nitride acene, either cis patterns or trans patterns have no definite symmetries. We argue that the symmetry properties will strongly affect the optical properties and lead to contrast optical conductivities between the cis and trans patterns in polyacene, paracyanogen and boron-nitride acene.By using the time-dependent Hartree-Fock method, we simulate the lattice evolution process in polyacene, paracyanogen and boron-nitride acene after they are photoexcited. We find that any kind of photons can not break the symmetry of the initial state. Due to this symmetry-preserving law, phase transitions in polyacene and paracyangen behave as the one−way switchings: Only trans patterns can be well converted into cis ones, but the reverse conversions are forbidden. Since boron-nitride acene has no definite symmetries in any lattice configuration, the symmetry-preserving law does not work and the phase transitions between cis and trans patterns are bidirectional.

2014-03-25

甲第11372号

博士(理学)

(主査) 教授 山本 昌司, 教授 小野寺 彰, 教授 石橋 晃 （電子科学研究所）, 講師 大原 潤

理学院（物性物理学専攻）

博士論文

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