Dual Space Analyzing Based on Symmetry Properties for Phonons of Si Quantum Dot  

作　　者：QIN Guo-Yi REN Shang-Fen ZHANG Zhi-Yong 

机构地区：[1]Department of Physics, Nanjing University, Nanjing 210093, China Department of Physics, Illinois State University, Normal, IL 61790-4560, USA Department of Physics, Tianjin Normal University, Tianjin 300074, China

出　　处：《Communications in Theoretical Physics》2002年第7期91-98,共8页理论物理通讯（英文版）

基　　金：国家重点基础研究发展计划(973计划)，国家自然科学基金，美国国家自然科学基金

摘　　要：Phonon modes in spherical Si quantum dots (QDs) with up to 7.9 nm in diameter are calculated by using the projection operators of the group theory into valence force field model. The phonons of dot modes in each of five irreducible representations (symmetries) are classified by using a dual space analysis method. It is found that the bulk-like modes with localization radius much smaller than the dot's radius have clearly pronounced bulk specific-κdefinite bulk band (one in six modes). In Si dots of all sizes, each specific bulk-like dot mode has specific symmetry.TO dot modes and bulk-like X-derived TA and LA dot modes red-shift in frequency with decreasing dot size. There is almost not LO/TO mixing for bulk-like modes. As for the surface-like modes localized at the periphery of the dot,their eigenmodes have not a dominant bulk specific-κ point parentage or a dominant BZ parentage around some special point. They are a superposition of many bulk bands with κ from all over the bulk BZ. They have much significant mode mixing than the bulk-like phonons. The classification of dot modes based on the symmetry of group theory will bring advantageous to the discussion of Ramam spectrum, electron-phonon interaction and other phonon-assisted effects in QDs.

关 键 词：PHONON modes  quantum dots  dual space ANALYZING 

分 类 号：O4[理学—物理]