京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20892号 / 理博第4344号 / 新制||理||1624(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 高橋 義朗, 教授 川上 則雄, 教授 田中 耕一郎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(理学) / 甲第24402号 / 理博第4901号 / 新制||理||1700(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 川上 則雄, 教授 佐々 真一, 教授 高橋 義朗 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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The main focus of the thesis is to have better understanding of the atomic and electronic structures, vibrational dynamics and thermodynamics of metallic surfaces and bi-metallic nanoparticles (NPs) via a multi-scale simulational approach. The research presented here involves the study of the physical and chemical properties of metallic surfaces and NPs that are useful to determine their functionality in building novel materials. The study follows the 'bottom-up' approach for which the knowledge gathered at the scale of atoms and NPs serves as a base to build, at the macroscopic scale, materials with desired physical and chemical properties. We use a variety of theoretical and computational tools with different degrees of accuracy to study problems in different time and length scales. Interactions between the atoms are derived using both Density Functional Theory (DFT) and Embedded Atom Method (EAM), depending on the scale of the problem at hand. For some cases, both methods are used for the purpose of comparison. For revealing the local contributions to the vibrational dynamics and thermodynamics for the systems possessing site-specific environments, a local approach in real-space is used, namely Real Space Green's Function method (RSGF). For simulating diffusion of atoms/clusters and growth on metal surfaces, Molecular Statics (MS) and Molecular Dynamics (MD) methods are employed.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21549号 / 理博第4456号 / 新制||理||1640(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 高橋 義朗, 教授 田中 耕一郎, 教授 前野 悦輝 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Nanoscale structures play a fundamental role in diverse scientific areas, including biology and information technology. It is necessary to develop methods that can observe nanoscale structures and dynamic processes that involve them. Colloidal plasmonic nanoparticles (plasmonic “atoms”) and their clusters (plasmonic “molecules”) are nanoscale objects with remarkable optical properties that provide new opportunities for sensing and imaging on the relevant length and time scales. Many biology questions require optically monitoring of the dynamic behavior of biological systems on single molecule level. In contrast to the commonly used fluorescent probes which have the problem of bleaching, blinking and relatively weak signals, plasmonic probes display superb brightness, persistency and photostability, thus enable long observation time and high temporal and spacial resolutions. When plasmonic atoms are clustered together, their resonances redshift while the intensities increase as a result of plasmon coupling. These optical responses are dependent on the interparticle gaps and the overall geometry, which makes plasmonic molecules capable of detecting biomolecule clustering and measuring nanometer scale distance fluctuations. In this dissertation, individual plasmonic atoms are firstly evaluated as imaging probe and their interactions with lipid membrane are tested on a newly developed on-chip black lipid membrane system. Subsequently, plasmonic dimers (plasmon rulers) prepared through DNA-programmed self-assembly are monitored to detect the mechanical properties of single biopolymers. Measurement of the spring constant of short (tens of nucleotides or base pairs) DNAs is demonstrated through plasmon coupling microscopy. Colloidal plasmonic atoms of various materials, sizes and shapes scatter vivid colors in the full-visible range. Assembling them into plasmonic molecules provides additional degrees of freedom for color manipulation. More importantly, the electric field in the gaps of plasmonic molecules can be enhanced by several orders of magnitude, which is highly desirable in single molecule sensing applications. In this dissertation, the fundamentals of plasmonic coupling are investigated through one-dimensional gold nanosphere chains. Using the directed self-assembly approach, multichromatic color-switchable plasmonic nanopixels composed of plasmonic atoms and molecules of various materials, sizes, shapes and geometries are integrated in one image with nanometer precision, which facilitates the encoding of complex spectral features with high relevance in security tagging and high density optical data storage. / 2017-01-01T00:00:00Z

The coupling of light to ensembles of strongly interacting Rydberg atoms via electromagnetically induced transparency (EIT) has emerged as a particularly promising approach towards quantum nonlinear optics, allowing freely propagating photons to acquire long-ranged effective interactions of unprecedented strength. This thesis explores different photon interaction mechanisms enabled by this general approach, and examines how these can be utilized for various different practical applications. Considering dissipative photon interactions, we first examine the effect of blockade-induced photon scattering on the spatial coherence of collective Rydberg excitations stored in an atomic medium, and how this influences the efficiency of photon storage and retrieval. Based on this developed understanding, we examine the performance of single-photon switching capabilities enabled by dissipative scattering and establish optimized switching protocols over a range of parameters. We then generalize this to consider the many-body decoherence of multiple stored excitations. Here we identify a correlated coherence protection mechanism in which photon scattering from one excitation can preserve the spatial coherence of all others in the medium, and consider the utility of this effect for implementing robust single-photon subtraction. We then outline a new approach towards coherent quantum nonlinear optics via Rydberg-EIT, in which the emergent photon interaction features intrinsically suppressed photon losses. The underlying idea exploits Rydberg blockade to modify rather than break EIT conditions for multiple photons in close proximity, the effect of which alters the underlying dispersion relation of light propagation in a coherent fashion. We devise a specific implementation of this general mechanism fostering a reflective optical nonlinearity and discuss how this can enable efficient single-photon routing with a multitude of unique practical applications.

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