La seconde génération de rubans supraconducteurs utilisant une couche déposée et épitaxiée de supraconducteur YBa2Cu3O7-x (YBCO) est étudiée de façon intense (coated conductors). Une architecture simple à bas coût a été choisie, avec une seule couche tampon de La2Zr2O7 (LZO), épitaxiée sur un ruban de Ni95W5 texturé bi-axialement. L’objectif de cette thèse était d’identifier les paramètres pertinents du processus de texturation sur des rubans d’alliage Ni95W5 laminés par APERAM à partir d’une coulée industrielle et ceux contrôlant l’épitaxie de la couche tampon de (LZO). Le rôle de la fonctionnalisation du substrat pour l’épitaxie de cet oxyde sur la surface du métal a été en particulier étudié. Parallèlement, la faisabilité d’un procédé de recuit de texturation et de fonctionnalisation du substrat métallique au défilé, en vue d’un traitement continu pour un développement industriel, a été étudiée. / The second generation of superconducting tapes using a deposited layer and epitaxialsuperconductor YBa2Cu3O7-x (YBCO) is studied intensively (coated conductors). A simple lowcostarchitecture was chosen, with one buffer layer La2Zr2O7 (LZO), epitaxially grown on aribbon of biaxially textured Ni95W5. The aim of this thesis was to identify the relevant processparameters texturing ribbons Ni95W5 alloy rolled by APERAM from an industrial casting, andthose controlling the epitaxial buffer layer (LZO). The role of the functionalization of thesubstrate for epitaxy of the oxide on the metal surface has been particularly studied. Meanwhile,the feasibility of an annealing process and functionalization texturing of the metal substrate rollto roll, in view of a continuous treatment for an industrial development, was studied.

Nous utilisons un microscope combinant microscopie à force atomique (AFM) et microscopie à effet tunnel (STM) à très basse température (~100 mK) afin d'étudier des nanocircuits mésoscopiques. Pour effectuer l'AFM dans ces conditions, nous utilisons un diapason en quartz recouvert de deux électrodes sur l'une desquelles est collée la pointe. Lorsque le diapason vibre on peut alors localiser en AFM un échantillon conducteur sur un substrat isolant, puis stopper les vibration pour réaliser des spectroscopies tunnel le long de la partie conductrice. Nous utilisons des pointes de platine-iridium ce qui nous permet de mesurer la densité d'états électronique locale. Nous nous sommes intéressés aux jonctions Josephson hybrides composées d'un îlot d'environ 1 µm de métal normal (cuivre) séparant deux supraconducteurs (aluminium). Ces échantillons sont réalisées par lithographie électronique et évaporation sous angle.Les courbes courant-tension de ces jonctions deviennent hystérétiques à très basse température ce qui est vraisemblablement dû à la dissipation thermique dans la partie normale. Nous avons pu localiser de manière fiable des échantillons uniques et effectuer simultanément des mesures en transport et des spectroscopies locales. Nous avons vu que la densité d'états du supraconducteur varie continuement à proximité du métal normal. Nous avons également observé un chauffage du supraconducteur avec le courant traversant la jonction. La mesure de la densité d'états du supraconducteur permet alors d'estimer la température électronique dans l'échantillon. La comparaison avec notre modèle thermique montre que l'énergie thermique produite dans le métal normal semble être évacuée mieux que prévu. / We use a microscope combining atomic force microscopy (AFM) and scanning tunneling microscopy (STM) at very low temperature (~100 mK) to study mesoscopic nanocircuits. To perform AFM measurements, we use quartz tuning forks covered with metallic electrodes on which we glue the tip. By using the tuning fork as a dynamic force sensor, we can localize the sample. Then, switching off the oscillation, we can perform local spectroscopies along the conductive part. We use platinum-iridium coated tips to measure the local density of states. This work is focused on hybrid Josephson junctions composed of a normal metal (copper) island of approximately 1 µm separating two superconductors (aluminium). These samples are made by electronic lithography and shadow evaporation.The current-voltage characteristics of these junctions become hysteretic at very low temperature because of thermal dissipation in the normal part. We achieved the localization of a unique sample and performed simultaneously transport measurements and local spectroscopies. We observed that the density of states of the superconductor varies continuously close to the normal metal. We also observed heating in the superconductor when the junction is current biased. The measure of the density of states of the superconductors gives an estimation of the electronic temperature in the sample. The comparison with our thermal model shows that the energy produced in the normal metal seems to be evacuated better than expected.

Submitted by Vinícius Suzuki Souto (suzukivini@gmail.com) on 2018-04-27T18:06:31Z No. of bitstreams: 1 Dissertação Vinícius Suzuki Souto.pdf: 5513174 bytes, checksum: 923fabb773c616a9e9f0d554496fd95f (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-04-27T19:05:42Z (GMT) No. of bitstreams: 1 souto_vs_me_ilha.pdf: 5405824 bytes, checksum: 3de7af056a8457da11b1a8f93dfe53ed (MD5) / Made available in DSpace on 2018-04-27T19:05:42Z (GMT). No. of bitstreams: 1 souto_vs_me_ilha.pdf: 5405824 bytes, checksum: 3de7af056a8457da11b1a8f93dfe53ed (MD5) Previous issue date: 2018-02-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Nesse trabalho estudou-se a dinâmica e os fatores de formação de vórtices cinemáticos em supercondutores mesoscópicos sem gap (gapless). Os resultados foram comparados com aqueles de um sistema com gap (gap-like). Para tal, as simulações computacionais foram direcionadas para a solução das equações generalizadas de Ginzburg-Landau dependente do tempo (GTDGL). Primeiramente simulamos amostras homogêneas onde verificou-se que, no sistema gap-like, as correntes se concentram no centro da amostra, com isso, há formação de vórtices cinemáticos. Para criar artificialmente o acúmulo de correntes no centro da amostra, inserimos uma constrição e assim, obtivemos a formação de vórtices cinemáticos em supercondutores gapless. A dinâmica é sempre com um par se formando nas bordas da amostra e se aniquilando no centro. Nota-se que, além da formação de VAv (início do estado resistivo) ocorrer em valores distintos da densidade de corrente aplicada para as diferentes amostras, a corrente crítica apresenta uma pequena diferença entre as amostras gapless e gap-like. Vale ressaltar que parâmetros como o tamanho dos contatos elétricos e a constrição afetam a corrente crítica da amostra, bem como a velocidade média do vórtice cinemático. / In this work we study the dynamics and the formation of kinematic vortices in gapless mesoscopic superconductors. The results were compared to those ones of a gap-like system. Then computational simulations were carried out to solve the Generalized Time-Dependent Ginzburg-Landau equations (GTDGL). Firtly, we simulated homogeneous gap-like and gapless samples where it was found that, in the rst one, the currents concentrate in the center of the sample and then, there was the formation of kinematic vortices. To arti cially promote the crowding of the currents in the center of the sample, we worked with samples a constriction. In this way, kinematic vortices in gapless superconductors were formed. The dynamic is always with a pair forming at the edges of the sample and annihilating in the center. It is noted that, besides the formation of a vortex (antivortex) (begin of resistive state) occurs at distinct values of the applied current density for diferent samples, the electric critical current presents a tiny di erence between gapless and gap-like samples. It is worth mentioning that parameters such as the size of electrical contacts and constriction a ect the critical current of the sample as well as the average velocity of the kinematic vortex. / 131002/2016-3

Orientador: Cláudio Luiz Carvalho / Banca: Victor Ciro Solano Reynoso / Banca: Alexander Polasek / Resumo: Devido a grande preocupação em se desenvolver novos materiais e técnicas para suprir a necessidade por novos recursos e atender com maior comodidade e eficiência a população mundial, estão surgindo novas áreas de pesquisas que visam suprir esta deficiência, seja criando novas tecnologias, ou mesmo aprimorando as técnicas existentes a fim de se obter um melhor aproveitamento dos recursos já existentes. Assim, estamos nos interessando por um ramo da ciência pouco conhecido, mas com um potencial muito elevado a ser descoberto, estamos falando dos materiais supercondutores, que pouco se sabe a respeito deles, porém muito já se faz com os mesmos. Desta maneira estamos apostando numa área mista, onde não usaremos os materiais supercondutores como sendo meramente condutores de energia e sim como dispositivos eletrônicos. Então, começamos o nosso trabalho, desenvolvendo materiais supercondutores na forma de filmes finos que é a base para o desenvolvimento desses dispositivos. Sendo assim escolhemos o sistema BSCCO, que tem como base os seguintes elementos, Bismuto, Estrôncio, Cálcio, Cobre e Oxigênio e que pode apresentar uma temperatura de transição da fase condutora para a fase supercondutora na faixa de 35 - 110K. Deste modo, nos propomos a estudar este tipo de material e desenvolver filmes finos, capazes de serem usados como ...(Resumo completo, clicar acesso eletronico abaixo) / Abstract: Due to great concern in developing new materials and techniques to supply the need for new resources and to assist with larger comfort and efficiency the world population, new areas of researches that seek to supply this deficiency are appearing, by creating new technologies, or even improving the existent techniques in order to obtain a better use of the resources already existent. Like this, we are being interested in a branch of the little known science, but with a very high potential to be discovered, we are talking about the superconductor materials, that little it is known regarding them. However it is much already done with the same ones. In this way we are betting in a mixed area, where we won't use the superconducting materials as being merely drivers of energy but like electronic devices. Then, we began our work, developing superconductor materials in the form of thin films that is the base for the development of those devices. The system BSCCO was chose because it has composed by the following elements, Bismuth, Strontium, Calcium, Copper and Oxygen and that it may present a transition temperature of the conductive phase for the superconductive phase in the range of 35 - 110K. This way, we have studied this material type and to develop thin films, capable of be used as base for electronic devices. In our work we ...(Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-12-17T14:55:12Z (GMT). No. of bitstreams: 1 HugoMCAM_TESE.pdf: 1103719 bytes, checksum: a172421f313d978128130ee22edd6743 (MD5) Previous issue date: 2013-07-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The main objective in this work is the analysis of resonance frequency microstrip structures with glass fiber and electromagnetic band gap (EBG/PBG) substrate and analysis of microstrip antennas with rectangular patch of superconductor of high critical temperature (HTS). In this work was used the superconductors YBCO (critical temperature of 90K), SnBaCaCuOy (critical temperature of 160K), and Sn5InCa2Ba4Cu10Oy (critical temperature of 212K) with results in Gigahertz and Terahertz. Was used microstrip antennas arrays planar and linear phase and linear phase planar with patch with superconductor. It presents a study of the major theories that explain superconductivity. In phase arrays were obtained the factors arrays for such configurations, and the criteria of phase and spacing between the elements compound in the array, which were examined in order to get a main lobe with high directivity and high gain. In the analysis we used the method of Transverse Transmission Line (TTL) used in domain of the Fourier Transform (FTD). The LTT is a full wave method, which obtains the electromagnetic field in terms of the components transverse of the structure. The addition of superconductive patch is made using the boundary condition resistive complex. Results are obtained resonance frequency as a function of the parameters of the antenna, radiation patterns of the E and H Planes, for the phase antenna arrays in linear and planar configurations, for different values of the phase and the spacing between elements / Este trabalho tem como objetivo principal a an?lise da frequ?ncia de resson?ncia em estruturas de microfita, com substrato de banda eletromagn?tica proibida (PBG/EBG) e fibra de vidro, e an?lise de antenas de microfita, com patch retangular supercondutor de alta temperatura cr?tica. Neste trabalho foram utilizados os supercondutores YBCO (temperatura cr?tica de 90K), SnBaCaCuOy (temperatura cr?tica de 160K),e Sn5InCa2Ba4Cu10Oy (temperatura cr?tica de 212K) com resultados das frequ?ncias de resson?ncia em Gigahertz (microondas) e Terahertz (fot?nica/nanotecnologia). S?o realizadas aplica??es em arranjos lineares e planares de antenas de microfita com varia??o de fase, usando o patch supercondutor. ? apresentado um estudo das principais teorias que explicam a supercondutividade. Nos arranjos de fase foram obtidos os fatores de arranjos para tais configura??es, e os crit?rios da fase e do espa?amento entre os elementos compondo o arranjo, ao qual foram examinados com o objetivo de obter um l?bulo principal com alta diretividade e alto ganho. Na an?lise utilizou-se o m?todo da Linha de Transmiss?o Transversa (LTT), aplicado no dom?nio da transformada de Fourier (FTD). O LTT ? um m?todo de onda completa, em que se obt?m os campos eletromagn?ticos em termos dos componentes transversais ? estrutura. A inclus?o do patch supercondutor ? feita utilizando-se a condi??o de contorno complexa resistiva. S?o obtidos resultados da frequ?ncia de resson?ncia em fun??o dos par?metros da antena, diagramas de radia??o dos planos el?tricos e magn?ticos, para os arranjos de fase de antenas nas configura??es lineares e planares para diferentes valores da fase e espa?amento entre os elementos

The vortex fluctuations have proved to be responsible for the onset of dissipation in thin type-II superconducting Aims. There is also growing evidence that dissipation in high- temperature superconductors exhibits the same kind of two-dimensional (2D) behavior. However, a proper analysis of these materials requires a thorough understanding of the two-dimensional fluctuations. This thesis may be considered to consist of two parts. The first is concerned with two models that have often been used as models for 2D superconductors, the 2D Coulomb gas and the 2D XY model. The second part contains analyses related to high-temperature sup er conductivity. Through analysis of some renormalization equations for the Kosterlitz-Thouless (KT) transition, it is shown that the region governed by the KT critical behavior is very small and only applies at very low values for the flux-flow resistance. It is concluded that this critical behavior not is observable in superconductors, and, furthermore, that the only available method to test for 2D fluctuations at the onset of resistance, is through comparison with the 2D resistance scaling function. The critical temperature for the 2D XY model is determined by means of a finite- size scaling relation for the helicity modulus. The linearly screened potential in the XY model is written in terms of a correlation function. The analogy to the 2D Coulomb gas is found to be exact with a temperature-dependent bare interaction and a new expression for vorticity. It is also demonstrated that the Coulomb gas scaling concept may be applied to XY-type models. An analysis of resistance data for YBCO/PBCO superlattices in terms of the 2D resistance scaling function gives evidence for 2D behavior in the cases with large separation of the superconducting layers. In the superlattices with stronger interlayer coupling, the crossover to three-dimensional behavior is seen as a deviation from the scaling function as Tc is approached from above. The anisotropic three-dimensional (3D) XY model is examined as a model for high- temperature superconductors. It is shown that the density of vortices above Tc are closely equal in the anisotropic 3D model and the 2D model. This is taken as evidence that the 3D to 2D crossover found in the superlattices also is present in the anisotropic 3D XY model. / digitalisering@umu.se

The simplest model for superconductor electrodynamics are the London equations, which treats the impact of electromagnetic fields on the current density as a localized phenomenon. However, the charge carriers of superconductivity are quantum mechanical objects, and their wavefunctions are delocalized within the superconductor, leading to non-local effects. The Pippard equation is the generalization of London electrodynamics which incorporates this intrinsic non-locality through the introduction of a new superconducting characteristic length, \xi_0, called the Pippard coherence length. When building nano-scale superconducting devices, the inclusion of the coherence length into electrodynamics calculations becomes paramount. In this thesis, we provide numerical calculations of various electrodynamic quantities of interest in the non-local regime, and discuss their implications for building superconducting devices. We place special emphasis on Superconducting QUantum Inteference Devices (SQUIDs), and their usage as flux quantum bits (qubits) in quantum computation. One of the main limitations of these flux qubits is the presence of intrinsic flux noise, which leads to decoherence of the qubits. Although the origin of this flux noise is not known, there is evidence that it is related to spin impurities within the superconducting material. We present calculations which show that the flux noise in the non-local regime is signi cantly different from the local case. We also demonstrate that non-local electrodynamics greatly affect the self-inductance of the qubit. / Graduate

La jonction Josephson (JJ) est le composé de base de nombreux circuits électroniques supraconducteurs (SQUID, détecteurs d’ondes millimétriques, logique RSFQ). Avec la découverte des supraconducteurs HTc (à haute température critique), d’intenses recherches ont été entreprises pour réaliser des JJ fonctionnant à la température de l’azote liquide (77 K) permettant l’utilisation d’une cryogénie compacte. Toutefois, la complexité de ces matériaux a longtemps rendu difficile le développement d’une technologie viable et simple à mettre en œuvre. Parmi les méthodes de fabrication de jonctions, celle utilisant l’irradiation par faisceau d’ions a atteint un niveau de maturité suffisamment important pour pouvoir envisager la production de circuits comportant plusieurs milliers de JJ à HTc.Le but de ma thèse repose sur la fabrication, la caractérisation et l’étude des propriétés électromagnétiques de réseaux de jonctions Josephson réalisés dans des films minces d’YBa2Cu3O7-d. par la méthode d’irradiation ionique. / The Josephson junction (JJ) is the basis of many compound superconducting electronic circuits (SQUID detectors millimeter wave RSFQ logic). With the discovery of HTS superconductors (high critical temperature), intensive research has been undertaken to make JJ operating at the temperature of liquid nitrogen (77 K) allowing the use of a compact cryogenics. However, the complexity of these materials has long hampered the development of a viable technology and simple to implement. Among the junctions manufacturing methods, one using the ion beam irradiation has reached a sufficiently high degree of maturity to be able to envisage the production of circuits having thousands of JJ to HTS.The aim of my thesis is based on the fabrication, characterization and study of the electromagnetic properties of Josephson arrays achieved in thin films of YBa2Cu3O7-d. by the ion irradiation method.

In this thesis, the results of analyzing the electronic structure of two iron-based superconductors: FeSe and LiFeAs are presented. To access the electronic structure, angle-resolved photoemission spectroscopy was used. In our analysis, we focus on the structure of the superconducting gap and the influence of nematicity on the electronic structure. We have revealed changes in the electronic structure of FeSe caused by nematicity in all parts of the Brillouin zone. A scale of these changes is smaller than it was believed earlier. Also, we have observed an anomalous shift of the dispersions in opposite directions with temperature in this material. We have observed anisotropic superconducting gap on all sheets of the Fermi surfaces of both: FeSe and LiFeAs. We have shown that in LiFeAs, rotational symmetry is broken in the superconducting state, which manifests not only in the gap symmetry but also in the shapes of the Fermi surfaces sheets. This result indicates a realization of a novel phenomenon of superconductivity-induced nematicity:1 Iron-based superconductors 1.1 Introduction to iron-based superconductors 1.2 LiFeAs - special iron-based superconductor 1.3 FeSe - structurally simplest iron-based superconductor 2 Angle-Resolved Photoemission 3 Temperature evolution of the electronic structure of FeSe 3.1 Effects of nematicity from low-temperature measurements 3.2 Temperature dependent shift of the dispersions 3.3 Discussion and conclusions 4 Three-dimensional superconducting gap in FeSe 4.1 Superconducting gap on the electron-like pockets 4.2 Superconducting gap on the hole-like pocket 4.3 Discussion and conclusions 5 Superconductivity-induced nematicity in LiFeAs 5.1 Superconducting gap 5.2 Nematicity 5.3 Discussion and conclusions Summary

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18052号 / 理博第3930号 / 新制||理||1567(附属図書館) / 30910 / 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 松田 祐司, 准教授 芝内 孝禎, 教授 石田 憲二 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM