Dissertationen zum Thema „Supraconducteur désordonné“
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AKAABOUNE, NOR-EDDINE. „Diagramme de phase (H,T) du supraconducteur organique (TMTSF)2ClO4 faiblement désordonné“. Phd thesis, Université Paris Sud - Paris XI, 2002. http://tel.archives-ouvertes.fr/tel-00002215.
Der volle Inhalt der QuelleAkaaboune, Nor-Eddine. „Diagramme de phase (H, T) du supraconducteur organique (TMTSF)2ClO4 faiblement désordonné“. Paris 11, 2002. https://tel.archives-ouvertes.fr/tel-00002215.
Der volle Inhalt der QuelleThe present thesis work, was focusing in particular, on the superconducting state of quasi one dimensional organic conductor (TMTSF)2ClO4. We have determined a new vortex phase diagram of this compound, by interlayer transport measurement, performed under magnetic field applied perpendicular to the layers. Starting from an analysis of the critical current and the superconducting fluctuations, we have demonstrated that the electronic structure of (TMTSF)2ClO4 is three dimensional in nature and the transport along the weakest conductivity axis (c-axis) is very coherent although the coupling is weak in this direction. In the mixed state, the pinning energy in the liquid phase shows a 1/H dependence which corresponds to the plastic bending of the flux line lattice. Finally, we have also studied the effect of the disorder introduced by different thermal cooling rates. Our results show strong modifications on the superconducting parameters
Marrache-Kikuchi, Claire. „Effets dimensionnels dans un système désordonné au voisinage de la Transition Supraconducteur-Isolant“. Habilitation à diriger des recherches, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00929767.
Der volle Inhalt der QuelleMarrache-Kikuchi, Claire. „Effets dimensionnels dans un système désordonné au voisinage des transitions métal-isolant et supraconducteur-isolant“. Phd thesis, Université Paris Sud - Paris XI, 2006. http://tel.archives-ouvertes.fr/tel-00325067.
Der volle Inhalt der QuelleMarrache-Kikuchi, Claire Akiko. „Effets dimensionnels dans un système désordonné au voisinage des transitions métal-isolant et supraconducteur-isolant“. Paris 11, 2006. https://tel.archives-ouvertes.fr/tel-00325067.
Der volle Inhalt der QuelleLow temperature transport in disordered conducting materials imply quantum interference, Coulomb repulsion, and superconducting fluctuations. Since 2D is the lower critical dimension for the existence of metallic and superconducting states, we have studied two quantum phase transitions – the Superconductor-to-Insulator Transition (SIT) and the Metal-to-Insulator Transition (MIT) – when the thickness of a disordered system – here a-NbSi – is lowered. The underlying problem is the transition between the different states and the conditions for a 2D metal to exist. We have studied the field and disorder-induced SIT. The principal characteristics we have observed (renormalization, role of the field orientation) are well explained by M. P. A. Fisher's theory. However, we do not find the critical exponents values and a universal resistance at the transition as predicted by this theory. Concerning the MIT, we have decreased the thickness of a metallic system to reach the dimension 2 and an insulating state. In both transitions, the passage to the insulating state clearly shows the existence of dissipative states at zero temperature that are not predicted by conventional theories. We propose an interpretation of all our results that implies the existence of a novel phase in 2D, a Bose Metal, between the superconducting and the metallic states. This new state has been predicted by recent theories. We trace the corresponding phase diagram for the model system NbSi with respect to concentration and film thickness
Crauste, Olivier. „Étude des transitions de phases quantiques supraconducteur -- isolant, métal -- isolant dans des matériaux amorphes désordonnés proches de la dimension 2“. Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00579256.
Der volle Inhalt der QuelleCouëdo, François. „Transitions de phase quantiques dans les systèmes désordonnés de basse dimension“. Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00990782.
Der volle Inhalt der QuelleStanisavljević, Ognjen. „High kinetic inductance-based microwave photon detection“. Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP038.
Der volle Inhalt der QuelleSingle photon detectors at visible frequencies have been essential tools in many areas of quantum technology, such as quantum key distribution or quantum optics. However, realizing highly efficient continuous single microwave photon detectors remains challenging. In this thesis, we propose and implement a microwave photon detector based on a superconducting tunnel junction coupled to a microwave cavity. Incident photons at resonator frquency are absorbed by the junction via inelastic quasiparticle tunneling, resulting in measurable photo-assisted tunneling current. To increase the inealstic tunneling rate, the resonator is fabricated in granular aluminium, leading to the mode characteristic impedance on the order of quantum of resistance. By measuring the current due to higher order processes, we calibrate the detector and estimate the quantum efficiency to be 0.83 --- an order of magnitude higher than reported in literature for detectors based on photo-assisted tunneling. In addition to the photo-assisted current, the power emitted by the sample is measured, and it is shown that the same device could be utilized to effectively cool superconducting circuits. We discuss the compatibility of the implemented photon detector with charge counting techniques required for discerning individual electrons, such as RF-SETs. We realize an RF-SET using a high-impedance granular aluminum resonator, and show high photon absorption for suitable bias and gate voltages. Additionally, we measure the charge sensitivity of this device as low as 5e-5 e/sqrt(Hz). Thus, the experiments in this work show that combining a radio-frequency single-electron transistor with a high efficiency photon to electron converter based on inelastic tunneling could lead to a practical single microwave photon counter
Van, Der Beek Cornelis Jacominus. „Thermodynamique des vortex dans les supraconducteurs désordonnés“. Habilitation à diriger des recherches, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00483670.
Der volle Inhalt der QuelleDubouchet, Thomas. „Spectroscopie locale à basse température dans des systèmes supraconducteurs désordonnés“. Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENY036.
Der volle Inhalt der QuelleThis thesis presents a study combining tunneling spectroscopy, point-contact Andreev spectroscopy and electronic transport on disordered superconducting indium oxide samples. Transport measurements reveal a diverging resistivity from room temperature shortcut by superconductivity at low temperature. This behavior shows that our samples are in the vicinity of the metal-insulator Anderson transition. Tunneling spectroscopy highlights a rather unusual superconducting state with a pseudogap regime above the critical temperature. It evolves at low temperature into an inhomogeneous system composed of both superconducting Cooper pairs and Cooper pairs without phase coherence, localized by the disorder. Comparison between different samples shows that incoherent Cooper pairs proliferate with increasing level of disorder, what indicates that superconductor-insulator transition in indium oxide is governed by the progressive localization of Cooper pairs. Besides, using our STM, we have continuously analyzed the local conductance between tunneling regime and contact regime. Andreev spectroscopy thus reveals a new energy scale related to the superconducting phase coherence and independent from spatial fluctuations of the density of states measured in tunneling regime. This shows that disorder induces a dichotomy between the pairing energy characterizing the binding of electrons into pairs and the coherence energy specific to macroscopic superconductivity
Dubouchet, Thomas. „Spectroscopie locale à basse température dans des systèmes supraconducteurs désordonnés“. Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00576226.
Der volle Inhalt der QuellePautrat, Alain. „Etude des réseaux de vortex supraconducteurs et de systèmes électroniques désordonnés“. Habilitation à diriger des recherches, Université de Caen, 2009. http://tel.archives-ouvertes.fr/tel-00431683.
Der volle Inhalt der QuelleRopers, Bruno. „Synthèse et propriétés physiques de matériaux composites désordonnés supraconducteurs YBaCuO-argent“. Bordeaux 1, 1992. http://www.theses.fr/1992BOR10523.
Der volle Inhalt der QuelleDi, Scala Nicolas. „TRANSITION DE DÉPIÉGEAGE DANS LES RÉSEAUX DE VORTEX SUPRACONDUCTEURS : ÉTUDE PAR SIMULATION NUMÉRIQUE“. Phd thesis, Université François Rabelais - Tours, 2012. http://tel.archives-ouvertes.fr/tel-00741545.
Der volle Inhalt der QuelleSvetogorov, Aleksandr. „Théorie de sauts de phase quantiques dans des supraconducteurs uni-dimensionnels désordonnés“. Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY036.
Der volle Inhalt der QuelleIn this thesis quantum phase slips in one-dimensional superconductors are studied. One-dimensional superconductors can be represented by two physical systems: a superconducting wire and a Josephson junction chain. A superconducting wire can be considered one-dimensional, if its transverse dimensions are smaller than the superconducting coherence length. In one-dimensional systems fluctuations strongly influence the system properties. The quantum phase slips correspond to quantum tunneling between different phase configurations along the superconductor. They can be of two types. Coherent quantum phase slips do not involve dissipation and only shift energy levels of the system. Incoherent quantum phase slips lead to a dissipative relaxation in the system.We start with studying an incoherent phase-slip process in a single underdamped current-biased Josephson junction. This process corresponds to dissipative tunneling between weakly broadened levels in neighboring minima of the tilted washboard potential. We derive an expression for the voltage peaks near the resonant values of the external current, which correspond to matching energies of the lowest level in one minimum and an excited level in the lower neighboring minimum. This process is analogous to resonant Zener breakdown known for electrons in a superlattice subject to a strong electric field.We continue with studying coherent quantum phase slips in a Josephson junction chain. First, we determine the amplitude of a coherent quantum phase slip in a homogeneous chain. It has already been shown that the amplitude is determined by the imaginary-time instanton action, which can be divided into the local (corresponding to phase winding by 2π on one junction) and environmental (corresponding to phase readjustment in the rest of the chain, which is determined by gapless Mooij-Schön modes) parts. We derive a numerical correction to the environmental part of the action, going beyond logarithmic precision. Second, we study the effect of spatial periodic modulations of the chain parameters on the coherent quantum phase slip process. We calculate the corrections both to the local and environmental part of the coherent quantum phase slip action and show that both of them can be significant, depending on the chain and modulations parameters. Then, we study the effect of two types of quenched disorder: random spatial modulation of the junction areas and random induced background charges. The main result is that the dominant contribution to the coherent quantum phase slip action is local. We also study the statistics of the mesoscopic fluctuations of the quantum phase slips amplitude and show that it can be non-Gaussian for chains which are not sufficiently long.Finally, we consider one-dimensional superconducting wires. There is no microscopic theory available for the fast phase winding in the phase-slip core, where the order parameter is suppressed. However, the slow phase readjustment process, determined by the Mooij-Schön modes with frequencies lower than 2Δ, is analogous to that in Josephson junction chains, so the resulting environmental part of the coherent quantum phase slip action takes the same form. Therefore, we discuss how our results, obtained for Josephson junction chains, can be applied to inhomogeneous superconducting wires
Humbert, Vincent. „Etude des états fondamentaux dans des systèmes supraconducteurs désordonnés de dimension 2“. Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS149/document.
Der volle Inhalt der QuelleAn initially superconducting 3D material can have different ground states, depending on its disorder : superconducting, metallic or insulating. At lower dimensionality, Anderson localization theoretically forbids any metallic state. A change in disorder then induces a direct Superconductor-to-Insulator Transition (SIT). The presence of strong Coulomb interactions, which are not taken into account in conventional theories, may disrupt this paradigm and enable the emergence of 2D metallic phases, thus complicating the generally admitted picture for the SIT. Indeed, recent work has revealed the existence of two distinct metallic phases in a-NbxSi1-x thin films, in between the superconducting and insulating states.During this work, we have studied the low frequency transport properties of amorphous NbxSi1-x films at low temperatures (T<1K), in order to characterize the evolution of their ground state with disorder. In our films, disorder has been tuned by varying the heat treatment temperature, the thickness or the composition. We have then focused on the destruction of these metallic states, giving rise to an insulating state. Through the analysis of conduction laws in the insulating regime, we have quantified the evolution of its properties – in particular its characteristic energies – as disorder is varied. We could then conclude that the insulating phase can essentially be accounted for by a fermionic model. At lower disorder level, in the 2D metallic phase neighboring the insulator, we have evidenced precursor signs of the insulating state which continuously evolve until and through the 2D Metal-to-Insulator Transition. We offer an interpretation of all our results implying the existence of two parallel channels which relative importance is determined by the sample disorder level : one is fermionic, the other governed by superconducting fluctuations which persist even when the macroscopic phase coherence is lost. The metallic state is then dominated by the latter, whereas, in the insulator, fermionic excitations prevail.In a second part, we report on the experimental development of a calibration device for the broadband reflectometry measurement of thin films at microwave frequencies (GHz) and low temperatures (T<4K). This apparatus aims at measuring, during a single cool down, the reflection of known references as well as of the sample. The obtained calibration enables to obtain the absolute value of the films complex impedance, independently of the microwave environment. The results obtained on superconducting Vanadium films, compared with theories of superconductivity, enabled a first validation of the setup and of its working principle. This calibration device is therefore operational to measure more complex systems, such as thin films in the vicinity of the SIT
Bocquet, Marc. „Chaînes de Spins, Fermions de Dirac, et Systèmes Désordonnés“. Phd thesis, Ecole Polytechnique X, 2000. http://tel.archives-ouvertes.fr/tel-00001560.
Der volle Inhalt der QuelleAberkane, Clementine. „Nano-scale electronic inhomogeneities in ultra-thin superconducting NbN“. Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066644/document.
Der volle Inhalt der QuelleIn order to better understand the various processes taking place at the superconductor-insulator transition (SIT), we have probed simultaneously the global and local electronic properties of NbN ultrathin films, elaborated ex-situ on sapphire substrate. The transition was approached by reducing the films thickness, increasing the normal state square resistance to several kiloOhms. The corresponding Tc's of the studied films ranged from about Tc≈15K, which is close to TC-bulk, to Tc≈3.8K (Tc/TC-bulk≈0.23). In the range 0.4TC-bulk
Aberkane, Clementine. „Nano-scale electronic inhomogeneities in ultra-thin superconducting NbN“. Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066644.
Der volle Inhalt der QuelleIn order to better understand the various processes taking place at the superconductor-insulator transition (SIT), we have probed simultaneously the global and local electronic properties of NbN ultrathin films, elaborated ex-situ on sapphire substrate. The transition was approached by reducing the films thickness, increasing the normal state square resistance to several kiloOhms. The corresponding Tc's of the studied films ranged from about Tc≈15K, which is close to TC-bulk, to Tc≈3.8K (Tc/TC-bulk≈0.23). In the range 0.4TC-bulk