Heat shrink tubing is used to insulate wire conductors, protect wires, and to create cable entry seals in wire harnessing industries. Performing this sensitive process manually is time consuming, the results are strongly dependent on the operator’s expertise, and the process presents safety concerns. Alternatively, automating the process minimizes the operators’ direct interaction, decreases the production cost over the long term, and improves quantitative and qualitative production indicators dramatically. This thesis introduces the automation of a heat shrink tubing prototype machine that benefits the wire harnessing industry. The prototype consists of an instrumented heat chamber on a linear positioning system, and is fitted with two heat guns. The chamber design allows for the directing of hot air from the heat guns onto the wire harness uniformly through radially-distributed channels. The linear positioning system is designed to move the heat chamber along the wire harness as the proper shrinkage temperature level is reached. Heat exposure time as a major factor in the heat shrink tubing process can be governed by controlling the linear speed of the heat chamber. A control unit manages the actuator position continuously by measuring the chamber’s speed and temperature. A model-based design approach is followed to design and test the controller, and MATLAB/Simulink is used as the simulation environment. A programmable logic controller is selected as the controller implementation platform. The control unit performance is examined and its responses follow the simulation results with adequate accuracy.

Mott insulators are a family of materials in which strong electron-electron interactions induce an unconventional insulating state in the system that would otherwise behave as an electrical conductor according to the non-interacting band theory. In particular, the nature of the Mott metal-insulator transition (MIT) has been the subject of intense research interest because it can involve a complicated interplay between magnetic and electronic properties. In some Mott systems, Mott transitions occur in the one-step process, from an antiferromagnetic insulator (AFI) to a paramagnetic metal phase (PMM), while in other Mott systems a two-step transition with an intermediate antiferromagnetic metal (AFM) phase can be observed. Since 2015, the muon spin relaxation (𝜇SR) group at Columbia University started systematic 𝜇SR studies on a series of Mott systems, including one-step transition Mott systems 𝑅𝐸NiO₃ and V₂O₃, as well as two-step transition Mott systems Ba(Co, Ni)S₂, Ni(S, Se)₂ and (La, Sr)VO₃. This dissertation first introduces the comprehensive 𝜇SR research on multiple families of Mott systems conducted by our 𝜇SR group, including 𝑅𝐸NiO₃, V₂O₃, and BaCoS₂. Then the 𝜇SR experimental findings on the Mott system NiS₂₋ₓSeₓ will be presented, which is the most extensively studied material in this thesis. The NiS₂₋ₓSeₓ system is of particular interest because there is a large region of intermediate AFM state emerging between AFI and PMM states with Se doping, making it an ideal platform to provide information on static magnetism in the AFM state and thus can help us better understand the evolution of magnetic NiS₂₋ₓSeₓ, with our key findings being: (1) The AFM state of the NiS₂₋ₓSeₓ system shows significantly random spin correlations, and the magnetic order is suppressed by a gradual reduction of the ordered moment size, with a nearly full ordered volume fraction until very close to the AFM-PMM boundary. (2) No signature of dynamic critical behavior was observed in the thermal phase transition, indicating a first-order thermal phase transition. The next part of this dissertation presents our computational simulations on the NiS₂₋ₓSeₓ system. Dipolar field simulations have shown that only the combination of easy axis randomization and Ni moment dilution in NiS₂ can lead to the internal field distribution corresponding to the observed 𝜇SR spectrum in the AFM region. Also, this picture could qualitatively explain the neutron and muon results consistently, thus reconciling the seemingly contradicting experimental results by 𝜇SR and the previous neutron scattering studies shown in the AFM region. Furthermore, we propose a percolation model that can capture both the charge and spin connections of the interpenetrating percolating spin and charge networks in the NiS₂₋ₓSeₓsystem, which raises the possibility of "compromising metallicity and magnetic order" in the two-step Mott transition evolving AFI to AFM to PMM states in NiS₂₋ₓSeₓ.

La thèse porte sur l'étude théorique des propriétés électroniques à la surface de l’oxyde de métal de transition SrTiO3. Ce matériau est la pierre angulaire de l'électronique des oxydes, un nouveau domaine de recherche qui a pour but d'enquêter sur les oxydes de métaux de transition en tant que candidats post-silicium pour une émergence future de nouveaux composants électroniques. Le SrTiO3 est en soi un système étonnant : dans sa plus pure composition chimique, c’est un bon isolant avec une large bande interdite. Cependant, en le dopant avec de petites quantités d'autres éléments, il se transforme en un métal à haute mobilité d'électrons. Le SrTiO3 a également saisi l'attention en raison de sa capacité à accueillir des gaz d'électrons bidimensionnels (2DEGs) quand il est interfacé avec certains oxydes polaires. Ces 2DEGs présentent des propriétés fascinantes, la plus visible étant la coexistence du magnétisme et de la supraconductivité.La surface du SrTiO3 peut également accueillir des 2DEGs, sans avoir besoin de s'interfacer avec d'autres matériaux ; dans ce cas, les électrons participant aux transports sont générés par des lacunes d'oxygène créées à la surface. Cette observation est remarquable, car le SrTiO3 offre une structure simple où les propriétés des 2DEGs peuvent être étudiées.Cette thèse s’articule autour des deux axes. Tout d'abord, elle étudie la bicouche STO orientée 111, formée de seulement deux cellules unitaires. Deuxièmement, elle analyse les puits quantiques générés par les postes vacants de l'oxygène à la surface 111 du STO. Les deux sujets sont abordés en utilisant des modèles de liaison forte, dans lesquels le Hamiltonien incorpore différents termes liés aux énergies sur place, aux interactions de saut et au couplage spin-orbite. A partir de ces calculs, j’ai réalisé une analyse exhaustive des propriétés, du caractère et de la parité des orbitaux des bandes de valence et de conduction, ainsi que des états de bord dans la bicouche 111. / The thesis is focused on the theoretical study of the electronic properties at the surface of the transition metal oxide STO. This material is the cornerstone of oxide electronics, an emerging research area that has the goal of investigating transition metal oxides as post-silicon candidates for a future emerging new electronics. STO is in itself an astounding system; in its purest chemical composition is a good ban-insulator with a wide bandgap. Nevertheless, upon doing it with tiny amounts of other elements it transforms itself in a metal with high electron mobility. Even more remarkably, at the lowest temperatures, typically below 300mK, it goes superconductor. And adding to these properties, strain induces also ferroelectricity in this material. Over the last years, STO has also grabbed attention because of its ability of hosting two-dimensional electron gas (2DEGs) when it is interfaced with some polar oxides. Such 2DEGs exhibit fascinating properties, the most conspicuous is the coexistence of magnetism and superconductivity.The surface of STO can host 2DEGs too, without need of interfacing it to other materials; in this case the electrons participating in transport are generated by oxygen vacancies created at the surface. This is remarkable observation, as it affords a simpler structure where the 2DEGs properties can be studied. In spite of the accumulated knowledge, still a better fundamental comprehension is required of the electronic structure of the quantum wells at the surfaces oriented along the 111 direction, for which the perovskite structure is reminiscent of the celebrated honeycomb-like structure of graphene. Contrary to the latter, in which electrons are in s- and p- states, 111 quantum wells in STO would host electrons in d-bands. Higher electronic correlations are then expected, that may bring new fascinating physics.The outline of this Thesis has two main branches: first, it studies the 111-oriented STO bilayer, formed by just two unit cells; secondly it analyzes the quantum wells generated by Oxygen vacancies at the 111-surface of STO. Both subjects are approached using tight-binding models in which the Hamiltonian incorporates different terms related to on-site energies, hopping interactions or spin-orbit coupling. From these calculations, I have carried out an exhaustive analysis of the orbital character and parity properties of valence and conduction bands, as well as edge states in the 111 bilayer. Tight-binding calculations have also shed light on the orbital character, space location and extension and energy of electronic states generated by oxygen vacancies at the 001 surface of STO.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18062号 / 理博第3940号 / 新制||理||1568(附属図書館) / 30920 / 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 石田 憲二, 准教授 藤本 聡 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18779号 / 理博第4037号 / 新制||理||1581(附属図書館) / 31730 / 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 前野 悦輝 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Topological insulators (TIs) are a class of quantum materials, which behave as insulators in the bulk, yet possess gapless spin-polarized surface states, which are robust against nonmagnetic impurities. The unique properties of TIs make them attractive not only for studying various fundamental phenomena in condensed matter and particle physics, but also as promising candidates for applications ranging from spintronics to quantum computation. Within the topological insulator realm, a great deal of focus has been placed on discovering new quantum materials, however, ideal multi-modal quantum materials have yet to be found. Here we study alpha-PdBi2, KFe2Te2, and DySb compounds including others within these families with high-resolution angle-resolved photoemission spectroscopy (ARPES) complimented by first principles calculations. We observe unique phase changes and phenomena across their transition temperatures. Our work paves a new direction in material discovery and application related to their unique electronic properties.

Barium Strontium Titanate (BST) was deposited on Pt/ZrO2 / SiO2/Si substrates using liquid source metal organic chemical vapor deposition. A stoichiometry series was deposited with various GrII/Ti ratios (0.658 to 1.022) and a temperature series was deposited at 550 to 700°C. The thin films were characterized using transmission electron microscopy. Both series of samples contained cubic perovskite BST and an amorphous phase. The grain size increased and the volume fraction of amorphous phase decreased with increasing deposition temperature. The electrical and microstructural properties improved as the GrII/Ti ratio approached 1 and deteriorated beyond 1. This research demonstrates that BST thin films are a strong candidate for future MOS transistor gate insulator applications.

Over the last decades, both band topology and Anderson transitions, as well as their interplay, have been well understood in the context of time-independent energy-conserved systems. This switches the research focus in this field from theoretical descriptions to experimental designs, realizations, and engineering. In such a background, time-dependent perturbations and coupling between quantum systems and environments become the main concern. Along this route, this dissertation first studies the properties of a Chern insulator, one of the simplest topological systems, under time-periodic disorder. We reveal that in certain cases disorder fully localizes the bulk, but surprisingly has a positive effect on the edge, propagating edge states exist throughout the full spectrum. Along this direction, we further explore disorder effects in a network model constructed by arrays of unitary scattering matrices. Here, we go beyond previous works and show that also the shape of network (lattice symmetries) is important. It will result in a new type of topological phase, known as a higher-order topological phase, in which the topological states of a d-dimensional system have a dimension less than (d − 1). Afterwards, we focus on a network model with gain and loss, which breaks energy conservation. Here, we find the system now exhibits a 'supermetal' behavior that surpasses the conventional ballistic transport for perfect metals. At the end of this dissertation, we perform a study on the non-Hermitian defect in time-periodic systems. Our study shows that a boundary defect, due to its non-Hermiticity, can stop the propagation of chiral edge states, which should otherwise be the most robust manifestations of topology in quantum systems.

No description available.

In this dissertation, we used a combination of synchrotron-based x-ray spectroscopic techniques such as angle-resolved photoelectron spectroscopy (ARPES), soft x-ray ARPES, hard x-ray photoelectron spectroscopy (HAXPES), and soft x-ray absorption spectroscopy (XAS) to investigate momentum-resolved and angle-integrated electronic structure of advanced three- and two-dimensional materials and interfaces. The results from the experiments were compared to several types of state-of-the-art first-principles theoretical calculations. In the first part of this dissertation we investigated the effects of spin excitons on the surface states of samarium hexaboride (SmB6), which has gained a lot of interest since it was proposed to be a candidate topological Kondo insulator. Here, we utilized high-resolution (overall resolution of approximately 3 meV) angle-resolved and angle-integrated valence-band photoemission measurements at cryogenic temperatures (1.2 K and 20 K) to show evidence for a V-shap / Physics