Дисертації з теми "Quantum oscillation in insulator"
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Sato, Yuki. "Quantum oscillations and charge-neutral fermions in Kondo insulator YbB₁₂." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263447.
Повний текст джерелаBègue, Frédéric. "Isolants topologiques et magnétisme." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30392/document.
Повний текст джерелаThe discovery of the quantum Hall effect by von Klitzing in 1980 paved the way for what is now known as topological band theory. In this theory, we are interested not only in the energy spectra of the electrons in crystals, but also in the topological structure of the bands. A new phase of matter was discovered thanks to this theory : the topological insulators. Topological insulators are unique in the sense that they behave like trivial insulators in the bulk, but possess metallic edge states. In this thesis, we are particularly interested in so-called Z2 topological insulators, whose edge states are protected by time reversal symmetry : they cannot disappear in the presence of a perturbation that respects this symmetry, without the system undergoing a quantum phase transition. For three-dimensional topological insulators, we propose an experimental criterion based on magnetic quantum oscillations to identify a special kind of topological insulators : the strong topological insulator. In two dimensions, we study the consequences of time reversal symmetry breaking due to anti-ferromagnetic order. In this case, the important symmetry is time reversal times a trans- lation. In this context, we first establish an analytical expression for systems that also have inversion symmetry. We then adapt three numerical methods usually employed for time reversal symmetric systems : the reconnection phase method, the Wannier charge center method and the explicit construction of edge states. We show that they are useful to probe the topology of models for which no methods were available ; such as non-centrosymmetric systems
Semeniuk, Konstantin. "Correlated low temperature states of YFe2Ge2 and pressure metallised NiS2." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274346.
Повний текст джерелаKhan, Hasan. "Quantum Fluctuations Across the Superconductor-Insulator Transition." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1553188107263297.
Повний текст джерелаTan, Hong'En. "High pressure quantum oscillation study of BiTeI and Bi2Te3." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/284884.
Повний текст джерелаDoiron-Leyraud, Nicolas. "Quantum oscillation and high pressure studies on correlated metals." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619930.
Повний текст джерелаMottahedeh, Roya. "Various aspects of quantum Hall effect." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306508.
Повний текст джерелаRenberg, Rasmus. "Superconductor-Insulator Quantum Phase Transitions in a Dissipative Environment." Thesis, KTH, Fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-239615.
Повний текст джерелаHsu, Yu-Te. "Unconventional Fermi surface in insulating SmB6 and superconducting YBa2Cu3O6+x probed by high magnetic fields." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/280314.
Повний текст джерелаLi, Li. "Study of Metal-Insulator-Metal Diodes for Photodetection." University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1367319217.
Повний текст джерелаSchroeder, Brett. "Surface modification enhanced semiconductor-on-insulator heteroepitaxy /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9808.
Повний текст джерелаLam, Jennifer. "The nature of the metal-insulator transition in SiGe quantum wells." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20977.pdf.
Повний текст джерелаPiekarek, Mateusz. "High-extinction ratio optical filtering for silicon-on-insulator quantum photonics platform." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715763.
Повний текст джерелаLam, Jennifer Eleanor. "The nature of the metal-insulator transition in silicon germanide quantum wells." Thesis, University of Ottawa (Canada), 1997. http://hdl.handle.net/10393/4399.
Повний текст джерелаZiegler, Johannes [Verfasser], and Dieter [Akademischer Betreuer] Weiss. "Quantum transport in HgTe topological insulator nanostructures / Johannes Ziegler ; Betreuer: Dieter Weiss." Regensburg : Universitätsbibliothek Regensburg, 2019. http://d-nb.info/1180719573/34.
Повний текст джерелаFrancheteau, Anaïs. "Superconducting silicon on insulator and silicide-based superconducting MOSFET for quantum technologies." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY092/document.
Повний текст джерелаSuperconducting transport through a silicon MOSFET can open up many new possibilities ranging from fundamental research to industrial applications. In this thesis, we investigate the electric transport properties of a MOSFET built with superconducting source and drain contacts. Due to their advantages in terms of scalability and reproducibility, we want to integrate superconducting materials compatible with CMOS technology, thus exploiting the reliable and mature silicon technology. The idea is to realize a new type of superconducting circuits in a transistor geometry in which a non-dissipative supercurrent flowing through the device from source to drain will be modulated by a gate: a JOFET. One important outcome is the realization of superconducting qubits in a perfectly reproducible and mature technology. However, at low temperature and with the reduction of the size of the devices, two antagonistic phenomena appear. The dissipation-free transport of Cooper pairs competes with lossy single-particle processes due to Coulomb interactions. The goal is to understand how these two conflicting properties manifest in such hybrid devices. In this thesis, I studied two different ways of introducing superconductivity in the devices. We deployed a high boron doping and a laser annealing provided by well-controlled out-of-equilibrium doping techniques to make the silicon superconducting. Although highly boron-doped silicon has been known to be superconducting since 2006, superconductivity of SOI, the basic brick of some transistors, was never tested before. We aim at adapting those doping techniques on SOI in order to make it superconducting and to integrate it in transistor-like devices. In a second project, we study source and drain contacts fabricated with superconducting silicides such as PtSi. Such Schottky barrier MOSFETs with superconducting PtSi contacts are elaborated at the CEA/LETI. Measurements at very low temperature revealed the competition between superconductivity and Coulomb interactions and moreover, have brought evidence of superconductivity in PtSi based silicon Schottky barrier MOSFET
Di, Mauro Marco. "Flavor mixing in quantum field theory and quantum information." Doctoral thesis, Universita degli studi di Salerno, 2011. http://hdl.handle.net/10556/194.
Повний текст джерелаAfter reviewing the formalism for describing flavor mixing, both in Quantum Mechanics and Quantum Field Theory, some consequences along three different directions are studied. First, it is proposed that flavor mixing can be a viable candidate for spontaneous supersymmetry breaking, due to the nontrivial vacuum structure induced by it. After the statement of the conjecture, an explicit proof in a simple case is given. Second, the properties of flavor states as entangled states both in QM and QFT are studied. By interpreting such states as multipartite mode–entangled states, both the correlation content and the decoherence effects are studied. Third, a possible new interpretation of flavor mixing as induced by an external vector field is proposed, and it is shown how this solves some problems of the usual formalism in connection with Lorentz and Poincar´e violation. Some phenomenological consequences of this picture are pointed out, as well as some intriguing physical interpretations. [edited by author]
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Hussain, Mallik Mohd Raihan. "Effective Nonlinear Susceptibilities of Metal-Insulator and Metal-Insulator-Metal Nanolayered Structures." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1591207594352716.
Повний текст джерелаBoukahil, Mounir. "Quantum criticality and Fermisurface instabilities investigation by pressure and quantum oscillation measurements on Ce and Ybbased heavy fermion compounds." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY090/document.
Повний текст джерелаThe superconductivity had been thought to be incompatible with the magnetism, because the former originates from the weak attractive leading to the formation of Cooper pairs, whereas the latter is based on the strong Coulomb repulsive force, leading also to strong electronic correlations. Unconventional superconductors,which include heavy fermion systems, high-Tc cuprates, organic superconductors, and iron-pnictides, is a major topic of condensed matter physics. In all these systems, it has been understood that magnetism can even plays an important role for the pairing mechanism, so that both phenomena can coexist and even favour each other.Our target is on heavy fermion systems, namely uranium and rare earth compounds, where the 5f or 4f electrons which have a dual nature (itinerant/localized), play an important role. More precisely, we will focus on the ferromagnetic superconductors and their quantum criticality. In this field, new materials open new frontiers of research. The student will participate in this stream. He will learn and develop the fundamental crystal growth techniques, such as Czochralski, flux, and Bridgeman method. Since high quality single crystals are essential to elucidate the superconducting properties, a lot of efforts will be devoted to improve the quality of the samples. The next target is the quantum oscillation measurements, which allow a detailed microscopic observation of the heavy electronic state and of the topology of the Fermi surface. They require both very low temperature and high fields, like the study of the field induced superconducting phases in these compounds (like URhGe or UCoGe). The student will perform the measurements under extreme conditions, namely high fields up to 15T in SPSMS, or up to 30T in LNCMI, at low temperatures down to 30 mK, and high pressure up to 3 GPa.From the educational point of view, it is ideal that the student starts to synthesize a material, characterizes it, performs the low temperature measurements by him/herself throughout the PhD period, and get used to the exciting measurements under extreme conditions in a large scale facility like the LNCMI. Such a wide spectrum is rather rare in Europe, but our group („SPSMS/LNCMI) can provide such a unique opportunity, helping the student to become an independent researcher. It should be noted that the experiments in SPSMS and LNCMI are quite complementary each other. For quantum oscillation study, high fields, low temperatures and high quality singles are inevitably important. In general, the precise measurements at high fields up to 15T would be enough in order to determine the Fermi surface topology and the effective mass, which canbe done in SPSMS. However, the specific case, such as Lifshitz transition, field induced quantum critical phenomena, requires higher fields than 15T, which can be achieved by the resistive magnet in LNCMI.This project is supported by the ANR (CORMAT, SINUS) and the ERC starting grant “NewHeavyFermion”.Recently in SPSMS we purchased a top-loading dilution refrigerator for the quantum oscillation measurements, and started the installation. By the end of this summer, hopefully we detect the first de Haas-van Alphen signal at high fields up to 15T and at temperatures down to 30mK. Furthermore, we started to install the flux crystal growth equipment this month, involving the reconstruction of the room for the safe treatment of uranium compounds
Qiu, Lei. "Exploring 2D Metal-Insulator Transition in p-GaAs Quantum Well with High rs." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1386337954.
Повний текст джерелаBonneau, Damien. "Integrated quantum photonics at telecommunication wavelength in silicon-on-insulator and lithium niobate platforms." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664624.
Повний текст джерелаTenasini, Giulia. "Quantum transport in monolayer WTe2." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14897/.
Повний текст джерелаPerez, Barraza Julia Isabel. "Ultrasmall silicon quantum dots for the realization of a spin qubit." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708003.
Повний текст джерелаWatson, Deborah Lee. "Quantum interference effects in the magnetoresistance of semiconductor structures near the metal to insulator transition." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286547.
Повний текст джерелаO'Neal, Jared. "A Numerical Study of a Disorder-driven 2D Mott Insulator-to-Metal Quantum Phase Transition." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492701913534985.
Повний текст джерелаSchönle, Joachim. "Quantum transport studies for spintronics implementation : from supramolecular carbon nanotube systems to topological crystalline insulator." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY022/document.
Повний текст джерелаMolecular electronics is one of the most intriguing fields of modern research, which could bring forth a modular and scalable building system for nanoscale spintronics applications. A particularly promising example are single-molecule magnets, which have already successfully shown to be suitable for spin valve or spin qubit operations. One of the biggest challenges of the field is the integration of these nanometer-sized objects in complex circuits in order to allow for detection and manipulation of moleculear spin states. As shown in recent years by the NanoSpin group, carbon nanotubes (CNTs) can serve as such type of carrier for the single-molecule magnets, combining features of both constituents.A corner stone of this thesis project was hence the development of a dependable fabrication technique for high-quality CNT devices, controllable by multiple local gate electrodes in order to enable local control of molecular hybrid systems. A process based on conventional one-chip fabrication was developed from scratch, for which optimization of sample design, lithography and deposition techniques as well as material choices had to be carefully incorporated, in order to accomodate the restrictions imposed by the CNT growth conditions on the prevention of leakage currents. We succeeded in producing clean CNT devices, which could support a double dot configuration, tunable from p- to n-type characteristics. The segments created in this way can be stabily controlled over the entire device length and should hence provide a suitable backbone to study molecular physics.Topological matter constitutes an enticing platform to investigate both fundamental principles as well as possible applications from spintronics to quantum computation. Topological crystalline insulators, with tin telluride ( SnTe ) as a prime example, represent a new state of matter within this zoo of 3D topological materials. Soon after first experimental realizations, suggestions were made about the possibility of an unconventional type of superconductivity hosted at the interface between topological matter and conventional superconductors. Possible implications of such systems include Cooper pairing with finite momentum, the FFLO phase, or topological quantum computing, based on peculiar excitations, called Majorana bound states.This thesis project aimed to participate in the investigation of signs of unconventional superconductivity in SnTe . Transport experiments on bare films in Hall bar geometries and superconducting hybrid devices, realized as both Josephson junctions and SQUIDs, are discussed. A surprisingly strong coupling of SnTe to Ta superconductor was found and dependencies of superconductivity on sample geometries, temperature and magnetic field were investigated. The current-phase relation was analyzed in the limit of strong kinetic effects. Electrostatic gating and rf exposure was explored, but predominant physics in such configurations turned out to be of purely conventional type, pointing out the importance of improvements on the material side.In-plane magnetic field measurements gave rise to the manifestation of ϕ0-SQUIDs with tunable 0−π-transitions, providing evidence for possible controlled transitions from trivial superconductivity to unconventional coupling regimes in SnTe
Hussain, Mallik Mohd Raihan. "Nonlinear Electromagnetic Radiation from Metal-Insulator-Metal Tunnel Junctions." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1490823061190116.
Повний текст джерелаClarke, Warrick Robin Physics Faculty of Science UNSW. "Quantum interaction phenomena in p-GaAs microelectronic devices." Awarded by:University of New South Wales. School of Physics, 2006. http://handle.unsw.edu.au/1959.4/32259.
Повний текст джерелаVELLEI, ANTONIO. "Silicon-on-insulator nanowires as spintronic device for quantum computing: design, processing, fabrication and electrical characterization." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2011. http://hdl.handle.net/10281/20213.
Повний текст джерелаRosenbach, Daniel [Verfasser], Daniel [Akademischer Betreuer] Schäpers, and Markus [Akademischer Betreuer] Morgenstern. "Quantum transport and induced superconductivity in selectively deposited topological insulator devices / Daniel Rosenbach ; Daniel Schäpers, Markus Morgenstern." Aachen : Universitätsbibliothek der RWTH Aachen, 2021. http://d-nb.info/1240480407/34.
Повний текст джерелаRatnadurai, Rudraskandan. "Development of a Reliable Metal-Insulator-Metal Bilayer Tunnel Junction for Wideband Detectors." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4394.
Повний текст джерелаRepellin, Cécile. "Numerical study of fractional topological insulators." Thesis, Paris, Ecole normale supérieure, 2015. http://www.theses.fr/2015ENSU0028/document.
Повний текст джерелаTopological insulators are band insulators which are fundamentally different from atomic insulators. Only a non-local quantity called topological invariant can distinguish these two phases. The quantum Hall effect is the first example of a topological insulator, but the same phase can arise in the absence of a magnetic field, and is called a Chern insulator. In the presence of strong interactions, topological insulators may host exotic excitations called anyons. The fractional quantum Hall effect is the only experimentally realized example of such phase. In this manuscript, we study the conditions of emergence of different types of fractional topological insulators, using numerical simulations. We first look at the fractional quantum Hall effect on the torus. We introduce a new projective construction of exotic quantum Hall states that complements the existing construction. We study the low energy excitations on the torus of two of the most emblematic quantum Hall states, the Laughlin and Moore-Read states. We propose and validate model wave functions to describe them. We apply this knowledge to characterize the excitations of the Laughlin state in Chern insulators. We show the stability of other fractional quantum Hall states in Chern insulators, the composite fermion, Halperin and NASS states. We explore the physics of fractional phases with no equivalent in a quantum Hall system, using two different strategies: first by choosing a model with a higher value of the topological invariant, second by adding time-reversal symmetry, which changes the nature of the topological invariant
Ellis, Jason Keith. "Emergent Phenomena in Classical and Quantum Systems: Cellular Dynamics in E. coli and Spin-Polarization in Fermi Superfluids." [Kent, Ohio] : Kent State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1256932939.
Повний текст джерелаLam, Ping Koy, and Ping Lam@anu edu au. "Applications of Quantum Electro-Optic Control and Squeezed Light." The Australian National University. Faculty of Science, 1999. http://thesis.anu.edu.au./public/adt-ANU20030611.170800.
Повний текст джерелаKonishi, Hideki. "Collisional stability of localized metastable ytterbium atoms immersed in a Fermi sea of lithium." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225386.
Повний текст джерелаKessel, Maximilian [Verfasser], Hartmut [Gutachter] Buhmann, and Grzegorz [Gutachter] Karczewski. "HgTe shells on CdTe nanowires: A low-dimensional topological insulator from crystal growth to quantum transport / Maximilian Kessel ; Gutachter: Hartmut Buhmann, Grzegorz Karczewski." Würzburg : Universität Würzburg, 2017. http://d-nb.info/1132995868/34.
Повний текст джерелаLiang, Dong. "Semiconductor Nanowires: Synthesis and Quantum Transport." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1327641946.
Повний текст джерелаForino, Paola Caterina. "Nuclear magnetic resonance study of the electron doped Dirac-Mott Insulator double perovskite Ba2Na(1-x)CaxOsO6." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Знайти повний текст джерелаDauphin, Alexandre. "Cold atom quantum simulation of topological phases of matter." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209076.
Повний текст джерелаIl existe cependant des phases qui échappent à la description de Landau. Il s'agit des phases quantiques topologiques. Celles-ci constituent un nouveau paradigme et sont caractérisées par un ordre global défini par un invariant topologique. Ce dernier classe les objets ou systèmes de la manière suivante: deux objets appartiennent à la même classe topologique s'il est possible de déformer continument le premier objet en le second. Cette propriété globale rend le système robuste contre des perturbations locales telles que le désordre.
Les atomes froids constituent une plateforme idéale pour simuler les phases quantiques topologiques. Depuis l'invention du laser, les progrès en physique atomique et moléculaire ont permis un contrôle de la dynamique et des états internes des atomes. La réalisation de gaz quantiques,tels que les condensats de Bose-Einstein et les gaz dégénérés de Fermi, ainsi que la réalisation de réseaux optiques à l'aide de faisceaux lasers, permettent d'étudier ces nouvelles phases de la matière et de simuler aussi la physique du solide cristallin.
Dans cette thèse, nous nous concentrons sur l'etude d'isolants topologiques avec des atomes froids. Ces derniers sont isolants de volume mais possèdent des états de surface qui sont conducteurs, protégés par un invariant topologique. Nous traitons trois sujets principaux. Le premier sujet concerne la génération dynamique d'un isolant topologique de Mott. Ici, les interactions engendrent l'isolant topologique et ce, sans champ de jauge de fond. Le second sujet concerne la détection des isolants topologiques dans les expériences d'atomes froids. Nous proposons deux méthodes complémentaires pour caractériser celles-ci. Finalement, le troisième sujet aborde des thèmes au-delà de la définition standard d'isolant topologique. Nous avons d'une part proposé un algorithme efficace pour calculer la conductivité de Berry, la contribution topologique à la conductivité transverse lorsque l'énergie de Fermi se trouve dans une bande d'énergie. D'autre part, nous avons utilisé des méthodes pour caractériser les propriétés quantiques topologiques de systèmes non-périodiques.
L'étude des isolants topologiques dans les expériences d'atomes froids est un sujet de recherche récent et en pleine expansion. Dans ce contexte, cette thèse apporte plusieurs contributions théoriques pour la simulation de systèmes quantiques sur réseau avec des atomes froids.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Foell, III Charles Alden. "Luminescent properties of Pb-based (PbX) colloidal quantum dots (CQDs) in vacuum, on silicon and integrated with a silicon-on-insulator (SOI) photonic integrated circuit (PIC)." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57665.
Повний текст джерелаScience, Faculty of
Physics and Astronomy, Department of
Graduate
Ekanayake, Sobhath Ramesh Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Qubit control-pulse circuits in SOS-CMOS technology for a Si:P quantum computer." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/43096.
Повний текст джерелаDuchon, Eric Nicholas. "Quantum Phase Transitions in the Bose Hubbard Model and in a Bose-Fermi Mixture." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386002245.
Повний текст джерелаFRANCESCHINI, PAOLO. "NOVEL SCHEMES FOR ULTRAFAST MANIPULATION OF QUANTUM MATERIALS." Doctoral thesis, Università Cattolica del Sacro Cuore, 2022. http://hdl.handle.net/10280/111822.
Повний текст джерелаThe possibility to control the electronic properties on-demand on an ultrafast time scale represents one of the most exciting challenges towards the realization of new generation photonic and electronic devices. Triggered by this, in the last decades the research activity focused its attention to different solid-state platforms. Among all, dielectric nanostructures (and metamaterials) and correlated materials represent the most promising candidate for the implementation of devices endowed by new functionalities. Apart from the specific features making dielectrics more suitable for photonic applications and correlated materials for electronic devices, both categories exhibit new functionalities if subjected to an external stimulus in the form of excitation light pulses shorter than the relaxation timescale of the internal degrees of freedom of the system. Indeed, the out-of-equilibrium state achieved upon photoexcitation exhibits electronic and optical properties highly different from those at equilibrium. Therefore, the aim of this thesis work consists in the development of new methods and experimental approaches capable to induce, measure, and control new functionalities in complex materials on an ultrafast time scale.
Wang, Fang. "Quantum phase transitions and fluctuations in space charge doped one unit-cell Bi2Sr2CaCu2O8+x." Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS436.
Повний текст джерелаThe superconductor-insulator transition in two dimensions is a continuous quantum phase transition at absolute zero temperature driven by external parameters like disorder, magnetic field, or carrier concentration. Such transitions have been induced in a variety of two dimensional superconductors by tuning different external parameters and studied with a finite-size scaling analysis. There is however not much uniformity in the findings as both the superconducting systems and the tuning parameters are diverse. In this thesis, we first fabricated high quality of one unit-cell BSCCO-2212 samples with anodic bonding technique, an original method of exfoliation developed in our laboratory for preparing high quality 2D crystals from layered bulk materials. Then we revealed the superconductor-insulator transition in the fabricated one unit-cell Bi2.1Sr1.9CaCu2O8+x by space charge doping, which in an effective field effect electrostatic doping technique. We determined the related critical parameters and develop a reliable way to estimate doping in the non-superconducting region, a crucial and central problem in these materials. Finite-size scaling analysis yields a critical doping of 0.057 holes/Cu, a critical resistance of ~ 6.85 kΩ and a scaling exponent product νz ~ 1.57. These results, together with earlier work in other materials, provide a coherent picture of the superconductor-insulator transition and its bosonic nature in the underdoped regime of emerging superconductivity in high critical temperature superconductors. Then in the latter part of this thesis, we also investigated the effects of inhomogeneity and fluctuations on superconducting transition on mesoscopic and nanoscopic scale both with simulation and with simulations and with analysis of transport measurements. The use of an ultra-thin sample also facilitates analysis on two fronts. Firstly, in two dimensions fluctuation phenomena related to the superconducting transition are exacerbated, making the analysis of changes in widths easier. Secondly aspects related to percolation and clustering can be easily simulated and compared with analytical models. Especially, the effects of fluctuations on the overdoped and underdoped side of the phase diagram of one unit-cell BSCCO-2212 are discussed. We discovered that the fluctuation regime in the underdoped part of the phase diagram is fundamentally different from that in the part where p > 0.19. We discussed the possible behaviour of cooper pairs related to our experimental results, as well as one existing theoretical explanation (BEC-BCStransition)
Monniello, Leonard. "Excitation résonante de boîtes quantiques pour la génération d'états non-classiques de la lumière." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066052/document.
Повний текст джерелаDevelopments in quantum information require controlling and manipulating quantum bits. Among solid state emitters, semiconductor quantum dots seem promising to realize quantum bits. First, the nanometric size of those structures leads to the confinement of the carriers in the three directions of space, so that their energy spectrum becomes atom-like. Furthermore, they can easily be integrated into electronic and optic devices. Such structures are studied for their optical properties, especially the emission of single and indistinguishable photons, which are quantum states of light. In the present work InAs/GaAs quantum dots have been studied under resonant excitation with picosecond laser pulses. One-dimensional waveguiding geometry has been used to suppress the scattered excitation laser allowing the observation of a single dot resonant luminescence. The coupling between the laser and the dot leads to the Rabi oscillations regime which enables to address a coherent superposition of states in the two-level system, meaning a quantum bit. However, the coupling between the dot and its environment changes the coherence properties of the dots, limiting the time during which operations on the qubits are possible. Two main phenomena have been observed and studied: the interaction between the dots and the longitudinal acoustic phonons of the GaAs matrix and the coupling with the electromagnetic mode. Finally, the photon emission statistics of the quantum dots have been studied, showing that quantum dots are on demand good emitters of indistinguishable single photons
Santos-Cottin, David. "Propriétés électroniques et de transport du semi-métal corrélé quasi-2D BaNiS2." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066139/document.
Повний текст джерелаThis work aims to clarify the mechanism of the metal-insulator transition (MIT) driven by doping x in the quasi-2D BaCo1-xNixS2 system. First of all, synthesize of high quality single crystals with substitution level x varying in the full 0 - 1 range was fundamental. It appears that the mechanism of the metal-insulator transition is associated to a continuous modification of metal-sulfurs distances. Then, we focus on an investigated the electronic properties of BaNiS2, precursor metallic phase of the MIT. Studies of the electronic structure of BaNiS2 by angle-resolved photoemission spectroscopy (ARPES) and by quantum oscillation measurements reveal the existence of two pockets at the Fermi surface: an electron-like 2D pocket centered in Γ(Z) and a hole-like pocket quasi-2D at mi-distance along ΓM(ZA) with a conic-like dispersion in kz = 0 . Furthermore, data also show a very large spin-orbit splitting at Γ and Z which is unexpected in a 3d metal compound. From previous studies, we developed a model to explain magnetotransport properties of BaNiS2. This model involves that BaNiS2 is a three carriers compensated metal: a majority holes p1 and electrons e1 carriers with moderate mobilities and a minor holes p2 carriers with a high mobility. The two different holes carries observed in magneto-transport could be explain by an important variation of the hole-like pocket dispersion along kz. Measures realized during this thesis are consistent and allowed to know precisely the form of the Fermi surface of BaNiS2 and its electronic properties which are more bi-dimensional than predict by conventional calculation
Pournia, Seyyedesadaf. "Exploring the Photoresponse and Optical Selection Rules in the Semiconductor Nanowires, Topological Quantum Materials and Ferromagnetic Semiconductor Nanoflakes using Polarized Photocurrent Spectroscopy." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627666632280473.
Повний текст джерелаEriksson, Hjalmar. "From the quantum Hall effect to topological insulators : A theoretical overview of recent fundamental developments in condensed matter physics." Thesis, Uppsala University, Theoretical Physics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126860.
Повний текст джерелаIn this overview I describe the simplest models for the quantum Hall and quantum spin Hall effects, and give some general indications as to the description of topological insulators. As a background to the theoretical models I will first trace the development leading up to the description of topological insulators . Then I will present Laughlin's original model for the quantum Hall effect and briefly discuss its limitations. After that I will describe the Kane and Mele model for the quantum spin Hall effect in graphene and discuss its relation to a general quantum spin Hall system. I will conclude by giving a conceptual description of topological insulators and mention some potential applications of such states.
Demion, Arnaud. "Transport électronique dans le graphène et les isolants topologiques 2D en présence de désordre magnétique." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4349.
Повний текст джерелаIn this thesis, we study the effect of a magnetic disorder on the electronic transport properties of graphene and HgTe-type 2D topological insulators. Graphene and topological insulators are materials whose electronic excitations are treated as massless Dirac fermions.The influence of magnetic impurities on the transport properties of graphene is investigated in the regime of strong applied electric fields. As a result of electron-hole pair creation, the response becomes nonlinear and dependent on the magnetic polarization.We investigate a transition between a two-dimensional topological insulator conduction state, characterized by a conductance G = 2 (in conductance quantum) and a Chern insulator with G = 1, induced by polarized magnetic impurities
Thomas, Candice. "Strained HgTe/CdTe topological insulators, toward spintronic applications." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY090/document.
Повний текст джерелаWith graphene-like transport properties governed by massless Dirac fermions and a topological protection preventing from backscattering phenomena, topological insulators, characterized by an insulating bulk and conducting surfaces, are of main interest to build low power consumption electronic building-blocks of primary importance for future electronics.Indeed, the absence of disorder, the generation of dissipation-less spin-polarized current or even the possibility to generate pure spin current without magnetic materials are some of the promises of these new materials.The objective of this PhD thesis has been to experimentally demonstrate the eligibility of HgTe three dimensional topological insulator system for applications and especially for spintronics.To do so, strong efforts have been dedicated to the improvement of the growth process by molecular beam epitaxy.Chemical composition, strain, defect density and sharpness of the HgTe interfaces have been identified as the major parameters of study and improvement to ensure HgTe inverted band structure, bulk gap opening and to emphasize the resulting topological surface state electronic properties. Verification of the topological nature of this system has then been performed using low temperature magneto-transport measurements of Hall bars designed with various HgTe thicknesses. It is worth noting that the high desorption rate of Hg has made the nanofabrication process more complex and required the development of a low temperature process adapted to this constraint. While the thicker samples have evidenced very complex transport signatures that need to be further investigated and understood, the thickness reduction has led to the suppression of any additional contributions, such as bulk or even side surfaces, and the demonstration of quantum Hall effect with vanishing resistance. Consequently, we have managed to demonstrate direct evidences of Dirac fermions by temperature dependent analysis of the quantum Hall effect. The next step has been to use the topological properties and especially the locking predicted between momentum and spin to test the HgTe potential for spintronics. Spin pumping experiments have demonstrated the power of these topological structures for spin injection and detection. Moreover, the implementation of HgTe into simple p-n junction has also been investigated to realize a first spin-based logic element