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Showing papers on "High-temperature superconductivity published in 2004"


Journal ArticleDOI
TL;DR: The arguments suggesting that metallic hydrogen, either as a monatomic or paired metal, should be a candidate for high temperature superconductivity are shown to apply to alloys of metallic hydrogen where hydrogen is a dominant constituent, for example, in the dense group IVa hydrides.
Abstract: The arguments suggesting that metallic hydrogen, either as a monatomic or paired metal, should be a candidate for high temperature superconductivity are shown to apply with comparable weight to alloys of metallic hydrogen where hydrogen is a dominant constituent, for example, in the dense group IVa hydrides. The attainment of metallic states should be well within current capabilities of diamond anvil cells, but at pressures considerably lower than may be necessary for hydrogen.

860 citations


Journal ArticleDOI
29 Jul 2004-Nature
TL;DR: In this paper, the scaling relation of the superfluid density with the superconducting transition temperature (T(c) was shown to hold regardless of doping level, nature of dopant (electrons versus holes), crystal structure and type of disorder, and direction.
Abstract: Since the discovery of superconductivity at elevated temperatures in the copper oxide materials there has been a considerable effort to find universal trends and correlations amongst physical quantities, as a clue to the origin of the superconductivity. One of the earliest patterns that emerged was the linear scaling of the superfluid density (rho(s)) with the superconducting transition temperature (T(c)), which marks the onset of phase coherence. This is referred to as the Uemura relation, and it works reasonably well for the underdoped materials. It does not, however, describe optimally doped (where T(c) is a maximum) or overdoped materials. Similarly, an attempt to scale the superfluid density with the d.c. conductivity (sigma(dc)) was only partially successful. Here we report a simple scaling relation (rho(s) proportional, variant sigma(dc)T(c), with sigma(dc) measured at approximately T(c)) that holds for all tested high-T(c) materials. It holds regardless of doping level, nature of dopant (electrons versus holes), crystal structure and type of disorder, and direction (parallel or perpendicular to the copper-oxygen planes).

229 citations



BookDOI
01 Jan 2004
TL;DR: In this paper, the authors proposed a discrete sine magneto-optical approach for the analysis of superconducting materials, which is based on the Dirick-Brockman approach.
Abstract: Preface. Group photo. List of contributors. Overview. Paving the way for the success of magneto-optics H.-U. Habermeier. Comparison of magneto-optical imaging with other local magnetic probes S.J. Bending, et al. MOI of superconductors. Magneto-optical investigation of superconducting materials A.A. Polyanskii, et al. Quantitative magneto-optics: Flux, current and electrical field imaging Ch. Jooss, et al. Magneto-optical imaging of Josephson vortices in layered superconductors V.K. Vlasko-Vlasov, et al. Magneto-optic investigation of magnetic flux penetration on a nanosecond timescale B. Biehler, et al. Magneto-optical imaging of superconducting vortices T.H. Johansen, et al. Magneto-optical imaging of pattern formation in the vortex landscape R.J. Wijngaarden, et al. MO-Imaging of granular and structured high temperature superconductors M.R. Koblischka, A. Koblischka-Veneva. First order transition of the vortex lattice in disordered Bi-2212 crystals K. van der Beek, et al. Magneto-optical measurements of the lifetime spectrum of transient vortex states in BSCCO B. Kalisky, et al. Magneto-optical imaging of crossing-lattices state in Bi2Sr2CaCu2O8+y T. Tamegai, et al. Strong 3D-correlation in the vortex system of Bi2212:Pb L.S. Uspenskaya, et al. Magneto-optical investigation of the vortex order-disorder phase transition in BSCCO B. Kalisky, et al. Magneto-optical studies of chemical inhomogeneities in Bi2212 single crystals N. Chikumoto, et al. Optimization of Bi2223 tape fabrication procedure with the help of magneto-optical imaging M. Roussel, et al. Magneto-optical imaging of cracking in high temperature superconducting films and tapes under tensile strain I.B. Rutel,et al. Magneto-optical imaging of magnetic screening in superconducting wires A.V. Pan, et al. Magneto-optical imaging of small angle grain boundaries on different bi-crystalline substrates K. Guth, et al. Low-angle grain boundaries of YBCO in external magnetic fields J. Albrecht. Electrodynamics of superconducting YBCO films with confined correlated nanodefects E. Mezzetti, et al. Magneto-optical studies of YBCO thick films in the critical state Z.X. Ye, et al. Modifying the current distribution of grain boundaries in YBCO films E. Brinkmeier, et al. Magneto-optical imaging of vortex penetration in patterned YBCO thin film near Tc S. Flament, et al. Proton irradiation induced effects on YBCO films analysed by magneto-optics L. Gozzelino, et al. Flux dynamics in current-carrying superconductors A.V. Bobyl, et al. Effect of substrate orientation and hydrogen impurities on flux penetration in Nb thin films M.S. Welling, et al. Flux jumps in magnesium diboride D.V. Shantsev, et al. Dendritic flux instabilities in Nb3Sn and NbN thin films I. Rudnev, et al. Thermo-magnetic instability as limiting mechanism for electrical current density in MgB2 thin films F. Laviano, et al. Surface penetration of high-Tc superconductors for MO imaging A. Koblischka-Veneva, M.R. Koblischka. Superconductor magneto-optics and theory E.H. Brandt. Inversion of the Biot-Savart law: An approach based on discrete sine and cosine transforms M. Dirickx, et al. MOI of magnetic materials. Domain structure and magnetic anisotrophy in Ga1-xMnxAs U. Welp, et al. Forensic imaging of magnetic tapes using magnetic garnet indicator films C. Krafft, et al. Manipulating magnetic particles

66 citations


Journal ArticleDOI
TL;DR: Magnetization results of YBa2Cu3O7−d films processed with interlayers of CeO2 inclusions are presented in this paper, where unexpected flux pinning results that are different from previous observations with nanoparticulate layered inclusions were observed.
Abstract: Magnetization results of YBa2Cu3O7−d films processed with interlayers of CeO2 inclusions are presented. Unexpected flux pinning results that are different from previous observations with nanoparticulate layered inclusions were observed. Flux pinning was found to be in some cases either slightly improved at either low fields 8T although degraded, sometimes severely, at interim magnetic fields. Most unexpectedly, the pinning performance of the various samples rapidly converges as the temperature is reduced from 77 to 65K, causing all films to have similar Jc(H) behavior at 65K even though dramatically different at 77K.

51 citations


Journal ArticleDOI
TL;DR: In this article, a numerical method is proposed to analyze the electromagnetic behavior of systems that include high-temperature superconductors, using the finite element method and the critical state model, and it solves two-dimensional and axially symmetric problems.
Abstract: A numerical method is proposed to analyze the electromagnetic behavior of systems that include high-temperature superconductors. The algorithm uses the finite-element method and the critical-state model, and it solves two-dimensional and axially symmetric problems that include superconductors and other materials. The main advantages of the algorithm are its speed, its robustness, and its ease of coupling with circuit equations. This method is used to analyze two different systems: 1) Magnet-superconductor levitation system-the levitation forces are calculated. In order to validate the model, experimental results of such a system are obtained and compared with simulation results. 2) Nine-wire superconducting cable. Parallel and series-type configurations of the current driven in the wires are analyzed. Hysteresis ac losses are also calculated and compared for both scenarios.

43 citations


Book
P Ford, G Saunders1
30 Jul 2004
TL;DR: The Rise of the Superconductors as discussed by the authors is an ideological chronology of the science that has produced superconductors, from high quality thin-films to frictionless transportation, their applications in industries such as telecommunications, environment and geology, medicine, nuclear physics, and security are just the beginning.
Abstract: High-temperature superconductors are one of the most active and exciting areas of condensed matter physics research. From high-quality thin-films to friction-less transportation, their applications in industries such as telecommunications, environment and geology, medicine, nuclear physics, and security are just the beginning.The Rise of the Superconductors is an ideological chronology of the science that has produced superconductors. Beginning with the first liquefaction of helium, the book presents the discovery of the Meissner effect and the development of type II superconductors before discussing the impact of Bednorz and Muller's Nobel prize-winning research in high temperature ceramic superconductors. Authors seamlessly introduce the rise of Tc materials, whose layer-like nature, anisotropic behavior, and other properties are discussed in Chapter 4. The next chapter is devoted to the discovery, development, and characteristics of organic superconductors, particularly in fullerene materials, whose discovery earned the Nobel Prize in Chemistry in 1996.The authors then examine the properties and theoretical developments explaining the behavior of simple superconductors, highlighting their impact on theoretical physics. Subsequent chapters analyze the technological advances, production challenges, and future directions of large- and small-scale applications, Josephson effects, the development of SQUID technology, and the specific behavior of high temperature superconductors. The Rise of the Superconductors concludes with a brief look at the struggle for technical superiority between the U.S. and Japan, European contributions, and commentary on the current state of the art.

33 citations


Journal ArticleDOI
TL;DR: In this paper, a field effect device was used to modify the number of holes in the surface layers of 4 to 10 unit cell Nd1.2Ba1.8Cu3Oy epitaxial films grown on (100) SrTiO3 substrates.
Abstract: Using a field effect device we modified the number of holes in the surface layers of 4 to 10 unit cell Nd1.2Ba1.8Cu3Oy (NBCO) epitaxial films grown on (100) SrTiO3 substrates. The results obtained on a set of 12 devices demonstrate that it is possible to induce reversible changes of the hole density of NBCO films by field effect. It is found that the field effect becomes less pronounced increasing the film thickness. Insulating–superconducting transition was observed in one 8 unit cell NBCO field effect device.

31 citations


Journal ArticleDOI
TL;DR: In this article, a fast method based on the finite element method is proposed to solve 2D and axially symmetric problems that contain superconducting materials, where an E-J power law together with an A-V formulation is used to calculate the induction of currents in the superconductor due to time-varying external magnetic fields or forced transport current.
Abstract: Numerical methods for calculating the current and field distribution in high-temperature superconductors under non-uniform time-varying fields are being investigated. The highly non-linear behaviour of superconductors makes them difficult to analyse and computationally expensive. This non-linear behaviour is often accounted for through a non-linear E–J constitutive law. This paper proposes a fast method based on the finite element method to solve 2D and axially symmetric problems that contain superconducting materials. An E–J power law together with an A–V formulation is used to calculate the induction of currents in the superconductor due to time-varying external magnetic fields or forced transport current. Experimental data of a magnet-above-superconductor system is obtained in order to validate the model. In the experimental set-up a magnet is brought towards a superconducting puck at different speed rates and is also vibrated on top of it. The force between the magnet and the superconductor is measured and is found to vary with both time and frequency of excitation.

28 citations


Journal ArticleDOI
TL;DR: In this paper, the transport properties of superconducting polycrystalline GdSr2RuCu2O8 have been studied by resistivity versus temperature measurements in external magnetic fields up to 8 T. The analysis of the experimental data shows that an activated pinning mechanism is present with low values of the pinning energy and that an irreversibility line (IL) can be identified as the limit of dissipation due to a 2D vortex motion.
Abstract: Transport properties of superconducting polycrystalline GdSr2RuCu2O8 have been studied by resistivity versus temperature measurements in external magnetic fields up to 8 T. The analysis of the experimental data shows that an activated pinning mechanism is present with low values of the pinning energy and that an irreversibility line (IL) can be identified as the limit of dissipation due to a two-dimensional (2D) vortex motion. Comparing these results with those commonly observed in the case of other high temperature superconductors, a similarity with the 2D vortex motion for BSCCO is observed. This fact has been discussed considering the possible role played by the magnetic Ru ions on the superconducting properties of the compound.

27 citations


Journal ArticleDOI
TL;DR: In this article, the superconducting order parameter in electron-doped high-temperature superconductors is calculated by fluctuation exchange approximation applied to a two-dimensional Hubbard model.
Abstract: The superconducting order parameter in electron-doped high-temperature superconductors is calculated by fluctuation exchange approximation applied to a two-dimensional Hubbard model. In contrast to hole-doped cases, the so-called hot spots are located near the diagonals of the Brillouin zone in the electron-doped superconductors; this is found to result in the nonmonotonic angular dependence of the order parameter of d x 2 - y 2 symmetry. This agrees with the implication obtained from electronic Raman scattering experiments, and the direct observation of this angular dependence is direct evidence of the superconductivity induced by antiferromagnetic spin fluctuations.

Journal ArticleDOI
TL;DR: Ginzburg and Leggett as discussed by the authors showed that the Ginzburg-Landau theory could be extended to include this new type of superconductors, which today are in common use.
Abstract: Superconducting material is used, for example, in magnetic resonance imaging for medical examinations and particle accelerators in physics. Knowledge about superfluid liquids can give us deeper insight into the ways in which matter behaves in its lowest and most ordered state. Work by the author on superconduction in liquid helium established the existence of type II superconductors and proved that vortex lattices exist in superfluid helium, in the presence of magnetic fields. He showed that the Ginzburg–Landau theory could be extended to include this “new” type of superconductors, which today are in common use. His work on phase transitions of these superconductors under the influence of magnetic fields was groundbreaking, although he has worked in many other areas since then. He was awarded the Nobel prize in 2003 “for pioneering contributions to the theory of superconductors and superfluids” with V. L. Ginzburg and A. J. Leggett.

Journal ArticleDOI
TL;DR: In this article, a fermiology approach to the computation of the magnetic susceptibility measured by neutron scattering in hole-doped high-T-c superconductors was used to estimate the effects on the incommensurate peaks caused by higher d-wave harmonics.
Abstract: Using a fermiology approach to the computation of the magnetic susceptibility measured by neutron scattering in hole-doped high-T-c superconductors, we estimate the effects on the incommensurate peaks caused by higher d-wave harmonics of the superconducting order parameter induced by underdoping. The input parameters for the Fermi surface and d-wave gap are taken directly from angle-resolved photoemission experiments on Bi2Sr2CaCu2O8+x (Bi2212). We find that higher d-wave harmonics lower the momentum-dependent spin gap at the incommensurate peaks as measured by the lowest spectral edge of the imaginary part in the frequency dependence of the magnetic susceptibility of Bi2212. This effect is robust whenever the fermiology approach captures the physics of high-T-c superconductors. At energies above the resonance we observe diagonal incommensurate peaks. We show that the crossover from parallel incommensuration below the resonance energy to diagonal incommensuration above it is connected to the values and the degeneracies of the minima of the two-particle energy continuum.

Journal ArticleDOI
TL;DR: In this article, the structural, transport, and magnetic properties of a series of samples in which the LSMO layer thickness is fixed at eight unit cells and that of YBCO varied from one to six unit cells were investigated.
Abstract: Oxide multilayers composed of ferromagnetic metallic layers of La0.67Sr0.33MnO3 (LSMO) and superconducting cuprate YBa2Cu3O7 (YBCO) were grown on LaAlO3 substrates by high-pressure dc sputtering. We have investigated the structural, transport, and magnetic properties of a series of samples in which the LSMO layer thickness is fixed at eight unit cells and that of YBCO varied from one to six unit cells. The superconducting transition temperature Tc0 determined from the resistance measurement is higher than the temperature of the onset of the diamagnetic response Td0. This result is discussed in the frames of the model proposed by E. B. Sonin and I. Felner [Phys. Rev. B. 57, R14000 (1998)] for a ferromagnetic superconductor. The model suggests the presence of the spontaneous vortex phase in the temperature interval Td0

Journal ArticleDOI
TL;DR: In this paper, the Vector-Controlled Model (VCM) has been used to model the force interaction between superconductors and external magnetic fields for practical multi-polar configurations.
Abstract: To describe the wide range of possible applications of high temperature superconductors (HTSCs) (e.g. magnetic bearings, levitation systems or electrical machines) several appropriate calculation algorithms have been developed. They determine the force interaction between a superconductor and any even multidimensional magnetic field excitation system. Especially good agreements between experiments and computed results have been obtained for the Vector‐Controlled Model, which seems to be the best approximation of the macroscopic superconductivity behaviour. The validation of this model by means of measurements makes it a powerful tool for the design and optimisation of any HTSC application in the field of force generation. It can be used not only for the designing of levitation applications, but also to help the understanding of the flux penetration, flux trapping and magnetisation of bulk superconductors in non‐uniform magnetic fields. By means of this model, the force interaction between superconductors and external magnetic fields for practical multi‐polar configurations, e.g. superconducting levitation systems or inherently stable superconducting bearings has been determined. Furthermore, the time dependency of the forces taking flux flow and flux creep into account, can be considered.

Journal ArticleDOI
TL;DR: In this article, experimental conditions for simultaneous measurements of transport coefficients of high temperature superconductors in zero and non-zero magnetic fields are analyzed and a new experimental set-up built based on a closed cycle helium refrigerator is suggested.

Journal ArticleDOI
TL;DR: In this paper, the spontaneous current and spontaneous phase difference are manifestations of the time-reversal symmetry (T ) breaking states in the system, and the phase dependences of spontaneous current flows along the interface are analyzed.
Abstract: The modern physics of superconductivity can be called the physics of unconventional superconductivity. The discovery of the d-wave symmetry of the order parameter in high-temperature superconductors and the triplet superconductivity in compound Sr2RuO4 has caused a huge stream of theoretical and experimental investigations of unconventional superconductors. In this review we discuss some novel aspects of the Josephson effect which are related to the symmetry of the order parameter. The most intriguing of them is spontaneous current generation in an unconventional weak link. The example of a Josephson junction in the form of a grain boundary between two disorientated d-wave or f-wave superconductors is considered in detail. Josephson current–phase relations and the phase dependences of the spontaneous current that flows along the interface are analyzed. The spontaneous current and spontaneous phase difference are manifestations of the time-reversal symmetry (T ) breaking states in the system. We analyzed t...

Journal ArticleDOI
TL;DR: In this paper, the authors measured the ac losses in three disk-shaped YBa2Cu3O7 (YBCO) films, which were deposited on SrTiO3 by the pulsed-laser-deposition technique and had thicknesses, d, of 2, 10, and 30 μm, measured in perpendicular applied ac magnetic fields to ∼014 T at 10 Hz in liquid nitrogen.
Abstract: The ac losses in three disk-shaped YBa2Cu3O7 (YBCO) films, which were deposited on SrTiO3 by the pulsed-laser-deposition technique and had thicknesses, d, of 02, 10, and 30 μm, were measured in perpendicular applied ac magnetic fields to ∼014 T at 10 Hz in liquid nitrogen The losses at low fields were found to be a strong function of the film thickness The measured losses were compared with the theoretically calculated losses The ac losses calculated using a field-independent critical-current density, the Bean model [J R Clem and A Sanchez, Phys Rev B 50, 9355 (1994)], agreed very well with the 02-μm-thick film, while the calculated losses agreed well with the measured ones when a field-dependent critical-current density, the Kim model [D V Shantsev, Y M Galperin, and T H Johansen, Phys Rev B 61, 9699 (2000)], was used for the films of thickness 10 and 30 μm However, a surprising discrepancy was found in the values of Bc and B0 for thinner YBCO films depending on whether they were

Journal ArticleDOI
Sen Zhou1, Ziqiang Wang1
TL;DR: In this article, a large-scale model of a doped Mott insulator in connection to high-${T}_{c}$ superconductors was proposed and solved in the large-$N$ limit.
Abstract: We study the $t\text{\ensuremath{-}}J\text{\ensuremath{-}}V$ model of a doped Mott insulator in connection to high-${T}_{c}$ superconductors. The nearest neighbor Coulomb interaction $(V)$ is treated quantum mechanically on equal footing as the antiferromagnetic exchange interaction $(J)$. Motivated by the $SU(2)$ symmetry at half-filling, we construct a large-$N$ theory which allows a systematic study of the interplay between staggered flux order and superconductivity upon doping. We solve the model in the large-$N$ limit and obtain the ground state properties and the phase diagram as a function of doping. We discuss the competition and the coexistence of the staggered flux and the $d$-wave superconductivity in the underdoped regime and the disappearance of superconductivity in the overdoped regime.

Journal ArticleDOI
TL;DR: In this paper, the advantages of high pressure in studying high T c superconductors (HTSs) were discussed, and the crystal structure assembly of HTSs was described on the basis of the extended infinite layer model.
Abstract: We discuss the advantages of high pressure in studying high T c superconductors (HTSs). HTSs, in general, can be viewed as perovskite derivatives containing a [CuO2] plane. We will describe the crystal structure assembly of HTSs on the basis of the ‘extended infinite layer model’. Then, we introduce some topics related to high pressure synthesized superconductors in A–Cu–O systems (A represents alkaline earth elements) like the Cu-12(n − 1)n superconducting homologous series. Also included in the article is the high pressure high temperature synthesized Cl-02(n-1)n superconducting homologous series, highlighting the ‘apical oxygen doping’ mechanism to generate p-type superconductivity.

BookDOI
01 Jan 2004
TL;DR: From the combination of knowledge and actions, someone can improve their skill and ability as discussed by the authors. This is why, the students, workers, or even employers should have reading habit for books.
Abstract: From the combination of knowledge and actions, someone can improve their skill and ability. It will lead them to live and work much better. This is why, the students, workers, or even employers should have reading habit for books. Any book will give certain knowledge to take all benefits. This is what this high temperature superconductivity 2 tells you. It will add more knowledge of you to life and work better. Try it and prove it.

Proceedings ArticleDOI
22 Jul 2004
TL;DR: Normal zone generation and propagation measurements were conducted on Ag-coated YBa2Cu3O7−δ/Ni-alloy coated conductors in this paper, where the samples were conduction cooled by a cryocooler in a vacuum, establishing nearly adiabatic conditions.
Abstract: Normal zone generation and propagation measurements were conducted on Ag‐coated YBa2Cu3O7−δ/Ni‐alloy coated conductors. The samples were conduction cooled by a cryocooler in a vacuum, establishing nearly adiabatic conditions. A NiCr wire heater was pulsed to generate a localized normal region allowing measurements of quench energies, at which the normal zone propagates. The normal zone propagation velocities are also reported.

Journal ArticleDOI
TL;DR: Angle-resolved photoemission spectroscopy reveals very surprising strain-induced effects on the electronic band dispersion of epitaxial La2-xSrxCuO4-delta thin films, requiring a radical departure from commonly accepted notions about strain effects on high temperature superconductors.
Abstract: A Comment on the Letter by M. Abrecht et al., Phys. Rev. Lett. 91, 057002 (2003).. The authors of the Letter offer a Reply.

Book ChapterDOI
TL;DR: For classical superconductors, it took about half a century from their discovery to arrive at technically applicable materials as discussed by the authors and only about a third of this time has elapsed for High-Temperature Superconductors (HTS) where a number of technically applicable material species is now already available.
Abstract: For classical superconductors it took about half a century from their discovery to arrive at technically applicable materials. Only about a third of this time has elapsed for High-Temperature Superconductors (“ HTS” ) where a number of technically applicable materials species is now already available.

Proceedings ArticleDOI
06 Jun 2004
TL;DR: In this paper, the performance of high temperature superconducting (HTS) preselect receive filters for satellite communication at 30 GHz was compared with metal-based planar filters.
Abstract: The objective of this study is to show the interest of superconductivity at 30 GHz compared to traditional planar technologies used at ambient and low temperatures. This paper presents the design and the measures at 77 K of high temperature superconducting (HTS) preselect receive filters for satellite communication. Comparisons of HTS and metal based planar filters have shown the performance gap between both at 30 GHz.

Book ChapterDOI
01 Oct 2004


Journal ArticleDOI
TL;DR: In this paper, the Froehlich-Coulomb multi-polaron model of high-temperature superconductivity was extended to the strong coupling regime with the long-range electron-phonon interaction.
Abstract: Strong electron-phonon interactions in cuprates and other high-temperature superconductors have gathered support over the last decade in a large number of experiments. Here I briefly introduce the Froehlich-Coulomb multi-polaron model of high-temperature superconductivity, which includes strong on-site repulsive correlations and the long-range Coulomb and electron-phonon (e-ph) interactions. Our extension of the BCS theory to the strong-coupling regime with the long-range \emph{unscreened} electron-phonon interaction could naturally explain the isotope effects, unconventional thermomagnetic transport, and checkerboard modulations of the tunnelling density of states in cuprates.

Journal ArticleDOI
TL;DR: In this article, an overview of research at the authors' department on the manufacturing of superconductors, especially Ag/BSCCO tape produced by the oxide-powder-in-tube method (OPIT), is presented.

Patent
Ursus Krüger1, Raymond Ullrich1
08 Dec 2004
TL;DR: In this paper, the cold gas spraying method uses particles (19) which are chemical components of high temperature superconductors, e.g., YBa 2Cu 3O 7.
Abstract: Cold gas spraying method uses particles (19) which are chemical components of high temperature superconductors, e.g. YBa 2Cu 3O 7. They are sprayed onto a substrate (13) with a crystal structure corresponding to that of the superconductors. The gas is a reactive gas, especially oxygen, and is built into the superconductor layer.