Electronic transport properties of free-base tape-porphyrin molecular wires studied by self-consistent tight-binding calculations

作     者：Katsunori Tagami Masaru Tsukada Takuya Matsumoto Tomoji Kawai 

作者机构：Department of Molecular Engineering Graduate School of Bioscience and Biotechnology Tokyo Institute of Technology 4259 Nagatsuta-cho Midori-ku Yokohama-shi Kanagawa 226-8501 Japan Department of Physics Graduate School of Science University of Tokyo Hongo 7-3-1 Bunkyou-ku Tokyo 113-0033 Japan The Institute of Scientific and Industrial Research Osaka University 8-1 Mihogaokoa Ibaraki Osaka 567-0047 Japan Core Research for Evolutional Science and Technology (CREST) Japan Science & Technology Corporation (JST) Kawaguchi Center Building Hon-cho 4-1-8 Kawaguchi Saitama 332-0012 Japan 

出 版 物：《Physical Review B》 (物理学评论B辑：凝聚态物质与材料物理学)

年 卷 期：2003年第67卷第24期

页      面：245324-245324页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

摘      要：We investigated by theoretical calculations the electronic states and the transport properties of one of the oligoporphyrin molecular wires, the free-base tape-porphyrins. Inside these molecules the adjacent building blocks, referred to as porphyrin macrocycles, are linked by three conjugating C-C bonds aligned in parallel. We found that the origin of the extremely small highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps of these molecules is the strong coupling between the unoccupied π orbitals of each macrocycle. Then we considered the molecular bridges where these porphyrin molecules are bridged between the aluminum electrodes. We found that the conductances have large values and that the current increases nearly in proportion to the applied bias. These features are explained by the strong hybridization of the HOMO with the electrode wave functions and by the wide bandwidth of the tape porphyrins. Finally we studied the current distribution inside the tape-porphyrin wire. The current is found to flow in an anisotropic way, i.e., it seems to flow along the spatial distribution of the HOMO of the tape porphyrins, reflecting the strong hybridization of the HOMO with the electrode wave functions.