Sample records for superconducting energy gaps

  1. Abrupt onset of a second energy gap at the superconducting transition of underdoped Bi2212

    SciTech Connect

    Hussain, Zahid; Lee, W.S.; Vishik, I.M.; Tanaka, K.; Lu, D.H.; Sasagawa, T.; Nagaosa, N.; Devereaux, T.P.; Hussain, Z.; Shen, Z.-X.

    2007-05-26

    he superconducting gap--an energy scale tied to the superconducting phenomena--opens on the Fermi surface at the superconducting transition temperature (Tc) in conventional BCS superconductors. In underdoped high-Tc superconducting copper oxides, a pseudogap (whose relation to the superconducting gap remains a mystery) develops well above Tc (refs 1, 2). Whether the pseudogap is a distinct phenomenon or the incoherent continuation of the superconducting gap above Tc is one of the central questions in high-Tc research3, 4, 5, 6, 7, 8. Although some experimental evidence suggests that the two gaps are distinct9, 10, 11, 12, 13, 14, 15, 16, 17, 18, this issue is still under intense debate. A crucial piece of evidence to firmly establish this two-gap picture is still missing: a direct and unambiguous observation of a single-particle gap tied to the superconducting transition as function of temperature. Here we report the discovery of such an energy gap in underdoped Bi2Sr2CaCu2O8+delta in the momentum space region overlooked in previous measurements. Near the diagonal of Cu?O bond direction (nodal direction), we found a gap that opens at Tc and has a canonical (BCS-like) temperature dependence accompanied by the appearance of the so-called Bogoliubov quasi-particles, a classical signature of superconductivity. This is in sharp contrast to the pseudogap near the Cu?O bond direction (antinodal region) measured in earlier experiments19, 20, 21.

  2. Introduction to Superconductivity Energy gap Andreev Reflection Theory Procedure and Results Conclusion A study of Andreev Reflection in Nb/Ge/Al

    E-print Network

    Petta, Jason

    Introduction to Superconductivity Energy gap Andreev Reflection Theory Procedure and Results Department of Physics Princeton University August 10, 2007 #12;Introduction to Superconductivity Energy gap Andreev Reflection Theory Procedure and Results Conclusion Introduction to Superconductivity

  3. Search for Superconducting Energy Gap in UPt3 by Point-Contact Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gouchi, Jun; Sumiyama, Akihiko; Yamaguchi, Akira; Motoyama, Gaku; Kimura, Noriaki; Yamamoto, Etsuji; Haga, Yoshinori; ?nuki, Yoshichika

    2015-03-01

    We have investigated the differential resistance of the point contacts between heavy-fermion superconductor UPt3 and a normal metal Pt, which were fabricated using a commercial piezo-electric actuator, and retried the observation of the energy gap of UPt3. A V-shaped dip is observed in both normal and superconducting states and disappeared around TK ~ 20 K, suggesting that it is related to the Kondo effect. Below the superconducting transition temperature, a shallow double-minimum structure, which indicates the energy gap, has been observed for the contacts on the faces perpendicular to the a-, b- and c-axes of UPt3.

  4. Direct observation of the superconducting energy gap developing in the conductivity spectra of niobium

    E-print Network

    Roshchin, Igor V.

    is evaluated using infrared reflection measurements. Below the 8.31-K superconducting tran- sition temperature played a critical role in the confirmation of the Bardeen-Cooper-Schrieffer BCS theory of super through thin Sn and Pb films,4 which helped to establish the existence of the super- conducting energy gap

  5. Anisotropy of the Fermi surface, Fermi velocity, many-body enhancement, and superconducting energy gap in Nb

    NASA Astrophysics Data System (ADS)

    Crabtree, G. W.; Dye, D. H.; Karim, D. P.; Campbell, S. A.; Ketterson, J. B.

    1987-02-01

    The detailed angular dependence of the Fermi radius kF, the Fermi velocity vF(k), the many-body enhancement factor ?(k), and the superconducting energy gap ?(k), for electrons on the Fermi surface of Nb are derived with use of the de Haas-van Alphen (dHvA) data of Karim, Ketterson, and Crabtree [J. Low Temp. Phys. 30, 389 (1978)], a Korringa-Kohn-Rostoker parametrization scheme, and an empirically adjusted band-structure calculation of Koelling. The parametrization is a nonrelativistic five-parameter fit allowing for cubic rather than spherical symmetry inside the muffin-tin spheres. The parametrized Fermi surface gives a detailed interpretation of the previously unexplained ?, ?', and ?'' orbits in the dHvA data. Comparison of the parametrized Fermi velocities with those of the empirically adjusted band calculation allow the anisotropic many-body enhancement factor ?(k) to be determined. Theoretical calculations of the electron-phonon interaction based on the tight-binding model agree with our derived values of ?(k) much better than those based on the rigid-muffin-tin approximation. The anisotropy in the superconducting energy gap ?(k) is estimated from our results for ?(k), assuming weak anisotropy.

  6. Effects of spiral electric gaps in superconducting cyclotrons

    NASA Astrophysics Data System (ADS)

    Gordon, M. M.

    1980-03-01

    The K = 500 MeV superconducting cyclotron being built here has an RF system containing three dees with spiral electric gaps. These gaps produce a significant force component transverse to the ion orbits. An analysis is presented which shows nevertheless that the effect of such gaps does not alter the relevant orbit period, in accordance with an unpublished theorem due to McMillan. The structure of the "Spiral Gap" orbit program is then described. This program calculates ion orbits in a given magnetic field and provides a systematic treatment of the transverse as well as the longitudinal electric force resulting from spiral electric gaps. Sample results are presented which show that there is no significant difference in the phase-energy history of ion orbits accelerated with spiral or non-spiral electric gaps. A discussion of central ray orbits and accelerated equilibrium orbits is also presented together with analytical and computer results.

  7. Extended Supersymmetry in Gapped and Superconducting Graphene

    E-print Network

    V. K. Oikonomou

    2014-11-30

    In view of the many quantum field theoretical descriptions of graphene in $2+1$ dimensions, we present another field theoretical feature of graphene, in the presence of defects. Particularly, we shall be interested in gapped graphene in the presence of a domain wall and also for superconducting graphene in the presence of a vortex. As we explicitly demonstrate, the gapped graphene electrons that are localized on the domain wall are associated with four $N=2$ one dimensional supersymmetries, with each pair combining to form an extended $N=4$ supersymmetry with non-trivial topological charges. The case of superconducting graphene is more involved, with the electrons localized on the vortex being associated with $n$ one dimensional supersymmetries, which in turn combine to form an $N=2n$ extended supersymmetry with no-trivial topological charges. As we shall prove, all supersymmetries are unbroken, a feature closely related to the number of the localized fermions and also to the exact form of the associated operators. In addition, the corresponding Witten index is invariant under compact and odd perturbations.

  8. Transient increase of the energy gap of superconducting NbN thin films excited by resonant narrow-band terahertz pulses.

    PubMed

    Beck, M; Rousseau, I; Klammer, M; Leiderer, P; Mittendorff, M; Winnerl, S; Helm, M; Gol'tsman, G N; Demsar, J

    2013-06-28

    Observations of radiation-enhanced superconductivity have thus far been limited to a few type-I superconductors (Al, Sn) excited at frequencies between the inelastic scattering rate and the superconducting gap frequency 2?/h. Utilizing intense, narrow-band, picosecond, terahertz pulses, tuned to just below and above 2?/h of a BCS superconductor NbN, we demonstrate that the superconducting gap can be transiently increased also in a type-II dirty-limit superconductor. The effect is particularly pronounced at higher temperatures and is attributed to radiation induced nonthermal electron distribution persisting on a 100 ps time scale. PMID:23848912

  9. Temperature dependence of superconducting gap and penetration depth for MgB2

    NASA Astrophysics Data System (ADS)

    Karakaya, Seniye; Ozbas, Omer

    2012-09-01

    In this study, we have investigated both the temperature dependence of magnetic penetration depth and superconducting energy gap for magnesium diboride (MgB2) by considering several models such as Bardeen-Cooper-Schrieffer (BCS), two fluids and two band Eliashberg model. These models are compared with each others and available literature results. Several studies reported that MgB2 has two different superconducting gaps. That is, the multi-band superconductor MgB2 exhibits two dimensional (2D) ?-band and three-dimensional (3D) ?-band superconductivity and have the remarkably high critical temperature (Tc= 39K) all of the metallic superconductors. So, recently it has attracted great attention. The superconductivity in MgB2 has been analyzed by using two band Eliashberg model. We also have calculated the temperature dependence of the superconducting gaps (?? and ??) and compared them with the available experimental data and the other theoretical predictions.

  10. Nodal to Nodeless Superconducting Energy-Gap Structure Change Concomitant with Fermi-Surface Reconstruction in the Heavy-Fermion Compound CeCoIn5

    NASA Astrophysics Data System (ADS)

    Kim, Hyunsoo; Tanatar, M. A.; Flint, R.; Petrovic, C.; Hu, Rongwei; White, B. D.; Lum, I. K.; Maple, M. B.; Prozorov, R.

    2015-01-01

    The London penetration depth ? (T ) was measured in single crystals of Ce1 -xRxCoIn5 , R =La , Nd, and Yb down to Tmin?50 mK (Tc/Tmin˜50 ) using a tunnel-diode resonator. In the cleanest samples ? ? (T ) is best described by the power law ? ? (T )?Tn, with n ˜1 , consistent with the existence of line nodes in the superconducting gap. Substitutions of Ce with La, Nd, and Yb lead to similar monotonic suppressions of Tc; however, the effects on ? ? (T ) differ. While La and Nd substitution leads to an increase in the exponent n and saturation at n ˜2 , as expected for a dirty nodal superconductor, Yb substitution leads to n >3 , suggesting a change from nodal to nodeless superconductivity. This superconducting gap structure change happens in the same doping range where changes of the Fermi-surface topology were reported, implying that the nodal structure and Fermi-surface topology are closely linked.

  11. Higher order corrections to Color superconducting gaps

    E-print Network

    Deog Ki Hong; Taekoon Lee; Dong-Pil Min; D. Seo; Chaejun Song

    2003-05-07

    We find a (nonlocal) gauge where the wavefunction renormalization constant does not get any corrections for all momenta in the hard-dense loop approximation. In this gauge, we solve the Schwinger-Dyson equations for the diquark condensate in dense QCD to calculate the Cooper pair gap. We determine not only the exponent but also the prefactor of the gap in a gauge independent way. We find that the higher order corrections increase the gap only by about 1.6 times to the leading order gap at Coulomb gauge.

  12. Nodal to Nodeless Superconducting Energy-Gap Structure Change Concomitant with Fermi-Surface Reconstruction in the Heavy-Fermion Compound CeCoIn_{5}.

    PubMed

    Kim, Hyunsoo; Tanatar, M A; Flint, R; Petrovic, C; Hu, Rongwei; White, B D; Lum, I K; Maple, M B; Prozorov, R

    2015-01-16

    The London penetration depth ?(T) was measured in single crystals of Ce_{1-x}R_{x}CoIn_{5}, R=La, Nd, and Yb down to T_{min}?50??mK (T_{c}/T_{min}?50) using a tunnel-diode resonator. In the cleanest samples ??(T) is best described by the power law ??(T)?T^{n}, with n?1, consistent with the existence of line nodes in the superconducting gap. Substitutions of Ce with La, Nd, and Yb lead to similar monotonic suppressions of T_{c}; however, the effects on ??(T) differ. While La and Nd substitution leads to an increase in the exponent n and saturation at n?2, as expected for a dirty nodal superconductor, Yb substitution leads to n>3, suggesting a change from nodal to nodeless superconductivity. This superconducting gap structure change happens in the same doping range where changes of the Fermi-surface topology were reported, implying that the nodal structure and Fermi-surface topology are closely linked. PMID:25635560

  13. Noise and Bandwidth Measurements of Diffusion-Cooled Nb Hot-Electron Bolometer Mixers at Frequencies Above the Superconductive Energy Gap

    NASA Technical Reports Server (NTRS)

    Wyss, R. A.; Karasik, B. S.; McGrath, W. R.; Bumble, B.; LeDuc, H.

    1999-01-01

    Diffusion-cooled Nb hot-electron bolometer (HEB) mixers have the potential to simultaneously achieve high intermediate frequency (IF) bandwidths and low mixer noise temperatures for operation at THz frequencies (above the superconductive gap energy). We have measured the IF signal bandwidth at 630 GHz of Nb devices with lengths L = 0.3, 0.2, and 0.1 micrometer in a quasioptical mixer configuration employing twin-slot antennas. The 3-dB EF bandwidth increased from 1.2 GHz for the 0.3 gm long device to 9.2 GHz for the 0.1 gm long device. These results demonstrate the expected 1/L squared dependence of the IF bandwidth at submillimeter wave frequencies for the first time, as well as the largest EF bandwidth obtained to date. For the 0.1 gm device, which had the largest bandwidth, the double sideband (DSB) noise temperature of the receiver was 320-470 K at 630 GHz with an absorbed LO power of 35 nW, estimated using the isothermal method. A version of this mixer with the antenna length scaled for operation at 2.5 THz has also been tested. A DSB receiver noise temperature of 1800 plus or minus 100 K was achieved, which is about 1,000 K lower than our previously reported results. These results demonstrate that large EF bandwidth and low-noise operation of a diffusion-cooled HEB mixer is possible at THz frequencies with the same device geometry.

  14. On Pokrovskii's anisotropic gap equations in superconductivity theory

    NASA Astrophysics Data System (ADS)

    Yang, Yisong

    2003-11-01

    An existence and uniqueness theorem for Pokrovskii's zero-temperature anisotropic gap equation is proved. Furthermore, it is shown that Pokrovskii's finite-temperature equation is inconsistent with the Bardeen-Cooper-Schrieffer (BCS) theory. A reformulation of the anisotropic gap equation is presented along the line of Pokrovskii and it is shown that the new equation is consistent with the BCS theory for the whole temperature range. As an application, the Markowitz-Kadanoff model for anisotropic superconductivity is considered and a rigorous proof of the half-integer-exponent isotope effect is obtained. Furthermore, a sharp estimate of the gap solution near the transition temperature is established.

  15. Superconducting dark energy

    E-print Network

    Liang, Shi-Dong

    2015-01-01

    Based on the analogy with superconductor physics we consider a scalar-vector-tensor gravitational model, in which the dark energy action is described by a gauge invariant electromagnetic type functional. By assuming that the ground state of the dark energy is in a form of a condensate with the U(1) symmetry spontaneously broken, the gauge invariant electromagnetic dark energy can be described in terms of the combination of a vector and of a scalar field (corresponding to the Goldstone boson), respectively. The gravitational field equations are obtained by also assuming the possibility of a non-minimal coupling between the cosmological mass current and the superconducting dark energy. The cosmological implications of the dark energy model are investigated for a Friedmann-Robertson-Walker homogeneous and isotropic geometry for two particular choices of the electromagnetic type potential, corresponding to a pure electric type field, and to a pure magnetic field, respectively. The time evolution of the scale fact...

  16. Lipschitz continuity and monotone decreasingness of the solution to the BCS gap equation for superconductivity

    E-print Network

    Shuji Watanabe; Ken Kuriyama

    2014-11-27

    In the preceding work \\cite{watanabe3}, it is shown that the solution to the BCS gap equation for superconductivity is continuous with respect to both the temperature and the energy under the restriction that the temperature is very small. Without this restriction, we show in this paper that the solution is continuous with respect to both the temperature and the energy, and that the solution is Lipschitz continuous and monotonically decreasing with respect to the temperature.

  17. Energy gaps in high-transition-temperature cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Hashimoto, Makoto; Vishik, Inna M.; He, Rui-Hua; Devereaux, Thomas P.; Shen, Zhi-Xun

    2014-07-01

    The spectral energy gap is an important signature that defines states of quantum matter: insulators, density waves and superconductors have very different gap structures. The momentum-resolved nature of angle-resolved photoemission spectroscopy (ARPES) makes it a powerful tool to characterize spectral gaps. ARPES has been instrumental in establishing the anisotropic d-wave structure of the superconducting gap in high-transition-temperature (Tc) cuprates, which is different from the conventional isotropic s-wave superconducting gap. Shortly afterwards, ARPES demonstrated that an anomalous gap above Tc, often termed the pseudogap, follows a similar anisotropy. The nature of this poorly understood pseudogap and its relationship with superconductivity has since become the focal point of research in the field. To address this issue, the momentum, temperature, doping and materials dependence of spectral gaps have been extensively examined with significantly improved instrumentation and carefully matched experiments in recent years. This article overviews the current understanding and unresolved issues of the basic phenomenology of gap hierarchy. We show how ARPES has been sensitive to phase transitions, has distinguished between orders having distinct broken electronic symmetries, and has uncovered rich momentum- and temperature-dependent fingerprints reflecting an intertwined and competing relationship between the ordered states and superconductivity that results in multiple phenomenologically distinct ground states inside the superconducting dome. These results provide us with microscopic insights into the cuprate phase diagram.

  18. Superconducting magnetic energy storage

    SciTech Connect

    Hassenzahl, W.

    1988-08-01

    Recent programmatic developments in Superconducting Magnetic Energy Storage (SMES) have prompted renewed and widespread interest in this field. In mid 1987 the Defense Nuclear Agency, acting for the Strategic Defense Initiative Office, issued a request for proposals for the design and construction of SMES Engineering Test Model (ETM). Two teams, one led by Bechtel and the other by Ebasco, are now engaged in the first phase of the development of a 10 to 20 MWhr ETM. This report presents the rationale for energy storage on utility systems, describes the general technology of SMES, and explains the chronological development of the technology. The present ETM program is outlined; details of the two projects for ETM development are described in other papers in these proceedings. The impact of high T/sub c/ materials on SMES is discussed. 69 refs., 3 figs., 3 tabs.

  19. Mathematical analysis of the multiband BCS gap equations in superconductivity

    NASA Astrophysics Data System (ADS)

    Yang, Yisong

    2005-01-01

    In this paper, we present a mathematical analysis for the phonon-dominated multiband isotropic and anisotropic BCS gap equations at any finite temperature T. We establish the existence of a critical temperature T so that, when Tgap solution, representing the superconducting phase; when T>T, the only nonnegative gap solution is the zero solution, representing the normal phase. Furthermore, when T=T, we prove that the only gap solution is the zero solution and that the positive gap solution depend on the temperature Tgap solution tends to zero, which enables us to determine the critical temperature T. In the isotropic case where the entries of the interaction matrix K are all constants, we are able to derive an elegant T equation which says that T depends only on the largest positive eigenvalue of K but does not depend on the other details of K. In the anisotropic case, we may derive a similar T equation in the context of the Markowitz-Kadanoff model and we prove that the presence of anisotropic fluctuations enhances T as in the single-band case. A special consequence of these results is that the half-unity exponent isotope effect may rigorously be proved in the multiband BCS theory, isotropic or anisotropic.

  20. Superconducting energy storage

    SciTech Connect

    Giese, R.F.

    1993-10-01

    This report describes the status of energy storage involving superconductors and assesses what impact the recently discovered ceramic superconductors may have on the design of these devices. Our description is intended for R&D managers in government, electric utilities, firms, and national laboratories who wish an overview of what has been done and what remains to be done. It is assumed that the reader is acquainted with superconductivity, but not an expert on the topics discussed here. Indeed, it is the author`s aim to enable the reader to better understand the experts who may ask for the reader`s attention, support, or funding. This report may also inform scientists and engineers who, though expert in related areas, wish to have an introduction to our topic.

  1. Superconducting gap structure of the 115s revisited

    NASA Astrophysics Data System (ADS)

    Ronning, F.; Zhu, J.-X.; Das, Tanmoy; Graf, M. J.; Albers, R. C.; Rhee, H. B.; Pickett, W. E.

    2012-07-01

    Density functional theory calculations of the electronic structure of Ce- and Pu-based heavy fermion superconductors in the so-called 115 family are performed. The gap equation is used to consider which superconducting order parameters are most favorable assuming a pairing interaction that is peaked at (?, ?, qz)—the wavevector for the antiferromagnetic ordering found in close proximity. In addition to the commonly accepted dx2-y2 order parameter, there is evidence that an extended s-wave order parameter with nodes is also plausible. We discuss whether these results are consistent with current observations and possible measurements that could help distinguish between these scenarios.

  2. In-gap states of a quantum dot coupled between a normal and a superconducting lead.

    PubMed

    Bara?ski, J; Doma?ski, T

    2013-10-30

    We study the in-gap states of a quantum dot hybridized with one conducting and another superconducting electrode. The proximity effect suppresses the electronic states in the entire subgap regime |?| < ?, where ? denotes the energy gap of the superconductor. The Andreev scattering mechanism can induce, however, some in-gap states whose line-broadening (inverse life-time) is controlled by the hybridization of the quantum dot with the normal electrode. We show that the number of such Andreev bound states is substantially dependent on the competition between the Coulomb repulsion and the induced on-dot pairing. We discuss the signatures of these in-gap states in the tunneling conductance, especially in a low-bias regime. PMID:24107469

  3. Superconducting energy storage magnet

    NASA Technical Reports Server (NTRS)

    Boom, Roger W. (Inventor); Eyssa, Yehia M. (Inventor); Abdelsalam, Mostafa K. (Inventor); Huang, Xianrui (Inventor)

    1993-01-01

    A superconducting magnet is formed having composite conductors arrayed in coils having turns which lie on a surface defining substantially a frustum of a cone. The conical angle with respect to the central axis is preferably selected such that the magnetic pressure on the coil at the widest portion of the cone is substantially zero. The magnet structure is adapted for use as an energy storage magnet mounted in an earthen trench or tunnel where the strength the surrounding soil is lower at the top of the trench or tunnel than at the bottom. The composite conductor may be formed having a ripple shape to minimize stresses during charge up and discharge and has a shape for each ripple selected such that the conductor undergoes a minimum amount of bending during the charge and discharge cycle. By minimizing bending, the working of the normal conductor in the composite conductor is minimized, thereby reducing the increase in resistance of the normal conductor that occurs over time as the conductor undergoes bending during numerous charge and discharge cycles.

  4. Energy gaps in ?-graphdiyne nanoribbons

    SciTech Connect

    Niu, X. N.; Yang, D. Z.; Si, M. S., E-mail: sims@lzu.edu.cn; Xue, D. S., E-mail: xueds@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2014-04-14

    ?-graphdiyne is a novel predicted Dirac cone material, which is similar to graphene. But the absence of a band gap significantly limits its practical applications. In order to extend this limitation, an opening of energy gap is needed. To this end, we resort to the nanoribbon structure of ?-graphdiyne. This is a conventional proposal to open up the energy gaps in nanomaterials. The results show that both the armchair and the zigzag ?-graphdiyne nanoribbons do generate energy gaps, which are width-dependent. In addition, the underlying mechanism of this opening is explored. The former is ascribed to the combination of quantum confinement and edges' effect, while the latter arises from the edge magnetic ordering. These novel nanoribbons with opening energy gaps would be potentially used in electronic devices.

  5. A constrained theory of non-BCS type superconductivity in gapped Graphene

    E-print Network

    Vivek M. Vyas; Prasanta K. Panigrahi

    2011-07-27

    We show that gapped Graphene, with a local constraint that current arising from the two valley fermions are exactly equal, shows a non-BCS type superconductivity. Unlike the conventional mechanisms, this superconductivity phenomenon does not require any pairing. We estimate the critical temperature for superconducting-to-normal transition via Berezinskii-Kosterlitz-Thouless mechanism, and find that it is proportional to the gap.

  6. The imaginary part of the gap function in color superconductivity

    E-print Network

    Bo Feng; Defu Hou; Jiarong Li; Hai-cang Ren

    2006-09-16

    We clarify general properties of the energy gap regarding its functional dependence on the energy-momentum dictated by the invariance under a space inversion or a time reversal. Then we derive perturbatively the equation of the imaginary part of the gap function for dense QCD in weak coupling and generalize our results from 2SC case to CFL case. We confirm that the imaginary part is down by $g$ relative to the real part in weak coupling. The numerical results show that, up to the leading order, the imaginary part is no larger than one MeV at extremely large densities and can be as large as several MeV the densities are of physical interest.

  7. Smoothness of the Gap Function in the BCS-Bogoliubov Theory of Superconductivity

    E-print Network

    Shuji Watanabe

    2010-06-07

    We deal with the gap equation in the BCS-Bogoliubov theory of superconductivity, where the gap function is a function of the temperature $T$ only. We show that the squared gap function is of class $C^2$ on the closed interval $[\\,0,\\,T_c\\,]$. Here, $T_c$ stands for the transition temperature. Furthermore, we show that the gap function is monotonically decreasing on $[0,\\,T_c]$ and obtain the behavior of the gap function at $T=T_c$. We mathematically point out some more properties of the gap function.

  8. Signature of superconductivity in UBe13 as seen by neutron scattering: Superconducting and magnetic energy scales

    NASA Astrophysics Data System (ADS)

    Hiess, A.; Schneidewind, A.; Stockert, O.; Fisk, Z.

    2014-06-01

    We here present inelastic neutron scattering results on the strongly correlated cubic superconductor UBe13 (Tc = 0.85 K) obtained on a large single crystal by high-resolution cold neutron three-axis spectroscopy. We observed spin dynamics at a unique momentum space position building up below T ˜50 K and changing significantly on entering the superconducting state. The observed short-range longitudinal character of the correlations can be understood as a result of competing magnetic interactions. The energy dependence in the normal state reflects the energy scales determined from specific heat, whereas the low-temperature data suggest the opening of a superconducting gap. Our findings are consistent with a superconducting order parameter exhibiting s ± or d-wave symmetry and placing pure UBe13 in the strong coupling regime.

  9. Phenomenological approach to the superconducting gap of Bi 2Sr 2CaCu 2O 8+ ?

    NASA Astrophysics Data System (ADS)

    Kitamura, Michihide; Irie, Akinobu; Oya, Gin-ichiro

    2005-07-01

    A self-consistent gap equation is modified for purely two-dimensional d symmetry singlet Cooper-pairs, and numerically solved by introducing a phenomenological pair interaction potential. It is found that the calculations including the pair interaction potential well reproduce the temperature dependence of the normalized superconducting gap of Bi 2Sr 2CaCu 2O 8+ ? and showed that the present calculations are consistent with the condition of the free energy minimum. It is pointed out that the attractive pair interaction potential introduced here may be related to the spin-exchange interaction on a spin singlet state.

  10. Computation of the Field in an Axial Gap, Trapped-Flux Type Superconducting Electric Machine

    E-print Network

    Shen, Zejun; Ainslie, Mark D.; Campbell, Archie M.; Cardwell, David A.

    2014-11-04

    Abstract—The Bulk Superconductivity Group at the University of Cambridge is currently investigating the use of high temper- ature superconductors in wire and bulk form to increase the electrical and magnetic loading of an axial gap, trapped flux... electric machines are an importantapplication of superconducting materials in both bulk and wire forms. Bulk high temperature superconductors, in partic- ular, are capable of trapping magnetic fields greater than 17 T below 30 K [1], [2], as well as up to 3...

  11. Observation of a possible superconducting gap in silicene on Ag(111) Lan Chen, Baojie Feng, and Kehui Wu

    E-print Network

    Wang, Wei Hua

    Observation of a possible superconducting gap in silicene on Ag(111) surface Lan Chen, Baojie Feng of a possible superconducting gap in silicene on Ag(111) surface Lan Chen, Baojie Feng, and Kehui Wua) Institute in silicene on Ag(111) substrate by scanning tunneling spectroscopy. The temperature-dependence measurement

  12. Downsized superconducting magnetic energy storage systems

    NASA Astrophysics Data System (ADS)

    Palmer, David N.

    Scaled-down superconductive magnetic energy storage systems (DSMES) and superconductive magnetic energy power sources (SMEPS) are proposed for residential, commercial/retail, industrial off-peak and critical services, telephone and other communication systems, computer operations, power back-up/energy storages, power sources for space stations, and in-field military logistics/communication systems. Recent advances in high-Tc superconducting materials technology are analyzed. DSMES/SMEPS concepts are presented, and design, materials, and systems requirements are discussed. Problems ar identified, and possible solutions are offered. Comparisons are made with mechanical and primary and secondary energy storage and conversion systems.

  13. Superconductivity: Phenomenology

    SciTech Connect

    Falicov, L.M.

    1988-08-01

    This document discusses first the following topics: (a) The superconducting transition temperature; (b) Zero resistivity; (c) The Meissner effect; (d) The isotope effect; (e) Microwave and optical properties; and (f) The superconducting energy gap. Part II of this document investigates the Ginzburg-Landau equations by discussing: (a) The coherence length; (b) The penetration depth; (c) Flux quantization; (d) Magnetic-field dependence of the energy gap; (e) Quantum interference phenomena; and (f) The Josephson effect.

  14. Shape Resonances in superconducting gaps in a 2DEG at oxide- oxide interface

    NASA Astrophysics Data System (ADS)

    Bianconi, A.; Innocenti, D.; Valletta, A.; Perali, A.

    2014-08-01

    In multiband superconductivity, the case where the single electron hopping between different Fermi surface spots of different symmetry is forbidden by selection rules is recently attracting a large interest. The focus is addressed to superconductivity made of multiple condensates with different symmetry where the chemical potential crosses a 2.5 Lifshitz transition. This can now be investigated experimentally by fine-tuning of the chemical potential in the range of tens meV around a band edge using gate voltage control. We discuss here the case of a superconducting two-dimensional electron gas (2DEG), at the interface between two insulating oxides confined within a slab of 5 nanometers thickness, where the electronic structure is made of subbands generated by quantum size effects. We obtain shape resonances in the superconducting gaps, characterisc gaps to Tc ratios and the BCS-BEC crossover in the upper subband for different pairing strength in the shallow Fermi surface, pointing toward the best configurations for enhanced superconductivity in 2DEG.

  15. High speed superconducting flywheel system for energy storage

    NASA Astrophysics Data System (ADS)

    Bornemann, H. J.; Urban, C.; Boegler, P.; Ritter, T.; Zaitsev, O.; Weber, K.; Rietschel, H.

    1994-12-01

    A prototype of a flywheel system with auto stable high temperature superconducting bearings was built and tested. The bearings offered good vertical and lateral stability. A metallic flywheel disk, ø 190 mm x 30 mm, was safely rotated at speeds up to 15000 rpm. The disk was driven by a 3 phase synchronous homopolar motor/generator. Maximum energy capacity was 3.8 Wh, maximum power was 1.5 KW. The dynamic behavior of the prototype was tested, characterized and evaluated with respect to axial and lateral stiffness, decay torques (bearing drag), vibrational modes and critical speeds. The bearings supports a maximum weight of 65 N at zero gap, axial and lateral stiffness at 1 mm gap were 440 N/cm and 130 N/cm, respectively. Spin down experiments were performed to investigate the energy efficiency of the system. The decay rate was found to depend upon background pressure in the vacuum chamber and upon the gap width in the bearing. At a background pressure of 5x10 -4 Torr, the coefficient of friction (drag-to-lift ratio) was measured to be 0.000009 at low speeds for 6 mm gap width in the bearing. Our results indicate that further refinement of this technology will allow operation of higly efficient superconducting flywheels in the kWh range.

  16. Raising gradient limitations in 2.1 GHz superconducting photonic band gap accelerator cavities

    NASA Astrophysics Data System (ADS)

    Simakov, Evgenya I.; Arsenyev, Sergey A.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Suvorova, Natalya A.; Tajima, Tsuyoshi; Boulware, Chase H.; Grimm, Terry L.

    2014-06-01

    We report results from recent 2.1 GHz superconducting radio frequency (SRF) photonic band gap (PBG) resonator experiments at Los Alamos. Two 2.1 GHz PBG cells with elliptical rods were fabricated and tested at high power in a liquid helium bath at the temperatures of 4 K and below 2 K. The described SRF PBG cells were designed with a particular emphasis on changing the shape of the PBG rods to reduce peak surface magnetic fields and at the same time to preserve its effectiveness at damping higher-order-modes. The superconducting PBG cavities have great potential for damping long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. The cells performed in accordance with simulation's predictions and the maximum achieved accelerating gradient was 18.3 MV/m. This represents a 30% increase over gradients previously demonstrated in superconducting PBG cavities with round rods.

  17. Raising gradient limitations in 2.1?GHz superconducting photonic band gap accelerator cavities

    SciTech Connect

    Simakov, Evgenya I., E-mail: smirnova@lanl.gov; Arsenyev, Sergey A.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Suvorova, Natalya A.; Tajima, Tsuyoshi [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States); Boulware, Chase H.; Grimm, Terry L. [Niowave, Inc., 1012 North Walnut Street, Lansing, Michigan 48906 (United States)

    2014-06-16

    We report results from recent 2.1?GHz superconducting radio frequency (SRF) photonic band gap (PBG) resonator experiments at Los Alamos. Two 2.1?GHz PBG cells with elliptical rods were fabricated and tested at high power in a liquid helium bath at the temperatures of 4?K and below 2?K. The described SRF PBG cells were designed with a particular emphasis on changing the shape of the PBG rods to reduce peak surface magnetic fields and at the same time to preserve its effectiveness at damping higher-order-modes. The superconducting PBG cavities have great potential for damping long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. The cells performed in accordance with simulation's predictions and the maximum achieved accelerating gradient was 18.3 MV/m. This represents a 30% increase over gradients previously demonstrated in superconducting PBG cavities with round rods.

  18. Molecular pairing and fully gapped superconductivity in Yb-doped CeCoIn(5).

    PubMed

    Erten, Onur; Flint, Rebecca; Coleman, Piers

    2015-01-16

    The recent observation of fully gapped superconductivity in Yb doped CeCoIn_{5} poses a paradox, for the disappearance of nodes suggests that they are accidental, yet d-wave symmetry with protected nodes is well established by experiment. Here, we show that composite pairing provides a natural resolution: in this scenario, Yb doping drives a Lifshitz transition of the nodal Fermi surface, forming a fully gapped d-wave molecular superfluid of composite pairs. The T^{4} dependence of the penetration depth associated with the sound mode of this condensate is in accordance with observation. PMID:25635559

  19. Molecular Pairing and Fully Gapped Superconductivity in Yb-doped CeCoIn5

    NASA Astrophysics Data System (ADS)

    Erten, Onur; Flint, Rebecca; Coleman, Piers

    2015-01-01

    The recent observation of fully gapped superconductivity in Yb doped CeCoIn5 poses a paradox, for the disappearance of nodes suggests that they are accidental, yet d -wave symmetry with protected nodes is well established by experiment. Here, we show that composite pairing provides a natural resolution: in this scenario, Yb doping drives a Lifshitz transition of the nodal Fermi surface, forming a fully gapped d -wave molecular superfluid of composite pairs. The T4 dependence of the penetration depth associated with the sound mode of this condensate is in accordance with observation.

  20. Enlarged Photonic Band Gap in Heterostructure of Metallic Photonic and Superconducting Photonic Crystals

    Microsoft Academic Search

    Khem B. Thapa; Sanjay Srivastava; Sarika Tiwari

    2010-01-01

    We show theoretically that the frequency range of photonic band gap of a hetero-structure which is made of a metallic photonic\\u000a and superconducting photonic crystal can be enlarged due to the combination of the reflection band properties of the superconductor–dielectric\\u000a (PC1) and metallic–dielectric (PC2) periodic structures. The transmittance and band structure of the considered structures\\u000a are calculated using simple transfer

  1. High-Resolution Scanning Tunneling Spectroscopy of Magnetic Impurity Induced Bound States in the Superconducting Gap of Pb Thin Films

    NASA Astrophysics Data System (ADS)

    Ji, Shuai-Hua; Zhang, Tong; Fu, Ying-Shuang; Chen, Xi; Ma, Xu-Cun; Li, Jia; Duan, Wen-Hui; Jia, Jin-Feng; Xue, Qi-Kun

    2008-06-01

    Tunneling spectra for individual atoms and dimers of Mn and Cr adsorbed on superconducting Pb thin films were measured by a low temperature scanning tunneling microscope. Multiple-resonance structures within the superconducting gap on the adsorbates were resolved and interpreted as the magnetic impurity-induced bound states associated with different scattering channels. The experiment demonstrates a spectroscopic approach to characterizing the spin states of magnetic structures and exploring the competition between superconductivity and magnetism at the nanometer scale.

  2. Energy Gaps in Graphene Nanoribbons

    Microsoft Academic Search

    Young-Woo Son; Marvin L. Cohen; Steven G. Louie

    2006-01-01

    Based on a first-principles approach, we present scaling rules for the band\\u000agaps of graphene nanoribbons (GNRs) as a function of their widths. The GNRs\\u000aconsidered have either armchair or zigzag shaped edges on both sides with\\u000ahydrogen passivation. Both varieties of ribbons are shown to have band gaps.\\u000aThis differs from the results of simple tight-binding calculations or solutions

  3. Two Energy Gaps and Fermi-Surface ``Arcs'' in NbSe2

    NASA Astrophysics Data System (ADS)

    Borisenko, S. V.; Kordyuk, A. A.; Zabolotnyy, V. B.; Inosov, D. S.; Evtushinsky, D.; Büchner, B.; Yaresko, A. N.; Varykhalov, A.; Follath, R.; Eberhardt, W.; Patthey, L.; Berger, H.

    2009-04-01

    Using angle-resolved photoemission spectroscopy, we report on the direct observation of the energy gap in 2H-NbSe2 caused by the charge-density waves (CDW). The gap opens in the regions of the momentum space connected by the CDW vectors, which implies a nesting mechanism of CDW formation. In remarkable analogy with the pseudogap in cuprates, the detected energy gap also exists in the normal state (T>T0) where it breaks the Fermi surface into “arcs,” it is nonmonotonic as a function of temperature with a local minimum at the CDW transition temperature (T0), and it forestalls the superconducting gap by excluding the nested portions of the Fermi surface from participating in superconductivity.

  4. Two energy gaps and Fermi-surface "arcs" in NbSe2.

    PubMed

    Borisenko, S V; Kordyuk, A A; Zabolotnyy, V B; Inosov, D S; Evtushinsky, D; Büchner, B; Yaresko, A N; Varykhalov, A; Follath, R; Eberhardt, W; Patthey, L; Berger, H

    2009-04-24

    Using angle-resolved photoemission spectroscopy, we report on the direct observation of the energy gap in 2H-NbSe2 caused by the charge-density waves (CDW). The gap opens in the regions of the momentum space connected by the CDW vectors, which implies a nesting mechanism of CDW formation. In remarkable analogy with the pseudogap in cuprates, the detected energy gap also exists in the normal state (T>T0) where it breaks the Fermi surface into "arcs," it is nonmonotonic as a function of temperature with a local minimum at the CDW transition temperature (T0), and it forestalls the superconducting gap by excluding the nested portions of the Fermi surface from participating in superconductivity. PMID:19518731

  5. Field dependence of the superconducting gap in YPd2Sn: A ?SR and NMR study

    NASA Astrophysics Data System (ADS)

    Morenzoni, E.; Saadaoui, H.; Amato, A.; Baines, C.; Luetkens, H.; Pomjakushina, E.; Pikulski, M.; Shiroka, T.

    2014-12-01

    We have performed muon spin rotation/relaxation and 119Sn nuclear magnetic resonance (NMR) measurements to study the vortex state of polycrystalline samples of YPd2Sn (Tc = 5.4 K), over a wide range of applied magnetic fields up to Bc2(T). Measurements in the vortex state provide the temperature dependence of the effective magnetic penetration depth ?(T) and the field dependence of the superconducting gap ?(0). The results are consistent with a very dirty s-wave BCS superconductor with ?(0) = 212(1) nm, a gap ?(0) = 0.85(3) meV, and a Ginzburg-Landau coherence length ?GL(0) ? 23 nm. The ?SR data in a broad range of applied fields are well reproduced by taking into account a field-related reduction of the effective superconducting gap. Interestingly, the ratio 2?(0)/(kBTc) appears to a good approximation to be field-independent, with a value at low field of 3.85(9), implying a field dependence of the gap . We discuss the significance of this result.

  6. Evolution of superconducting gap and metallic ground state in cuprates from transport

    NASA Astrophysics Data System (ADS)

    Taillefer, Louis

    2006-03-01

    We report on fundamental characteristics of the ground state of cuprates in the limit of T=0, for both normal and superconducting states, obtained from transport measurements on high-quality single crystals of YBCO and Tl-2201, as a function of hole concentration. The superconducting gap is extracted from thermal conductivity; it is found to scale with the superconducting transition temperature throughout the overdoped regime, with a gap-to-Tc ratio of 5 [1]. The normal state is accessed by suppressing superconductivity with magnetic fields up to 60 T and is characterized by the limiting behavior of its electrical resistivity; while carrier localization is observed in YBCO at low temperature for carrier concentrations p below 0.1 hole/planar Cu, at p=0.1 and above the material remains highly metallic down to T=0 [2]. This shows that the non-superconducting state of underdoped cuprates, deep in the pseudogap phase, is remarkably similar to that of strongly overdoped cuprates, e.g. at p=0.3. We compare these results with similar measurements on other cuprates and discuss their implication for our understanding of the cuprate phase diagram. [1] In collaboration with: D.G. Hawthorn, S.Y. Li, M. Sutherland, E. Boaknin, R.W. Hill, C. Proust, F. Ronning, M. Tanatar, J. Paglione, D. Peets, R. Liang, D.A. Bonn, W.N. Hardy, and N.N. Kolesnikov. [2] In collaboration with: C. Proust, M. Sutherland, N. Doiron- Leyraud, S.Y. Li, R. Liang, D.A. Bonn, W.N. Hardy, N.E. Hussey, S. Adachi, S. Tajima, J. Levallois, and M. Narbone.

  7. Isotropic multi-gap superconductivity in BaFe1.9Pt0.1As2 from thermal transport and spectroscopic measurements

    NASA Astrophysics Data System (ADS)

    Ziemak, Steven; Kirshenbaum, K.; Saha, S. R.; Hu, R.; Reid, J.-Ph; Gordon, R.; Taillefer, L.; Evtushinsky, D.; Thirupathaiah, S.; Büchner, B.; Borisenko, S. V.; Ignatov, A.; Kolchmeyer, D.; Blumberg, G.; Paglione, J.

    2015-01-01

    Thermal conductivity, point contact spectroscopy, angle-resolved photoemission and Raman spectroscopy measurements were performed on BaFe1.9Pt0.1As2 single crystals obtained from the same synthesis batch in order to investigate the superconducting energy gap structure using multiple techniques. Low temperature thermal conductivity was measured in the superconducting state as a function of temperature and magnetic field, revealing an absence of quasiparticle excitations in the T\\to 0 limit up to 15 T applied magnetic fields. Point-contact Andreev reflection spectroscopy measurements were performed as a function of temperature using the needle-anvil technique, yielding features in the conductance spectra at both 2.5 meV and 7.0 meV scales consistent with a multi-gap scenario. Angle-resolved photoemission spectroscopy probed the electronic band structure above and below the superconducting transition temperature of Tc = 23 K, revealing an isotropic gap of magnitude ˜ 3 meV on both electron and hole pockets. Finally, Raman spectroscopy was used to probe quasiparticle excitations in multiple channels, showing a threshold energy scale of 3 meV below Tc. Overall, we find strong evidence for an isotropic gap structure with no nodes or deep minima in this system, with a 3 meV magnitude gap consistently observed and a second, larger gap suggested by point-contact spectroscopy measurements. We discuss the implications that the combination of these results reveal about the superconducting order parameter in the BaFe2?xPtxAs2 doping system and how this relates to similar substituted iron pnictides.

  8. High temperature superconducting magnetic energy storage for future NASA missions

    NASA Technical Reports Server (NTRS)

    Faymon, Karl A.; Rudnick, Stanley J.

    1988-01-01

    Several NASA sponsored studies based on 'conventional' liquid helium temperature level superconductivity technology have concluded that superconducting magnetic energy storage has considerable potential for space applications. The advent of high temperature superconductivity (HTSC) may provide additional benefits over conventional superconductivity technology, making magnetic energy storage even more attractive. The proposed NASA space station is a possible candidate for the application of HTSC energy storage. Alternative energy storage technologies for this and other low Earth orbit missions are compared.

  9. Phonon anomaly and anisotropic superconducting gap in noncentrosymmetric Li2(Pd1-xPtx)3B

    NASA Astrophysics Data System (ADS)

    Eguchi, G.; Peets, D. C.; Kriener, M.; Yonezawa, S.; Bao, G.; Harada, S.; Inada, Y.; Zheng, G.-q.; Maeno, Y.

    2013-04-01

    We report the systematic investigation of the specific heat of the noncentrosymmetric superconductor Li2(Pd1-xPtx)3B as a function of x. There is a large deviation of the phononic specific heat from the conventional Debye specific heat for Pt-rich samples. In contrast with the fully gapped conventional behavior for small x, a power-law temperature dependence of the electronic specific heat is observed even at x=0.5. These results manifest a strongly anisotropic or nodal superconducting gap even at x=0.5 and a nodal superconducting gap for x?0.9.

  10. Observation of multiple superconducting gaps in Fe1+ySexTe1-x through Andreev reflection

    NASA Astrophysics Data System (ADS)

    de, Debtanu; Diaz-Pinto, Carlos; Wu, Zheng; Hor, Pei-Herng; Peng, Haibing

    2011-03-01

    Iron-based superconductors have been under intensive study because of the high transition temperature and the intriguing physical mechanisms involving the superconductivity and magnetic orders. Theoretical studies on the role of spin fluctuation suggest unconventional S wave pairing and multiple superconducting (SC) gaps due to the five disjoint Fermi surfaces. However, this multiple SC-gap scenario has yet to be confirmed in experiments. Here we report the experimental observation of five SC gaps in Fe1+ySexTe1-x from Andreev reflection spectra, along with negative differential conductance dips due to the pair breaking related to the largest SC gap. The evolution of the multiple SC gaps is further investigated as a function of both temperature and magnetic field. For the largest SC gap, the Andreev reflection signal persists above bulk Tc, suggesting the existence of phase incoherent Cooper pairs.

  11. Modular superconducting magnetic energy storage inductor

    SciTech Connect

    Logan, J.R.

    1992-09-08

    This patent describes a modular superconducting magnetic energy storage inductor apparatus. It comprises an annular dewar structure oriented in a substantially horizontal plane and containing a cryogenic fluid; a plurality of winding modules each comprising a multilayer, layer wound winding of superconducting material, the winding modules staked one on top of another in the annular dewar and immersed in the cryogenic fluid; means interconnecting the plurality of winding modules in at least one electrical circuit; and shorting switch means comprising for each winding module a single shorting switch connected across the winding of the winding module and selectively shorting the winding during an emergency dump of the cryogenic fluid from the dewar.

  12. Enhanced Superconducting Gaps in the Trilayer High-Temperature Bi2Sr2Ca2Cu3O10+? Cuprate Superconductor

    NASA Astrophysics Data System (ADS)

    Ideta, S.; Takashima, K.; Hashimoto, M.; Yoshida, T.; Fujimori, A.; Anzai, H.; Fujita, T.; Nakashima, Y.; Ino, A.; Arita, M.; Namatame, H.; Taniguchi, M.; Ono, K.; Kubota, M.; Lu, D. H.; Shen, Z.-X.; Kojima, K. M.; Uchida, S.

    2010-06-01

    We report the first observation of the multilayer band splitting in the optimally doped trilayer cuprate Bi2Sr2Ca2Cu3O10+? (Bi2223) by angle-resolved photoemission spectroscopy. The observed energy bands and Fermi surfaces are originated from the outer and inner CuO2 planes (OP and IP). The OP band is overdoped with a large d-wave gap around the node of ?0˜43meV while the IP is underdoped with an even large gap of ?0˜60meV. These energy gaps are much larger than those for the same doping level of the double-layer cuprates, which leads to the large Tc in Bi2223. We propose possible origins of the large superconducting gaps for the OP and IP: (1) minimal influence of out-of-plane disorder and a proximity effect and (2) interlayer tunneling of Cooper pairs between the OP and IP.

  13. Study on the energy criterion of cuprate superconductivity

    E-print Network

    Gu Jiapu

    2010-02-09

    In this paper, we use the variation of spontaneous magnetization to describe the influence of electron holes in cuprate superconductors, and use competitive energy relations to explore the superconductivity rule and energy criterion, on this basis, we can deduce a clear physical image of superconducting phase diagram and superconducting mechanism.

  14. Energy Flow and Rapidity Gaps Between Jets in Photoproduction

    E-print Network

    Energy Flow and Rapidity Gaps Between Jets in Photoproduction Angela Wyatt October 2001 Particle#ractive DIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.3 Rapidity Gaps Between Jets . . . . . . . . . . . . . . . . . . . . 65 4.3.4 Definition of Rapidity Gap Events . . . . . . . . . . . . . . . . 67 5 Data Selection

  15. Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba1-xKxFe2As2

    SciTech Connect

    Kim, H [Ames Laboratory; Tanatar, M A [Ames Laboratory; Straszheim, W E [Ames Laboratory; Cho, K [Ames Laboratory; Murphy, J [Iowa State University; Spyrison, N [Iowa State University; Reid, J -Ph [Universite de Sherbrooke; Shen, Bing [Nanjing University; Wen, Hai-Hu [Nanjing University; Fernandes, R M [University of Minnesota; Prozorov, R [Ames Laboratory

    2014-07-01

    The in-plane London penetration depth ??(T) was measured using a tunnel diode resonator technique in single crystals of Ba1?xKxFe2As2 with doping levels x ranging from heavily underdoped, x=0.16 (Tc=7K), to nearly optimally doped, x=0.34 (Tc=39K). Exponential saturation of ??(T) in the T?0 limit is found in optimally doped samples, with the superfluid density ?s(T)?[?(0)/?(T)]2 quantitatively described by a self-consistent ? model with two nodeless isotropic superconducting gaps. As the doping level is decreased towards the extreme end of the superconducting dome at x=0.16, the low-temperature behavior of ??(T) becomes nonexponential and is best described by the power law ??(T)?T2, characteristic of strongly anisotropic gaps. The change between the two regimes happens within the range of coexisting magnetic/nematic order and superconductivity, x<0.25, and is accompanied by a rapid rise in the absolute value of ??(T) with underdoping. This effect, characteristic of the competition between superconductivity and other ordered states, is very similar to but of significantly smaller magnitude than what is observed in the electron-doped Ba(Fe1?xCox)2As2 compounds. Our study suggests that the competition between superconductivity and magnetic/nematic order in hole-doped compounds is weaker than in electron-doped compounds, and that the anisotropy of the superconducting state in the underdoped iron pnictides is a consequence of the anisotropic changes in the pairing interaction and in the gap function promoted by both magnetic and nematic long-range orders.

  16. Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba1-xKxFe2As2

    NASA Astrophysics Data System (ADS)

    Kim, H.; Tanatar, M. A.; Straszheim, W. E.; Cho, K.; Murphy, J.; Spyrison, N.; Reid, J.-Ph.; Shen, Bing; Wen, Hai-Hu; Fernandes, R. M.; Prozorov, R.

    2014-07-01

    The in-plane London penetration depth ?? (T) was measured using a tunnel diode resonator technique in single crystals of Ba1-xKxFe2As2 with doping levels x ranging from heavily underdoped, x =0.16 (Tc=7K), to nearly optimally doped, x =0.34 (Tc=39K). Exponential saturation of ?? (T) in the T ?0 limit is found in optimally doped samples, with the superfluid density ?s(T)?[?(0)/?(T)]2 quantitatively described by a self-consistent ? model with two nodeless isotropic superconducting gaps. As the doping level is decreased towards the extreme end of the superconducting dome at x =0.16, the low-temperature behavior of ?? (T) becomes nonexponential and is best described by the power law ??(T )?T2, characteristic of strongly anisotropic gaps. The change between the two regimes happens within the range of coexisting magnetic/nematic order and superconductivity, x <0.25, and is accompanied by a rapid rise in the absolute value of ?? (T) with underdoping. This effect, characteristic of the competition between superconductivity and other ordered states, is very similar to but of significantly smaller magnitude than what is observed in the electron-doped Ba(Fe1-xCox)2As2 compounds. Our study suggests that the competition between superconductivity and magnetic/nematic order in hole-doped compounds is weaker than in electron-doped compounds, and that the anisotropy of the superconducting state in the underdoped iron pnictides is a consequence of the anisotropic changes in the pairing interaction and in the gap function promoted by both magnetic and nematic long-range orders.

  17. Low-energy phonons and superconductivity in Sn0.8In0.2Te

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Schneeloch, J. A.; Zhong, R. D.; Rodriguez-Rivera, J. A.; Harriger, L. W.; Birgeneau, R. J.; Gu, G. D.; Tranquada, J. M.; Xu, Guangyong

    2015-02-01

    We present neutron scattering measurements on low-energy phonons from a superconducting (Tc=2.7 K ) Sn0.8In0.2Te single-crystal sample. The longitudinal acoustic phonon mode and one transverse acoustic branch have been mapped out around the (002) Bragg peak for temperatures of 1.7 and 4.2 K. We observe a substantial energy width of the transverse phonons at energies comparable to twice the superconducting gap; however, there is no change in this width between the superconducting and normal states, and the precise origin of this energy width anomaly is not entirely clear. We also confirm that the compound is well ordered, with no indications of structural instability.

  18. Pushing the Gradient Limitations of Superconducting Photonic Band Gap Structure Cells

    SciTech Connect

    Simakov, Evgenya I. [Los Alamos National Laboratory; Haynes, William B. [Los Alamos National Laboratory; Kurennoy, Sergey S. [Los Alamos National Laboratory; Shchegolkov, Dmitry [Los Alamos National Laboratory; O'Hara, James F. [Los Alamos National Laboratory; Olivas, Eric R. [Los Alamos National Laboratory

    2012-06-07

    Superconducting photonic band gap resonators present us with unique means to place higher order mode couples in an accelerating cavity and efficiently extract HOMs. An SRF PBG resonator with round rods was successfully tested at LANL demonstrating operation at 15 MV/m. Gradient in the SRF PBG resonator was limited by magnetic quench. To increase the quench threshold in PBG resonators one must design the new geometry with lower surface magnetic fields and preserve the resonator's effectiveness for HOM suppression. The main objective of this research is to push the limits for the high-gradient operation of SRF PBG cavities. A NCRF PBG cavity technology is established. The proof-of-principle operation of SRF PBG cavities is demonstrated. SRF PBG resonators are effective for outcoupling HOMs. PBG technology can significantly reduce the size of SRF accelerators and increase brightness for future FELs.

  19. Operation of a test bed axial-gap brushless dc rotor with a superconducting stator

    SciTech Connect

    McKeever, J.W.; Sohns, C.W.; Schwenterly, S.W.; Young, R.W. Sr.; Campbell, V.W.; Hickey, M.H.; Ott, G.W. [Oak Ridge National Lab., TN (United States); Bailey, J.M. [Tennessee Univ., Knoxville, TN (United States)

    1993-08-01

    A variable-speed axial-gap motor with a stator consisting of four liquid helium cooled superconducting electromagnets (two pole pairs) was built and proof tested up to 608 rpm in November 1990 as a tool for joint industry-laboratory evaluation of coils fabricated from high-temperature oxide superconductors. A second rotor was fabricated with improved materia winding configuration, and wire type, and the drive system was modified to eliminate current spiking. The modified motor was characterized to design speed, 188 rad/s (1800 rpm), to acquire a performance baseline for future comparison with that of high-temperature superconducting (HIS) wire. As it becomes commercially available, HTS wire will replace the low-temperature electromagnet wire in a stator modified to control wire temperatures between 4 K and 77 K. Measurements of the superconducting electromagnetic field and locked rotor torque as functions of cryocurrent and dc current through two phases of the rotor, respectively, provided data to estimate power that could be developed by the rotor. Back emf and parasitic mechanical and electromagnetic drag torques were measured as functions of angular velocity to calculate actual rotor power developed and to quantify losses, which reduce the motor`s efficiency. A detailed measurement of motor power at design speed confirmed the developed power equation. When subsequently operated at the 33-A maximum available rotor current, the motor delivered 15.3 kill (20.5 hp) to the load. In a final test, the cryostat was operated at 2500 A, 200 A below its critical current. At rotor design current of 60 A and 2500 A stator current, the extrapolated developed power would be 44.2 kill (59.2 hp) with 94% efficiency.

  20. Operation of a test bed axial-gap brushless DC rotor with a superconducting stator

    SciTech Connect

    McKeever, J.W.; Sohns, C.W.; Schwenterly, S.W.; Young, R.W. Sr.; Campbell, V.W.; Hickey, M.H.; Ott, G.W. [Oak Ridge National Lab., TN (United States); Bailey, J.M. [Univ. of Tennessee, Knoxville, TN (United States)

    1994-12-31

    A variable-speed axial-gap motor with a stator consisting of four liquid helium cooled superconducting electromagnets (two pole pairs) was built and proof tested up to 608 rpm in November 1990 as a tool for joint industry-laboratory evaluation of coils fabricated from high-temperature oxide superconductors. A second rotor was fabricated with improved material, winding configuration, and wire type, and the drive system was modified to eliminate current spiking. The modified motor was characterized to design speed, 188 rad/s (1800 rpm), to acquire a performance baseline for future comparison with that of high-temperature superconducting (HTS) wire. As it becomes commercially available, HTS wire will replace the low-temperature electromagnet wire in a stator modified to control wire temperatures between 4 K and 77 K. Measurements of the superconducting electromagnetic field and locked rotor torque as functions of cryocurrent and dc current through two phases of the rotor, respectively, provided data to estimate power that could be developed by the rotor. Back emf and parasitic mechanical and electromagnetic drag torques were measured as functions of angular velocity to calculate actual rotor power developed and to quantify losses, which reduce the motor`s efficiency. A detailed measurement of motor power at design speed confirmed the developed power equation. When subsequently operated at the 33-A maximum available rotor current, the motor delivered 15.3 kW (20.5 hp) to the load. In a final test, the cryostat was operated at 2500 A, 200 A below its critical current. At rotor design current of 60 A and 2500 A stator current, the extrapolated developed power would be 44.2 kW (59.2 hp) with 94% efficiency.

  1. Pseudo-gap as a signature of inhomogeneous superconductivity in oxide interfaces

    NASA Astrophysics Data System (ADS)

    Bucheli, D.; Caprara, S.; Grilli, M.

    2015-04-01

    We present an explanation for recent tunneling experiments in LaAlO3/SrTiO3 interfaces which is based on the strongly inhomogeneous character of these interfaces. The measurements report signatures of superconductivity in the tunneling spectra while the global resistance of the sample is finite, i.e., a pseudo-gap state. In addition, even when the global resistance vanishes the zero-bias conductance remains finite. We show that these observations can be described by a model of superconducting (SC) islands embedded in a metallic background. The local critical temperatures of the SC island are randomly distributed, some of them necessarily exceeding the critical temperature for global percolation to the zero resistance state. Consequently, tunneling spectra display a suppression of the density of states and coherence peaks already well above the percolative transition. The temperature dependence of the spectra suggests that a sizable fraction of the metallic background becomes SC by proximity effect when the temperature is lowered.

  2. Closing the energy gap through passive energy expenditure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development of obesity is a gradual process occurring when daily energy intake persistently exceeds energy expenditure (EE). Typical daily weight gain is attributed to an energy gap or excess of stored energy of 15 to 50 kcal/day. Sedentary jobs likely promote weight gain. Standing may be a passive ...

  3. Method for measuring the momentum-dependent relative phase of the superconducting gap of high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Flatté, M. E.; Quinlan, S.; Scalapino, D. J.

    1993-10-01

    The phase variation of the superconducting gap over the (normal) Fermi surface of the high-temperature superconductors remains a significant unresolved question. Is the phase of the gap constant, does it change sign, or is it perhaps complex\\? A detailed answer to this question would provide important constraints on various pairing mechanisms. Here we propose a new method for measuring the relative gap phase on the Fermi surface which is direct, is angle-resolved, and probes the bulk. The required experiments involve measuring phonon linewidths in the normal and superconducting state, with resolution available in current facilities. We primarily address La1.85Sr0.15CuO4 material, but also propose a more detailed study of a specific phonon in Bi2Sr2CaCu2O8.

  4. Superconducting magnetic energy storage for asynchronous electrical systems

    DOEpatents

    Boenig, H.J.

    1984-05-16

    It is an object of the present invention to provide superconducting magnetic energy storage for a plurality of asynchronous electrical systems. It is a further object of the present invention to provide load leveling and stability improvement in a plurality of independent ac systems using a single superconducting magnetic energy storage coil.

  5. Utility benefits of superconducting magnetic energy storage

    SciTech Connect

    Schoenung, S.M. (W.J. Schafer Association, Inc., Pleasanton, CA (US)); Ender, R.C. (Ebasco Services, Inc., Kennebunk, ME (US)); Walsh, T.E. (Bechtel National, Inc., San Francisco, CA (USA))

    1989-01-01

    Superconducting magnetic energy storage (SMES) is being developed for use as an advanced power source for electric utilities. The most obvious use of SMES will be in load-leveling, but many other valuable applications of SMES, such as spinning reserve and frequency stabilization, are possible within a utility system. With an engineering test model scheduled for operation in the near future, a number of utilities have begun to analyze quantitatively the potential benefits of SMES. These benefits are found to vary with the size and characteristics of the utility as well as with the power and energy capacity of the SMES unit, with operating benefits outweigh load-leveling benefits for a small unit.

  6. Determination of the electron-phonon coupling constants from the experimental temperature dependences of superconducting gaps in MgB2

    NASA Astrophysics Data System (ADS)

    Kuzmichev, S. A.; Kuzmicheva, T. E.; Tchesnokov, S. N.

    2014-05-01

    Experimental temperature dependences ??, ?( T) of the energy of superconducting gaps for MgB2 samples with the critical temperatures 22 K < T c < 41 K have been fitted by selecting the renormalized electron-phonon coupling constants ? ij with the use of the Moskalenko-Shul system of equations, the expression for the frequency of collective plasma oscillations obtained by Leggett for two-gap superconductors, and two fitting parameters. We previously obtained the dependences ??, ?( T) by the multiple Andreev reflection spectroscopy of superconductor-constriction-superconductor junctions based on MgB2 with various degree of disorder of the crystal structure. It has been shown that the intraband pairing constants are decisive for the superconductivity mechanism in MgB2; in this case, ? V ?? V ??/ V ?? = 8-22 and the ratio of the interband constants ? can range from 3 to 11. The set of the Eliashberg coupling constants ? {/ij 0} has been qualitatively determined for relatively pure MgB2 with maximum values T c ? 40 K. The leading constant is 0.7 < ?{??/0} ? ?{eff/0} < 0.9 and depends on the choice of the upper integration limit in the Bardeen-Cooper-Schrieffer (BCS) model and the effective Coulomb repulsion ?{iff/*}. The characteristic ratio for the gap in the ? band is 2??/ k B T c = 5.0-6.5.

  7. Development of superconducting magnetic bearing with superconducting coil and bulk superconductor for flywheel energy storage system

    NASA Astrophysics Data System (ADS)

    Arai, Y.; Seino, H.; Yoshizawa, K.; Nagashima, K.

    2013-11-01

    We have been developing superconducting magnetic bearing for flywheel energy storage system to be applied to the railway system. The bearing consists of a superconducting coil as a stator and bulk superconductors as a rotor. A flywheel disk connected to the bulk superconductors is suspended contactless by superconducting magnetic bearings (SMBs). We have manufactured a small scale device equipped with the SMB. The flywheel was rotated contactless over 2000 rpm which was a frequency between its rigid body mode and elastic mode. The feasibility of this SMB structure was demonstrated.

  8. Method for making mirrored surfaces comprising superconducting material

    DOEpatents

    Early, J.T.; Hargrove, R.S.

    1989-12-12

    Superconducting mirror surfaces are provided by forming a mirror surface from a material which is superconductive at a temperature above about 40 K and adjusting the temperature of the surface to that temperature at which the material is superconducting. The mirror surfaces are essentially perfect reflectors for electromagnetic radiation with photon energy less than the superconducting band gap.

  9. Single W- and Z-boson production as a probe for rapidity gaps at the Superconducting Super Collider

    Microsoft Academic Search

    H. Chehime; D. Zeppenfeld

    1993-01-01

    The cross sections for the production of single W's and Z's via electroweak boson fusion are calculated for pp collisions at the Superconducting Super Collider (SSC). We present general event characteristics of the qq-->qqW and qq-->qqZ signals and the dominant ba ckgrounds for leptonic decays of the W or Z. Special emphasis is given to the study of rapidity gap

  10. Distinct Fermi Surface Topology and Nodeless Superconducting Gap in a Tl0:58Rb0:42Fe1:72Se2 Superconductor

    E-print Network

    Tian, Weidong

    -based superconductors reported so far. The Fermi surface around the M point shows a nearly isotropic superconducting gap) superconductors [6]. It is important to explore whether the high-Tc superconductiv- ity mechanism in this new FeDistinct Fermi Surface Topology and Nodeless Superconducting Gap in a ðTl0:58Rb0:42�Fe1:72Se2

  11. Superconductivity

    SciTech Connect

    Langone, J.

    1989-01-01

    This book explains the theoretical background of superconductivity. Includes discussion of electricity, material fabrication, maglev trains, the superconducting supercollider, and Japanese-US competition. The authors reports the latest discoveries.

  12. Superconductivity and fusion energy—the inseparable companions

    NASA Astrophysics Data System (ADS)

    Bruzzone, Pierluigi

    2015-02-01

    Although superconductivity will never produce energy by itself, it plays an important role in energy-related applications both because of its saving potential (e.g., power transmission lines and generators), and its role as an enabling technology (e.g., for nuclear fusion energy). The superconducting magnet’s need for plasma confinement has been recognized since the early development of fusion devices. As long as the research and development of plasma burning was carried out on pulsed devices, the technology of superconducting fusion magnets was aimed at demonstrations of feasibility. In the latest generation of plasma devices, which are larger and have longer confinement times, the superconducting coils are a key enabling technology. The cost of a superconducting magnet system is a major portion of the overall cost of a fusion plant and deserves significant attention in the long-term planning of electricity supply; only cheap superconducting magnets will help fusion get to the energy market. In this paper, the technology challenges and design approaches for fusion magnets are briefly reviewed for past, present, and future projects, from the early superconducting tokamaks in the 1970s, to the current ITER (International Thermonuclear Experimental Reactor) and W7-X projects and future DEMO (Demonstration Reactor) projects. The associated cryogenic technology is also reviewed: 4.2 K helium baths, superfluid baths, forced-flow supercritical helium, and helium-free designs. Open issues and risk mitigation are discussed in terms of reliability, technology, and cost.

  13. Upper critical field of KFe2As2 under pressure: A test for the change in the superconducting gap structure

    NASA Astrophysics Data System (ADS)

    Taufour, Valentin; Foroozani, Neda; Tanatar, Makariy A.; Lim, Jinhyuk; Kaluarachchi, Udhara; Kim, Stella K.; Liu, Yong; Lograsso, Thomas A.; Kogan, Vladimir G.; Prozorov, Ruslan; Bud'ko, Sergey L.; Schilling, James S.; Canfield, Paul C.

    2014-06-01

    We report measurements of electrical resistivity under pressure to 5.8 GPa, magnetization to 6.7 GPa, and ac susceptibility to 7.1 GPa in KFe2As2. The previously reported change of slope in the pressure dependence of the superconducting transition temperature Tc(p) at a pressure p*˜1.8 GPa is confirmed, and Tc(p) is found to be nearly constant above p* up to 7.1 GPa. The T-p phase diagram is very sensitive to the pressure conditions as a consequence of the anisotropic uniaxial pressure dependence of Tc. Across p*, a change in the behavior of the upper critical field is revealed through a scaling analysis of the slope of Hc_2 with the effective mass as determined from the A coefficient of the T2 term of the temperature-dependent resistivity. We show that this scaling provides a quantitative test for the changes of the superconducting gap structure and suggests the development of a kz modulation of the superconducting gap above p* as a most likely explanation.

  14. Upper critical field of KFe2As2 under pressure: A test for the change in the superconducting gap structure

    SciTech Connect

    Taufour, Valentin [Ames Laboratory; Foroozani, Neda [Washington University; Tanatar, Makariy A. [Ames Laboratory; Lim, Jinhyuk [Washington University; Kaluarachchi, Udhara [Iowa State University; Kim, Stella K. [Ames Laboratory; Liu, Yong [Ames Laboratory; Lograsso, Thomas A. [Ames Laboratory; Kogan, Vladimir G. [Ames Laboratory; Prozorov, Ruslan; Bud'ko, Sergey L. [Ames Laboratory; Schilling, James S. [Washington University; Canfield, Paul C. [Ames Laboratory

    2014-06-01

    We report measurements of electrical resistivity under pressure to 5.8 GPa, magnetization to 6.7 GPa, and ac susceptibility to 7.1 GPa in KFe2As2. The previously reported change of slope in the pressure dependence of the superconducting transition temperature Tc(p) at a pressure p??1.8 GPa is confirmed, and Tc(p) is found to be nearly constant above p? up to 7.1 GPa. The T?p phase diagram is very sensitive to the pressure conditions as a consequence of the anisotropic uniaxial pressure dependence of Tc. Across p?, a change in the behavior of the upper critical field is revealed through a scaling analysis of the slope of Hc2 with the effective mass as determined from the A coefficient of the T2 term of the temperature-dependent resistivity. We show that this scaling provides a quantitative test for the changes of the superconducting gap structure and suggests the development of a kz modulation of the superconducting gap above p? as a most likely explanation.

  15. Superconducting Magnetic Energy Storage (SMES) Program

    NASA Astrophysics Data System (ADS)

    Rogers, J. D.

    1985-05-01

    The 30 MJ, 10 MW superconducting magnetic energy storage (SMES) system was devised to interact in the Western US Power System as an alternate means to damp unstable oscillations at 0.35 Hz on the Pacific HVAC Interites. The operating limits of the 30 MJ SMES unit were established, and different means of controlling real and reactive power were tested. The unit can follow a sinusoidal power demand signal with an amplitude of up to 8.6 MW with the converter working in a 12 pulse mode. When the converter operates in the constant VAR mode, a time varying real power demand signal of up to 5 MW can be met. It was shown that the Pacific ac Interite has current and reactive power variations of the same frequency as the modulating frequency of the SMES device. The reliability of the SMES subsystems with a narrow band noise input was assessed. Parameters of the ac power system were determined. Converter short circuit tests, load tests under various control conditions, dc breaker tests for coil current interruption, and converter failure mode tests were conducted. The experimental operation of the SMES system is concluded.

  16. Energy and Color Flow in Dijet Rapidity Gaps

    Microsoft Academic Search

    Gianluca Oderda; George Sterman

    1998-01-01

    When rapidity gaps in high- pT dijet events are identified by energy flow in the central region, they may be calculated from factorized cross sections in perturbative QCD, up to corrections that behave as inverse powers of the central region energy. Although power-suppressed corrections may be important, a perturbative calculation of dijet rapidity gaps in pp¯ scattering, using a valence

  17. Toroidal constant-tension superconducting magnetic energy storage units

    DOEpatents

    Herring, J. Stephen (Idaho Falls, ID)

    1992-01-01

    A superconducting magnetic energy storage unit is provided in which the magnet is wound in a toroidal fashion such that the magnetic field produced is contained only within the bore of the magnet, and thus producing a very low external field. The superconducting magnet includes a coolant channel disposed through the wire. The bore of the magnet comprises a storage volume in which cryogenic coolant is stored, and this volume supplies the coolant to be delivered to the coolant channel in the magnet.

  18. Anisotropy of the superconducting gap in the iron-based superconductor BaFe2(As1-xPx)2

    PubMed Central

    Yoshida, T.; Ideta, S.; Shimojima, T.; Malaeb, W.; Shinada, K.; Suzuki, H.; Nishi, I.; Fujimori, A.; Ishizaka, K.; Shin, S.; Nakashima, Y.; Anzai, H.; Arita, M.; Ino, A.; Namatame, H.; Taniguchi, M.; Kumigashira, H.; Ono, K.; Kasahara, S.; Shibauchi, T.; Terashima, T.; Matsuda, Y.; Nakajima, M.; Uchida, S.; Tomioka, Y.; Ito, T.; Kihou, K.; Lee, C. H.; Iyo, A.; Eisaki, H.; Ikeda, H.; Arita, R.; Saito, T.; Onari, S.; Kontani, H.

    2014-01-01

    We report peculiar momentum-dependent anisotropy in the superconducting gap observed by angle-resolved photoemission spectroscopy in BaFe2(As1-xPx)2 (x = 0.30, Tc = 30?K). Strongly anisotropic gap has been found only in the electron Fermi surface while the gap on the entire hole Fermi surfaces are nearly isotropic. These results are inconsistent with horizontal nodes but are consistent with modified s± gap with nodal loops. We have shown that the complicated gap modulation can be theoretically reproduced by considering both spin and orbital fluctuations. PMID:25465027

  19. Energy and water potential of the Southeastern Anatolia Project (GAP)

    Microsoft Academic Search

    Kamil Kaygusuz

    1999-01-01

    This article gives an overview of energy and water potential of the Southeastern Anatolia Project (GAP) in Turkey. This integrated socioeconomic development project is one of the largest of its kind in the world. The GAP region is rich in water and soil resources. The Euphrates and Tigris Rivers represent over 28% of the nation's water supply by rivers, and

  20. Optimal emitter-collector gap for thermionic energy converters

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Hyung; Bargatin, Igor; Melosh, Nicholas A.; Howe, Roger T.

    2012-04-01

    In this letter, we calculate numerically the emitter-collector gaps that maximize the power conversion efficiency of vacuum thermionic energy converters (TECs). The optimum arises because efficiency drops both at very large gaps, due to space-charge limitations on the TEC current, and at very small gaps, due to the increased parasitic heat loss via near-field radiative heat transfer. For typical TECs made with cesiated tungsten electrodes, the optimal gaps range from 900 nm to 3 ?m and are approximately equal to the characteristic wavelength of the emitter thermal radiation, as given by Wien's displacement law.

  1. Convergence of Meissner minimisers of the Ginzburg-Landau energy of superconductivity as

    E-print Network

    Monneau, Régis

    Convergence of Meissner minimisers of the Ginzburg-Landau energy of superconductivity as #20; ! +1 Ecole des Ponts et Chaussées Abstract The Meissner solution of a smooth cylindrical superconducting by a vortex of superconducting current. The cores of these tubes comprise non-superconducting (normal

  2. Tests of the nuclear equation of state and superfluid and superconducting gaps using the Cassiopeia A neutron star

    E-print Network

    Wynn C. G. Ho; Khaled G. Elshamouty; Craig O. Heinke; Alexander Y. Potekhin

    2015-01-15

    The observed rapid cooling of the Cassiopeia A neutron star can be interpreted as being caused by neutron and proton transitions from normal to superfluid and superconducting states in the stellar core. Here we present two new Chandra ACIS-S Graded observations of this neutron star and measurements of the neutron star mass M and radius R found from consistent fitting of both the X-ray spectra and cooling behavior. This comparison is only possible for individual nuclear equations of state. We test phenomenological superfluid and superconducting gap models which mimic many of the known theoretical models against the cooling behavior. Our best-fit solution to the Cassiopeia A data is one in which the (M,R) = (1.44 Msun,12.6 km) neutron star is built with the BSk21 equation of state, strong proton superconductor and moderate neutron triplet superfluid gap models, and a pure iron envelope or a thin carbon layer on top of an iron envelope, although there are still large observational and theoretical uncertainties.

  3. Tests of the nuclear equation of state and superfluid and superconducting gaps using the Cassiopeia A neutron star

    NASA Astrophysics Data System (ADS)

    Ho, Wynn C. G.; Elshamouty, Khaled G.; Heinke, Craig O.; Potekhin, Alexander Y.

    2015-01-01

    The observed rapid cooling of the Cassiopeia A neutron star can be interpreted as being caused by neutron and proton transitions from normal to superfluid and superconducting states in the stellar core. Here we present two new Chandra ACIS-S Graded observations of this neutron star and measurements of the neutron star mass M and radius R found from consistent fitting of both the x-ray spectra and cooling behavior. This comparison is only possible for individual nuclear equations of state. We test phenomenological superfluid and superconducting gap models which mimic many of the known theoretical models against the cooling behavior. Our best-fit solution to the Cassiopeia A data is one in which the (M ,R ) =(1.44 MSun,12.6 km) neutron star is built with the BSk21 equation of state, strong proton superconductor and moderate neutron triplet superfluid gap models, and a pure iron envelope or a thin carbon layer on top of an iron envelope, although there are still large observational and theoretical uncertainties.

  4. Doping dependence of low-energy quasiparticle excitations in superconducting Bi2212

    PubMed Central

    2013-01-01

    The doping-dependent evolution of the d-wave superconducting state is studied from the perspective of the angle-resolved photoemission spectra of a high-Tc cuprate, Bi2Sr2CaCu2 O8+? (Bi2212). The anisotropic evolution of the energy gap for Bogoliubov quasiparticles is parametrized by critical temperature and superfluid density. The renormalization of nodal quasiparticles is evaluated in terms of mass enhancement spectra. These quantities shed light on the strong coupling nature of electron pairing and the impact of forward elastic or inelastic scatterings. We suggest that the quasiparticle excitations in the superconducting cuprates are profoundly affected by doping-dependent screening. PMID:24314035

  5. Energy gap of Kronig-Penney-type hydrogenated graphene superlattices

    E-print Network

    Lee, Joo-Hyoung

    The electronic structure of graphene-graphane superlattices with armchair interfaces is investigated with first-principles density-functional theory. By separately varying the widths, we find that the energy gap Eg is ...

  6. Superconductivity

    SciTech Connect

    Mayo, J.L.

    1988-01-01

    The author presents treatment of the field of superconductivity, from its inception in 1911 to the present day. Its discussions range from scientific aspects to applications in business, medicine, etc. This book provides definitions and a selective bibliography.

  7. Energy and Color Flow in Dijet Rapidity Gaps

    E-print Network

    Oderda, G; Oderda, Gianluca; Sterman, George

    1998-01-01

    When rapidity gaps in high-$p_T$ dijet events are identified by energy flow in the central region, they may be calculated from factorized cross sections in perturbative QCD, up to corrections that behave as inverse powers of the central region energy. Although power-suppressed corrections may be important, a perturbative calculation of dijet rapidity gaps in ${\\rm p}\\bar{\\rm p}$ scattering successfully reproduces the overall features observed at the Tevatron. In this formulation, the average color content of the hard scattering is well-defined. We find that hard dijet rapidity gaps in quark-antiquark scattering are not due to singlet exchange alone.

  8. Energy and Color Flow in Dijet Rapidity Gaps

    E-print Network

    Gianluca Oderda; George Sterman

    1998-06-30

    When rapidity gaps in high-$p_T$ dijet events are identified by energy flow in the central region, they may be calculated from factorized cross sections in perturbative QCD, up to corrections that behave as inverse powers of the central region energy. Although power-suppressed corrections may be important, a perturbative calculation of dijet rapidity gaps in ${\\rm p}\\bar{\\rm p}$ scattering successfully reproduces the overall features observed at the Tevatron. In this formulation, the average color content of the hard scattering is well-defined. We find that hard dijet rapidity gaps in quark-antiquark scattering are not due to singlet exchange alone.

  9. Controlling the band gap energy of cluster-assembled materials.

    PubMed

    Mandal, Sukhendu; Reber, Arthur C; Qian, Meichun; Weiss, Paul S; Khanna, Shiv N; Sen, Ayusman

    2013-11-19

    Cluster-assembled materials combine the nanoscale size and composition-dependent properties of clusters, which have highly tunable magnetic and electronic properties useful for a great variety of potential technologies. To understand the emergent properties as clusters are assembled into hierarchical materials, we have synthesized 23 cluster-assembled materials composed of As7(3-)-based motifs and different countercations and measured their band gap energies. We found that the band gap energy varies from 1.09 to 2.21 eV. In addition, we have carried out first principles electronic structure studies to identify the physical mechanisms that enable control of the band gap edges of the cluster assemblies. The choice of counterion has a profound effect on the band gap energy in ionic cluster assemblies. The top of the valence band is localized on the arsenic cluster, while the conduction band edge is located on the alkali metal counterions. Changing the counterion changes the position of the conduction band edge, enabling control of the band gap energy. We can also vary the architecture of the ionic solid by incorporating cryptates as counterions, which provide charge but are separated from the clusters by bulky ligands. Higher dimensionality typically decreases the band gap energy through band broadening; however band gap energies increased upon moving from zero-dimensional (0D) to two-dimensional (2D) assemblies. This is because internal electric fields generated by the counterion preferentially stabilize the adjacent lone pair orbitals that mark the top of the valence band. Thus, the choice of the counterion can control the position of the conduction band edge of ionic cluster assemblies. In addition, the dimensionality of the solid via internal electric fields can control the valence band edge. Through covalently linking arsenic clusters into composite building blocks, we have also been able to tune the band gap energy. We used a theoretical description based on cluster orbital theory to provide microscopic understanding of the electronic character of the composite building blocks and the observed variations in the band gap energy. Also, we have shown how dimeric linkers can be used to control the band gap energy. Lastly, we also investigated the effects of charge transfer complexes of M(CO)3 on the band gap energy. PMID:23734558

  10. Orbital-selective metal-insulator transition and gap formation above TC in superconducting Rb(1-x)Fe(2-y)Se2.

    PubMed

    Wang, Zhe; Schmidt, M; Fischer, J; Tsurkan, V; Greger, M; Vollhardt, D; Loidl, A; Deisenhofer, J

    2014-01-01

    Understanding the origin of high-temperature superconductivity in copper- and iron-based materials is one of the outstanding tasks of current research in condensed matter physics. Even the normal metallic state of these materials exhibits unusual properties. Here we report on a hierarchy of temperatures T(c)gap)superconducting Rb(1-x)Fe(2-y)Se(2) observed by THz spectroscopy (T(c)=critical temperature of the superconducting phase; T(gap)=temperature below which an excitation gap opens; T(met)=temperature below which a metallic optical response occurs). Above T(met)=90 K the material reveals semiconducting characteristics. Below T(met) a coherent metallic THz response emerges. This metal-to-insulator-type, orbital-selective transition is indicated by an isosbestic point in the temperature dependence of the optical conductivity and dielectric constant at THz frequencies. At T(gap)= 61 K, a gap opens in the THz regime and then the superconducting transition occurs at T(c)=32 K. This sequence of temperatures seems to reflect a corresponding hierarchy of the electronic correlations in different bands. PMID:24469424

  11. Is There an Energy Efficiency Gap?

    E-print Network

    Allcott, Hunt Volney

    Many analysts of the energy industry have long believed that energy efficiency offers an enormous "win-win" opportunity: through aggressive energy conservation policies, we can both save money and reduce negative externalities ...

  12. Power applications of high-temperature superconductivity: Variable speed motors, current switches, and energy storage for end use

    SciTech Connect

    Hawsey, R.A. [Oak Ridge National Lab., TN (United States); Banerjee, B.B.; Grant, P.M. [Electric Power Research Inst., Palo Alto, CA (United States)

    1996-08-01

    The objective of this project is to conduct joint research and development activities related to certain electric power applications of high-temperature superconductivity (HTS). The new superconductors may allow development of an energy-efficient switch to control current to variable speed motors, superconducting magnetic energy storage (SMES) systems, and other power conversion equipment. Motor types that were considered include induction, permanent magnet, and superconducting ac motors. Because it is impractical to experimentally alter certain key design elements in radial-gap motors, experiments were conducted on an axial field superconducting motor prototype using 4 NbTi magnets. Superconducting magnetic energy storage technology with 0.25--5 kWh stored energy was studied as a viable solution to short duration voltage sag problems on the customer side of the electric meter. The technical performance characteristics of the device wee assembled, along with competing technologies such as active power line conditioners with storage, battery-based uninterruptible power supplies, and supercapacitors, and the market potential for SMES was defined. Four reports were prepared summarizing the results of the project.

  13. Superconducting Gap and Symmetry in FeSe1?xTex Studied by Specific Heat in Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Konno, Takuya; Adachi, Tadashi; Imaizumi, Masato; Noji, Takashi; Kawamata, Takayuki; Koike, Yoji

    2014-09-01

    In order to investigate details of the superconducting (SC) gap in the iron-chalcogenide superconductors, the specific heat, C, of FeSe1?xTex with x = 0.6–1 has been measured in magnetic fields. Using the two-gap model, it has been found that the smaller SC gap is significantly depressed by the application of magnetic field, resulting in the increase of the slope of the C/T vs T2 plot at low temperatures. From the specific-heat measurements at very low temperatures down to 0.4 K, it has been found that the enhancement of the residual electronic-specific-heat-coefficient in the ground state, ?0, by the application of magnetic field is much smaller than that expected for superconductors with the typical s- or d-wave SC paring symmetry, which is in sharp contrast to the significant enhancement of ?0 observed in the iron-pnictide superconductors. These results are discussed in relation to the multi-band effect in the iron-based superconductors.

  14. Langmuir vacuum and superconductivity

    SciTech Connect

    Veklenko, B. A. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

    2012-06-15

    It is shown that, in the 'jelly' model of cold electron-ion plasma, the interaction between electrons and the quantum electromagnetic vacuum of Langmuir waves involves plasma superconductivity with an energy gap proportional to the energy of the Langmuir quantum.

  15. Charge-order-maximized momentum-dependent superconductivity

    E-print Network

    Loss, Daniel

    ARTICLES Charge-order-maximized momentum- dependent superconductivity T. KISS1,2 *, T. YOKOYA1 Charge ordering and superconductivity are observed in the phase diagrams of a variety of materials-density-wave (CDW) and superconducting transitions show an energy gap in the single- particle density of states

  16. Battery energy storage and superconducting magnetic energy storage for utility applications: A qualitative analysis

    SciTech Connect

    Akhil, A.A.; Butler, P.; Bickel, T.C.

    1993-11-01

    This report was prepared at the request of the US Department of Energy`s Office of Energy Management for an objective comparison of the merits of battery energy storage with superconducting magnetic energy storage technology for utility applications. Conclusions are drawn regarding the best match of each technology with these utility application requirements. Staff from the Utility Battery Storage Systems Program and the superconductivity Programs at Sandia National contributed to this effort.

  17. Scaling of Superconducting Switches for Extraction of Magnetic Energy

    Microsoft Academic Search

    Amalia Ballarino; Thomas Taylor

    2010-01-01

    In certain cases it is necessary to extract the energy from a superconducting magnet when it quenches, in order to limit the heat generated by the event and thus prevent irreversible damage. This is usually achieved by opening a contact breaker across a resistor in the circuit feeding the magnet. For the heavy currents used to excite large magnets such

  18. Control Aspects of the Tacoma Superconducting Magnetic Energy Storage Project

    Microsoft Academic Search

    J. F. Hauer; H. J. Boenig

    1987-01-01

    On February 16, 1983, a 10 MW\\/30 MJ superconducting magnetic energy storage unit was energized at the Bonneville Power Administration (BPA) substation in Tacoma, Washington. The unit was retired a year later, after extensive tests directed toward its experimental use as a small-signal stabilizer for the Pacific AC Intertie. This paper addresses the control aspects of the project. These include

  19. Power conditioning systems for superconductive magnetic energy storage

    Microsoft Academic Search

    R. H. Lasseter; S. G. Jalali

    1991-01-01

    Two power conditioning systems for superconductive magnetic energy storage (SMES) are presented. One power conditioning system is based on a hybrid current sourced inverter (CSI), the second is a combination of a DC chopper with a voltage sourced inverter (VSI). Both of these systems have independent control of real and reactive power. These systems have a significant reduction in MVA

  20. Superconducting magnetic energy storage: a cost and sizing study

    Microsoft Academic Search

    H. D. Shaw; J. D. Morgan; M. D. Anderson

    1980-01-01

    Two applications for superconducting magnetic energy storage (SMES) devices in power systems are studied. One is for peak shaving, and the other is for load leveling. Consideration is given to placing these devices near load centers to reduce the line losses. For (SMES) cases studied using smaller size devices at several load centers, the line losses are lowered. By comparing

  1. Feasible utility scale Superconducting Magnetic Energy Storage system

    SciTech Connect

    Loyd, R.J.; Schoenung, S.M.; Nakamura, T.; Lieurance, D.W.; Hilal, M.A.; Rogers, J.D.; Purcell, J.R.; Hassenzahl, W.V.

    1986-01-01

    This paper presents the latest design features and estimated costs of a 5000 MWh/1000 MW Superconducting Magnetic Energy Storage (SMES) plant. SMES is proposed as a commercially viable technology for electric utility load leveling. The primary advantage of SMES over other electrical energy storage technologies is its high net roundtrip efficiency. Other features include rapid availability and low maintenance and operating costs. Economic comparisons are made with other energy storage options and with gas turbines. In a diurnal load leveling application, a superconducting coil can be charged from the utility grid during off-peak hours. The ac grid is connected to the dc magnetic coil through a power conversion system that includes an inverter/rectifier. Once charged, the superconducting coil conducts current, which supports an electromagnetic field, with virtually no losses. During hours of peak load, the stored energy is discharged to the grid by reversing the charging process. The principle of operation of a SMES unit is shown in Fig. 1. For operation in the superconducting mode, the coil is maintained at extremely low temperature by immersion in a bath of liquid helium.

  2. Toroidal constant-tension superconducting magnetic energy storage units

    DOEpatents

    Herring, J.S.

    1992-11-03

    A superconducting magnetic energy storage unit is provided in which the magnet is wound in a toroidal fashion such that the magnetic field produced is contained only within the bore of the magnet, and thus producing a very low external field. The superconducting magnet includes a coolant channel disposed through the wire. The bore of the magnet comprises a storage volume in which cryogenic coolant is stored, and this volume supplies the coolant to be delivered to the coolant channel in the magnet. 6 figs.

  3. Probabilities of rapidity gaps in high energy interactions

    E-print Network

    A. B. Kaidalov; V. A. Khoze; A. D. Martin; M. G. Ryskin

    2001-05-15

    We show that high energy hadronic reactions which contain a rapidity gap and a hard subprocess have a specific dependence on the kinematic variables, which results in a characteristic behaviour of the survival probability of the gap. We incorporate this mechanism in a two-channel eikonal model to make an essentially parameter-free estimate of diffractive dijet production at the Tevatron, given the diffractive structure functions measured at HERA. The estimates are in surprising agreement with the measurements of the CDF collaboration. We briefly discuss the application of the model to other hard processes with rapidity gaps.

  4. Multifrequency modes in superconducting resonators: Bridging frequency gaps in off-resonant couplings

    NASA Astrophysics Data System (ADS)

    Andersen, Christian Kraglund; Mølmer, Klaus

    2015-02-01

    A superconducting quantum interference device (SQUID) inserted in a superconducting waveguide resonator imposes current and voltage boundary conditions that makes it suitable as a tuning element for the resonator modes. If such a SQUID element is subject to a periodically varying magnetic flux, the resonator modes acquire frequency sidebands. In this work we calculate the multifrequency eigenmodes of resonators coupled to periodically driven SQUIDs and we use the Lagrange formalism to propose a theory for their quantization. The elementary excitations of a multifrequency mode can couple resonantly to physical systems with different transition frequencies and this makes the resonator an efficient quantum bus for state transfer and coherent quantum operations in hybrid quantum systems. As an example of the application of our multifrequency modes, we determine their coupling to transmon qubits with different frequencies and we present a bichromatic scheme for entanglement and gate operations.

  5. Energy BandGap Engineering of Graphene Nanoribbons

    Microsoft Academic Search

    Melinda Y. Han; Barbaros Ozyilmaz; Yuanbo Zhang; Philip Kim

    2007-01-01

    We investigate electronic transport in lithographically patterned graphene\\u000aribbon structures where the lateral confinement of charge carriers creates an\\u000aenergy gap near the charge neutrality point. Individual graphene layers are\\u000acontacted with metal electrodes and patterned into ribbons of varying widths\\u000aand different crystallographic orientations. The temperature dependent\\u000aconductance measurements show larger energy gaps opening for narrower ribbons.\\u000aThe sizes

  6. Probabilities of rapidity gaps in high energy interactions

    Microsoft Academic Search

    A. B. Kaidalov; V. A. Khoze; A. D. Martin; M. G. Ryskin

    2001-01-01

    .   We show that high energy hadronic reactions which contain a rapidity gap and a hard subprocess have a specific dependence\\u000a on the kinematic variables, which results in a characteristic behaviour of the survival probability of the gap. We incorporate\\u000a this mechanism in a two-channel eikonal model to make an essentially parameter-free estimate of diffractive dijet production\\u000a at the Tevatron,

  7. ESR spectrometer with a loop-gap resonator for cw and time resolved studies in a superconducting magnet.

    PubMed

    Simon, Ferenc; Murányi, Ferenc

    2005-04-01

    The design and performance of an electron spin resonance spectrometer operating at 3 and 9 GHz microwave frequencies combined with a 9-T superconducting magnet are described. The probehead contains a compact two-loop, one gap resonator, and is inside the variable temperature insert of the magnet enabling measurements in the 0-9T magnetic field and 1.5-400 K temperature range. The spectrometer allows studies on systems where resonance occurs at fields far above the g approximately 2 paramagnetic condition such as in antiferromagnets. The low quality factor of the resonator allows time resolved experiments such as, e.g., longitudinally detected ESR. We demonstrate the performance of the spectrometer on the NaNiO2 antiferromagnet, the MgB2 superconductor, and the RbC60 conducting alkaline fulleride polymer. PMID:15780920

  8. Energy dependence of the survival probability of large rapidity gaps

    Microsoft Academic Search

    E. Gotsman; E. Levin; U. Maor

    1998-01-01

    The energy dependence for the survival probability of large rapidity gaps (LRG) , is calculated in an Eikonal model assuming a Gaussian opacity. The parameters determining are evaluated directly from experimental data, without further recourse to models. We find that decreases with increasing energy, in line with recent results for LRG dijet production at the Tevatron.

  9. Energy dependence of the survival probability of large rapidity gap

    E-print Network

    E. Gotsman; E. Levin; U. Maor

    1998-04-26

    The energy dependence for the survival probability of large rapidity gaps (LRG) $$, is calculated in an Eikonal model assuming a Gaussian opacity. The parameters determining $$ are evaluated directly from experimental data, without further recourse to models. We find that $$ decreases with increasing energy, in line with recent results for LRG dijet production at the Tevatron.

  10. Rapidity gaps in minijets production at Tevatron energies

    E-print Network

    G. Calucci; R. Ragazzon; D. Treleani

    1996-11-07

    Multiparton interactions modify the high energy hadronic cross section to produce minijets with a rapidity gap in the distribution of secondaries. At Tevatron energy the correction to the single scattering term is large for transverse momenta smaller than 6 GeV.

  11. Superconductivity

    SciTech Connect

    Rosen, J.

    1988-06-01

    Superconducting materials can conduct dc electricity-sometimes in enormous currents-with to resistance. They can cause a locomotive to levitate. They have been tested in noteworthy projects. But they must still overcome several economic as well as technical constraints. This article discusses some of these obstacles.

  12. Superconductivity:

    NASA Astrophysics Data System (ADS)

    Sacchetti, N.

    In this paper a short historical account of the discovery of superconductivity and of its gradual development is given. The physical interpretation of its various aspects took about forty years (from 1911 to 1957) to reach a successful description of this phenomenon in terms of a microscopic theory At the very end it seemed that more or less everything could be reasonably interpreted even if modifications and refinements of the original theory were necessary. In 1986 the situation changed abruptly when a cautious but revolutionary paper appeared showing that superconductivity was found in certain ceramic oxides at temperatures above those up to then known. A rush of frantic experimental activity started world-wide and in less than one year it was shown that superconductivity is a much more widespread phenomenon than deemed before and can be found at temperatures well above the liquid air boiling point. The complexity and the number of the substances (mainly ceramic oxides) involved call for a sort of modern alchemy if compounds with the best superconducting properties are to be manufactured. We don't use the word alchemy in a deprecatory sense but just to emphasise that till now nobody can say why these compounds are what they are: superconductors.

  13. STRIPES AND SUPERCONDUCTIVITY IN CUPRATE SUPERCONDUCTORS

    SciTech Connect

    TRANQUADA, J.M.

    2005-08-22

    One type of order that has been observed to compete with superconductivity in cuprates involves alternating charge and antiferromagnetic stripes. Recent neutron scattering studies indicate that the magnetic excitation spectrum of a stripe-ordered sample is very similar to that observed in superconducting samples. In fact, it now appears that there may be a universal magnetic spectrum for the cuprates. One likely implication of this universal spectrum is that stripes of a dynamic form are present in the superconducting samples. On cooling through the superconducting transition temperature, a gap opens in the magnetic spectrum, and the weight lost at low energy piles up above the gap; the transition temperature is correlated with the size of the spin gap. Depending on the magnitude of the spin gap with respect to the magnetic spectrum, the enhanced magnetic scattering at low temperature can be either commensurate or incommensurate. Connections between stripe correlations and superconductivity are discussed.

  14. Free-Energy Difference Between Normal and Superconducting States

    Microsoft Academic Search

    John Bardeen; Michael Stephen

    1964-01-01

    The Eliashberg expression for the free-energy difference between superconducting and normal states for an electron-phonon interaction model is evaluated so as to estimate the errors involved in expressions based on the weak-coupling limit. It is shown that the major correction comes from the difference in self-energy terms Sigma1s and Sigma1n and is relatively of order [(Deltaomega0)ln(Deltaomega0)]2, where omega0 is an

  15. Studies of power conditioning circuits for superconductive magnetic energy store

    Microsoft Academic Search

    J. Wang; J. Skiles; R. Kustom; T. Ise; F. Tsang; J. Cleary

    1988-01-01

    The superconductive magnetic energy store (SMES) approach to utility-load leveling has the potential for very high energy conversion efficiency and fast response to changes in load demands. It can be used to improve utility system operation economics and system stabilities. The power-conditioning circuit interfacing an SMES and a utility network consists of thyristor or gate-turn-off (GTO) device bridges of the

  16. Is There an Energy Efficiency Gap?

    E-print Network

    Alcott, Hunt

    2012-01-17

    Many analysts have argued that energy efficiency investments offer an enormous “win-win” opportunity to both reduce negative externalities and save money. This overview paper presents a simple model of investment in ...

  17. Is There An Energy Efficiency Gap?

    E-print Network

    Allcott, Hunt

    2012-01-17

    Many analysts have argued that energy efficiency investments offer an enormous “win-win” opportunity to both reduce negative externalities and save money. This overview paper presents a simple model of investment in ...

  18. Momentum Dependence of Superconducting Gap, Strong-Coupling Dispersion Kink, And Tightly Bound Cooper Pairs in the High-T(C)(Sr,Ba)(1-X)(K,Na)(X)Fe(2) As(2) Superconductors

    SciTech Connect

    Wray, L.; Qian, D.; Hsieh, D.; Xia, Y.; Li, L.; Checkelsky, J.G.; Pasupathy, A.; Gomes, K.K.; Parker, C.V.; Fedorov, A.V.; Chen, G.F.; Luo, J.L.; Yazdani, A.; Ong, N.P.; Wang, N.L.; Hasan, M.Z.

    2009-05-28

    We present a systematic angle-resolved photoemission spectroscopic study of the high-T{sub c} superconductor class (Sr/Ba){sub 1-x}K{sub x}Fe{sub 2}As{sub 2}. By utilizing a photon-energy-modulation contrast and scattering geometry we report the Fermi surface and the momentum dependence of the superconducting gap, {triangle}(k{open_square}). A prominent quasiparticle dispersion kink reflecting strong scattering processes is observed in a binding-energy range of 25--55 meV in the superconducting state, and the coherence length or the extent of the Cooper pair wave function is found to be about 20 {angstrom}, which is uncharacteristic of a superconducting phase realized by the BCS-phonon-retardation mechanism. The observed 40{+-}15 meV kink likely reflects contributions from the frustrated spin excitations in a J{sub 1}-J{sub 2} magnetic background and scattering from the soft phonons. Results taken collectively provide direct clues to the nature of the pairing potential including an internal phase-shift factor in the superconducting order parameter which leads to a Brillouin zone node in a strong-coupling setting.

  19. Color-Superconducting Gap in the Presence of a Magnetic Field

    E-print Network

    Efrain J. Ferrer; Vivian de la Incera; Cristina Manuel

    2006-05-17

    We explore the effects of an external magnetic field in the structure and magnitude of the diquark condensate in a three massless quark flavor color superconductor. It is shown that the long-range component $\\widetilde{B}$ of the external magnetic field that penetrates the color-flavor locked (CFL) phase modifies its gap structure, producing a new phase of lower symmetry. Our analysis is performed within an NJL effective field theory with four-fermion interactions, inspired by one-gluon exchange. Using Ritus' method, we compute the quark propagators in the presence of a background magnetic field, and derive the gap equations for arbitrary values of the field. An analytical solution is found for strong magnetic fields. A main outcome of our study is that the $\\widetilde{B}$ field tends to strengthen the gaps that get contributions from pairs of $\\widetilde{Q}$-charged quarks. These gaps are enhanced through the field-dependent density of states of the $\\widetilde{Q}$-charged quarks on the Fermi surface. Our considerations are relevant for the study of highly magnetized compact stars.

  20. Doping-dependent anisotropic superconducting gap in Na1-?(Fe1-xCox)As from London penetration depth

    SciTech Connect

    Cho, Kyuil; Tanatar, Makariy A.; Spyrison, Nicholas; Kim, Hyunsoo; Song, Y.; Dai, Pengcheng; Zhang, C.L.; Prozorov, Ruslan

    2012-07-30

    The London penetration depth was measured in single crystals of self-doped Na1-?FeAs (from under doping to optimal doping, Tc from 14 to 27 K) and electron-doped Na(Fe1-xCox)As with x ranging from undoped, x=0, to overdoped, x=0.1. In all samples, the low-temperature variation of the penetration depth exhibits a power-law dependence, ??(T)=ATn, with the exponent that varies in a domelike fashion from n˜1.1 in the underdoped, reaching a maximum of n˜1.9 in the optimally doped, and decreasing again to n˜1.3 on the overdoped side. While the anisotropy of the gap structure follows a universal domelike evolution, the exponent at optimal doping, n˜1.9, is lower than in other charge-doped Fe-based superconductors (FeSCs). The full-temperature range superfluid density, ?s(T)=?(0)/?(T)2, at optimal doping is also distinctly different from other charge-doped FeSCs but is similar to isovalently substituted BaFe2(As1-xPx)2, believed to be a nodal pnictide at optimal doping. These results suggest that the superconducting gap in Na(Fe1-xCox)As is highly anisotropic even at optimal doping.

  1. Numerical analysis of magnetic field in superconducting magnetic energy storage

    SciTech Connect

    Kanamaru, Y. (Kanazawa Inst. of Technology, 7-1 Ohgigaoka, Nonoichi, Ishikawa 921 (JP)); Amemiya, Y. (Chiba Inst. of Tech., Narashino (Japan))

    1991-09-01

    This paper reports that the superconducting magnetic energy storage (SMES) is more useful than the other systems of electric energy storage because of larger stored energy and higher efficiency. The other systems are the battery, the flywheel, the pumped-storage power station. Some models of solenoid type SMES are designed in U.S.A. and Japan. But a high magnetic field happens by the large scale SMES in the living environment, and makes the erroneous operations of the computer display, the pacemaker of the heart and the electronic equipments. We study some fit designs of magnetic shielding of the solenoidal type SMES for reduction of the magnetic field in living environment. When some superconducting shielding coils are over the main storage coil, magnetic field reduces remarkably than the case of non shielding coil. The calculated results of the magnetic field are obtained y the finite element method.

  2. The calculation of band gap energy in zinc oxide films

    NASA Astrophysics Data System (ADS)

    Arif, Ali; Belahssen, Okba; Gareh, Salim; Benramache, Said

    2015-01-01

    We investigated the optical properties of undoped zinc oxide thin films as the n-type semiconductor; the thin films were deposited at different precursor molarities by ultrasonic spray and spray pyrolysis techniques. The thin films were deposited at different substrate temperatures ranging between 200 and 500 °C. In this paper, we present a new approach to control the optical gap energy of ZnO thin films by concentration of the ZnO solution and substrate temperatures from experimental data, which were published in international journals. The model proposed to calculate the band gap energy with the Urbach energy was investigated. The relation between the experimental data and theoretical calculation suggests that the band gap energies are predominantly estimated by the Urbach energies, film transparency, and concentration of the ZnO solution and substrate temperatures. The measurements by these proposal models are in qualitative agreements with the experimental data; the correlation coefficient values were varied in the range 0.96–0.99999, indicating high quality representation of data based on Equation (2), so that the relative errors of all calculation are smaller than 4%. Thus, one can suppose that the undoped ZnO thin films are chemically purer and have many fewer defects and less disorder owing to an almost complete chemical decomposition and contained higher optical band gap energy.

  3. The role of gap analyses in energy assurance planning.

    PubMed

    Shea, Katherine

    2013-01-01

    Energy-related emergencies, such as power outages or interruptions to other energy supplies, can arise from a number of factors. Common causes include severe weather events--such as snowstorms, hurricanes, or summer storms with strong winds--as well as energy infrastructure that is overburdened, aging, or in need of repair. As past experience indicates, jurisdictions will continue to experience severe weather events, as well as confront infrastructure issues that make future power outages likely. As a result, state and local governments have turned to energy assurance planning, an energy-specific form of planning that helps jurisdictions prepare for and recover from energy emergencies. Energy assurance recognizes that power loss/disruption cannot be eradicated completely, but jurisdictions can mitigate the impact of power loss through effective planning. This article discusses the role of energy assurance planning and provides a description of what energy assurance means and why developing such plans at the state and local levels is important. In addition, this article discusses the role of statutory gap analyses in energy assurance planning and discusses how a gap analysis can be used by planners to identify trends and gaps in energy assurance. To provide context, a recently conducted statutory gap analysis analyzing national emergency backup power trends is provided as a case study. A summary of this project and key findings is included. Finally, this article briefly touches on legislation as an alternative to energy assurance planning, and provides summaries of recent legislative proposals introduced in the aftermath of Hurricane Sandy. PMID:24180061

  4. Size and symmetry of the superconducting gap in the f.c.c. Cs3C60 polymorph close to the metal-Mott insulator boundary

    PubMed Central

    Poto?nik, Anton; Krajnc, Andraž; Jegli?, Peter; Takabayashi, Yasuhiro; Ganin, Alexey Y.; Prassides, Kosmas; Rosseinsky, Matthew J.; Ar?on, Denis

    2014-01-01

    The alkali fullerides, A3C60 (A = alkali metal) are molecular superconductors that undergo a transition to a magnetic Mott-insulating state at large lattice parameters. However, although the size and the symmetry of the superconducting gap, ?, are both crucial for the understanding of the pairing mechanism, they are currently unknown for superconducting fullerides close to the correlation-driven magnetic insulator. Here we report a comprehensive nuclear magnetic resonance (NMR) study of face-centred-cubic (f.c.c.) Cs3C60 polymorph, which can be tuned continuously through the bandwidth-controlled Mott insulator-metal/superconductor transition by pressure. When superconductivity emerges from the insulating state at large interfullerene separations upon compression, we observe an isotropic (s-wave) ? with a large gap-to-superconducting transition temperature ratio, 2?0/kBTc = 5.3(2) [?0 = ?(0 K)]. 2?0/kBTc decreases continuously upon pressurization until it approaches a value of ~3.5, characteristic of weak-coupling BCS theory of superconductivity despite the dome-shaped dependence of Tc on interfullerene separation. The results indicate the importance of the electronic correlations for the pairing interaction as the metal/superconductor-insulator boundary is approached. PMID:24584087

  5. Energy Gaps in the Failed High-Tc Superconductor La_1.875Ba_0.125CuO_4

    SciTech Connect

    He, R.

    2010-05-04

    A central issue on high-T{sub c} superconductivity is the nature of the normal-state gap (pseudogap) in the underdoped regime and its relationship with superconductivity. Despite persistent efforts, theoretical ideas for the pseudogap evolve around fluctuating superconductivity, competing order and spectral weight suppression due to many-body effects. Recently, while some experiments in the superconducting state indicate a distinction between the superconducting gap and pseudogap, others in the normal state, either by extrapolation from high-temperature data or directly from La{sub 1.875}Ba{sub 0.125}CuO{sub 4} (LBCO-1/8) at low temperature, suggest the ground-state pseudogap is a single gap of d-wave form. Here we report angle-resolved photoemission (ARPES) data from LBCO-1/8, collected with improved experimental conditions, that reveal the ground-state pseudogap has a pronounced deviation from the simple d-wave form. It contains two distinct components: a d-wave component within an extended region around the node and the other abruptly enhanced close to the antinode, pointing to a dual nature of the pseudogap in this failed high-T{sub c} superconductor which involves a possible precursor pairing energy scale around the node and another of different but unknown origin near the antinode.

  6. Energy Gaps in the Failed High-Tc Superconductor La1.875Ba0.125CuO4

    SciTech Connect

    Not Available

    2011-08-11

    A central issue in high-T{sub c} superconductivity is the nature of the normal-state gap (pseudogap) in the underdoped regime and its relationship with superconductivity. Despite persistent efforts, theoretical ideas for the pseudogap evolve around fluctuating superconductivity, competing order, and spectral weight suppression due to many-body effects. Recently, although some experiments in the superconducting state indicate a distinction between the superconducting gap and pseudogap, others in the normal state, either by extrapolation from high-temperature data or directly from La{sub 1.875)Ba{sub 0.125}CuO{sub 4} (LBCO-1/8) at low temperature, suggest the ground-state pseudogap is a single gap of d-wave form. Here, we report angle-resolved photoemission data from LBCO-1/8, collected with improved experimental conditions, that reveal the ground-state pseudogap has a pronounced deviation from the simple d-wave form. It contains two distinct components: a d-waev component within an extended region around the node and the other abruptly enhanced close to the antinode, pointing to a dual nature of the pseudogap in this failed high-T{sub c} superconductor that involves a possible precursor-pairing energy scale around the node and another of different but unknown origin near the antinode.

  7. Energy Gaps in the Failed High-Tc Superconductor La_1.875Ba_0.125Cu_O4

    SciTech Connect

    Tanaka, K.

    2011-08-19

    A central issue on high-T{sub c} superconductivity is the nature of the normal-state gap (pseudogap) in the underdoped regime and its relationship with superconductivity. Despite persistent efforts, theoretical ideas for the pseudogap evolve around fluctuating superconductivity, competing order and spectral weight suppression due to many-body effects. Recently, while some experiments in the superconducting state indicate a distinction between the superconducting gap and pseudogap, others in the normal state, either by extrapolation from high-temperature data or directly from La{sub 1.875}Ba{sub 0.125}CuO{sub 4} (LBCO-1/8) at low temperature, suggest the ground-state pseudogap is a single gap of d-wave form. Here we report angle-resolved photoemission (ARPES) data from LBCO-1/8, collected with improved experimental conditions, that reveal the ground-state pseudogap has a pronounced deviation from the simple d-wave form. It contains two distinct components: a d-wave component within an extended region around the node and the other abruptly enhanced close to the antinode, pointing to a dual nature of the pseudogap in this failed high-T{sub c} superconductor which involves a possible precursor pairing energy scale around the node and another of different but unknown origin near the antinode.

  8. Convergence of Meissner minimisers of the Ginzburg-Landau energy of superconductivity as

    E-print Network

    Chapman, Jon

    Convergence of Meissner minimisers of the Ginzburg-Landau energy of superconductivity as #20; ! +1 cylindrical superconducting domain subject to a uniform applied axial magnetic #12;eld is examined. Under as vortices, since they are each circled by a vortex of superconducting current. The cores of these tubes

  9. Superconducting magnetic energy storage apparatus structural support system

    DOEpatents

    Withers, Gregory J. (Bolingbrook, IL); Meier, Stephen W. (Bolingbrook, IL); Walter, Robert J. (Batavia, IL); Child, Michael D. (Naperville, IL); DeGraaf, Douglas W. (Downers Grove, IL)

    1992-01-01

    A superconducting magnetic energy storage apparatus comprising a cylindrical superconducting coil; a cylindrical coil containment vessel enclosing the coil and adapted to hold a liquid, such as liquefied helium; and a cylindrical vacuum vessel enclosing the coil containment vessel and located in a restraining structure having inner and outer circumferential walls and a floor; the apparatus being provided with horizontal compression members between (1) the coil and the coil containment vessel and (2) between the coil containment vessel and the vacuum vessel, compression bearing members between the vacuum vessel and the restraining structure inner and outer walls, vertical support members (1) between the coil bottom and the coil containment vessel bottom and (2) between the coil containment vessel bottom and the vacuum vessel bottom, and external supports between the vacuum vessel bottom and the restraining structure floor, whereby the loads developed by thermal and magnetic energy changes in the apparatus can be accommodated and the structural integrity of the apparatus be maintained.

  10. Localization of metal-induced gap states at the metal-insulator interface: Origin of flux noise in SQUIDs and superconducting qubits

    SciTech Connect

    Choi, SangKook; Lee, Dung-Hai; Louie, Steven G.; Clarke, John

    2009-10-10

    The origin of magnetic flux noise in Superconducting Quantum Interference Devices with a power spectrum scaling as 1/f (f is frequency) has been a puzzle for over 20 years. This noise limits the decoherence time of superconducting qubits. A consensus has emerged that the noise arises from fluctuating spins of localized electrons with an areal density of 5 x 10(17)m(-2). We show that, in the presence of potential disorder at the metal-insulator interface, some of the metal-induced gap states become localized and produce local moments. A modest level of disorder yields the observed areal density.

  11. Massive polarons in large-energy-gap polymers

    Microsoft Academic Search

    R. P. McCall; J. M. Ginder; M. G. Roe; G. E. Asturias; E. M. Scherr; A. G. MacDiarmid; A. J. Epstein

    1989-01-01

    We present evidence for the existence of defect states with large mass and low mobility in the conducting polymer polyaniline. This large-energy-gap polymer has been shown to have properties significantly different from many other conducting polymers. Photoinduced infrared absorption studies presented here are consistent with the photogeneration of charged polarons. Analysis within the amplitude mode (Peierls) formalism indicates that these

  12. Microcomputer control for the superconducting magnetic energy storage system

    SciTech Connect

    Seamons, M.J.; Criscuolo, A.L.

    1981-01-01

    The microcomputer-based, automatic control and data acquisition system for the Superconducting Magnetic Energy Storage system is described. A brief discussion of the function of SMES and identification of its major systems is followed by a detailed discussion of the control and data acquisition system. The distributed control and data acquisition architecture, interprocessor timing and communications, task scheduler, master-slave relationship, and man/machine interface are some of the topics discussed.

  13. Low energy excitations in amorphous superconducting ZrCu alloys

    NASA Astrophysics Data System (ADS)

    Schink, H. J.; Löhneysen, H. v.; Sander, W.; Samwer, K.

    1981-08-01

    The low temperature specific heat C of a series of amorphous superconducting Zr xCu 1-x alloys (0.6 < x < 0.74) was measured between 0.1 K and 3 K. For T << T c all samples show a contribution C ? T. This corroborates that low energy excitations with a constant density of states which are at the origin of this contribution are an intrinsic feature of the amorphous state.

  14. A multilevel power conditioning system for superconductive magnetic energy storage

    Microsoft Academic Search

    Hui Li; Thomas L. Baldwin; Cesar A. Luongo; Da Zhang

    2005-01-01

    The introduction of multilevel converters makes possible the use of pulse width modulation (PWM) converters and fast switching medium power devices like insulated gate bipolar transistors (IGBTs) for high-voltage, high-power applications, such as flexible ac transmission systems (FACTS). This paper proposes a five-level voltage source inverter (VSI)-chopper for a superconductive magnetic energy storage (SMES) power conditioning system (PCS). The circuit

  15. Concept of Cold Energy Storage for Superconducting Flywheel Energy Storage System

    Microsoft Academic Search

    Jisung Lee; Sangkwon Jeong; Young Hee Han; Byung Jun Park

    2011-01-01

    A superconducting flywheel energy storage (SFES) system is an energy storage device with unprecedented small kinetic energy loss by utilizing diamagnetic levitation property of superconductor. The system, therefore, is expected to be one of the most promising candidates in the application of renewable energy field such as PV (photovoltaic) or wind energy development where the power generation is intermittent. An

  16. Optical and electrical properties of thin superconducting films

    NASA Technical Reports Server (NTRS)

    Covington, Billy C.; Jing, Feng Chen

    1990-01-01

    Infrared spectroscopic techniques can provide a vital probe of the superconducting energy gap which is one of the most fundamental physical properties of superconductors. Currently, the central questions regarding the optical properties of superconductors are how the energy gap can be measured by infrared techniques and at which frequency the gap exists. An effective infrared spectroscopic method to investigate the superconducting energy gap, Eg, was developed by using the Bomem DA 3.01 Fourier Transformation Spectrophotometer. The reflectivity of a superconducting thin film of YBaCuO deposited on SrTiO3 was measured. A shoulder was observed in the superconducting state reflectance R(sub S) at 480/cm. This gives a value of Eg/kT(sub c) = 7.83, where k is the Boltzmann constant and T(sub c) is the superconducting transition temperature, from which, it is suggested that YBaCuO is a very strong coupling superconductor.

  17. Quasiparticle Gaps and Exciton Coulomb Energies in Si Nanoshells

    SciTech Connect

    Frey, K. [University of Illinois, Chicago; Idrobo Tapia, Juan C [ORNL; Tiago, Murilo L [ORNL; Reboredo, Fernando A [ORNL; Ogut, Serdar [University of Illinois, Chicago

    2009-01-01

    Quasiparticle gaps and exciton Coulomb energies of H-passivated spherical Si nanoshells are computed using rst principles SCF and GW methods. We nd that the quasiparticle gap of a nanoshell depends on both its inner radius R1 (weakly) and outer radius R2 (strongly). These dependences on R1 and R2 are mostly consistent with electrostatics of a metallic shell. We also nd that the unscreened Coulomb energy ECoul in Si nanoshells has a somewhat unexpected size dependence at xed outer radius R2: ECoul decreases as the nanoshell becomes more conning, contrary to what one would expect from quantum connement eects. We show that this is a consequence of an increase in the average electron-hole distance, giving rise to reduced exciton Coulomb energies in spite of the reduction in the conning nanoshell volume.

  18. Glide-Plane Symmetry and Superconducting Gap Structure of Iron-Based Superconductors

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Berlijn, T.; Hirschfeld, P. J.; Scalapino, D. J.; Maier, T. A.

    2015-03-01

    We consider the effect of glide-plane symmetry of the Fe-pnictogen/chalcogen layer in Fe-based superconductors on pairing in spin fluctuation models. Recent theories have proposed that so-called ? -pairing states with nonzero total momentum can be realized and possess exotic properties such as odd parity spin singlet symmetry and time-reversal symmetry breaking. Here we show that ? pairing is inevitable when there is orbital weight at the Fermi level from orbitals with even and odd mirror reflection symmetry in z ; however, by explicit calculation, we conclude that the gap function that appears in observable quantities is identical to that found in earlier, 1 Fe per unit cell pseudocrystal momentum calculations.

  19. Glide-plane symmetry and superconducting gap structure of iron-based superconductors.

    PubMed

    Wang, Y; Berlijn, T; Hirschfeld, P J; Scalapino, D J; Maier, T A

    2015-03-13

    We consider the effect of glide-plane symmetry of the Fe-pnictogen/chalcogen layer in Fe-based superconductors on pairing in spin fluctuation models. Recent theories have proposed that so-called ?-pairing states with nonzero total momentum can be realized and possess exotic properties such as odd parity spin singlet symmetry and time-reversal symmetry breaking. Here we show that ? pairing is inevitable when there is orbital weight at the Fermi level from orbitals with even and odd mirror reflection symmetry in z; however, by explicit calculation, we conclude that the gap function that appears in observable quantities is identical to that found in earlier, 1 Fe per unit cell pseudocrystal momentum calculations. PMID:25815960

  20. The Slot Gap Model for Pulsar High-Energy Emission

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alexander

    2004-01-01

    A new picture of pulsar high-energy emission is proposed that is different from both the traditional polar cap and outer gap models, but combines elements of each. The slot gap model is based on electron acceleration along the edge of the open field region from the neutron star surface to near the light cylinder. Along the last open field line, the pair formation front rises to very high altitude forming a slot gap, where the accelerating electric field is unscreened by pairs. Electrons continue to accelerate to high altitudes in the slot gap, reaching a radiation reaction-limited energy of several TeV. The resulting radiation pattern features sharp caustics on the trailing edge of the open field region, allowing for the possibility of double-peaked pulse profiles very similar to those observed in gamma-ray pulsars. Since emission from a large range of altitudes arrives in phase, this model very naturally explains the phase alignment of radiation at all wavelengths from the Crab pulsar.

  1. Anisotropic Superconducting Gap and Elongated Vortices with Caroli-De Gennes-Matricon States in the New Superconductor Ta4Pd3Te16.

    PubMed

    Du, Zengyi; Fang, Delong; Wang, Zhenyu; Li, Yufeng; Du, Guan; Yang, Huan; Zhu, Xiyu; Wen, Hai-Hu

    2015-01-01

    The superconducting state is formed by the condensation of a large number of Cooper pairs. The normal state electronic properties can give significant influence on the superconducting state. For usual type-II superconductors, the vortices are cylinder like with a round cross-section. For many two dimensional superconductors, such as Cuprates, albeit the in-plane anisotropy, the vortices generally have a round shape. In this paper we report results based on the scanning tunnelling microscopy/spectroscopy measurements on a newly discovered superconductor Ta4Pd3Te16. The chain-like conducting channels of PdTe2 in Ta4Pd3Te16 make a significant anisotropy of the in-plane Fermi velocity. We suggest at least one anisotropic superconducting gap with gap minima or possible node exists in this multiband system. In addition, elongated vortices are observed with an anisotropy of ?||b/?&bottom?b ? 2.5. Clear Caroli-de Gennes-Matricon states are also observed within the vortex cores. Our results will initiate the study on the elongated vortices and superconducting mechanism in the new superconductor Ta4Pd3Te16. PMID:25797138

  2. Anisotropic Superconducting Gap and Elongated Vortices with Caroli-De Gennes-Matricon States in the New Superconductor Ta4Pd3Te16

    PubMed Central

    Du, Zengyi; Fang, Delong; Wang, Zhenyu; Li, Yufeng; Du, Guan; Yang, Huan; Zhu, Xiyu; Wen, Hai-Hu

    2015-01-01

    The superconducting state is formed by the condensation of a large number of Cooper pairs. The normal state electronic properties can give significant influence on the superconducting state. For usual type-II superconductors, the vortices are cylinder like with a round cross-section. For many two dimensional superconductors, such as Cuprates, albeit the in-plane anisotropy, the vortices generally have a round shape. In this paper we report results based on the scanning tunnelling microscopy/spectroscopy measurements on a newly discovered superconductor Ta4Pd3Te16. The chain-like conducting channels of PdTe2 in Ta4Pd3Te16 make a significant anisotropy of the in-plane Fermi velocity. We suggest at least one anisotropic superconducting gap with gap minima or possible node exists in this multiband system. In addition, elongated vortices are observed with an anisotropy of ?||b/?&bottom?b ? 2.5. Clear Caroli-de Gennes-Matricon states are also observed within the vortex cores. Our results will initiate the study on the elongated vortices and superconducting mechanism in the new superconductor Ta4Pd3Te16. PMID:25797138

  3. Orbital-selective metal-insulator transition and gap formation above TC in superconducting Rb1-xFe2-ySe2

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Schmidt, M.; Fischer, J.; Tsurkan, V.; Greger, M.; Vollhardt, D.; Loidl, A.; Deisenhofer, J.

    2014-01-01

    Understanding the origin of high-temperature superconductivity in copper- and iron-based materials is one of the outstanding tasks of current research in condensed matter physics. Even the normal metallic state of these materials exhibits unusual properties. Here we report on a hierarchy of temperatures Tcsuperconducting Rb1-xFe2-ySe2 observed by THz spectroscopy (Tc=critical temperature of the superconducting phase; Tgap=temperature below which an excitation gap opens; Tmet=temperature below which a metallic optical response occurs). Above Tmet=90?K the material reveals semiconducting characteristics. Below Tmet a coherent metallic THz response emerges. This metal-to-insulator-type, orbital-selective transition is indicated by an isosbestic point in the temperature dependence of the optical conductivity and dielectric constant at THz frequencies. At Tgap=61?K, a gap opens in the THz regime and then the superconducting transition occurs at Tc=32?K. This sequence of temperatures seems to reflect a corresponding hierarchy of the electronic correlations in different bands.

  4. Exporting superconductivity across the gap: Proximity effect for semiconductor valence-band states due to contact with a simple-metal superconductor

    NASA Astrophysics Data System (ADS)

    Moghaddam, A. G.; Kernreiter, T.; Governale, M.; Zülicke, U.

    2014-05-01

    The proximity effect refers to the phenomenon whereby superconducting properties are induced in a normal conductor that is in contact with an intrinsically superconducting material. In particular, the combination of nanostructured semiconductors with bulk superconductors is of interest because these systems can host unconventional electronic excitations such as Majorana fermions when the semiconductor's charge carriers are subject to a large spin-orbit coupling. The latter requirement generally favors the use of hole-doped semiconductors. On the other hand, basic symmetry considerations imply that states from typical simple-metal superconductors will predominantly couple to a semiconductor's conduction-band states and, therefore, in the first instance generate a proximity effect for band electrons rather than holes. In this article, we show how the superconducting correlations in the conduction band are transferred also to hole states in the valence band by virtue of interband coupling. A general theory of the superconducting proximity effect for bulk and low-dimensional hole systems is presented. The interplay of interband coupling and quantum confinement is found to result in unusual wave-vector dependencies of the induced superconducting gap parameters. One particularly appealing consequence is the density tunability of the proximity effect in hole quantum wells and nanowires, which creates new possibilities for manipulating the transition to nontrivial topological phases in these systems.

  5. Photonic Band Gap resonators for high energy accelerators

    SciTech Connect

    Schultz, S.; Smith, D.R. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics; Kroll, N. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics]|[Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1993-12-31

    We have proposed that a new type of microwave resonator, based on Photonic Band Gap (PBG) structures, may be particularly useful for high energy accelerators. We provide an explanation of the PBG concept and present data which illustrate some of the special properties associated with such structures. Further evaluation of the utility of PBG resonators requires laboratory testing of model structures at cryogenic temperatures, and at high fields. We provide a brief discussion of our test program, which is currently in progress.

  6. Analysis of the rapidity gap probability at CERN collider energies

    Microsoft Academic Search

    S. Hegyi

    1992-01-01

    The rapidity gap probability, i.e., the probability of detecting no particles in a given rapidity interval is investigated in proton-antiproton collisions at CERN collider energies. A scaling behaviour is found in the central rapidity domain, similar to the scaling of the void probability in the Perseus-Pisces supercluster region of galaxies. This observation confirms that the recently proposed linked-pair approximation for

  7. Effective low-energy theory for superconducting topological insulators

    NASA Astrophysics Data System (ADS)

    Hao, Lei; Lee, Ting-Kuo

    2015-03-01

    Candidate pairings of superconducting topological insulators support interesting surface Andreev bound states (SABSs) known as Majorana fermions. As these materials are described by a two-orbital Bernevig–Hughes–Zhang type model, a general understanding of the low-energy physics such as the possible kinds of SABSs are difficult. By virtue of an analogy between a topological insulator and a time reversal invariant topological superconductor, we propose a simple and intuitive method of constructing the low-energy effective models for superconducting topological insulators like CuxBi2Se3. Depending on the value of the chemical potential and for experimentally relevant model parameters, the low-energy properties of these superconductors are shown to be determined by one copy or two copies of single-orbital effective models. If the effective pairing potential shows sign reversal upon reflection by the surface, one Kramers' pair or two Kramers' pairs of SABSs are expected to appear. Explicit analytical calculations in terms of the effective low energy model reproduce the dispersions of the numerically confirmed two pairs of SABSs for a commonly studied pairing.

  8. Effective low-energy theory for superconducting topological insulators.

    PubMed

    Hao, Lei; Lee, Ting-Kuo

    2015-03-18

    Candidate pairings of superconducting topological insulators support interesting surface Andreev bound states (SABSs) known as Majorana fermions. As these materials are described by a two-orbital Bernevig-Hughes-Zhang type model, a general understanding of the low-energy physics such as the possible kinds of SABSs are difficult. By virtue of an analogy between a topological insulator and a time reversal invariant topological superconductor, we propose a simple and intuitive method of constructing the low-energy effective models for superconducting topological insulators like CuxBi2Se3. Depending on the value of the chemical potential and for experimentally relevant model parameters, the low-energy properties of these superconductors are shown to be determined by one copy or two copies of single-orbital effective models. If the effective pairing potential shows sign reversal upon reflection by the surface, one Kramers' pair or two Kramers' pairs of SABSs are expected to appear. Explicit analytical calculations in terms of the effective low energy model reproduce the dispersions of the numerically confirmed two pairs of SABSs for a commonly studied pairing. PMID:25705794

  9. ORNL Superconducting Technology Program for Electric Energy Systems

    SciTech Connect

    Hawsey, R.A. (comp.)

    1993-02-01

    The Oak Ridge National Laboratory (ORNL) Superconducting Technology Program is conducted as part of a national effort by the US Department of Energy's (DOE's) Office of Conservation and Renewable Energy to develop the technology base needed by US industry for commercial development of electric power applications of high-temperature superconductivity. The two major elements of this program are wire development and systems development. This document describes the major research and development activities for this program together with related accomplishments. The technical progress reported was summarized from information prepared for the FY 1992 Peer Review of Projects, conducted by DOE's Office of Program Analysis, Office of Energy Research. This ORNL program is highly leveraged by the staff and other resources of US industry and universities. Interlaboratory teams are also in place on a number of industry-driven projects. Patent disclosures, working group meetings, staff exchanges, and joint publications and presentations ensure that there is technology transfer to US industry. Working together, the collaborative teams are making tremendous progress in solving the scientific and technical issues necessary for the commercialization of long lengths of practical high-temperature superconductor wire and wire products.

  10. Topological phase transitions with and without energy gap closing

    NASA Astrophysics Data System (ADS)

    Yang, Yunyou; Li, Huichao; Sheng, L.; Shen, R.; Sheng, D. N.; Xing, D. Y.

    2013-08-01

    Topological phase transitions in a three-dimensional (3D) topological insulator (TI) with an exchange field of strength g are studied by calculating spin Chern numbers C±(kz) with momentum kz as a parameter. When |g| exceeds a critical value gC, a transition of the 3D TI into a Weyl semimetal occurs, where two Weyl points appear as critical points separating kz regions with different first Chern numbers. For |g| < gC, C±(kz) undergo a transition from ±1 to 0 with increasing |kz| to a critical value kCz. Correspondingly, surface states exist for |kz| < kCz, and vanish for |kz| ? kCz. The transition at |kz| = kCz is accompanied by closing of the bulk spin spectrum gap rather than the energy gap.

  11. Critical temperature and energy gap for the BCS equation

    SciTech Connect

    Hainzl, Christian; Seiringer, Robert [Departments of Mathematics and Physics, University of Alabama at Birmingham, 1300 University Boulevard, Birmingham, Alabama 35294 (United States); Department of Physics, Princeton University, Princeton, New Jersey 08542-0708 (United States)

    2008-05-01

    We derive upper and lower bounds on the critical temperature T{sub c} and the energy gap {xi} (at zero temperature) for the BCS gap equation, describing spin-(1/2) fermions interacting via a local two-body interaction potential {lambda}V(x). At weak coupling {lambda}<<1 and under appropriate assumptions on V(x), our bounds show that T{sub c}{approx}A exp(-B/{lambda}) and {xi}{approx}C exp(-B/{lambda}) for some explicit coefficients A, B, and C depending on the interaction V(x) and the chemical potential {mu}. The ratio A/C turns out to be a universal constant, independent of both V(x) and {mu}. Our analysis is valid for any {mu}; for small {mu}, or low density, our formulas reduce to well-known expressions involving the scattering length of V(x)

  12. Design of a 4.5 MJ/1 MW sectored toroidal superconducting energy storage magnet

    NASA Astrophysics Data System (ADS)

    Bhunia, Uttam; Akhter, Javed; Nandi, Chinmay; Pal, Gautam; Saha, Subimal

    2014-09-01

    A 4.5 MJ/1 MW superconducting magnetic energy storage (SMES) system is being developed at VECC centre, Kolkata. The magnet system consists of the cryostat and coil assembly comprising eight superconducting solenoid coils made of custom-made NbTi based Rutherford-type cable and arranged in toroidal fashion with finite inter-sector gap. Since the strong electromagnetic force distributed to the coil is asymmetric and non-uniform in nature, a precise 3-D finite element analysis (FEA) has been carried out to design a mechanically stable coil and support structure under various operational scenarios. The results reveal that maximum stress developed on coil and its support structure is below allowable stress limit. Extensive transient analysis has also been carried out to evaluate transient loss and assess the feasibility of using helium re-condensation technology with commercially available cryo-refrigerators. Finally, quench protection scenario has also been discussed suitable for this toroidal-type SMES system. The article investigates the design concept of the cryostat and coil assembly.

  13. Specific heat in magnetic fields and superconducting gap structure in FeSe1-xTex (0.6 ? x ? 1)

    NASA Astrophysics Data System (ADS)

    Konno, Takuya; Adachi, Tadashi; Imaizumi, Masato; Noji, Takashi; Kawamata, Takayuki; Koike, Yoji

    2014-09-01

    Specific heat has been measured in magnetic fields at low temperatures down to 0.4 K in the iron-chalcogenide superconductors of FeSe1-xTex, in order to investigate details of the superconducting (SC) gap. Using the two-gap model, it has been found that the smaller SC gap is significantly depressed by the application of magnetic field. Moreover, it has been found that the enhancement of the residual electronic-specific-heat-coefficient in the ground state by the application of magnetic field is much smaller than that expected for superconductors with the typical s-wave or d-wave SC paring symmetry. These results are discussed in relation to the multi-band effect in the iron-based superconductors.

  14. Superconducting fluctuations in the Luther-Emery liquid

    NASA Astrophysics Data System (ADS)

    Orignac, Edmond; Poilblanc, Didier

    2003-08-01

    The single-particle superconducting Green’s functions of a Luther-Emery liquid is computed by bosonization techniques. Using a formulation introduced by Poilblanc and Scalapino [Phys. Rev. B 66, 052513 (2002)], an asymptotic expression of the superconducting gap is deduced in the long wavelength and small frequency limit. Due to superconducting phase fluctuations, the gap exhibits as a function of size L a (1/L)1/2K? power-law decay as well as an interesting singularity at the spectral gap energy. Similarities and differences with the two-leg t-J ladder are outlined.

  15. Effects of Out-of-Plane Disorder on the Nodal Quasiparticle and Superconducting Gap in Single-Layer Bi_2Sr_1.6Ln_0.4CuO_6 delta (Ln = La, Nd, Gd)

    SciTech Connect

    Hashimoto, M.

    2011-01-04

    How out-of-plane disorder affects the electronic structure has been investigated for the single-layer cuprates Bi{sub 2}Sr{sub 1.6}Ln{sub 0.4}CuO{sub 6+{delta}} (Ln = La, Nd, Gd) by angle-resolved photoemission spectroscopy. We have observed that, with increasing disorder, while the Fermi surface shape and band dispersions are not affected, the quasi-particle width increases, the anti-nodal gap is enhanced and the superconducting gap in the nodal region is depressed. The results indicate that the superconductivity is significantly depressed by out-of-plane disorder through the enhancement of the anti-nodal gap and the depression of the superconducting gap in the nodal region.

  16. Survey of domestic research on superconducting magnetic energy storage

    SciTech Connect

    Dresner, L.

    1991-09-01

    This report documents the results of a survey of domestic research on superconducting magnetic energy storage (SMES) undertaken with the support of the Oak Ridge National Laboratory (ORNL) Superconductivity Pilot Center. Each survey entry includes the following: Name, address, and other telephone and facsimile numbers of the principal investigator and other staff members; funding for fiscal year 1991, 1992, 1993; brief descriptions of the program, the technical progress to date, and the expected technical progress; a note on any other collaboration. Included with the survey are recommendations intended to help DOE decide how best to support SMES research and development (R&D). To summarize, I would say that important elements of a well-rounded SMES research program for DOE are as follows. (1) Construction of a large ETM. (2) Development of SMES as an enabling technology for solar and wind generation, especially in conjunction with the ETM program, if possible. (3) Development of small SMES units for electric networks, for rapid transit, and as noninterruptible power supplies [uses (2), (3), and (4) above]. In this connection, lightweight, fiber-reinforced polymer structures, which would be especially advantageous for space and transportation applications, should be developed. (4) Continued study of the potential impacts of high-temperature superconductors on SMES, with construction as soon as feasible of small SMES units using high-temperature superconductors (HTSs).

  17. Survey of domestic research on superconducting magnetic energy storage

    SciTech Connect

    Dresner, L.

    1991-09-01

    This report documents the results of a survey of domestic research on superconducting magnetic energy storage (SMES) undertaken with the support of the Oak Ridge National Laboratory (ORNL) Superconductivity Pilot Center. Each survey entry includes the following: Name, address, and other telephone and facsimile numbers of the principal investigator and other staff members; funding for fiscal year 1991, 1992, 1993; brief descriptions of the program, the technical progress to date, and the expected technical progress; a note on any other collaboration. Included with the survey are recommendations intended to help DOE decide how best to support SMES research and development (R D). To summarize, I would say that important elements of a well-rounded SMES research program for DOE are as follows. (1) Construction of a large ETM. (2) Development of SMES as an enabling technology for solar and wind generation, especially in conjunction with the ETM program, if possible. (3) Development of small SMES units for electric networks, for rapid transit, and as noninterruptible power supplies (uses (2), (3), and (4) above). In this connection, lightweight, fiber-reinforced polymer structures, which would be especially advantageous for space and transportation applications, should be developed. (4) Continued study of the potential impacts of high-temperature superconductors on SMES, with construction as soon as feasible of small SMES units using high-temperature superconductors (HTSs).

  18. Superconducting magnetic energy storage (SMES) program, January 1-December 31, 1981

    SciTech Connect

    Rogers, J.D. (comp.)

    1982-02-01

    Work reported is on the development of a 30 MJ superconducting magnetic energy storage (SMES) unit for use by the Bonneville Power Administration (BPA) to stabilize power oscillations on their Pacific AC Intertie. The 30 MJ superconducting coil manufacture was completed. Design of the seismic mounting of the coil to the nonconducting dewar lid and a concrete foundation is complete. The superconducting application VAR (SAVAR) control study indicated a low economic advantage and the SAVAR program was terminated. An economic and technological evaluation of superconducting fault current limiter (SFCL) was completed and the results are reported.

  19. Infrared Study of Superconductivity: Grating Coupled Plasmons in Yttrium BARIUM(2) COPPER(3) OXYGEN(7) and Gap Features in BARIUM(1-X) Potassium(x) Bismuth OXYGEN(3)

    NASA Astrophysics Data System (ADS)

    Dunmore, Franklin John

    1995-01-01

    The electrodynamic properties of two different superconductors, Barium Potassium Bismuth Oxide (BKBO) and Yttrium Barium Copper Oxide (YBCO) have been studied using the technique of transmission Fourier transform spectroscopy with liquid helium temperature bolometric detection. Plasmon resonances have been observed in far infrared transmission measurements on superconducting YBCO films. An Aluminum/Nichrome grating is used to couple infrared radiation to collective two-dimensional plasma modes. The plasmon dispersion is measured by using different grating periods. The strength of the plasma resonances weaken, then disappear as the temperature approaches the critical temperature. The results are analyzed using a grating coupler theory that includes the hybridization of the plasmons with the diffraction modes. Data taken in a magnetic field of up to 12 Tesla are characteristic of the real part of the conductivity of the YBCO film increasing with field, behavior similar to that with increasing of temperature. These results are consistent with the inducement of vortices in the YBCO film. The far infrared transmission of BKBO thin films, grown on Magnesium Oxide (MgO) substrates, was measured in the frequency range from 15 to 200 wavenumbers, and temperature range from 9 to 100 Kelvin. There is a BCS -like peak in the transmission spectrum. The strong coupling Eliashberg theory gives a better description of the optical data than the weak coupling Mattis-Bardeen theory. For an 18 Kelvin critical temperature (T_{c }) sample the Eliashberg model extrapolated to zero temperature gives a London penetration depth of 5500+/-100A and an energy gap of 6.2 meV (50.1 wavenumbers, or 4.0 kT_{c }). Because BKBO is in the dirty limit, the strong coupling characteristics in the optical conductivity is adequately described by the Allen-Dynes parameter only, as opposed to the full Holstein structure due to the electron -phonon interaction alpha^2F(omega). .

  20. Cryogenic system for production testing and measurement of Fermilab energy saver superconducting magnets

    Microsoft Academic Search

    W. E. Cooper; A. J. Bianchi; R. K. Barger; F. B. Johnson; K. J. McGuire; K. D. Pinyan; F. R. Wilson

    1983-01-01

    The cryogenic system of the Fermilab Magnet Test Facility has been used to provide cooling for the testing of approximately 1200 Energy Saver superconducting magnets. The system provides liquid helium, liquid nitrogen, gas purification, and vacuum support for six magnet test stands. It provides for simultaneous high current testing of two superconducting magnets and non-high current cold testing of two

  1. Cryogenic system for production testing and measurement of Fermilab energy saver superconducting magnets

    Microsoft Academic Search

    W. E. Cooper; R. K. Barger; A. J. Bianchi; F. B. Johnson; K. J. McGuire; K. D. Pinyan; F. R. Wilson

    1983-01-01

    The cryogenic system of the Fermilab Magnet Test Facility has been used to provide cooling for the testing of approximately 1200 Energy Saver superconducting magnets. The system provides liquid helium, liquid nitrogen, gas purification, and vacuum support for six magnet test stands. It provides for simultaneous high current testing of two superconducting magnets and nonhigh current cold testing of two

  2. Parasitic Energy Loss in the LEP Superconducting Cavities

    NASA Astrophysics Data System (ADS)

    Hofmann, A.; Arduini, G.; Brüning, O.; Cavallari, G.; Gayet, P.; Haebel, E.; Jimenez, M.; Meincke, O.; Morpurgo, G.; Roy, G.; Schmickler, H.; Uythoven, J.; Wagner, A.; Zotter, B.

    1997-05-01

    The energy loss of bunches circulating in LEP has been determined by measuring the closed orbit as a function of current with the position monitors located at finite dispersion. This method has been used before in LEP to determine the longitudinal resistive impedance of different parts of the ring. In this experiment the loss in the two long straight sections containing only superconducting cavities was compared with the one occuring in sections having also copper cavities. The results confirm the impedance calculation of the two types of cavities including adjacent bellows. The accuracy was considerably improved by a simultaneous measurement of the orbits of bunches with different currents thus avoiding errors due to orbit drifts. In parallel with this beam based impedance measurement the power dissipation in different elements has been observed directly by local temperature measurements of cold cavity bellows and of HOM Ferrite absorbers. These observations are correlated with the change in cryogenics power consumption.

  3. A new boson-fermion model of superconductivity

    E-print Network

    Tian De Cao

    2012-10-09

    It is shown that the superconducting energy gap necessarily lead to the disappearance of some quasi-electrons, thus we suggest a new boson-fermion Hamiltonian to describe superconductivity. The new supercurrent equations are derived with this Hamiltonian. Some new results can be found besides the zero resistance effect, the Meissner effect and the magnetic flux quantum can be explained.

  4. Magnetic Energy Storage System: Superconducting Magnet Energy Storage System with Direct Power Electronics Interface

    SciTech Connect

    None

    2010-10-01

    GRIDS Project: ABB is developing an advanced energy storage system using superconducting magnets that could store significantly more energy than today’s best magnetic storage technologies at a fraction of the cost. This system could provide enough storage capacity to encourage more widespread use of renewable power like wind and solar. Superconducting magnetic energy storage systems have been in development for almost 3 decades; however, past devices were designed to supply power only for short durations—generally less than a few minutes. ABB’s system would deliver the stored energy at very low cost, making it ideal for eventual use in the electricity grid as a costeffective competitor to batteries and other energy storage technologies. The device could potentially cost even less, on a per kilowatt basis, than traditional lead-acid batteries.

  5. Opening and reversible control of a wide energy gap in uniform monolayer graphene

    PubMed Central

    Jeon, Cheolho; Shin, Ha-Chul; Song, Inkyung; Kim, Minkook; Park, Ji-Hoon; Nam, Jungho; Oh, Dong-Hwa; Woo, Sunhee; Hwang, Chan-Cuk; Park, Chong-Yun; Ahn, Joung Real

    2013-01-01

    For graphene to be used in semiconductor applications, a ‘wide energy gap' of at least 0.5?eV at the Dirac energy must be opened without the introduction of atomic defects. However, such a wide energy gap has not been realized in graphene, except in the cases of narrow, chemically terminated graphene nanostructures with inevitable edge defects. Here, we demonstrated that a wide energy gap of 0.74?eV, which is larger than that of germanium, could be opened in uniform monolayer graphene without the introduction of atomic defects into graphene. The wide energy gap was opened through the adsorption of self-assembled twisted sodium nanostrips. Furthermore, the energy gap was reversibly controllable through the alternate adsorption of sodium and oxygen. The opening of such a wide energy gap with minimal degradation of mobility could improve the applicability of graphene in semiconductor devices, which would result in a major advancement in graphene technology. PMID:24100763

  6. Ni-impurity effects on the superconducting gap of La2-xSrxCuO4 studied from the magnetic field and temperature dependence of the electronic specific heat

    NASA Astrophysics Data System (ADS)

    Kurosawa, T.; Momono, N.; Oda, M.; Ido, M.

    2012-04-01

    The magnetic field and temperature dependence of the electronic specific heat Cel have been systematically investigated in La2-xSrxCu1-yNiyO4 (LSCNO) in order to study Ni-impurity effects on the superconducting (SC) gap. In LSCNO with x = 0.15 and y = 0.015, the value of ? (?Cel/T) at T = 0 K, ?0, is enhanced under the magnetic field H applied along the c axis. The increment of ?0, ??0, follows the Volovik relation ??0 = AH, characteristic of the SC gap with line nodes, with prefactor A similar to that of a pure sample. The Cel/T versus T curve under H = 0 shows a d-wave-like SC anomaly with an abrupt increase at Tc and T-linear dependence at T ? Tc, although the ?0-value in the Cel/T versus T curve increases with increasing Ni concentrations. Interestingly, as the SC part of Cel/T, Cel/T - ?0 ? ?s, decreases in LSCNO, Tc is reduced in proportion to the decrease of ?s. These findings can be explained phenomenologically by a simple model in which Ni impurities bring about strong pair breaking at the edges of the coherent nodal part of the Fermi surface but in the vicinity of the nodes of the SC gap. The reduction of the SC condensation energy U0 in LSCNO, evaluated from Cel at T?Tc, is also understood by the same model.

  7. Interconnected Power Systems with Superconducting Magnetic Energy Storage

    NASA Astrophysics Data System (ADS)

    Nomura, Shinichi; Hagita, Takushi; Tsutsui, Hiroaki; Sato, Yoshihisa; Shimada, Ryuichi

    The objective of this work is to discuss the concept of back-to-back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back-to-back DC link. In this case, each converter of the back-to-back system is used as a power conditioning system for the SMES coils. Since the AC/DC converter can be designed independently of the frequency of the power system, a two-way switch is connected to the AC side of each converter. This two-way switch can select the interconnected power systems. By using the two-way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC/DC converters. For instance, lower-cost power of each power network can be stored through two converters during the off-peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back-to-back interconnection with SMES and discusses the optimal SMES configuration for a 300-MW class back-to-back interconnection.

  8. Energy gap induced by the surface optical polaron in graphene on polar substrates

    NASA Astrophysics Data System (ADS)

    Wang, Zi-Wu; Liu, Lei; Li, Zhi-Qing

    2015-03-01

    The polaron effects are investigated in the presence of a magnetic field based on the carrier-surface optical phonon coupling induced by the polar substrates under the graphene. We find that the energy gap is opened in the zero-energy Landau level due to the polaron effect. The magnitude of energy gap is consistent with recent experimental measurements. Moreover, the gap can be tuned by choosing the polarization of substrates and controlling the distance between graphene and polar substrate. The results obtained provide a possible explanation for the origin of energy gap opening and highlight the bandgap engineering of graphene on polar substrates.

  9. Topological superconductivity induced by ferromagnetic metal chains

    NASA Astrophysics Data System (ADS)

    Li, Jian; Chen, Hua; Drozdov, Ilya K.; Yazdani, A.; Bernevig, B. Andrei; MacDonald, A. H.

    2014-12-01

    Recent experiments have provided evidence that one-dimensional (1D) topological superconductivity can be realized experimentally by placing transition-metal atoms that form a ferromagnetic chain on a superconducting substrate. We address some properties of this type of system by using a Slater-Koster tight-binding model to account for important features of the electronic structure of the transition-metal chains on the superconducting substrate. We predict that topological superconductivity is nearly universal when ferromagnetic transition-metal chains form straight lines on superconducting substrates and that it is possible for more complex chain structures. When the chain is weakly coupled to the substrate and is longer than superconducting coherence lengths, its proximity-induced superconducting gap is ˜? ESO/J where ? is the s -wave pair potential on the chain, ESO is the spin-orbit splitting energy induced in the normal chain state bands by hybridization with the superconducting substrate, and J is the exchange splitting of the ferromagnetic chain d bands. Because of the topological character of the 1D superconducting state, Majorana end modes appear within the gaps of finite length chains. We find, in agreement with the experiment, that when the chain and substrate orbitals are strongly hybridized, Majorana end modes are substantially reduced in amplitude when separated from the chain end by less than the coherence length defined by the p -wave superconducting gap. We conclude that Pb is a particularly favorable substrate material for ferromagnetic chain topological superconductivity because it provides both strong s -wave pairing and strong Rashba spin-orbit coupling, but that there is an opportunity to optimize properties by varying the atomic composition and structure of the chain. Finally, we note that in the absence of disorder, a new chain magnetic symmetry, one that is also present in the crystalline topological insulators, can stabilize multiple Majorana modes at the end of a single chain.

  10. Underground rippled dewar system for 10,000 MWh superconductive energy storage magnets

    Microsoft Academic Search

    S. G. Ladkany

    1978-01-01

    The design and construction feasibility of a curved and rippled helium dewar system in deep rock tunnels is considered. Large superconductive energy-storage magnets present economical and efficient means for storing energy (1000 MWh to 10,000 MWh) in the form of high currents (100,000 to 300,000 A) and high magnetic fields (2 to 5 T). The rippled superconducting magnet system is

  11. Superconducting gamma and fast-neutron spectrometers with high energy resolution

    DOEpatents

    Friedrich, Stephan (San Jose, CA); , Niedermayr, Thomas R. (Oakland, CA); Labov, Simon E. (Berkeley, CA)

    2008-11-04

    Superconducting Gamma-ray and fast-neutron spectrometers with very high energy resolution operated at very low temperatures are provided. The sensor consists of a bulk absorber and a superconducting thermometer weakly coupled to a cold reservoir, and determines the energy of the incident particle from the rise in temperature upon absorption. A superconducting film operated at the transition between its superconducting and its normal state is used as the thermometer, and sensor operation at reservoir temperatures around 0.1 K reduces thermal fluctuations and thus enables very high energy resolution. Depending on the choice of absorber material, the spectrometer can be configured either as a Gamma-spectrometer or as a fast-neutron spectrometer.

  12. Mechanism of the size dependence of the superconducting transition of nanostructured Nb.

    PubMed

    Bose, Sangita; Raychaudhuri, Pratap; Banerjee, Rajarshi; Vasa, Parinda; Ayyub, Pushan

    2005-09-30

    A direct measurement of the superconducting energy gap by point contact spectroscopy in nanostructured Nb films shows that the gap decreases with a reduction in the average particle size. The superconducting T(c), obtained from transport and magnetic measurements, also decreases with size and scales with the energy gap. The size dependence of the superconducting properties in this intermediate coupling type II superconductor is therefore governed by changes in the electronic density of states rather than by phonon softening. Consistent with the Anderson criterion, no T(c) was observed for sizes below 8 nm. PMID:16241688

  13. Superconductive energy storage inductor-converter units for power systems

    Microsoft Academic Search

    H. A. Peterson; N. Mohan; R. W. Boom

    1975-01-01

    Large magnets with superconductive windings could serve to perform a power system function analogous to pumped storage hydro. A conventional Graetz bridge converter as used in dc transmission provides an ideal interface between the three-phase power system and the superconductive magnet or inductor. Such Inductor-Converter or I-C units, when properly controlled, provide significant power system benefits. Power reversibility is achievable

  14. Energy bands of atomic monolayers of various materials: Possibility of energy gap engineering

    Microsoft Academic Search

    Tatsuo Suzuki; Yushi Yokomizo

    2010-01-01

    The mobility of graphene is very high because the quantum Hall effects can be observed even at room temperature. Graphene has the potential of the material for novel devices because of this high mobility. But the energy gap of graphene is zero, so graphene cannot be applied to semiconductor devices such as transistors, LEDs, etc. In order to control the

  15. Origin of the variety of superconducting gap structure in iron-based superconductors: competition between orbital and spin fluctuations

    NASA Astrophysics Data System (ADS)

    Onari, Seiichiro; Saito, Tetsuro; Kontani, Hiroshi

    2012-02-01

    To understand the pairing mechanism in iron-based superconductors, we study the three-dimensional gap structure based on the orbital fluctuation theory. We focus on the fully-gapped state in (i) heavily electron-doped KFe2Se2 [1], nodal gap structure in (ii) isovalent-doped BaFe2(As,P)2, and strongly band-dependent gap structure in (iii) hole-doped (Ba,K)Fe2As2. Based on the three-dimensional ten orbital model for (i), we obtain orbital-fluctuation-mediated fully-gapped s++ wave state without sign reversal. For (ii), we reproduce the loop-shaped nodal structure on the electron-Fermi surface, due to the competition between orbital and spin fluctuations. For (iii), we obtain a drastic change in the gap structure by hole-doping, reflecting the variation of orbital fluctuations due to the topological change of electron-pockets. These results indicate the significant role of orbital fluctuations in iron-based superconductors. [1] Saito et al., PRB 83, 140512(R) (2011)

  16. Rapidity gaps and scaling in high energy interactions

    SciTech Connect

    Malik, S. [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)] [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

    1996-09-01

    The rapidity gap probability is investigated in varying symmetric bin sizes in proton-nucleus interactions at 800 GeV. It shows a scaling behavior and confirms the linked pair approximation for the {ital n}-particle cumulant correlation functions to high order. A comparison of the scaled rapidity gap probability is made with the negative binomial distribution. We also interpret the rapidity gap probability in the clan production model of hadronization and reanalyze the clan parameters in its light. {copyright} {ital 1996 The American Physical Society.}

  17. Superconductivity, cohesive energy density, and electron-atom ratio in metals

    NASA Technical Reports Server (NTRS)

    England, C.; Lawson, D. D.; Hrubes, J. D.

    1981-01-01

    It is shown that superconductivity above 8 K occurs in alloys and metallic compounds within relatively narrow regions of cohesive energy density with a sharp peak which includes Nb3Ge, SiV3, Nb3Ga, and NbN. When cross-correlated with the electron-atom ratio, high-temperature superconductivity can be observed in only a few regions. This suggests a search for superconductors with high-transition temperatures and critical fields within these regions.

  18. Commissioning Tests of the Bonneville Power Administration 30 MJ Superconducting Magnetic Energy Storage Unit

    Microsoft Academic Search

    H. J. Boenig; J. F. Hauer

    1985-01-01

    A 30 MJ (8.4 kWh) Superconducting Magnetic Energy Storage (SMES) unit with a 10 MW converter has been installed and commissioned at the Bonneville Power Administration (BPA) substation in Tacoma, Washington. This is the first large-scale application in the US of superconductivity in an electric utility system. The unit, which is capable of absorbing and releasing up to 10 MJ

  19. An electric field tunable energy band gap at silicene/(0001) ZnS interfaces.

    PubMed

    Houssa, M; van den Broek, B; Scalise, E; Pourtois, G; Afanas'ev, V V; Stesmans, A

    2013-03-21

    The interaction of silicene, the silicon counterpart of graphene, with (0001) ZnS surfaces is investigated theoretically, using first-principles simulations. The charge transfer occurring at the silicene/(0001) ZnS interface leads to the opening of an indirect energy band gap of about 0.7 eV in silicene. Remarkably, the nature (indirect or direct) and magnitude of the energy band gap of silicene can be controlled by an external electric field: the energy gap is predicted to become direct for electric fields larger than about 0.5 V Å(-1), and the direct energy gap decreases approximately linearly with the applied electric field. The predicted electric field tunable energy band gap of the silicene/(0001) ZnS interface is very promising for its potential use in nanoelectronic devices. PMID:23403806

  20. Experimental and analytical study of the DC breakdown characteristics of polypropylene laminated paper with a butt gap condition considering the insulation design of superconducting cable

    NASA Astrophysics Data System (ADS)

    Seo, In-jin; Choi, Won; Seong, Jae-gyu; Lee, Bang-wook; Koo, Ja-yoon

    2014-08-01

    It has been reported that the insulation design under DC stress is considered as one of the critical factors in determining the performance of high-voltage direct current (HVDC) superconducting cable. Therefore, it is fundamentally necessary to investigate the DC breakdown characteristics of the composite insulation system consisting of liquid nitrogen (LN2)/polypropylene-laminated-paper (PPLP). In particular, the insulation characteristics under DC polarity reversal condition should be verified to understand the polarity effect of the DC voltage considering the unexpected incidents taking place at line-commutated-converters (LCC) under service at a DC power grid. In this study, to examine the variation of DC electric field strength, the step voltage and polarity reversal breakdown tests are performed under DC stress. Also, we investigate the electric field distributions in a butt gap of the LN2/PPLP condition considering the DC polarity reversal by using simulation software.

  1. Simple Experimental Verification of the Relation between the Band-Gap Energy and the Energy of Photons Emitted by LEDs

    ERIC Educational Resources Information Center

    Precker, Jurgen W.

    2007-01-01

    The wavelength of the light emitted by a light-emitting diode (LED) is intimately related to the band-gap energy of the semiconductor from which the LED is made. We experimentally estimate the band-gap energies of several types of LEDs, and compare them with the energies of the emitted light, which ranges from infrared to white. In spite of…

  2. Theorem on the existence of a nonzero energy gap in adiabatic quantum computation

    E-print Network

    Da-Jian Zhang; Xiao-Dong Yu; D. M. Tong

    2014-10-14

    Adiabatic quantum computation, based on the adiabatic theorem, is a promising alternative to conventional quantum computation. The validity of an adiabatic algorithm depends on the existence of a nonzero energy gap between the ground and excited states. However, it is difficult to ascertain the exact value of the energy gap. In this paper, we put forward a theorem on the existence of nonzero energy gap for the Hamiltonians used in adiabatic quantum computation. It can help to effectively identify a large class of the Hamiltonians without energy-level crossing between the ground and excited states.

  3. Basic Research Needs for Superconductivity. Report of the Basic Energy Sciences Workshop on Superconductivity, May 8-11, 2006

    SciTech Connect

    Sarrao, J.; Kwok, W-K; Bozovic, I.; Mazin, I.; Seamus, J. C.; Civale, L.; Christen, D.; Horwitz, J.; Kellogg, G.; Finnemore, D.; Crabtree, G.; Welp, U.; Ashton, C.; Herndon, B.; Shapard, L.; Nault, R. M.

    2006-05-11

    As an energy carrier, electricity has no rival with regard to its environmental cleanliness, flexibility in interfacing with multiple production sources and end uses, and efficiency of delivery. In fact, the electric power grid was named ?the greatest engineering achievement of the 20th century? by the National Academy of Engineering. This grid, a technological marvel ingeniously knitted together from local networks growing out from cities and rural centers, may be the biggest and most complex artificial system ever built. However, the growing demand for electricity will soon challenge the grid beyond its capability, compromising its reliability through voltage fluctuations that crash digital electronics, brownouts that disable industrial processes and harm electrical equipment, and power failures like the North American blackout in 2003 and subsequent blackouts in London, Scandinavia, and Italy in the same year. The North American blackout affected 50 million people and caused approximately $6 billion in economic damage over the four days of its duration. Superconductivity offers powerful new opportunities for restoring the reliability of the power grid and increasing its capacity and efficiency. Superconductors are capable of carrying current without loss, making the parts of the grid they replace dramatically more efficient. Superconducting wires carry up to five times the current carried by copper wires that have the same cross section, thereby providing ample capacity for future expansion while requiring no increase in the number of overhead access lines or underground conduits. Their use is especially attractive in urban areas, where replacing copper with superconductors in power-saturated underground conduits avoids expensive new underground construction. Superconducting transformers cut the volume, weight, and losses of conventional transformers by a factor of two and do not require the contaminating and flammable transformer oils that violate urban safety codes. Unlike traditional grid technology, superconducting fault current limiters are smart. They increase their resistance abruptly in response to overcurrents from faults in the system, thus limiting the overcurrents and protecting the grid from damage. They react fast in both triggering and automatically resetting after the overload is cleared, providing a new, self-healing feature that enhances grid reliability. Superconducting reactive power regulators further enhance reliability by instantaneously adjusting reactive power for maximum efficiency and stability in a compact and economic package that is easily sited in urban grids. Not only do superconducting motors and generators cut losses, weight, and volume by a factor of two, but they are also much more tolerant of voltage sag, frequency instabilities, and reactive power fluctuations than their conventional counterparts. The challenge facing the electricity grid to provide abundant, reliable power will soon grow to crisis proportions. Continuing urbanization remains the dominant historic demographic trend in the United States and in the world. By 2030, nearly 90% of the U.S. population will reside in cities and suburbs, where increasingly strict permitting requirements preclude bringing in additional overhead access lines, underground cables are saturated, and growth in power demand is highest. The power grid has never faced a challenge so great or so critical to our future productivity, economic growth, and quality of life. Incremental advances in existing grid technology are not capable of solving the urban power bottleneck. Revolutionary new solutions are needed ? the kind that come only from superconductivity.

  4. Holographic Superconductivity with Gauss-Bonnet gravity

    E-print Network

    Ruth Gregory

    2010-12-07

    I review recent work on holographic superconductivity with Einstein-Gauss-Bonnet gravity, and show how the critical temperature of the superconductor depends on both gravitational backreaction and the Gauss-Bonnet parameter, using both analytic and numerical arguments. I also review computations of the conductivity, finding the energy gap, and demonstrating that there is no universal gap ratio, $\\omega_g/T_c$, for these superconductors.

  5. Signatures of Unconventional Superconductivity in Granular Aluminum

    NASA Astrophysics Data System (ADS)

    Bachar, N.; Pracht, U. S.; Farber, E.; Dressel, M.; Deutscher, G.; Scheffler, M.

    2015-04-01

    We present measurements of the complex transmission of superconducting granular aluminum thin films in the THz optical range. We discuss the dynamical conductivity and temperature-dependent energy gap of two films of different granular coupling. While the film of well-coupled grains follows the predictions for a conventional BCS superconductor, signatures of enhanced absorption are found at sub-gap frequencies when coupling is decreased. We discuss possible explanations which might account for the observed deviations from BCS theory.

  6. Characteristics of rapidity-gap distribution at cosmic-ray energies (~ 1012 eV)

    Microsoft Academic Search

    S. Roy; N. S. Arya; D. P. Goyal; A. Mozumder; P. K. Sengupta; S. Singh

    1980-01-01

    A phenomenological study of the rapidity-gap distribution for cosmic-ray N-N interactions at energies>~TeV has been reported. The observations indicate strong short-short correlations in rapidity gaps which support Snider's two-channel multiperipheral cluster model. The cluster size and cluster density at these energies have been estimated to be 6.5 and 1.0, respectively. It is found that with increasing energy, the cluster size

  7. Physical origin of photonic energy gaps in the propagation of surface plasmons on gratings

    Microsoft Academic Search

    W. L. Barnes; T. W. Preist; S. C. Kitson; J. R. Sambles

    1996-01-01

    We present an analytic model to describe the existence of photonic energy gaps in the propagation of surface plasmon polaritons on corrugated surfaces. We concentrate on elucidating the physical origin of the band gap, and accordingly we place strong emphasis on the physical reasoning and assumptions that we use. Our model is designed to give direct access to expressions for

  8. Generation of full polarization in ferromagnetic graphene with spin energy gap

    NASA Astrophysics Data System (ADS)

    Wu, Qing-Ping; Liu, Zheng-Fang; Chen, Ai-Xi; Xiao, Xian-Bo; Liu, Zhi-Min

    2014-12-01

    We propose a workable scheme for the generation of full spin polarization in ferromagnetic graphene system with strain or Rashba spin-orbit interaction. A spin energy gap can be opened in ferromagnetic graphene system in the presence of strain or Rashba spin-orbit interaction, leading to the full polarization in the spin energy gap. In addition, under the combined modulation of strain and Rashba spin-orbit interaction, the ferromagnetic graphene system can generate significantly large spin-polarized current with a full polarization in the spin energy gap. It is anticipated to apply such a phenomenon to design the electron spin devices based on the graphene.

  9. Power Flow Stabilization and Control of Microgrid with Wind Generation by Superconducting Magnetic Energy Storage

    Microsoft Academic Search

    Marcelo Gustavo Molina; Pedro Enrique Mercado

    2011-01-01

    High penetration of renewable energy sources such as wind generation in microgrids (MGs) causes fluctuations of power flow and significantly affects the power system (PS) operation. This can lead to severe problems, such as system frequency oscillations, and\\/or violations of power lines capability. With the proper control, superconducting magnetic energy storage (SMES) is able to signifi- cantly enhance the dynamic

  10. Sensing with superconducting point contacts.

    PubMed

    Nurbawono, Argo; Zhang, Chun

    2012-01-01

    Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolution spectroscopies. The so-called Andreev reflection process between normal metal and superconductor carries complex and rich information which can be utilized as powerful sensor when fully exploited. In this review, we would discuss recent experimental and theoretical developments in the supercurrent transport through superconducting point contacts and their relevance to sensing applications, and we would highlight their current issues and potentials. A true utilization of the method based on Andreev reflection analysis opens up possibilities for a new class of ultrasensitive sensors. PMID:22778630

  11. Sensing with Superconducting Point Contacts

    PubMed Central

    Nurbawono, Argo; Zhang, Chun

    2012-01-01

    Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolution spectroscopies. The so-called Andreev reflection process between normal metal and superconductor carries complex and rich information which can be utilized as powerful sensor when fully exploited. In this review, we would discuss recent experimental and theoretical developments in the supercurrent transport through superconducting point contacts and their relevance to sensing applications, and we would highlight their current issues and potentials. A true utilization of the method based on Andreev reflection analysis opens up possibilities for a new class of ultrasensitive sensors. PMID:22778630

  12. Direct observation of superconducting gap anisotropy in YNi2B2C : Angle-resolved photoemission spectroscopy

    Microsoft Academic Search

    Teruhisa Baba; Takayoshi Yokoya; Shunshuke Tsuda; Shik Shin; Tadataka Watanabe; Minoru Nohara; Hideaki Takagi; Tamio Oguchi

    2006-01-01

    In a borocarbide superconductor YNi2B2C(Tc=15K), various experimental results have shown the existence of a gap anisotropy with node. More recently even the direction and type of node have been reported. However, the type of the nodal structure (point or line) seems to be controversial. Also, the position of the node on Fermi surfaces, which is essential for determining the origin

  13. A Possible Mechanism of Quartet Condensation for Room Temperature Superconductivity

    Microsoft Academic Search

    Toshio Soda; Yoshiyuki Fukumoto

    2006-01-01

    We seek a possible room temperature superconductivity beyond the Cooper pairing mechanism through quartet condensation. A quartet consists of two kinds of electron pairs of a spin singlet with total momenta zero belonging to two different bands. We calculate the ground state energy, the energy gap, the excited state energy and the transition temperature by extending the BCS theory for

  14. Parton-parton elastic scattering and rapidity gaps at SSC and LHC energies

    SciTech Connect

    Duca, V.D.

    1993-08-01

    The theory of the perturbative pomeron, due to Lipatov and collaborators, is used to compute the probability of observing parton-parton elastic scattering and rapidity gaps between jets in hadron collisions at SSC and LHC energies.

  15. Parton-parton elastic scattering and rapidity gaps at Tevatron energies

    SciTech Connect

    Del Duca, V.; Tang, Wai-Keung

    1993-08-01

    The theory of the perturbative pomeron, due to Lipatov and collaborators, is used to compute the probability of observing parton-parton elastic scattering and rapidity gaps between jets in hadron collisions at Tevatron energies.

  16. Parton-Parton Elastic Scattering and Rapidity Gaps at Tevatron Energies

    E-print Network

    Vittorio Del Duca; Wai-Keung Tang

    1993-08-02

    The theory of the perturbative pomeron, due to Lipatov and collaborators, is used to compute the probability of observing parton-parton elastic scattering and rapidity gaps between jets in hadron collisions at Tevatron energies.

  17. Parton-Parton Elastic Scattering and Rapidity Gaps at Very High Energies

    E-print Network

    Vittorio Del Duca; Wai-Keung Tang

    1993-04-23

    The theory of the perturbative pomeron, due to Lipatov and collaborators, is used to compute the probability of observing parton-parton elastic scattering and rapidity gaps between jets in hadron collisions at very high energies.

  18. Parton-Parton Elastic Scattering and Rapidity Gaps at SSC and LHC Energies

    E-print Network

    Vittorio Del Duca

    1993-08-02

    The theory of the perturbative pomeron, due to Lipatov and collaborators, is used to compute the probability of observing parton-parton elastic scattering and rapidity gaps between jets in hadron collisions at SSC and LHC energies.

  19. Graphene field effect transistor without an energy gap

    PubMed Central

    Jang, Min Seok; Kim, Hyungjun; Son, Young-Woo; Atwater, Harry A.; Goddard, William A.

    2013-01-01

    Graphene is a room temperature ballistic electron conductor and also a very good thermal conductor. Thus, it has been regarded as an ideal material for postsilicon electronic applications. A major complication is that the relativistic massless electrons in pristine graphene exhibit unimpeded Klein tunneling penetration through gate potential barriers. Thus, previous efforts to realize a field effect transistor for logic applications have assumed that introduction of a band gap in graphene is a prerequisite. Unfortunately, extrinsic treatments designed to open a band gap seriously degrade device quality, yielding very low mobility and uncontrolled on/off current ratios. To solve this dilemma, we propose a gating mechanism that leads to a hundredfold enhancement in on/off transmittance ratio for normally incident electrons without any band gap engineering. Thus, our saw-shaped geometry gate potential (in place of the conventional bar-shaped geometry) leads to switching to an off state while retaining the ultrahigh electron mobility in the on state. In particular, we report that an on/off transmittance ratio of 130 is achievable for a sawtooth gate with a gate length of 80 nm. Our switching mechanism demonstrates that intrinsic graphene can be used in designing logic devices without serious alteration of the conventional field effect transistor architecture. This suggests a new variable for the optimization of the graphene-based device—geometry of the gate electrode. PMID:23671093

  20. Graphene field effect transistor without an energy gap.

    PubMed

    Jang, Min Seok; Kim, Hyungjun; Son, Young-Woo; Atwater, Harry A; Goddard, William A

    2013-05-28

    Graphene is a room temperature ballistic electron conductor and also a very good thermal conductor. Thus, it has been regarded as an ideal material for postsilicon electronic applications. A major complication is that the relativistic massless electrons in pristine graphene exhibit unimpeded Klein tunneling penetration through gate potential barriers. Thus, previous efforts to realize a field effect transistor for logic applications have assumed that introduction of a band gap in graphene is a prerequisite. Unfortunately, extrinsic treatments designed to open a band gap seriously degrade device quality, yielding very low mobility and uncontrolled on/off current ratios. To solve this dilemma, we propose a gating mechanism that leads to a hundredfold enhancement in on/off transmittance ratio for normally incident electrons without any band gap engineering. Thus, our saw-shaped geometry gate potential (in place of the conventional bar-shaped geometry) leads to switching to an off state while retaining the ultrahigh electron mobility in the on state. In particular, we report that an on/off transmittance ratio of 130 is achievable for a sawtooth gate with a gate length of 80 nm. Our switching mechanism demonstrates that intrinsic graphene can be used in designing logic devices without serious alteration of the conventional field effect transistor architecture. This suggests a new variable for the optimization of the graphene-based device--geometry of the gate electrode. PMID:23671093

  1. Superconductivity and the BCS-Bogoliubov Theory

    E-print Network

    Shuji Watanabe

    2010-06-07

    First, we reformulate the BCS-Bogoliubov theory of superconductivity from the viewpoint of linear algebra. We define the BCS Hamiltonian on $\\mathbb{C}^{2^{2M}}$, where $M$ is a positive integer. We discuss selfadjointness and symmetry of the BCS Hamiltonian as well as spontaneous symmetry breaking. Beginning with the gap equation, we give the well-known expression for the BCS state and find the existence of an energy gap. We also show that the BCS state has a lower energy than the normal state. Second, we introduce a new superconducting state explicitly and show from the viewpoint of linear algebra that this new state has a lower energy than the BCS state. Third, beginning with our new gap equation, we show from the viewpoint of linear algebra that we arrive at the results similar to those in the BCS-Bogoliubov theory.

  2. Reducing Resonant Vibration of a Rotor by Tuning the Gap between a Superconducting Bulk and a Permanent Magnet

    NASA Astrophysics Data System (ADS)

    Yubisui, Y.; Amano, R.; Sugiura, T.

    This study investigated passing through a critical speed of a rotor supported by a superconductor with an electromagnet. Here we adopted the idea that the gap between the superconductor and the rotor can be tuned variably by using electromagnetic force of the electromagnet so that the natural frequency or the stiffness can be changed. By using this method, it can be expected that resonant vibration be reduced. We developed an analytical model and then carried out numerical simulation. Numerical results show that considerable reduction of the resonant amplitude can be achieved by proper tuning of switching the electromagnet.

  3. Rugged superconducting detector for monitoring infrared energy sources in harsh environments

    NASA Astrophysics Data System (ADS)

    Laviano, F.; Gerbaldo, R.; Ghigo, G.; Gozzelino, L.; Minetti, B.; Rovelli, A.; Mezzetti, E.

    2010-12-01

    Broadband electromagnetic characterization of hot plasmas, such as in nuclear fusion reactors and related experiments, requires detecting systems that must withstand high flux of particles and electromagnetic radiations. We propose a rugged layout of a high temperature superconducting detector aimed at 3 THz collective Thomson scattering (CTS) spectroscopy in hot fusion plasma. The YBa2Cu3O7 - x superconducting film is patterned by standard photolithography and the sensing area of the device is created by means of high-energy heavy ion irradiation, in order to modify the crystal structure both of the superconducting film and of the substrate. This method diminishes process costs and resulting device fragility due to membrane or air-bridge structures that are commonly needed for MIR and FIR radiation detection. Moreover the sensing area of the device is wired by the same superconducting material and thus excellent mechanical strength is exhibited by the whole device, due to the oxide substrate. Continuous wave operation of prototype devices is demonstrated at liquid nitrogen temperature, for selected infrared spectra of broadband thermal energy sources. Several solutions, which exploit the advantages coming from the robustness of this layout in terms of intrinsic radiation hardness of the superconducting material and of the needed optical components, are analysed with reference to applications of infrared electromagnetic detectors in a tokamak machine environment.

  4. Superconductivity for Electric Systems

    E-print Network

    Superconductivity for Electric Systems Superconductivity Program Quarterly Progress Report For the Period January 1, 2007 to March 31, 2007 #12;2 Superconductivity Program Quarterly Progress Report Superconductivity Program Oak Ridge National Laboratory For: Department of Energy Office of Electricity Delivery

  5. Superconductivity for Electric Systems

    E-print Network

    Superconductivity for Electric Systems Superconductivity Program Quarterly Progress Report For the Period April 1, 2007, to June 30, 2007 #12;2 Superconductivity Program Quarterly Progress Report Superconductivity Program Oak Ridge National Laboratory For: Department of Energy Office of Electricity Delivery

  6. Superconductivity for Electric Systems

    E-print Network

    1 Superconductivity for Electric Systems Superconductivity Program Quarterly Progress Report For the Period October 1, 2006, to December 31, 2006 #12;2 Superconductivity Program Quarterly Progress Report Superconductivity Program Oak Ridge National Laboratory For U.S. Department of Energy Office of Electricity Delivery

  7. Effects of space charge in a compact superconducting energy recovery linac with a low energy

    NASA Astrophysics Data System (ADS)

    Hwang, Ji-Gwang; Kim, Eun-San; Miyajima, Tsukasa

    2012-08-01

    The Energy Recovery Linac (ERL) is one of the candidates for the next generation light sources, which is based on the 1.3 GHz superconducting radio frequency (SRF) linear accelerator. The ERL can produce high brilliance synchrotron radiation and a short pulse beam. We investigated the beam dynamics in the compact-Energy Recovery Linac (c-ERL) with a beam energy of 35 MeV, which is a prototype of the 5 GeV ERL at KEK. One of the main goals of our studies on the c-ERL is the emittance compensation in the merger section to achieve an emittance smaller than 1.0 mm mrad. In the case of the early commissioning phase, the injector system produces electron bunches of 5 MeV with a repetition rate of 1.3 GHz. The compensation of the emittance growth due to the space charge effect was investigated in order to achieve a small emittance at the exit of the merger. We discuss the results of a method to compensate the emittance growth which is based on beam envelope matching between the betatron function and the linear dispersion induced by the space charge force. We investigated the space charge effect when the beam energy in the superconducting RF section was changed. The effect of space charge in the arc section was also investigated. It is shown that the space charge effect in the c-ERL is an important source of distortion of the optics function. In this paper, we show the results on the analysis of the effect of space charge in the compact-ERL at KEK which has a low-energy beam.

  8. Development of an abort gap monitor for high-energy proton rings

    SciTech Connect

    Beche, Jean-Francois; Byrd, John; De Santis, Stefano; Denes, Peter; Placidi, Massimo; Turner, William; Zolotorev, Max

    2004-05-03

    The fill pattern in proton synchrotrons usually features an empty gap, longer than the abort kicker raise time, for machine protection. This gap is referred to as the ''abort gap'' and any particles, which may accumulate in it due to injection errors and diffusion between RF buckets, would be lost inside the ring, rather than in the beam dump, during the kicker firing. In large proton rings, due to the high energies involved, it is vital to monitor the build up of charges in the abort gap with a high sensitivity. We present a study of an abort gap monitor based on a photomultiplier with a gated microchannel plate, which would allow for detecting low charge densities by monitoring the synchrotron radiation emitted. We show results of beam test experiments at the Advanced Light Source using a Hamamatsu 5916U MCP-PMT and compare them to the specifications for the Large Hadron Collider

  9. Development of an Abort Gap Monitor for High-Energy Proton Rings

    NASA Astrophysics Data System (ADS)

    Beche, J.-F.; Byrd, J.; De Santis, S.; Denes, P.; Placidi, M.; Turner, W.; Zolotorev, M.

    2004-11-01

    The fill pattern in proton synchrotrons usually features an empty gap, longer than the abort kicker raise time, for machine protection. This gap is referred to as the "abort gap," and any particles, which may accumulate in it due to injection errors and diffusion between RF buckets, would be lost inside the ring, rather than in the beam dump, during the kicker firing. In large proton rings, due to the high energies involved, it is vital to monitor the build up of charges in the abort gap with a high sensitivity. We present a study of an abort gap monitor based on a photomultiplier with a gated microchannel plate, which would allow for detecting low charge densities by monitoring the synchrotron radiation emitted. We show results of beam test experiments at the Advanced Light Source using a Hamamatsu 5916U MCP-PMT and compare them to the specifications for the Large Hadron Collider.

  10. Optical conductivity of Ba0.6K0.4Fe2As2: The effect of in-plane and out-of-plane doping in the superconducting gap

    NASA Astrophysics Data System (ADS)

    Dai, Y. M.; Xu, B.; Shen, B.; Wen, H. H.; Qiu, X. G.; Lobo, R. P. S. M.

    2013-11-01

    We measured the in-plane optical conductivity of a nearly optimally doped (T_{c} = 39.1\\ \\text{K}) single crystal of Ba0.6K0.4Fe2As2. Upon entering the superconducting state the optical conductivity vanishes below \\sim20\\ \\text{meV} , indicating a fully gapped system. A quantitative modeling of the optical response of this material requires two different isotropic gaps, the larger of which dominates the London penetration depth. The temperature dependence of these gaps indicate a strong interband interaction, but no impurity-scattering-induced pair breaking is present. This contrasts to the large residual conductivity observed in optimally doped BaFe1.84Co0.08As2 and strongly supports an s_+/- gap symmetry for both compounds.

  11. Application of superconducting magnet energy storage to improve power system dynamic performance

    Microsoft Academic Search

    Y. Mitani; K. Tsuji; Y. Murakami

    1988-01-01

    The application of superconducting magnet energy storage (SMES) to the stabilization of a power system with long-distance bulk power transmission lines which has the problem of poorly damped power oscillations is presented. Control schemes for stabilization using SMES capable of controlling active and reactive power simultaneously in four quadrant ranges are proposed. The effective locations and the necessary capacities of

  12. ENERGY DEPOSITION WITHIN SUPERCONDUCTING COILS OF A 4-MW TARGET STATION

    E-print Network

    McDonald, Kirk

    .G Kirk, BNL, Upton, NY 11973, USA, R.J. Weggel, Particle Beam Lasers, Inc., Northridge, CA 91324, USA, K and the mercury jet are tilted with respect to the magnet axis to maximize collection of low-energy pions. A totalSn superconductor is only 14 T. The superconducting coils are shielded by tungsten-carbide (WC) beads cooled

  13. Automatic generation control of an interconnected hydrothermal power system considering superconducting magnetic energy storage

    Microsoft Academic Search

    Rajesh Joseph Abraham; D. Das; Amit Patra

    2007-01-01

    This paper presents the analysis of automatic generation control (AGC) of an interconnected hydrothermal power system in the presence of generation rate constraints (GRCs). The improvement of AGC with the addition of a small capacity superconducting magnetic energy storage (SMES) unit in either, as well as in both the areas are studied. Time domain simulations are used to study the

  14. Concepts of flywheels for energy storage using autostable high-T(sub c) superconducting magnetic bearings

    NASA Technical Reports Server (NTRS)

    Bornemann, Hans J.; Zabka, R.; Boegler, P.; Urban, C.; Rietschel, H.

    1994-01-01

    A flywheel for energy storage using autostable high-T(sub c) superconducting magnetic bearings has been built. The rotating disk has a total weight of 2.8 kg. The maximum speed is 9240 rpm. A process that allows accelerated, reliable and reproducible production of melt-textured superconducting material used for the bearings has been developed. In order to define optimum configurations for radial and axial bearings, interaction forces in three dimensions and vertical and horizontal stiffness have been measured between superconductors and permanent magnets in different geometries and various shapes. Static as well as dynamic measurements have been performed. Results are being reported and compared to theoretical models.

  15. Optical bistability via Josephson coupling energy in a superconducting quantum circuit

    NASA Astrophysics Data System (ADS)

    Hamedi, Hamid Reza

    2014-11-01

    A novel configuration is proposed to study optical bistability (OB) and optical multistability (OM) in a superconducting quantum circuit with a tunable V-type artificial molecule constructed by two superconducting Josephson charge qubits coupled with each other through a superconducting quantum interference device. We find that the ratio of the Josephson coupling energy to the capacitive coupling strength has a significant impact on creating optical bistability. The influence of other system parameters on bistable behavior of the artificial medium is then discussed. In particular, it is found that applying an incoherent pumping field can noticeably reduce the bistable threshold. We also realize a switch from OB to OM through proper tuning of detuning parameters. The controllability of OB and OM of this artificial molecule may be useful in building logic-gate devices for optical computing and quantum information processing and provide some new possibilities for solid-state quantum information science.

  16. The potential energy of a superconducting ring system locking magnetic flows in a gravity field

    NASA Astrophysics Data System (ADS)

    Bishaev, A. M.; Bush, A. A.; Gavrikov, M. B.; Kamentsev, K. E.; Kozintseva, M. V.; Saveliev, V. V.; Sigov, A. S.

    2012-10-01

    The possibility of creating a magnetic system of a plasma trap with levitating magnetic coils is under consideration. For this purpose, the analytical function of the potential energy of the system of several superconducting rings, which lock the required flows (at that, the one ring is fixed), versus the coordinates of free rings in the homogeneous gravity field under approximation of thin rings. Using calculations in the Mathcad medium, it is shown that, under definite values of parameters, there are equilibrium states of such a system. In the positions that corresponded to the calculated values, stable levitation states of the superconducting ring are observed experimentally in the field of another superconducting ring. The obtained results prove that a magnetic system can be created on the basis of a levitating quadrupole.

  17. IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 15, NO. 2, JUNE 2005 845 Energy Relaxation Times in a Nb Persistent

    E-print Network

    Orlando, Terry P.

    that connected to the room temperature electronics. (b) The quantum mechanical expectation valuesIEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 15, NO. 2, JUNE 2005 845 Energy Relaxation than 10 s, showing a strong potential of realizing quantum computa- tion with Nb-based superconducting

  18. Scaling up energy efficiency: bridging the action gap

    E-print Network

    concentrations, accelerating global warming and climate change. The importance of energy efficiency energy supply following the projected path is a grave threat to the global climate. Improving related to both energy security and the global climate. In the Reference Scenario of the International

  19. Distinct Fermi-momentum dependent energy gaps in deeply underdoped Bi2212.

    NASA Astrophysics Data System (ADS)

    Tanaka, K.; Lee, W. S.; Lu, D. H.; Fujimori, A.; Fujii, T.; Risdiana; Terasaki, I.; Fujita, K.; Ishikado, M.; Uchida, S.; Scalapino, D. J.; Devereaux, T. P.; Hussain, Z.; Shen, Z.-X.

    2007-03-01

    Our recent angle-resolved photoemission spectroscopy study of deeply underdoped cuprate superconductors Bi2Sr2(Ca,R)Cu2O8 (R = Y or Dy) (Bi2212) suggested the presence of two distinct energy gaps exhibiting different doping dependences [1]. One gap, associated with the antinodal region where no coherent peak is observed, increases with underdoping - a behavior known for more than a decade and considered as the general behavior of the gap in the underdoped regime. The other gap, associated with the near nodal regime where a coherent peak can be observed in energy distribution curves (EDCs), does not increase with less doping - a behavior not seen in the single particle spectra before. The theoretical implications of these findings and temperature dependence of the spectra will be discussed. [1] Science, in press. (http://www.sciencemag.org/cgi/content/abstract/1133411)

  20. Space applications of superconductivity

    NASA Technical Reports Server (NTRS)

    Sullivan, D. B.; Vorreiter, J. W.

    1979-01-01

    Some potential applications of superconductivity in space are summarized, e.g., the use of high field magnets for cosmic ray analysis or energy storage and generation, space applications of digital superconducting devices, such as the Josephson switch and, in the future, a superconducting computer. Other superconducting instrumentation which could be used in space includes: low frequency superconducting sensors, microwave and infrared detectors, instruments for gravitational studies, and high-Q cavities for use as stabilizing elements in clocks and oscillators.

  1. Study of superconducting magnetic bearing applicable to the flywheel energy storage system that consist of HTS-bulks and superconducting-coils

    NASA Astrophysics Data System (ADS)

    Seino, Hiroshi; Nagashima, Ken; Tanaka, Yoshichika; Nakauchi, Masahiko

    2010-06-01

    The Railway Technical Research Institute conducted a study to develop a superconducting magnetic bearing applicable to the flywheel energy-storage system for railways. In the first step of the study, the thrust rolling bearing was selected for application, and adopted liquid-nitrogen-cooled HTS-bulk as a rotor, and adopted superconducting coil as a stator for the superconducting magnetic bearing. Load capacity of superconducting magnetic bearing was verified up to 10 kN in the static load test. After that, rotation test of that approximately 5 kN thrust load added was performed with maximum rotation of 3000rpm. In the results of bearing rotation test, it was confirmed that position in levitation is able to maintain with stability during the rotation. Heat transfer properties by radiation in vacuum and conductivity by tenuous gas were basically studied by experiment by the reason of confirmation of rotor cooling method. The experimental result demonstrates that the optimal gas pressure is able to obtain without generating windage drag. In the second stage of the development, thrust load capacity of the bearing will be improved aiming at the achievement of the energy capacity of a practical scale. In the static load test of the new superconducting magnetic bearing, stable 20kN-levitation force was obtained.

  2. An outer gap model of high-energy emission from rotation-powered pulsars

    Microsoft Academic Search

    James Chiang; Roger W. Romani

    1994-01-01

    We describe a refined calculation of high-energy emission from rotation-powered pulsars based on the outer gap model of Cheng, Ho, & Ruderman (1986 a, b). In this calculation, vacuum gaps form in regions near the speed-of-light cylinder of the pulsar magnetosphere along the boundary between the closed and open field line zones. We have improved upon previous efforts to model

  3. Quasiparticle gaps and exciton Coulomb energies in Si nanoshells: First-principles calculations

    Microsoft Academic Search

    Kimberly Frey; Juan C. Idrobo; Murilo L. Tiago; Fernando A Reboredo; Serdar Ögüt

    2009-01-01

    Quasiparticle gaps and exciton Coulomb energies of H-passivated spherical Si nanoshells are computed using first-principles DeltaSCF method and selectively comparing to GW computations. We find that the quasiparticle gap of a nanoshell depends on both its inner radius R1 (weakly) and outer radius R2 (strongly). These dependences on R1 and R2 are mostly consistent with electrostatics of a metallic shell.

  4. Electronic energy gap correlation function and spectral density of anharmonic molecules at low temperatures I: Theory

    NASA Astrophysics Data System (ADS)

    Toutounji, Mohamad

    2015-01-01

    A closed-form expression for the electronic energy gap correlation function of anharmonic molecules weighed by their coupling strengths to the electronic transition is derived. These undamped anharmonic vibrations may be viewed as only linearly coupled phonons. The spectral density derived herein may be viewed as a spectrum of Franck-Condon factors for the phonons coupled linearly to the electronic transition in the low temperature limit. A formula for Morse oscillator reorganizational energy is derived. An approximate form for anharmonic energy gap correlation function is also provided, from which the spectral density of intramolecular vibrations is derived.

  5. A wideband vibration energy harvester based on a folded asymmetric gapped cantilever

    NASA Astrophysics Data System (ADS)

    Hu, Yating; Xu, Yong

    2014-02-01

    This paper reports a wideband multi-mass multi-spring piezoelectric vibration energy harvester (VEH) based on a folded asymmetric gapped cantilever, which enables multiple resonant modes formed by pure bending of every stage. Moreover, the heaviest proof mass is placed at the last stage of the cantilever to increase the harvested power. The VEH's energy conversion efficiency is further increased using the asymmetric gapped structure. A prototype has been developed and characterized. The experimental results match with finite element simulation well. The prototype was tested on an air conditioning unit to demonstrate its energy harvesting capability with a realistic broadband vibration source.

  6. Magnetic and Superconducting Properties of Vanadium Nanoconstrictions

    NASA Astrophysics Data System (ADS)

    Takata, Hiroki; Inagaki, Yuji; Kawae, Tatsuya; Ienaga, Koichiro; Tsujii, Hiroyuki

    2015-03-01

    We study the magnetic and superconducting properties in a paramagnetic vanadium (V) nanoconstriction with changing its size using a mechanically controllable break junction technique. In the normal state the magnetoresistance effect is observed below the diameter d ~ 8 nm. Moreover, a Fano resonance appears around zero-bias voltage in the differential conductance for the atomic-size contacts and changes shape as the size of the constriction changes. On the other hand, below the superconducting critical temperature the superconducting gap features in V contacts are largely different from those in Pb contacts which exhibit typical features expected in superconducting point contacts. Only a single Andreev anomaly at 2?, where ? is the superconducting energy gap, is observed in the spectra of the V contacts, while two anomalies at ? and 2? appear in the case of the Pb contacts. In the tunnel conductance regime, the structure of the superconducting quasiparticle tunneling density of states is not seen in the V spectra in contrast to the Pb spectra. The origin of these features is discussed.

  7. Peak power reduction and energy efficiency improvement with the superconducting flywheel energy storage in electric railway system

    NASA Astrophysics Data System (ADS)

    Lee, Hansang; Jung, Seungmin; Cho, Yoonsung; Yoon, Donghee; Jang, Gilsoo

    2013-11-01

    This paper proposes an application of the 100 kWh superconducting flywheel energy storage systems to reduce the peak power of the electric railway system. The electric railway systems have high-power characteristics and large amount of regenerative energy during vehicles’ braking. The high-power characteristic makes operating cost high as the system should guarantee the secure capacity of electrical equipment and the low utilization rate of regenerative energy limits the significant energy efficiency improvement. In this paper, it had been proved that the peak power reduction and energy efficiency improvement can be achieved by using 100 kWh superconducting flywheel energy storage systems with the optimally controlled charging or discharging operations. Also, economic benefits had been assessed.

  8. Growing energy gap threatens major disruptions. [Scenario for Michigan

    Microsoft Academic Search

    Dix

    1977-01-01

    Members of the Michigan legislature were advised that an economic solution to the problem of future fuel supplies is not consistent with physical facts. The impact of energy attrition on the relationships of business, industry, and individuals to each other and to the energy market is outlined in a scenario for Michigan. Industry is expected to operate in the present

  9. Rotochemical heating with a density-dependent superfluid energy gap in neutron stars

    NASA Astrophysics Data System (ADS)

    González-Jiménez, Nicolás; Petrovich, Cristóbal; Reisenegger, Andreas

    2010-08-01

    When a rotating neutron star loses angular momentum, the reduction of the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium, inducing reactions that release heat (rotochemical heating). This effect has previously been studied by Fernández and Reisenegger for neutron stars of non-superfluid matter and by Petrovich and Reisenegger for superfluid matter, finding that the system in both cases reaches a quasi-steady state, corresponding to a partial equilibration between compression, due to the loss of angular momentum, and reactions that try to restore the equilibrium. However, Petrovich and Reisenegger assumes a constant value of the superfluid energy gap, whereas theoretical models predict density-dependent gap amplitudes, and therefore gaps that depend on the location in the star. In this work, we try to discriminate between several proposed gap models, comparing predicted surface temperatures to the value measured for the nearest millisecond pulsar, J0437-4715.

  10. Energy-gap reduction in heavily doped silicon: Causes and consequences

    NASA Astrophysics Data System (ADS)

    Pantelides, Sokrates T.; Selloni, Annabella; Car, Roberto

    1985-02-01

    The authors review briefly the existing theoretical treatments of the various effects that contribute to the reduction of the energy gap in heavily doped Si, namely electron-electron and electron-impurity interactions and the effect of disorder in the impurity distribution. They then turn to the longstanding question why energy-gap reductions extracted from three different types of experiments have persistently produced values with substantial discrepancies, making it impossible to compare with theoretical values. First, they demonstrate that a meaningful comparison between theory and experiment can indeed be made if theoretical calculations are carried out for actual quantities that experiments measure, e.g. luminescence spectra, as recently done by Selloni and Pantelides. Then, they demonstrate that, independent of any theoretical calculations, the optical absorption spectra are fully consistent with the luminescence spectra and that the discrepancies in the energy-gap reductions extracted from the two sets of spectra are caused entirely by the curve-fitting procedures used in analyzing optical-absorption data. Finally, they show explicitly that, as already believed by many authors, energy-gap reductions extracted from electrical measurements on transistors do not correspond to true gap reductions. They identify two corrections that must be added to the values extracted from the electrical data in order to arrive at the true gap reductions and show that the resulting values are in good overall agreement with luminescence and absorption data. They, therefore, demonstrate that the observed reduction in emitter injection efficiency in bipolar transistors is not strictly due to a gap reduction, as generally believed, but to three very different effects.

  11. The energy trilogy: An integrated sustainability model to bridge wastewater treatment plant energy and emissions gaps

    NASA Astrophysics Data System (ADS)

    Al-Talibi, A. Adhim

    An estimated 4% of national energy consumption is used for drinking water and wastewater services. Despite the awareness and optimization initiatives for energy conservation, energy consumption is on the rise owing to population and urbanization expansion and to commercial and industrial business advancement. The principal concern is since energy consumption grows, the higher will be the energy production demand, leading to an increase in CO2 footprints and the contribution to global warming potential. This research is in the area of energy-water nexus, focusing on wastewater treatment plant (WWTP) energy trilogy -- the group of three related entities, which includes processes: (1) consuming energy, (2) producing energy, and (3) the resulting -- CO2 equivalents. Detailed and measurable energy information is not readily obtained for wastewater facilities, specifically during facility preliminary design phases. These limitations call for data-intensive research approach on GHG emissions quantification, plant efficiencies and source reduction techniques. To achieve these goals, this research introduced a model integrating all plant processes and their pertinent energy sources. In a comprehensive and "Energy Source-to-Effluent Discharge" pattern, this model is capable of bridging the gaps of WWTP energy, facilitating plant designers' decision-making for meeting energy assessment, sustainability and the environmental regulatory compliance. Protocols for estimating common emissions sources are available such as for fuels, whereas, site-specific emissions for other sources have to be developed and are captured in this research. The dissertation objectives were met through an extensive study of the relevant literature, models and tools, originating comprehensive lists of processes and energy sources for WWTPs, locating estimation formulas for each source, identifying site specific emissions factors, and linking the sources in a mathematical model for site specific CO2 e determination. The model was verified and showed a good agreement with billed and measured data from a base case study. In a next phase, a supplemental computational tool can be created for conducting plant energy design comparisons and plant energy and emissions parameters assessments. The main conclusions drawn from this research is that current approaches are severely limited, not covering plant's design phase and not fully considering the balance of energy consumed (EC), energy produced (EP) and the resulting CO2 e emission integration. Finally their results are not representative. This makes reported governmental and institutional national energy consumption figures incomplete and/or misleading, since they are mainly considering energy consumptions from electricity and some fuels or certain processes only. The distinction of the energy trilogy model over existing approaches is based on the following: (1) the ET energy model is unprecedented, prepared to fit WWTP energy assessment during the design and rehabilitation phases, (2) links the energy trilogy eliminating the need for using several models or tools, (3) removes the need for on-site expensive energy measurements or audits, (4) offers alternatives for energy optimization during plant's life-cycle, and (5) ensures reliable GHG emissions inventory reporting for permitting and regulatory compliance.

  12. Comparison of energy flows in deep inelastic scattering events with and without a large rapidity gap

    Microsoft Academic Search

    M. Derrick; D. Krakauer; S. Magill; B. Musgrave; J. Repond; J. Schlereth; R. Stanek; R. L. Talaga; J. Thron; F. Arzarello; R. Ayad; G. Bari; M. Basile; L. Bellagamba; D. Boscherini; A. Bruni; G. Bruni; P. Bruni; G. Cara Romeo; G. Castellini; M. Chiarini; L. Cifarelli; F. Cindolo; F. Ciralli; A. Contin; S. D'Auria; C. del Papa; F. Frasconi; P. Giusti; G. Iacobucci; G. Laurenti; G. Levi; G. Maccarrone; A. Margotti; T. Massam; R. Nania; C. Nemoz; F. Palmonari; A. Polini; G. Sartorelli; R. Timellini; Y. Zamora Garcia; A. Zichichi; A. Bargende; J. Crittenden; K. Desch; B. Diekmann; T. Doeker; L. Feld; A. Frey; M. Geerts; G. Geitz; M. Grothe; H. Hartmann; D. Haun; K. Heinloth; E. Hilger; H.-P. Jakob; U. F. Katz; S. M. Mari; A. Mass; S. Mengel; J. Mollen; E. Paul; Ch. Rembser; R. Schattevoy; J.-L. Schneider; D. Schramm; J. Stamm; R. Wedemeyer; S. Campbell-Robson; A. Cassidy; N. Dyce; B. Foster; S. George; R. Gilmore; G. P. Heath; H. F. Heath; T. J. Llewellyn; C. J. S. Morgado; D. J. P. Norman; J. A. O'Mara; R. J. Tapper; S. S. Wilson; R. Yoshida; R. R. Rau; M. Arneodo; L. Iannotti; M. Schioppa; G. Susinno; A. Bernstein; A. Caldwell; I. Gialas; J. A. Parsons; S. Ritz; F. Sciulli; P. B. Straub; L. Wai; S. Yang; P. Borzemski; J. Chwastowski; A. Eskreys; K. Piotrzkowski; M. Zachara; L. Zawiejski; L. Adamczyk; B. Bednarek; K. Eskreys; K. Jelen; D. Kisielewska; T. Kowalski; E. Rulikowska-Zarebska; L. Suszycki; J. Zajc; T. Kedzierski; A. Kotanski; M. Przybycien; L. A. T. Bauerdick; U. Behrens; J. K. Bienlein; S. Böttcher; C. Coldewey; G. Drews; M. Flasinski; D. J. Gilkinson; P. Göttlicher; B. Gutjahr; T. Haas; L. Hagge; W. Hain; D. Hasell; H. Heßling; H. Hultschig; Y. Iga; P. Joos; M. Kasemann; R. Klanner; W. Koch; L. Köpke; U. Kötz; H. Kowalski; W. Kröger; J. Krüger; J. Labs; A. Ladage; B. Löhr; M. Löwe; D. Lüke; J. Mainusch; O. Manczak; J. S. T. Ng; S. Nickel; D. Notz; K. Ohrenberg; M. Roco; M. Rohde; J. Roldán; U. Schneekloth; J. Schroeder; W. Schulz; F. Selonke; E. Stiliaris; T. Voß; D. Westphal; G. Wolf; C. Youngman; H. J. Grabosch; A. Leich; A. Meyer; C. Rethfeldt; S. Schlenstedt; G. Barbagli; P. Pelfer; G. Anzivino; S. de Pasquale; S. Qian; L. Votano; A. Bamberger; A. Freidhof; T. Poser; S. Söldner-Rembold; G. Theisen; T. Trefzger; N. H. Brook; P. J. Bussey; A. T. Doyle; I. Fleck; J. R. Forbes; V. A. Jamieson; C. Raine; D. H. Saxon; M. Stavrianakou; A. S. Wilson; A. Dannemann; U. Holm; D. Horstmann; H. Kammerlocher; B. Krebs; T. Neumann; R. Sinkus; K. Wick; E. Badura; B. D. Burow; A. Fürtjes; E. Lohrmann; J. Milewski; M. Nakahata; N. Pavel; G. Poelz; W. Schott; J. Terron; F. Zetsche; T. C. Bacon; R. Beuselinck; I. Butterworth; E. Gallo; V. L. Harris; B. H. Hung; K. R. Long; D. B. Miller; P. P. O. Morawitz; A. Prinias; J. K. Sedgbeer; A. F. Whitfield; U. Mallik; E. McCliment; M. Z. Wang; Y. Zhang; P. Cloth; D. Filges; S. H. An; S. M. Hong; C. O. Kim; T. Y. Kim; S. W. Nam; S. K. Park; M. H. Suh; S. H. Yon; R. Imlay; S. Kartik; H.-J. Kim; R. R. McNeil; W. Metcalf; V. K. Nadendla; F. Barreiro; G. Cases; R. Graciani; J. M. Hernández; L. Hervás; L. Labarga; J. del Peso; J. Puga; J. F. de Trocóniz; F. Ikraiam; J. K. Mayer; G. R. Smith; F. Corriveau; D. S. Hanna; J. Hartmann; L. W. Hung; J. N. Lim; C. G. Matthews; J. W. Mitchell; P. M. Patel; L. E. Sinclair; D. G. Stairs; M. St. Laurent; R. Ullmann; V. Bashkirov; B. A. Dolgoshein; A. Stifutkin; G. L. Bashindzhagyan; P. F. Ermolov; L. K. Gladilin; Y. A. Golubkov; V. D. Kobrin; V. A. Kuzmin; A. S. Proskuryakov; A. A. Savin; L. M. Shcheglova; A. N. Solomin; N. P. Zotov; S. Bentvelsen; M. Botje; F. Chlebana; A. Dake; J. Engelen; P. de Jong; M. de Kamps; P. Kooijman; A. Kruse; V. O'dell; A. Tenner; H. Tiecke; W. Verkerke; M. Vreeswijk; L. Wiggers; E. de Wolf; R. van Woudenberg; D. Acosta; B. Bylsma; L. S. Durkin; K. Honscheid; C. Li; T. Y. Ling; K. W. McLean; W. N. Murray; I. H. Park; T. A. Romanowski; R. Seidlein; D. S. Bailey; G. A. Blair; A. Byrne; R. J. Cashmore; A. M. Cooper-Sarkar; D. Daniels; R. C. E. Devenish; N. Harnew; M. Lancaster; P. E. Luffman; J. McFall; C. Nath; A. Quadt; H. Uijterwaal; R. Walczak; F. F. Wilson; T. Yip; G. Abbiendi; A. Bertolin; R. Brugnera; R. Carlin; F. dal Corso; M. de Giorgi; U. Dosselli; F. Gasparini; S. Limentani; M. Morandin; M. Posocco; L. Stanco; R. Stroili; C. Voci; J. Bulmahn; J. M. Butterworth; R. G. Feild; B. Y. Oh; J. J. Whitmore; G. D'Agostini; M. Iori; G. Marini; M. Mattioli; A. Nigro; J. C. Hart; N. A. McCubbin; K. Prytz; T. P. Shah; T. L. Short; E. Barberis; N. Cartiglia; T. Dubbs; C. Heusch; M. van Hook; B. Hubbard; W. Lockman; H. F.-W. Sadrozinski; A. Seiden; J. Biltzinger; R. J. Seifert; A. H. Walenta; G. Zech; H. Abramowicz; S. Dagan; A. Levy; T. Hasegawa; M. Hazumi; T. Ishii; M. Kuze; S. Mine; Y. Nagasawa; T. Nagira; M. Nakao; I. Suzuki; K. Tokushuku; S. Yamada

    1994-01-01

    Energy flows in deep inelastic electron-proton scattering are investigated at a centre-of-mass energy of 269 GeV for the range Q2 >= 10 GeV2 using the ZEUS detector. A comparison is made between events with and without a large rapidity gap between the hadronic system and the proton direction. The energy flows, corrected for detector acceptance and resolution, are shown for

  13. SUPERCONDUCTIVITY PROGRAM RESEARCH AND DEVELOPMENT High Temperature Superconductivity (HTS) is a technology with the potential

    E-print Network

    #12;SUPERCONDUCTIVITY PROGRAM RESEARCH AND DEVELOPMENT High Temperature Superconductivity (HTS-of-way. The Department of Energy's efforts to advance High Temperature Superconductivity combine major national strengths: the Superconductivity Partnership Initiative (SPI), the 2nd Generation Wire Initiative

  14. Superconducting magnetic energy storage (SMES) program. Progress report, January 1-December 31, 1980

    SciTech Connect

    Rogers, J.D. (comp.)

    1981-03-01

    Work is reported on the development of two superconducting magnetic energy storage (SMES) units. One is a 30-MJ unit for use by the Bonneville Power Administration (BPA) to stabilize power oscillations on their Pacific AC Intertie, and the second is a 1- to 10-GWh unit for use as a diurnal load leveling device. Emphasis has been on the stabilizing system. The manufacturing phase of the 30-MJ superconducting coil was initiated and the coil fabrication has advanced rapidly. The two converter power transformers were manufactured, successfully factory tested, and shipped. One transformer reached the Tacoma Substation in good condition; the other was dropped enroute and has been returned to the factory for rebuilding. Insulation of the 30-MJ coil has been examined for high voltage effects apt to be caused by transients such as inductive voltage spikes from the protective dump circuit. The stabilizing system converter and protective energy dump system were completed, factory tested, and delivered.

  15. Energy-gap dependence on the Mn mole fraction and temperature in CdMnTe crystal

    NASA Astrophysics Data System (ADS)

    Kim, K. H.; Bolotnikov, A. E.; Camarda, G. S.; Yang, G.; Hossain, A.; Cui, Y.; James, R. B.; Hong, J.; Kim, S. U.

    2009-07-01

    We measured the dependence of the energy gap in Bridgman-grown Cd1-xMnxTe crystals, 0?x?0.25, on the Mn mole fraction and temperatures from 40 to 300 K. We determined the Mn mole fraction and energy gap, respectively, from electron probe microanalysis and near-infrared Fourier-transform infrared transmission spectra. The energy gap increased linearly with an increase in the Mn content in the crystal and with a decrease in temperature. We formulated new equations from these experimental results, wherein we expressed the energy gap as a function of Mn mole fraction and temperature. Also, we compare our findings with published results.

  16. Visualizing superconductivity in FeSe nanoflakes on SrTiO3 by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Peng, Jun-Ping; Zhang, Hui-Min; Song, Can-Li; Ji, Shuai-Hua; Wang, Lili; He, Ke; Chen, Xi; Xue, Qi-Kun; Ma, Xu-Cun

    2015-02-01

    Scanning tunneling microscopy and spectroscopy have been employed to investigate the superconductivity in single unit-cell FeSe nanoflakes on SrTiO3 substrates. We find that the differential conductance d I /d V spectra are spatially nonuniform and fluctuate within the flakes as their area is reduced to below ˜150 nm2 . An enhancement in the superconductivity-related gap size as large as 25 % is observed. The superconductivity behavior disappears when the FeSe nanoflakes reduce to ˜40 nm2 . Compared to a previous report [Wang et al., Chin. Phys. Lett. 29, 037402 (2012), 10.1088/0256-307X/29/3/037402], the gap is asymmetric relative to the Fermi energy EF. All the features, particularly the fluctuating gap and quenched superconductivity, could be accounted for by quantum size effects. Our study helps to understand nanoscale superconductivity in low-dimensional systems.

  17. A bi-annular-gap magnetorheological energy absorber for shock and vibration mitigation

    NASA Astrophysics Data System (ADS)

    Bai, Xian-Xu; Wereley, Norman M.; Choi, Young-Tai; Wang, Dai-Hua

    2012-04-01

    For semi-active shock and vibration mitigation systems using magnetorheological energy absorbers (MREAs), the minimization of the field-off damper force of the MREA at high speed is of particular significance because the damper force due to the viscous damping at high speed becomes too excessive and thus the controllable dynamic force range that is defined by the ratio of the field-on damper force to the field-off damper force is significantly reduced. In this paper, a bi-annular-gap MREA with an inner-set permanent magnet is proposed to decrease the field-off damper force at high speed while keeping appropriate dynamic force range for improving shock and vibration mitigation performance. In the bi-annular-gap MREA, two concentric annular gaps are configured in parallel so as to decrease the baseline damper force and both magnetic activation methods using the electromagnetic coil winding and the permanent magnet are used to keep holding appropriate magnetic intensity in these two concentric annular gaps in the consideration of failure of the electric power supply. An initial field-on damper force is produced by the magnetic field bias generated from the inner-set permanent magnet. The initial damper force of the MREA can be increased (or decreased) through applying positive (or negative) current to the electromagnetic coil winding inside the bi-annular-gap MREA. After establishing the analytical damper force model of the bi-annular-gap MREA using a Bingham-plastic nonlinear fluid model, the principle and magnetic properties of the MREA are analytically validated and analyzed via electromagnetic finite element analysis (FEA). The performance of the bi-annular-gap MREA is also theoretically compared with that of a traditional single-annular- gap MREA with the constraints of an identical volume by the performance matrix, such as the damper force, dynamic force range, and Bingham number with respect to different excitation velocities.

  18. Superconductive energy storage. Volume IV. Final technical report revision, January 1976September 1981

    Microsoft Academic Search

    Hartwig; K. T. Jr

    1983-01-01

    The design history of Inductor-Converter (I-C) superconductive energy storage units includes first a solenoid in one deep tunnel, then segmented deep solenoids and finally a fifteen tunnel hour-glass system. Conductor research includes NbTi studies, welding of high purity and high strength aluminum components, moderate strength aluminum alloy development, conductor cruciform alloys and overall conductor fabrication studies. Cryogenic tests of boundary

  19. Multimodular current-source SPWM converters for a superconducting magnetic energy storage system

    Microsoft Academic Search

    Zhong-Chao Zhang; Boon-Teck Ooi

    1993-01-01

    The advantages of using multiple modules of the current-source, sinusoidal pulse-width-modulated (SPWM), three-phase, six-valve converters as the power conditioner for the superconducting magnetic energy system are highlighted. A high degree of controllability is obtained by using dynamic SPWM trilogic as the operating strategy. Very low switching losses are assured by using two carrier triangles per modulated cycle. By partial connection

  20. Plant and operational features of the BPA 30 MJ superconducting magnetic energy storage system

    SciTech Connect

    Rogers, J.D.; Hauer, J.F.

    1984-01-01

    A 30 MJ superconducting magnetic energy storage (SMES) system was designed and developed for application in the Western US Power System to damp power oscillations that limit high voltage ac transmission. The system is in place at the Bonneville Power Administration (BPA) Tacoma Substation and has been in an experimental use for over a year. Extended operations of the unit have been undertaken with success. The physical, electrical, and operational features of the SMES system are given.

  1. Intrinsic superconductivity in ABA-stacked trilayer graphene

    NASA Astrophysics Data System (ADS)

    Liu, Haiwen; Jiang, Hua; Xie, X. C.

    2012-12-01

    We study the phonon-mediated superconductivity in light doped ABA-stacked trilayer graphene system by means of two theoretical models. We find superconducting transition temperature TC can be greatly enlarged by tuning the Fermi energy away from neutral point. Utilizing realistic parameters, we find Tc is approximately 1 K even under weak doping condition EF = 0.1 eV. Specifically, we give out the analytical expression for superconductivity gap ? and superconducting transition temperature Tc for negative-U Hubbard model. Further, we consider the thermal fluctuation and calculate the Berezinskii-Kosterlitz-Thouless critical temperature TBKT. Besides, we consider a two-band BCS model in comparision with the negative-U Hubbard model. The results for both models are qualitatively consistent. Our study provides a promising possibility for realizing intrinsic superconductivity in multilayer graphene systems.

  2. An evaluation of fusion energy R&D gaps using Technology Readiness Levels

    E-print Network

    An evaluation of fusion energy R&D gaps using Technology Readiness Levels M. S. Tillack "readiness levels" as the basis for our R&D evaluation methodology TRL Generic Description (defense and qualified through test and demonstration. 9 Actual system proven through successful mission operations. page

  3. Unified Description of Rapidity Gaps and Energy Flows in DIS Final States

    Microsoft Academic Search

    A. Edin; G. Ingelman; J. Rathsman

    1996-01-01

    We show that the `orthogonal' characteristics of the observed rapidity gaps and large forward energy flows in deep inelastic scattering at HERA, can be described within a single framework. Our Monte Carlo model is based on perturbative QCD matrix elements and parton showers together with Lund string model hadronization, but has in addition a new mechanism for soft colour interactions

  4. Unified description of rapidity gaps and energy flows in DIS final states

    Microsoft Academic Search

    A. Edin; G. Ingelman; J. Rathsman

    1997-01-01

    We show that the 'orthogonal' characteristics of the observed rapidity gaps and large forward energy flows in deep inelastic scattering at HERA, can be described within a single framework. Our Monte Carlo model is based on perturbative QCD matrix elements and parton showers together with Lund string model hadronization, but has in addition a new mechanism for soft colour interactions

  5. Photoluminescence-based measurements of the energy gap and diffusion length of Zn3P2

    E-print Network

    Kimball, Gregory

    Photoluminescence-based measurements of the energy gap and diffusion length of Zn3P2 Gregory M 2009; accepted 20 August 2009; published online 14 September 2009 The steady-state photoluminescence-resolved photoluminescence decay measurements, implying minority-carrier diffusion lengths of 7 m. © 2009 American Institute

  6. Superconductivity-induced optical anomaly in an iron arsenide

    PubMed Central

    Charnukha, A.; Popovich, P.; Matiks, Y.; Sun, D. L.; Lin, C. T.; Yaresko, A. N.; Keimer, B.; Boris, A. V.

    2011-01-01

    One of the central tenets of conventional theories of superconductivity, including most models proposed for the recently discovered iron-pnictide superconductors, is the notion that only electronic excitations with energies comparable to the superconducting energy gap are affected by the transition. Here, we report the results of a comprehensive spectroscopic ellipsometry study of a high-quality crystal of superconducting Ba0.68K0.32Fe2As2 that challenges this notion. We observe a superconductivity-induced suppression of an absorption band at an energy of 2.5 eV, two orders of magnitude above the superconducting gap energy 2??20 meV. On the basis of density functional calculations, this band can be assigned to transitions from As-p to Fe-d orbitals crossing the Fermi level. We identify a related effect at the spin-density wave transition in parent compounds of the 122 family. This suggests that As-p states deep below the Fermi level contribute to the formation of the superconducting and spin-density wave states in the iron arsenides. PMID:21364558

  7. The optical band gap and surface free energy of polyethylene modified by electron beam irradiations

    NASA Astrophysics Data System (ADS)

    Abdul-Kader, A. M.

    2013-04-01

    In this study, investigations have been carried out on electron beam irradiated ultra high molecular weight polyethylene (UHMWPE). Polyethylene samples were irradiated with 1.5 MeV electron beam at doses ranging from 50 to 500 kGy. Modifications in optical properties and photoluminescence behavior of the polymer were evaluated by UV-vis and photoluminescence techniques. Changes of surface layer composition of UHMWPE produced by electron irradiations were studied by Rutherford back scattering spectrometry (RBS). The change in wettability and surface free energy induced by irradiations was also investigated. The optical absorption studies reveal that both optical band gap and Urbach's energy decreases with increasing electron dose. A correlation between energy gap and the number of carbon atoms in clusters is discussed. Photoluminescence spectra were reveal remarkable decrease in the integrated luminescence intensity with increasing irradiation dose. Contact angle measurements showed that wettability and surface free energy increases with increasing the irradiation dose.

  8. dc voltage holding experiments of vacuum gap for high-energy ion sources

    NASA Astrophysics Data System (ADS)

    Watanabe, Kazuhiro; Mizuno, Makoto; Ohara, Yoshihiro; Tanaka, Masanobu; Kobayashi, Kazuo; Takahashi, Eiki; Uede, Taisei

    1992-11-01

    dc voltage holding characteristics were investigated to obtain a data base for designing high-energy and high-power ion sources of neutral beam injectors. We confirmed that the voltage holding characteristics almost obey the clump theory in the experimental gap length of up to 50 mm. The magnetic field in the gap lowered the breakdown voltage in a gas discharge region higher than a pressure of 10-3 Torr. The breakdown voltage of 30% was reduced by seeding cesium on the electrode with one order higher density than that of actual ion source at the pressure region of lower than several mTorr.

  9. R&D of superconducting bearing technologies for flywheel energy storage systems

    NASA Astrophysics Data System (ADS)

    Koshizuka, N.

    2006-10-01

    Recent advances on superconducting magnetic bearing (SMB) technologies for flywheel energies storage systems (FESSs) are reviewed based on the results of NEDO flywheel project (2000-2004). We constructed a radial-type SMB model for 100 kW h class FESSs and evaluated the bearing characteristics. The SMB model consists of a superconducting stator of YBCO bulks and a NdFeB permanent magnet circuit. The levitation force density reached 11 N/cm 2 at 77 K, and the time decay of levitation force was suppressed in allowable ranges by adopting such techniques as “pre-loading” or “super-cooling” method. The rotation loss was reduced by means of improving the homogeneity of magnetic field distribution in both permanent magnet circuit and superconducting bulk stator. The availability of radial-type SMB for FESS was investigated by constructing 10 kW h class FESS using both SMB and active magnetic bearings. The operation test resulted in the energy storage of 5.0 kW h at rotation speed of 11,250 rpm. A further reduction of rotation losses is a crucial issue for its wide range of applications.

  10. Rapidity gaps and production of minijets in high-energy hadronic collisions

    E-print Network

    G. Calucci; R. Ragazzon; D. Treleani

    1996-10-24

    High energy hadronic interactions can produce a final state characterized by minijets separated by a large gap in the rapidity distribution of the produced secondary particles. We discuss the process by keeping into account the possibility of having multiple parton collisions in the hadronic interaction. At Tevatron energy the correction to the single scattering term induced by the presence of multiparton interactions is large for transverse momenta smaller than 6 GeV.

  11. Performance of Variable Energy Cyclotron Centre superconducting cyclotron liquid nitrogen distribution system

    NASA Astrophysics Data System (ADS)

    Pal, Gautam; Nandi, Chinmay; Bhattacharyya, Tamal Kumar; Chakrabarti, Alok

    2014-01-01

    The liquid nitrogen distribution at Variable Energy Cyclotron Centre, Kolkata, India K500 superconducting cyclotron uses parallel branches to cool the thermal shield of helium vessel housing the superconducting coil and the cryopanels. Liquid nitrogen is supplied to the thermal shields from a pressurised liquid nitrogen dewar. Direct measurement of flow is quite difficult and seldom used in an operational cryogenic system. The total flow and heat load of the liquid nitrogen system was estimated indirectly by continuous measurement of level in the liquid nitrogen tanks. A mathematical model was developed to evaluate liquid nitrogen flow in the parallel branches. The model was used to generate flow distribution for different settings and the total flow was compared with measured data.

  12. Performance of Variable Energy Cyclotron Centre superconducting cyclotron liquid nitrogen distribution system.

    PubMed

    Pal, Gautam; Nandi, Chinmay; Bhattacharyya, Tamal Kumar; Chakrabarti, Alok

    2014-01-01

    The liquid nitrogen distribution at Variable Energy Cyclotron Centre, Kolkata, India K500 superconducting cyclotron uses parallel branches to cool the thermal shield of helium vessel housing the superconducting coil and the cryopanels. Liquid nitrogen is supplied to the thermal shields from a pressurised liquid nitrogen dewar. Direct measurement of flow is quite difficult and seldom used in an operational cryogenic system. The total flow and heat load of the liquid nitrogen system was estimated indirectly by continuous measurement of level in the liquid nitrogen tanks. A mathematical model was developed to evaluate liquid nitrogen flow in the parallel branches. The model was used to generate flow distribution for different settings and the total flow was compared with measured data. PMID:24517753

  13. Gap Length Dependence of Electron Energy Distribution in Low-Pressure Ar Capacitively Coupled RF Discharges

    NASA Astrophysics Data System (ADS)

    Kimura, Takashi; Kaga, Kouji; Ohe, Kazuyuki

    2000-03-01

    The electron energy distribution function (EEDF) at the midplane was measured using a Langmuir probe in symmetrically capacitively coupled RF (13.56 MHz) Ar discharges by changing the gap length from 2 cm to 10 cm over the pressure range from 0.03 Torr to 0.1 Torr, while keeping the RF current constant at 140 mArms. The EEDFs measured at pressure lower than 0.05 Torr formed a bi-Maxwellian distribution over the measured gap length. On the other hand, the EEDF structure measured at pressure higher than 0.07 Torr changed from bi-Maxwellian to Maxwellian, and to Druyvesteyn distributions with increasing gap length. The gap length dependence of the EEDF structure in the high-energy region can be explained by the transition from the stochastic to the joule heating, while that in the low-energy region can be explained by comparing the elastic collision frequency and the e-e Coulomb collision frequency.

  14. Ion Desorption Stability in Superconducting High Energy Physics Proton Colliders

    SciTech Connect

    Turner, W.C.

    1995-05-29

    In this paper we extend our previous analysis of cold beam tube vacuum in a superconducting proton collider to include ion desorption in addition to thermal desorption and synchrotron radiation induced photodesorption. The new ion desorption terms introduce the possibility of vacuum instability. This is similar to the classical room temperature case but now modified by the inclusion of ion desorption coefficients for cryosorbed (physisorbed) molecules which can greatly exceed the coefficients for tightly bound molecules. The sojourn time concept for physisorbed H{sub 2} is generalized to include photodesorption and ion desorption as well as the usually considered thermal desorption. The ion desorption rate is density dependent and divergent so at the onset of instability the sojourn time goes to zero. Experimental data are used to evaluate the H{sub 2} sojourn time for the conditions of the Large Hadron Collider (LHC) and the situation is found to be stable. The sojourn time is dominated by photodesorption for surface density s(H{sub 2}) less than a monolayer and by thermal deposition for s(H{sub 2}) greater than a monolayer. For a few percent of a monolayer, characteristic of a beam screen, the photodesorption rate exceeds ion desorption rate by more than two orders of magnitude. The photodesorption rate corresponds to a sojourn time of approximately 100 sec. The paper next turns to the evaluation of stability margins and inclusion of gases heavier than H{sub 2} (CO, CO{sub 2} and CH{sub 4}), where ion desorption introduces coupling between molecular species. Stability conditions are worked out for a simple cold beam tube, a cold beam tube pumped from the ends and a cold beam tube with a co-axial perforated beam screen. In each case a simple inequality for stability of a single component is replaced by a determinant that must be greater than zero for a gas mixture. The connection with the general theory of feedback stability is made and it is shown that the gains of the diagonal uncoupled feedback loops are first order in the ion desorption coefficients whereas the gains of the off diagonal coupled feedback loops are second and higher order. For this reason it turns out that in practical cases stability is dominated by the uncoupled diagonal elements and the inverse of the largest first order closed loop gain is a useful estimate of the margin of stability. In contrast to the case of a simple cold beam tube, the stability condition for a beam screen does not contain the desorption coefficient for physisorbed molecules, even when the screen temperature is low enough that there is a finite surface density of them on the screen surface. Consequently there does not appear to be any particular advantage to operating the beam screen at high enough temperature to avoid physisorption. Numerical estimates of ion desorption stability are given for a number of cases relevant to LHC and all of the ones likely to be encountered were found to be stable. The most important case, a I % transparency beam screen at {approx}4.2 K, was found to have a stability safety margin of approximately thirty determined by ion desorption of CO. Ion desorption of H{sub 2} is about a factor of eighty less stringent than CO. For these estimates the beam tube surface was assumed to be solvent cleaned but otherwise untreated, for example by a very high temperature vacuum bakeout or by glow discharge cleaning.

  15. Technical Barriers, Gaps, and Opportunities Related to Home Energy Upgrade Market Delivery

    SciTech Connect

    Bianchi, M. V. A.

    2011-11-01

    This report outlines the technical barriers, gaps, and opportunities that arise in executing home energy upgrade market delivery approaches, as identified through research conducted by the U.S. Department of Energy's Building America program. The objective of this report is to outline the technical1 barriers, gaps, and opportunities that arise in executing home energy upgrade market delivery approaches, as identified through research conducted by the U.S. Department of Energy's (DOE) Building America program. This information will be used to provide guidance for new research necessary to enable the success of the approaches. Investigation for this report was conducted via publications related to home energy upgrade market delivery approaches, and a series of interviews with subject matter experts (contractors, consultants, program managers, manufacturers, trade organization representatives, and real estate agents). These experts specified technical barriers and gaps, and offered suggestions for how the technical community might address them. The potential benefits of home energy upgrades are many and varied: reduced energy use and costs; improved comfort, durability, and safety; increased property value; and job creation. Nevertheless, home energy upgrades do not comprise a large part of the overall home improvement market. Residential energy efficiency is the most complex climate intervention option to deliver because the market failures are many and transaction costs are high (Climate Change Capital 2009). The key reasons that energy efficiency investment is not being delivered are: (1) The opportunity is highly fragmented; and (2) The energy efficiency assets are nonstatus, low-visibility investments that are not properly valued. There are significant barriers to mobilizing the investment in home energy upgrades, including the 'hassle factor' (the time and effort required to identify and secure improvement works), access to financing, and the opportunity cost of capital and split incentives.

  16. Energy Flow and Rapidity Gaps Between Jets in Photoproduction at HERA

    E-print Network

    H1 Collaboration; C. Adloff

    2002-03-08

    Dijet events in photon-proton collisions in which there is a large pseudorapidity separation Delta eta > 2.5 between the two highest E_T jets are studied with the H1 detector at HERA. The inclusive dijet cross sections are measured as functions of the longitudinal momentum fractions of the proton and photon which participate in the production of the jets, x_pjet and x_gjet respectively, Delta eta, the pseudorapidity separation between the two highest E_T jets, and E_T^gap, the total summed transverse energy between the jets. Rapidity gap events are defined as events in which E_T^gap is less than E_T^cut, for E_T^cut varied between 0.5 and 2.0 GeV. The fraction of dijet events with a rapidity gap is measured differentially in Delta eta, x_pjet and x_gjet. An excess of events with rapidity gaps at low values of E_T^cut is observed above the expectation from standard photoproduction processes. This excess can be explained by the exchange of a strongly interacting colour singlet object between the jets.

  17. Secondary "smile"-gap in the density of states of a diffusive Josephson junction for a wide range of contact types

    NASA Astrophysics Data System (ADS)

    Reutlinger, J.; Glazman, L.; Nazarov, Yu. V.; Belzig, W.

    2014-07-01

    The superconducting proximity effect leads to strong modifications of the local density of states in diffusive or chaotic cavity Josephson junctions, which displays a phase-dependent energy gap around the Fermi energy. The so-called minigap of the order of the Thouless energy ETh is related to the inverse dwell time in the diffusive region in the limit ETh??, where ? is the superconducting energy gap. In the opposite limit of a large Thouless energy ETh??, a small new feature has recently attracted attention, namely, the appearance of a further secondary gap, which is around two orders of magnitude smaller compared to the usual superconducting gap. It appears in a chaotic cavity just below the superconducting gap edge ? and vanishes for some value of the phase difference between the superconductors. We extend previous theory restricted to a normal cavity connected to two superconductors through ballistic contacts to a wider range of contact types. We show that the existence of the secondary gap is not limited to ballistic contacts, but is a more general property of such systems. Furthermore, we derive a criterion which directly relates the existence of a secondary gap to the presence of small transmission eigenvalues of the contacts. For generic continuous distributions of transmission eigenvalues of the contacts, no secondary gap exists, although we observe a singular behavior of the density of states at ?. Finally, we provide a simple one-dimensional scattering model which is able to explain the characteristic "smile" shape of the secondary gap.

  18. Quantification of the energy gap in young overweight children. The PIAMA birth cohort study

    Microsoft Academic Search

    Saskia W van den Berg; Jolanda MA Boer; Salome Scholtens; Johan C de Jongste; Bert Brunekreef; Henriette A Smit; Alet H Wijga

    2011-01-01

    Background  Overweight develops gradually as a result of a long term surplus on the balance between energy intake and energy expenditure.\\u000a Aim of this study was to quantify the positive energy balance responsible for excess body weight gain (energy gap) in young\\u000a overweight children.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Reported data on weight and height were used of 2190 Dutch children participating in the PIAMA birth

  19. Point-contact spectroscopy investigation of superconducting-gap anisotropy in the nickel borocarbide compound LuNi2B2C

    E-print Network

    Bobrov, NL; Beloborod'ko, SI; Tyutrina, LV; Yanson, IK; Naugle, Donald G.; Rathnayaka, KDD.

    2005-01-01

    , in the ab plane by a larger gap. The deviation from the one-gap BCS model is pronounced in the temperature dependence of the gap in both directions. The temperature range, where the deviation occurs, is for the c direction approximately 1.5 times more than...

  20. Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission

    NASA Technical Reports Server (NTRS)

    White, Nicholas E. (Technical Monitor); Muslimov, Alex G.; Harding, Alice K.

    2003-01-01

    We revise the physics of primary electron acceleration in the "slot gap" (SG) above the pulsar polar caps (PCs), a regime originally proposed by Arons and Scharlemann (1979) in their electrodynamic model of pulsar PCs. We employ the standard definition of the SG as a pair-free space between the last open field lines and the boundary of the pair plasma column which is expected to develop above the bulk of the PC. The rationale for our revision is that the proper treatment of primary acceleration within the pulsar SGs should take into account the effect of the narrow geometry of the gap on the electrodynamics within the gap and also to include the effect of inertial frame dragging on the particle acceleration. We show that the accelerating electric field within the gap, being significantly boosted by the effect of frame dragging, becomes reduced because of the gap geometry by a factor proportional to the square of the SG width. The combination of the effects of frame dragging and geometrical screening in the gap region naturally gives rise to a regime of extended acceleration, that is not limited to favorably curved field lines as in earlier models, and the possibility of multiple-pair production by curvature photons at very high altitudes, up to several stellar radii. We present our estimates of the characteristic SG thickness across the PC, energetics of primaries accelerated within the gap, high-energy bolometric luminosities emitted from the high altitudes in the gaps, and maximum heating luminosities produced by positrons returning from the elevated pair fronts. The estimated theoretical high-energy luminosities are in good agreement with the corresponding empirical relationships for gamma-ray pulsars. We illustrate the results of our modeling of the pair cascades and gamma-ray emission from the high altitudes in the SG for the Crab pulsar. The combination of the frame-dragging field and high-altitude SG emission enables both acceleration at the smaller inclination angles and a larger emission beam, both necessary to produce widely-spaced double-peaked profiles.

  1. Superconductivity applications for infrared and microwave devices; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul B. (editor); Heinen, Vernon O. (editor)

    1990-01-01

    Various papers on superconductivity applications for IR and microwave devices are presented. The individual topics addressed include: pulsed laser deposition of Tl-Ca-Ba-Cu-O films, patterning of high-Tc superconducting thin films on Si substrates, IR spectra and the energy gap in thin film YBa2Cu3O(7-delta), high-temperature superconducting thin film microwave circuits, novel filter implementation utilizing HTS materials, high-temperature superconductor antenna investigations, high-Tc superconducting IR detectors, high-Tc superconducting IR detectors from Y-Ba-Cu-O thin films, Y-Ba-Cu0-O thin films as high-speed IR detectors, fabrication of a high-Tc superconducting bolometer, transition-edge microbolometer, photoresponse of YBa2Cu3O(7-delta) granular and epitaxial superconducting thin films, fast IR response of YBCO thin films, kinetic inductance effects in high-Tc microstrip circuits at microwave frequencies.

  2. Strain energy minimization in SSC (Superconducting Super Collider) magnet winding

    SciTech Connect

    Cook, J.M.

    1990-09-24

    Differential geometry provides a natural family of coordinate systems, the Frenet frame, in which to specify the geometric properties of magnet winding. By a modification of the Euler-Bernoulli thin rod model, the strain energy is defined with respect to this frame. Then it is minimized by a direct method from the calculus of variations. The mathematics, its implementation in a computer program, and some analysis of an SSC dipole by the program will be described. 16 refs.

  3. Impact of pseudo-gap states on the pinning energy and irreversibility field of high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Deutscher, Guy

    2014-09-01

    The existence of pseudo-gap states at energies larger than the coherence energy scale is shown to be at the origin of the difficulties encountered in achieving strong vortex pinning in the high Tc cuprates. Reduction or elimination of the pseudo-gap states by overdoping is effective in increasing the condensation energy and the irreversibility field. In YBa2Cu3O7, a full BCS state, with a single energy scale, can be restored, leading to the highest known irreversibility field and pinning strength. In the bismuthates, the detrimental effect of the pseudo-gap states can only be mitigated to some extent by overdoping.

  4. ORNL Superconducting Technology Program for Electric Energy Systems. Annual report for FY 1992

    SciTech Connect

    Hawsey, R.A. [comp.

    1993-02-01

    The Oak Ridge National Laboratory (ORNL) Superconducting Technology Program is conducted as part of a national effort by the US Department of Energy`s (DOE`s) Office of Conservation and Renewable Energy to develop the technology base needed by US industry for commercial development of electric power applications of high-temperature superconductivity. The two major elements of this program are wire development and systems development. This document describes the major research and development activities for this program together with related accomplishments. The technical progress reported was summarized from information prepared for the FY 1992 Peer Review of Projects, conducted by DOE`s Office of Program Analysis, Office of Energy Research. This ORNL program is highly leveraged by the staff and other resources of US industry and universities. Interlaboratory teams are also in place on a number of industry-driven projects. Patent disclosures, working group meetings, staff exchanges, and joint publications and presentations ensure that there is technology transfer to US industry. Working together, the collaborative teams are making tremendous progress in solving the scientific and technical issues necessary for the commercialization of long lengths of practical high-temperature superconductor wire and wire products.

  5. Effect of band gap energy on the electrical conductivity in doped ZnO thin film

    NASA Astrophysics Data System (ADS)

    Benramache, Said; Belahssen, Okba; Ben Temam, Hachemi

    2014-07-01

    The transparent conductive pure and doped zinc oxide thin films with aluminum, cobalt and indium were deposited by ultrasonic spray technique on glass substrate at 350 °C. This paper is to present a new approach to the description of correlation between electrical conductivity and optical gap energy with dopants' concentration of Al, Co and In. The correlation between the electrical and optical properties with doping level suggests that the electrical conductivity of the films is predominantly estimated by the band gap energy and the concentrations of Al, Co and In. The measurement in the electrical conductivity of doped films with correlation is equal to the experimental value, the error of this correlation is smaller than 13%. The minimum error value was estimated in the cobalt-doped ZnO thin films. This result indicates that such Co-doped ZnO thin films are chemically purer and have far fewer defects and less disorder owing to an almost complete chemical decomposition.

  6. Unified Description of Rapidity Gaps and Energy Flows in DIS Final States

    E-print Network

    A. Edin; G. Ingelman; J. Rathsman

    1996-05-11

    We show that the `orthogonal' characteristics of the observed rapidity gaps and large forward energy flows in deep inelastic scattering at HERA, can be described within a single framework. Our Monte Carlo model is based on perturbative QCD matrix elements and parton showers together with Lund string model hadronization, but has in addition a new mechanism for soft colour interactions which modifies the perturbative colour structure and thereby the hadronization. Effects of perturbative multiparton emission are investigated and the non-perturbative treatment of the proton remnant is discussed and comparison to the observed transverse energy flow is made. We investigate the resulting diffractive-like properties of the model; such as rapidity gap events, $t$- and $M_X$-distributions and the diffractive structure function in comparison to H1 data.

  7. Evolution of the N=50 shell gap energy towards $^{78}$Ni

    E-print Network

    J. Hakala; S. Rahaman; V. -V. Elomaa; T. Eronen; U. Hager; A. Jokinen; A. Kankainen; I. D. Moore; H. Penttilä; S. Rinta-Antila; J. Rissanen; A. Saastamoinen; T. Sonoda; C. Weber; J. Äystö

    2008-06-27

    Atomic masses of the neutron-rich isotopes $^{76-80}$Zn, $^{78-83}$Ga, $^{80-85}Ge, $^{81-87}$As and $^{84-89}$Se have been measured with high precision using the Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The masses of $^{82,83}$Ga, $^{83-85}$Ge, $^{84-87}$As and $^{89}$Se were measured for the first time. These new data represent a major improvement in the knowledge of the masses in this neutron-rich region. Two-neutron separation energies provide evidence for the reduction of the N=50 shell gap energy towards germanium Z=32 and a subsequent increase at gallium (Z=31). The data are compared with a number of theoretical models. An indication of the persistent rigidity of the shell gap towards nickel (Z=28) is obtained.

  8. Anisotropy of the energy gap structure of high- Tc oxides observed by STM/STS

    NASA Astrophysics Data System (ADS)

    Tanaka, Shukichi; Ueda, Eiji; Sato, Masatoshi; Tamasaku, Kenji; Uchida, Shin-ichi

    1996-05-01

    Differential tunneling conductances of high- Tc oxides have been measured by STM/STS with the tip approaches along the [100] and [110] directions, where [100] corresponds to the Cu?O?Cu direction of the CuO 2-planes. The superconducting gap observed along [110] has been found to be larger than that observed along [100] for all single crystals of La 2 - xSr xCuO 4 ( x = {0.10}/{0.15}) and YBa 2Cu 3O 7 used in the present study. Careful analyses by constructing a “ k-dependent tunnelling model” have shown that experimental results can be consistently understood by assuming ( x2 - y2)-like pair symmetry. The model calculates k-dependent tunneling probability which is mainly determined by the amplitude of the O2p ?-component of the electronic wave function at the tip point in the antibonding band formed of Cu 3d x2 - y2 and O 2p ? orbitals. The k-region which mainly contributes to the tunneling current is rather different from that around the tip-approach direction. The model can also explain several other characteristics of reported STM/STS data.

  9. Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

    NASA Technical Reports Server (NTRS)

    Nellis, W. J.; Mitchell, A. C.; Mccandless, P. C.; Erskine, D. J.; Weir, S. T.

    1992-01-01

    Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

  10. Development Of A Compact, High-energy Spark Gap Switch And Trigger Generator System

    Microsoft Academic Search

    D. Bhasavanich; S. S. Hitchcock; P. M. Creely; R. S. Shaw; H. G. Hammon; J. T. Naff

    1991-01-01

    High-energy switches and trigger generators are required for a range of capacitor banks in electric gun applications. We have developed a compact, long-lived spark gap and a matched series-injection trigger generator. The switch is of a two-electrode design using high density graphite electrodes. The demonstrated peak current capability is near 300 kA, with a charge transfer of 700 Cb, and

  11. Coherence and Decay of Higher Energy Levels of a Superconducting Transmon Qubit

    NASA Astrophysics Data System (ADS)

    Peterer, Michael J.; Bader, Samuel J.; Jin, Xiaoyue; Yan, Fei; Kamal, Archana; Gudmundsen, Theodore J.; Leek, Peter J.; Orlando, Terry P.; Oliver, William D.; Gustavsson, Simon

    2015-01-01

    We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive ? pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20 ? s for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information.

  12. Coherence and Decay of Higher Energy Levels of a Superconducting Transmon Qubit

    E-print Network

    Michael J. Peterer; Samuel J. Bader; Xiaoyue Jin; Fei Yan; Archana Kamal; Ted Gudmundsen; Peter J. Leek; Terry P. Orlando; William D. Oliver; Simon Gustavsson

    2014-12-12

    We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive $\\pi$-pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20 $\\mu$s for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information.

  13. Coherence and decay of higher energy levels of a superconducting transmon qubit.

    PubMed

    Peterer, Michael J; Bader, Samuel J; Jin, Xiaoyue; Yan, Fei; Kamal, Archana; Gudmundsen, Theodore J; Leek, Peter J; Orlando, Terry P; Oliver, William D; Gustavsson, Simon

    2015-01-01

    We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive ? pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20???s for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information. PMID:25615454

  14. 30-MJ superconducting magnetic energy storage for BPA transmission-line stabilizer

    SciTech Connect

    Schermer, R.I.

    1981-01-01

    The Bonneville Power Administration operates the transmission system that joins the Pacific Northwest and southern California. A 30 MJ (8.4 kWh) superconducting Magnetic Energy Storage (SMES) unit with a 10 MW converter can provide system damping for low frequency oscillations. The unit is scheduled to operate in late 1982. Progress to date is described. The coil is complete. All major components of the electrical and cryogenic systems have been received and testing has begun. Computer control hardware is in place and software development is proceeding. Support system components and dewar lid are being fabricated and foundation design is complete. A contract for dewar fabrication is being negotiated.

  15. 30 MJ superconducting magnetic energy storage stabilizing coil. Final report for construction

    SciTech Connect

    NONE

    1983-03-01

    This report covers Phase II, Fabrication and Delivery of the 30 MJ Superconducting Magnetic Energy Storage Stabilizing Coil. A history of the manufacturing and assembly phase of the magnet is presented. Major problems and solutions are summarized, and illustrations of the major operations are provided. The Quality Assurance program is described with a listing of all nonconformance reports. Design documentation is provided, including a Design Document Index, monthly progress reports, and a list of papers given on the project. Appendices to the report contain copies of released and revised design calculations, test reports, assembly procedure, and nonconformance reports and engineering dispositions.

  16. Large gap magnetic suspension system

    NASA Technical Reports Server (NTRS)

    Abdelsalam, Moustafa K.; Eyssa, Y. M.

    1991-01-01

    The design of a large gap magnetic suspension system is discussed. Some of the topics covered include: the system configuration, permanent magnet material, levitation magnet system, superconducting magnets, resistive magnets, superconducting levitation coils, resistive levitation coils, levitation magnet system, and the nitrogen cooled magnet system.

  17. Resistivity changes in superconducting-cavity-grade Nb following high-energy proton irradiation

    SciTech Connect

    Snead, C.L. Jr.; Hanson, A.; Greene, G.A. [and others

    1997-12-01

    Niobium superconducting rf cavities are proposed for use in the proton LINAC accelerators for spallation-neutron applications. Because of accidental beam loss and continual halo losses along the accelerator path, concern for the degradation of the superconducting properties of the cavities with accumulating damage arises. Residual-resistivity-ratio (RRR) specimens of Nb, with a range of initial RRR`s were irradiated at room temperature with protons at energies from 200 to 2000 MeV. Four-probe resistance measurements were made at room temperature and at 4.2 K both prior to and after irradiation. Nonlinear increases in resistivity simulate expected behavior in cavity material after extended irradiation, followed by periodic anneals to room temperature: For RRR = 316 material, irradiations to (2 - 3) x 10{sup 15} p/cm{sup 2} produce degradations up to the 10% level, a change that is deemed operationally acceptable. Without. periodic warming to room temperature, the accumulated damage energy would be up to a factor of ten greater, resulting in unacceptable degradations. Likewise, should higher-RRR material be used, for the same damage energy imparted, relatively larger percentage changes in the RRR will result.

  18. Energy gaps in the spin-wave spectrum of rare-earth orthoferrites in a magnetic field

    Microsoft Academic Search

    N. K. Dan'shin; G. G. Kramarchuk

    1993-01-01

    Temperature and field dependences of energy gaps in the spin-wave spectra at the boundaries of the orientational translation have been studied for thulium and ytterbium orthoferrites. It is shown that in transitions induced by a magnetic field, the gaps in the soft-mode spectra of iron as well as the rare earth are independent of temperature (field). A comparison of the

  19. Superconducting Memristors

    NASA Astrophysics Data System (ADS)

    Peotta, Sebastiano; Di Ventra, Massimiliano

    2014-09-01

    In his original work, Josephson predicted that a phase-dependent conductance should be present in superconducting tunnel junctions, an effect difficult to detect, mainly because it is hard to single it out from the usual nondissipative Josephson current. We propose a solution for this problem that consists of using different superconducting materials to realize the two junctions of a superconducting interferometer. According to the Ambegaokar-Baratoff relation the two junctions have different conductances if the critical currents are equal, thus the Josephson current can be suppressed by fixing the magnetic flux in the loop at half of a flux quantum without canceling the phase-dependent conductance. Our proposal can be used to study the phase-dependent conductance, an effect present in principle in all superconducting weak links. From the standpoint of nonlinear circuit theory, such a device is in fact an ideal memristor with possible applications to memories and neuromorphic computing in the framework of ultrafast and low-energy-consumption superconducting digital circuits.

  20. Interface superconductor with gap behaviour like a high-temperature superconductor.

    PubMed

    Richter, C; Boschker, H; Dietsche, W; Fillis-Tsirakis, E; Jany, R; Loder, F; Kourkoutis, L F; Muller, D A; Kirtley, J R; Schneider, C W; Mannhart, J

    2013-10-24

    The physics of the superconducting state in two-dimensional (2D) electron systems is relevant to understanding the high-transition-temperature copper oxide superconductors and for the development of future superconductors based on interface electron systems. But it is not yet understood how fundamental superconducting parameters, such as the spectral density of states, change when these superconducting electron systems are depleted of charge carriers. Here we use tunnel spectroscopy with planar junctions to measure the behaviour of the electronic spectral density of states as a function of carrier density, clarifying this issue experimentally. We chose the conducting LaAlO3-SrTiO3 interface as the 2D superconductor, because this electron system can be tuned continuously with an electric gate field. We observed an energy gap of the order of 40?microelectronvolts in the density of states, whose shape is well described by the Bardeen-Cooper-Schrieffer superconducting gap function. In contrast to the dome-shaped dependence of the critical temperature, the gap increases with charge carrier depletion in both the underdoped region and the overdoped region. These results are analogous to the pseudogap behaviour of the high-transition-temperature copper oxide superconductors and imply that the smooth continuation of the superconducting gap into pseudogap-like behaviour could be a general property of 2D superconductivity. PMID:24097347

  1. Photoluminescence Characteristics of Organic Host Materials with Wide Energy Gaps for Organic Electrophosphorescent Devices

    NASA Astrophysics Data System (ADS)

    Ayataka Endo,; Chihaya Adachi,

    2010-05-01

    The photoluminescence, i.e., fluorescence and phosphorescence, characteristics of host materials with wide energy gaps suitable for phosphorescence-based organic light-emitting diodes (OLEDs) are summarized. In the vacuum deposited films, the host materials show phosphorescent emission in the blue to green region and triplet energy levels of ET = 2.6--3.1 eV because of the presence of steric hindrance. An OLED containing 1,2,3,4-tetraphenyl-5-(3-pyridyl)benzene as a host and iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate as a blue emissive phosphorescent dopant exhibits an external electroluminescence efficiency of ˜12%.

  2. Photoluminescence Characteristics of Organic Host Materials with Wide Energy Gaps for Organic Electrophosphorescent Devices

    NASA Astrophysics Data System (ADS)

    Endo, Ayataka; Adachi, Chihaya

    2010-05-01

    The photoluminescence, i.e., fluorescence and phosphorescence, characteristics of host materials with wide energy gaps suitable for phosphorescence-based organic light-emitting diodes (OLEDs) are summarized. In the vacuum deposited films, the host materials show phosphorescent emission in the blue to green region and triplet energy levels of ET = 2.6-3.1 eV because of the presence of steric hindrance. An OLED containing 1,2,3,4-tetraphenyl-5-(3-pyridyl)benzene as a host and iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate as a blue emissive phosphorescent dopant exhibits an external electroluminescence efficiency of ˜12%.

  3. Vanishing Electronic Energy Loss of Very Slow Light Ions in Insulators with Large Band Gaps

    SciTech Connect

    Markin, S. N.; Primetzhofer, D.; Bauer, P. [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet Linz, A-4040 Linz (Austria)

    2009-09-11

    Electronic energy loss of light ions in nanometer films of materials with large band gaps has been studied for very low velocities. For LiF, a threshold velocity is observed at 0.1 a.u. (250 eV/u), below which the ions move without transferring energy to the electronic system. For KCl, a lower (extrapolated) threshold velocity is found, identical for H and He ions. For SiO{sub 2}, no clear velocity threshold is observed for He particles. For protons and deuterons, electronic stopping is found to perfectly fulfill velocity scaling, as expected for binary ion-electron interaction.

  4. Roles of superconducting magnetic bearings and active magnetic bearings in attitude control and energy storage flywheel

    NASA Astrophysics Data System (ADS)

    Tang, Jiqiang; Fang, Jiancheng; Ge, Shuzhi Sam

    2012-12-01

    Compared with conventional energy storage flywheel, the rotor of attitude control and energy storage flywheel (ACESF) used in space not only has high speed, but also is required to have precise and stable direction. For the presented superconducting magnetic bearing (SMB) and active magnetic bearing (AMB) suspended ACESF, the rotor model including gyroscopic couples is established originally by taking the properties of SMB and AMB into account, the forces of SMB and AMB are simplified by linearization within their own neighbors of equilibrium points. For the high-speed rigid discal rotor with large inertia, the negative effect of gyroscopic effect of rotor is prominent, the radial translation and tilting movement of rotor suspended by only SMB, SMB with equivalent PMB, or SMB together with PD controlled AMB are researched individually. These analysis results proved originally that SMB together with AMB can make the rotor be stable and make the radial amplitude of the vibration of rotor be small while the translation of rotor suspended by only SMB or SMB and PM is not stable and the amplitude of this vibration is large. For the stability of the high-speed rotor in superconducting ACESF, the AMB can suppress the nutation and precession of rotor effectively by cross-feedback control based on the separated PD type control or by other modern control methods.

  5. High Temperature Superconductivity in Cuprates: a model

    E-print Network

    P. R. Silva

    2010-07-16

    A model is proposed such that quasi-particles (electrons or holes) residing in the CuO2 planes of cuprates may interact leading to metallic or superconducting behaviors. The metallic phase is obtained when the quasi-particles are treated as having classical kinetic energies and the superconducting phase occurs when the quasi-particles are taken as extremely relativistic objects. The interaction between both kinds of particles is provided by a force dependent-on-velocity. In the case of the superconducting behavior, the motion of apical oxygen ions provides the glue to establish the Cooper pair. The model furnishes explicit relations for the Fermi velocity, the perpendicular and the in-plane coherence lengths, the zero-temperature energy gap, the critical current density, the critical parallel and perpendicular magnetic fields. All these mentioned quantities are expressed in terms of fundamental physical constants as: charge and mass of the electron, light velocity in vacuum, Planck constant, electric permittivity of the vacuum. Numerical evaluation of these quantities show that their values are close those found for the superconducting YBaCuO, leading to think the model as being a possible scenario to explain superconductivity in cuprates.

  6. COMMERCIALIZATION DEMONSTRATION OF MID-SIZED SUPERCONDUCTING MAGNETIC ENERGY STORAGE TECHNOLOGY FOR ELECTRIC UTILITYAPPLICATIONS

    SciTech Connect

    CHARLES M. WEBER

    2008-06-24

    As an outgrowth of the Technology Reinvestment Program of the 1990’s, an Agreement was formed between BWXT and the DOE to promote the commercialization of Superconducting Magnetic Energy Storage (SMES) technology. Business and marketing studies showed that the performance of electric transmission lines could be improved with this SMES technology by stabilizing the line thereby allowing the reserved stability margin to be used. One main benefit sought was to double the capacity and the amount of energy flow on an existing transmission line by enabling the use of the reserved stability margin, thereby doubling revenue. Also, electrical disturbances, power swings, oscillations, cascading disturbances and brown/black-outs could be mitigated and rendered innocuous; thereby improving power quality and reliability. Additionally, construction of new transmission lines needed for increased capacity could be delayed or perhaps avoided (with significant savings) by enabling the use of the reserved stability margin of the existing lines. Two crucial technical aspects were required; first, a large, powerful, dynamic, economic and reliable superconducting magnet, capable of oscillating power flow was needed; and second, an electrical power interface and control to a transmission line for testing, demonstrating and verifying the benefits and features of the SMES system was needed. A project was formed with the goals of commercializing the technology by demonstrating SMES technology for utility applications and to establish a domestic capability for manufacturing large superconducting magnets for both commercial and defense applications. The magnet had very low AC losses to support the dynamic and oscillating nature of the stabilizing power flow. Moreover, to economically interface to the transmission line, the magnet had the largest operating voltage ever made. The manufacturing of that design was achieved by establishing a factory with newly designed and acquired equipment, tooling, methods and skilled personnel. The final magnet system measured 14 feet in diameter, 10 feet in height, and weighed about 35 tons. The superconducting magnet and design technology was successfully implemented and demonstrated. The project was not successfully concluded however; as the critical planned final demonstration was not achieved. The utilities could not understand or clarify their future business needs and the regulatory requirements, because of the deregulation policies and practices of the country. Much uncertainty existed which prevented utilities from defining business plans, including asset allocation and cost recovery. Despite the technical successes and achievements, the commercial development could not be implemented and achieved. Thus, the demonstration of this enhancement to the utility’s transmission system and to the reliability of the nation’s electrical grid was not achieved. The factory was ultimately discontinued and the technology, equipment and product were placed in storage.

  7. Availability analysis of a 100 kWh superconducting magnetic energy storage

    NASA Astrophysics Data System (ADS)

    Maekinen, H.; Mikkonen, R.

    Superconducting Magnetic Energy Storage (SMES) is one of the possible and useful applications of modern superconducting technology. It is known that some loads on electricity distribution networks are particularly sensitive to short power interruptions and voltage sags. Different ranges of SMES applications have been widely discussed for large scale units (1 MWh - 1 GWh) as well as for small and medium scale units (1 kWh - 1 MWh). The major components of a SMES system are the superconducting magnet winding, the cryogenic refrigeration system and the power conditioning system, which interfaces the coil to the utility grid and applied load. The SMES winding is cooled by a cryogenic coolant: liquid helium for LTS (low temperature superconductor) wires; gaseous helium, liquid hydrogen or liquid nitrogen for HTS (high temperature superconductor) wires. In addition the higher operating temperature of HTS materials also means higher refrigeration efficiencies, greater reliability and easier acceptance within the utility community. It has been estimated that applying HTS materials in a SMES system will reduce the capital costs some 14-26 %. In this calculation it has been assumed that the price of HTS material is equivalent to that of LTS material. This report deals with the availability aspects of a 100 kWh SMES. A conceptual design of a reference unit has been used as a basis of the study. Therefore the lack of the detailed design leads to uncertainty in evaluating the failure data for single components. The failure rate data are mainly adopted from fusion data sources. This extrapolation is problematic, but in most cases the only way to get results at all. The method used is based on the failure modes, effects and criticality analysis, FMECA. Fault trees describe the outage logic based on the functional analysis. Event trees clarify the consequences of the primary events and the criticality of these consequences are expressed as system down times.

  8. Caffeine-containing energy drinks: beginning to address the gaps in what we know.

    PubMed

    Sorkin, Barbara C; Coates, Paul M

    2014-09-01

    Energy drinks are relatively new to the United States but are the fastest growing segment of the beverage market. Humans have a long history of consuming caffeine in traditional beverages, such as cocoa, coffee, tea, and yerba maté, but 2 workshops held at the Institute of Medicine (http://www.iom.edu/Activities/Nutrition/PotentialHazardsCaffeineSupplements/2013-AUG-05.aspx) and the NIH (http://ods.od.nih.gov/News/EnergyDrinksWorkshop2013.aspx) in 2013 highlighted many critical gaps in understanding the biologic and behavioral effects of the mixtures of caffeine, vitamins, herbs, sugar or other sweeteners, and other ingredients that typify caffeine-containing energy drinks (CCEDs). For example, different surveys over the same 2010–2012 timeframe report discrepant prevalence of CCED use by teenagers, ranging from 10.3% in 13–17 y olds to >30% of those in grades 10 and 12. Understanding of functional interactions between CCED ingredients, drivers of use, and biologic and behavioral effects is limited. The 4 speakers in the Experimental Biology 2014 symposium titled “Energy Drinks: Current Knowledge and Critical Research Gaps” described recent progress by their groups in extending our understanding of prevalence of CCED use, sources of caffeine in the United States, drivers of CCED use, and behavioral correlations and effects of CCEDs, including effects on attractiveness of both alcoholic and non-alcoholic beverages. PMID:25469387

  9. A simple method for determining band-gap energies from inhomogeneous electric field electroreflection spectra applied to GaAs

    Microsoft Academic Search

    H. Poras; H. Wang; G. J. Goldsmith; N. Pan

    1994-01-01

    A new method for determining band-gap energies using modulation spectroscopy is described. In contrast to the usual method for extracting transition energies from modulation spectra, which assumes a constant electric field distribution, this method pertains to cases where an inhomogeneous field exists. The band-gap determination applied herein to GaAs epilayers between 100 and 380 K takes advantage of a modulation

  10. Influence of hole doping on the superconducting state in graphane

    NASA Astrophysics Data System (ADS)

    Durajski, A. P.

    2015-03-01

    The unique properties of two-dimensional materials have recently been attracting a huge amount of interest from researchers. From the point of view of potential applications in nanoelectronics, fully hydrogenated graphene (graphane) seems to be of particular interest. In the present paper, we analyze theoretically the possible superconductivity in hole-doped graphane. In particular, within the framework of the strong-coupling Eliashberg theory of superconductivity, we determine the superconducting transition temperature, the energy gap, the free energy and entropy differences between the superconducting and normal states, the thermodynamic critical field and the specific heat. The results obtained suggest that hole-doped graphane could potentially be a superconductor with a high transition temperature, {{T}C}\\in < 76,108> K, and with a large value of the superconducting energy gap, 2? (0)\\in < 27,42> meV. Moreover, it was shown that the thermodynamic properties of hole-doped graphane cannot be correctly described using the BCS (Bardeen–Cooper–Schrieffer) theory due to the strong-coupling and retardation effects.

  11. Number theory, periodic orbits, and superconductivity in nanocubes

    NASA Astrophysics Data System (ADS)

    Mayoh, James; García-García, Antonio M.

    2014-07-01

    We study superconductivity in isolated superconducting nanocubes and nanosquares of size L in the limit of negligible disorder ? /?0?1 and kFL?1 for which mean-field theory and semiclassical techniques are applicable, with kF the Fermi wave vector, ? the mean level spacing, and ?0 the bulk gap. By using periodic orbit theory and number theory we find explicit analytical expressions for the size dependence of the superconducting order parameter. Our formalism takes into account contributions from both the spectral density and the interaction matrix elements in a basis of one-body eigenstates. The leading size dependence of the energy gap in three dimensions seems to be universal as it agrees with the result for chaotic grains. In the region of parameters corresponding to conventional metallic superconductors, and for sizes L ?10 nm, the contribution to the superconducting gap from the matrix elements is substantial (˜20%). Deviations from the bulk limit are still clearly observed even for comparatively large grains L ˜50 nm. These analytical results are in excellent agreement with the numerical solution of the mean-field gap equation.

  12. The role of solvents in framework dimensionality and their effect on band gap energy.

    PubMed

    Asha, K S; Kavyasree, P R; George, Anu; Mandal, Sukhendu

    2015-01-21

    The crystal growth rate and morphology can be modulated by tuning the ratio of the solvent in mixed solvents during synthesis. We present here a solvothermal method to synthesize a Cd-FDC based metal-organic framework with different morphologies by tuning the ratio of water in the DMF-water mixed solvent system without adding any other additives. With the increasing water volume ratio a series of crystals with different morphologies were synthesized. Among these we have isolated two single crystal structures, [Cd3(FDC)3(DMF)4(H2O)], and [DMA]2[Cd3(FDC)4]·2H2O, . Compound was synthesized from DMF with small amounts of water while was formed from 25 vol% of water in the DMF-water mixed solvent. Compound contains trimer clusters as building units, which are linked by the furan dicarboxylate ligand to form a two-dimensional structure. Compound also contains trimer clusters which are linked to each other to form a one-dimensional chain with the Cd-O-Cd linkage. This one-dimensional chain in turn is connected by the furan dicarboxylate ligand to form a three-dimensional structure. All these structures are characterized by SEM, XRD, TGA and IR. We have measured the band gap energy and measurements show that the values are decreasing from to . The lower band gap energy of may be due to the presence of infinite Cd-O-Cd linkages which split the states of the conduction band and reduces the band gap energy. PMID:25408115

  13. Theoretical study of some bis-verdazyl diradicals: singlet triplet energy gap

    NASA Astrophysics Data System (ADS)

    Chung, Gyusung; Lee, Duckhwan

    2001-12-01

    The bis-verdazyl diradical (BVD) system is closely examined by using the multiconfiguration wavefunctions as well as the density functional theory (DFT). The totally symmetric singlet ground state turns out to have strong multiconfiguration character at all levels of theory. The singlet ground state takes on the planar structure while the most stable triplet state corresponds to the twisted form. The MCSCF+MCQDPT2 calculations are shown to be sufficient to predict the singlet-triplet energy gap which is insensitive to the electronic characters of the ring substituents.

  14. Electronic structure of silicon quantum dots: Calculations of energy-gap redshifts due to oxidation

    NASA Astrophysics Data System (ADS)

    Nishida, Masahiko

    2005-07-01

    Electronic state calculations are performed self-consistently using the extended Hückel-type nonorthogonal tight-binding method for two different oxygen configurations (backbonded and double-bonded oxygen configurations) on the H-covered surface of spherical Si35H36, Si47H60, Si71H84, Si136H120, Si148H120, and Si172H120 quantum dots. The size dependence of the effect of oxygen on the electronic structure of the Si dots is studied. Energy gaps calculated for both oxygen configurations can explain oxidation-induced redshifts in photoluminescence (PL) observed in porous Si. However, the energy gaps calculated for the backbonded oxygen model are around 2.2eV and dipole allowed in all Si dots studied, whereas those for the double-bonded oxygen model are gradually decreased with the increase in size (2.3-1.7eV), and optical transitions are dipole forbidden in the Si dots near 1nm across and dipole allowed in the ones near 2nm in diameter. The results calculated for the backbonded oxygen model coincide well with the experimental fact that the PL-peak energies are fixed at ˜2.1eV when porous Si is exposed to air.

  15. Economic Operation of Long Distances Power Networks Using On-line Control of Superconducting Magnetic Energy Storage

    Microsoft Academic Search

    Seyed Mohammad; SADEGH ZADEH

    2007-01-01

    This paper investigates a two-purpose application for the superconducting magnetic energy storage (SMES) in order to remove its economic barriers for a wide spread promotion in power systems. A practical realization of the control method using the locally measurable signals is considered. A simulation case study is conducted to verify the performance of the proposed application. The results prove that

  16. Point-contact spectroscopy of the phononic mechanism of superconductivity in YB6

    NASA Astrophysics Data System (ADS)

    Szabó, P.; Girovský, J.; Pribulová, Z.; Ka?mar?ík, J.; Mori, T.; Samuely, P.

    2013-04-01

    Lortz et al (2006 Phys. Rev. B 73 024512) have utilized specific heat and resistivity measurements as ‘thermal spectroscopies’ to deconvolve the spectrum of the electron-phonon interaction in YB6, assuming a major role of the low frequency phonon mode in mediating superconductivity. Here, we present direct point-contact spectroscopy studies of the superconducting interaction in this system. As a result, the normalized superconducting gap reveals a strong coupling with 2?/kBTc = 4 and, moreover, the spectra contain nonlinearities typical of the electron-phonon interaction at energies around 8 meV. The measurements in a magnetic field evidence that the phonon features found in the second derivative of the current-voltage characteristics are due to the energy dependence of the superconducting energy gap as their energy position shrinks equally as the gap is closed. This provides direct proof that the superconducting coupling in the system is due to the low energy Einstein-like phonon mode associated with the yttrium ion vibrations, in perfect agreement with determinations from bulk measurements.

  17. Separating pairing from quantum phase coherence dynamics above the superconducting transition by femtosecond spectroscopy

    PubMed Central

    Madan, I.; Kurosawa, T.; Toda, Y.; Oda, M.; Mertelj, T.; Kusar, P.; Mihailovic, D.

    2014-01-01

    In classical superconductors an energy gap and phase coherence appear simultaneously with pairing at the transition to the superconducting state. In high-temperature superconductors, the possibility that pairing and phase coherence are distinct and independent processes has led to intense experimental search of their separate manifestations. Using femtosecond spectroscopy methods we now show that it is possible to clearly separate fluctuation dynamics of the superconducting pairing amplitude from the phase relaxation above the critical transition temperature. Empirically establishing a close correspondence between the superfluid density measured by THz spectroscopy and superconducting optical pump-probe response over a wide region of temperature, we find that in differently doped Bi2Sr2CaCu2O8+? crystals the pairing gap amplitude monotonically extends well beyond Tc, while the phase coherence shows a pronounced power-law divergence as T ? Tc, thus showing that phase coherence and gap formation are distinct processes which occur on different timescales. PMID:25014162

  18. Phase Structure and Instability Problem in Color Superconductivity

    E-print Network

    Kenji Fukushima

    2005-10-22

    We address the phase structure of color superconducting quark matter at high quark density. Under the electric and color neutrality conditions there appear various phases as a result of the Fermi surface mismatch among different quark flavors induced by finite strange quark mass; the color-flavor locked (CFL) phase where quarks are all energy gapped, the u-quark superconducting (uSC) phase where u-quarks are paired with either d- or s-quarks, the d-quark superconducting (dSC) phase that is the d-quark analogue of the uSC phase, the two-flavor superconducting (2SC) phase where u- and d-quarks are paired, and the unpaired quark matter (UQM) that is normal quark matter without pairing. Besides these possibilities, when the Fermi surface mismatch is large enough to surpass the gap energy, the gapless superconducting phases are expected. We focus our discussion on the chromomagnetic instability problem related to the gapless CFL (gCFL) onset and explore the instability regions on the phase diagram as a function of the temperature and the quark chemical potential. We sketch how to reach stable physical states inside the instability regions.

  19. Solving LFC problem in an interconnected power system using superconducting magnetic energy storage

    NASA Astrophysics Data System (ADS)

    Farahani, Mohsen; Ganjefar, Soheil

    2013-04-01

    This paper proposes the combination of a load frequency control (LFC) with superconducting magnetic energy storage (SMES) to solve the LFC problem in interconnected power systems. By using this combination, the speed damping of frequency and tie-line power flow deviations is considerably increased. A new control strategy of SMES is proposed in this paper. The problem of determining optimal parameters of PID and SMES control loop is considered as an optimization problem and a pattern search algorithm (PS) optimization is employed to solve it. The simulation results show that if an SMES unit is installed in an interconnected power system, in addition to eliminating oscillations and deviations, the settling time in the frequency and tie-line power flow responses is considerably reduced.

  20. Fabrication of superconducting materials by high-energy - high-rate processing

    SciTech Connect

    Lee, S.J.

    1988-01-01

    Techniques involving high energy-high rate processing were employed to fabricate superconducting materials. A homopolar generator (HPG), producing low voltage-high current electrical discharges of short duration, was used to consolidate powders through pulsed resistive heating, and a railgun, powered by a capacitor bank, was used to prepare thin films from source material accelerated electromagnetically to a substrate at ambient temperature. Bulk Nb-Ge samples formed by reactive sintering during the powder consolidation by the application of the HPG contain various phases (NbGe{sub 2}, Nb{sub 5}Ge{sub 3} and {beta}), and some evidence of Nb{sub 3}Ge exists. Thin films, synthesized by railgun deposition of Nb and Ge, contain hexagonal Nb{sub 5}Ge{sub 3}, as well as NbO{sub 2} and/or NbO and Nb particles in some cases, but Nb{sub 3}Ge is absent. Production of high-T{sub c} YBa{sub 2}Cu{sub 3}O{sub x} (123 compound) by conventional solid-state reaction and consolidation of this compound by high energy-high rate processing were examined under different experimental conditions. Calcining the precursor powders at 900{degree}C does not produce single-phase 123 compounds, whereas high-quality 123 phase forms on calcining at 925 and 950{degree}C. The best consolidated sample exhibits a resistive superconducting transition at 91.1 K with a transition width less than 1 K.

  1. Energy gap and optical dielectric constant of Pb 1- xCd xSe films

    NASA Astrophysics Data System (ADS)

    Baleva, M.; Maksimov, M.; Sendova, M.

    1987-11-01

    The transmission spectra of laser-deposited Pb 1- xCd xSe films ( x = 0, 0.02, 0.05, 0.08 and 0.12) have been measured over the energy range 0.1-0.65 eV at two different temperatures 90 and 300 K. From these spectra the dispersion of the refractive index and the absorption coefficient-energy dependence have been obtained. Thus the dependences of the gap and the optical dielectric constant on the Cd content x have been investigated. The experimental results have been discussed in the framework of the recently developed theoretical model by Volkov and Pankratov et al1,2.

  2. MECHANICAL STUDIES OF THE MULTI-GAP SPOKE CAVITY FOR EUROPEAN PROJECT HIPPI

    E-print Network

    Boyer, Edmond

    MECHANICAL STUDIES OF THE MULTI-GAP SPOKE CAVITY FOR EUROPEAN PROJECT HIPPI H. GASSOT , S. BLIVET Forschungszentrum Jülich proposed a multi-spoke H-cavity for the intermedi- ate energy section ( = 0:5) of high, and before that, all preliminary mechanical studies. A triple-spoke superconducting cavity has a more com

  3. Neutron-Rich Ti Isotopes And Possible N = 32 And N = 34 Shell Gaps

    SciTech Connect

    Dinca, D.-C.; Campbell, C.M.; Cook, J.M.; Oiliver, H.; Starosta, K.; Terry, J.R. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Janssens, R.V.F.; Zhu, S.; Carpenter, M.P.; Hammond, N.J.; Lauritsen, T.; Lister, C.J.; Moore, E.F.; Seweryniak, D. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Gade, A.; Bazin, D.; Glasmacher, T.; Lecouey, J.-L.; Mueller, W.F.; Yoneda, K. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States)] [and others

    2005-04-05

    The possible occurrence of sub-shell gaps at N = 32 and N = 34 in neutron-rich titanium isotopes is discussed in light of new experimental results from (i) deep-inelastic reactions measured with Gammasphere at the ATLAS facility at Argonne National Laboratory and from (ii) intermediate-energy Coulomb excitation performed at the National Superconducting Cyclotron Laboratory at Michigan State University.

  4. SUPERCONDUCTING PHOTOCATHODES.

    SciTech Connect

    SMEDLEY, J.; RAO, T.; WARREN, J.; SEKUTOWICZ, LANGNER, J.; STRZYZEWSKI, P.; LEFFERS, R.; LIPSKI, A.

    2005-10-09

    We present the results of our investigation of lead and niobium as suitable photocathode materials for superconducting RF injectors. Quantum efficiencies (QE) have been measured for a range of incident photon energies and a variety of cathode preparation methods, including various lead plating techniques on a niobium substrate. The effects of operating at ambient and cryogenic temperatures and different vacuum levels on the cathode QE have also been studied.

  5. Spin-bag mechanism of high-temperature superconductivity

    NASA Technical Reports Server (NTRS)

    Schrieffer, J. R.; Wen, X.-G.; Zhang, S.-C.

    1988-01-01

    A new approach to the theory of high-temperature superconductivity is proposed, based on the two-dimensional antiferromagnetic spin correlations observed in these materials over distances large compared to the lattice spacing. The spin ordering produces an electronic pseudogap which is locally suppressed by the addition of a hole. This suppression forms a bag inside which the hole is self-consistently trapped. Two holes are attracted by sharing a common bag. The resulting pairing interaction leads to a superconducting energy gap which is nodeless over the Femri surface.

  6. Energy losses in superconductive DC-electromagnets due to ferromagnetic movement

    SciTech Connect

    Ciesla, A.; Matras, A. [Univ. of Mining and Metallurgy, Krakow (Poland)] [Univ. of Mining and Metallurgy, Krakow (Poland)

    1996-05-01

    A DC-current, superconductive electromagnet is a source of the magnetic field in a separator matrix. This type of separator operates in a cyclic way. Therefore, it appears as very important to ensure the electromagnet stability during operation, i.e., range of parameters` changes that could maintain the magnet winding in the superconductive state. This means selecting parameter changes representing the magnet winding in the superconductive state.

  7. Superconducting transmission line particle detector

    DOEpatents

    Gray, K.E.

    1988-07-28

    A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non- superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slow electromagnetic wave propagating in a superconducting transmission line are used to resolve N/sup 2/ ambiguity of charged particle events. 6 figs.

  8. Superconducting transmission line particle detector

    DOEpatents

    Gray, Kenneth E. (Naperville, IL)

    1989-01-01

    A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non-superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slow electromagnetic wave propogating in a superconducting transmission line are used to resolve N.sup.2 ambiguity of charged particle events.

  9. Self-energy effects in cuprates and the dome-shaped behavior of the superconducting critical temperature

    NASA Astrophysics Data System (ADS)

    Buzon, Guillermo; Foussats, Adriana; Bejas, Matías; Greco, Andrés

    2014-01-01

    Hole-doped cuprates show a superconducting critical temperature Tc which follows a universal dome-shaped behavior as a function of doping. It is believed that the origin of superconductivity in cuprates is entangled with the physics of the pseudogap phase. An open discussion is whether the source of superconductivity is the same effect that causes the pseudogap properties. The t-J model treated in large-N expansion shows d-wave superconductivity triggered by nonretarded interactions, and an instability of the paramagnetic state to a flux phase or d-wave charge-density wave (d-CDW) state. In this paper we show that self-energy effects near the d-CDW instability may lead to a dome-shaped behavior of Tc. In addition, it is also shown that these self-energy contributions may describe several properties observed in the pseudogap phase. In this picture, although fluctuations responsible for the pseudogap properties lead to a dome-shaped behavior, they are not involved in pairing, which is mainly nonretarded.

  10. Doping-evolution of the superconducting gap in single crystals of (Ca1?xLa x )10(Pt3As8)(Fe2As2)5 superconductor from London penetration depth measurements

    NASA Astrophysics Data System (ADS)

    Cho, K.; Tanatar, M. A.; Ni, N.; Prozorov, R.

    2014-10-01

    The doping-evolution of the superconducting gap structure in iron-based superconductor (Ca1-xLa x )10(Pt3As8)(Fe2As2)5 (x = 0.04, 0.06, 0.09, 0.11, and 0.18) was probed by high—resolution measurements of the London penetration depth, ? (T). The samples spanned compositions from underdoped to slightly overdoped with superconducting critical temperatures, T c , from 12.7 K (x = 0.04) through (optimal) 23.3 K (x = 0.11) to 21.9 K (x = 0.18). The low-temperature variation (up to 0.3 T c ) of ? (T) was analysed using a power-law function, ? ? =A{{T}n}. For compositions close to the optimal doping, (x = 0.09, 0.11, and 0.18), characterized by {{T}c}\\gt 20 K, ? ? (T) shows a tendency to saturation, indicative of a full gap on the Fermi surface. Fitting over the lowest temperature range (T\\lt 0.1 {{T}c}) gives n = 2.6. This value is well outside the range 1?slant n?slant 2 expected for the line-nodal superconductor. The exponent n decreased to n˜ 2 in the two most underdoped compositions x = 0.04 (T c = 12.7 K) and 0.06 (T c = 18.2 K), implying the development of a notable gap anisotropy revealed by the enhanced influence of pair-breaking scattering. This decrease is accompanied by a significant increase of the total variation of the penetration depth ? ? in a fixed temperature interval (e.g., {{T}min }-0.3{{T}c}). Both the decrease of the exponent and the increase of the absolute value of ? ? in the underdoped regime are similar to the observations in other charge-doped iron-based superconductors, such as doped BaFe2As2 and NaFeAs, suggesting a universal behavior in iron-based superconductors.

  11. AN EVALUATION OF FUSION ENERGY R&D GAPS USING TECHNOLOGY READINESS LEVELS M. S. Tillack1

    E-print Network

    Raffray, A. René

    AN EVALUATION OF FUSION ENERGY R&D GAPS USING TECHNOLOGY READINESS LEVELS M. S. Tillack1 , A. D in an effort called the "ARIES Pathways Study". The goals of this study are to evaluate remaining R&D needs toward prac- tical fusion energy and to identify and evaluate possible "next step" devices to bridge

  12. Improved superconducting properties in bulk MgB2 prepared by high-energy milling of Mg and B powders

    NASA Astrophysics Data System (ADS)

    Wu, Y. F.; Lu, Y. F.; Yan, G.; Li, J. S.; Feng, Y.; Tang, H. P.; Chen, S. K.; Xu, H. L.; Li, C. S.; Zhang, P. X.

    2006-10-01

    MgB2 bulks were prepared by high-energy milling of Mg and B powders. The correlations between milling times, microstructure and superconducting properties were investigated in MgB2 bulks. The samples were characterized by x-ray diffraction (XRD), energy dispersive spectrometry (EDX) and scanning electron microscopy (SEM), and the magnetization properties were examined with a superconducting quantum interference device (SQUID) magnetometer. The investigations showed that high-energy milling is an effective approach for obtaining fine crystalline (40-100 nm) bulk MgB2 with good grain connectivity and high Jc performance. The critical current density reaches 2.0 × 106 A cm-2 at 15 K and 0.59 T, 5.7 × 105 A cm-2 at 2 T and 3.0 × 104 A cm-2 at 5 T.

  13. Numerical Methods for the Bogoliubov-Tolmachev-Shirkov model in superconductivity theory

    E-print Network

    Zhihao Ge; Ruihua Li

    2015-03-08

    In the work, the numerical methods are designed for the Bogoliubov-Tolmachev-Shirkov model in superconductivity theory. The numerical methods are novel and effective to determine the critical transition temperature and approximate to the energy gap function of the above model. Finally, a numerical example confirming the theoretical results is presented.

  14. Illusory Continuity without Sufficient Sound Energy to Fill a Temporal Gap: Examples of Crossing Glide Tones

    ERIC Educational Resources Information Center

    Kuroda, Tsuyoshi; Nakajima, Yoshitaka; Eguchi, Shuntarou

    2012-01-01

    The gap transfer illusion is an auditory illusion where a temporal gap inserted in a longer glide tone is perceived as if it were in a crossing shorter glide tone. Psychophysical and phenomenological experiments were conducted to examine the effects of sound-pressure-level (SPL) differences between crossing glides on the occurrence of the gap

  15. Characterization of phonon-mediated superconductivity in lithium doping borocarbide

    NASA Astrophysics Data System (ADS)

    Durajski, A. P.; Szcz??niak, R.

    2015-04-01

    The paper presents the superconducting properties determined for lithium doping borocarbide (Li2B3C). The Eliashberg theory is used to investigate the exact values of superconducting energy gap, critical temperature, electron effective mass, free energy and the remaining thermodynamic function which allowed us to determine dimensionless ratios, which significantly exceed the values arising from the Bardeen-Cooper-Schrieffer theory of superconductivity. In particular, the obtained results show that Li2B3C hold a promise as high-temperature superconductor with the critical temperature in the range from 76.72 K to 45.07 K for a wide range of Coulomb pseudopotential (?? ? <0.1,0.3>). Other thermodynamic properties strongly depend on the depairing electron correlations, exception is the electron effective mass at the critical temperature, which takes value independent of assumed Coulomb pseudopotential.

  16. Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Singh, Sandeep Kumar; Neek-Amal, M.; Peeters, F. M.

    2014-02-01

    The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C_{N_c} X_{N_x} (X = F or H). We studied GNFs with 10 < Nc < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference ? between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with Nc, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.

  17. Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy

    SciTech Connect

    Singh, Sandeep Kumar, E-mail: SandeepKumar.Singh@uantwerpen.be; Peeters, F. M., E-mail: Francois.Peeters@uantwerpen.be [Department of Physics, University of Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Neek-Amal, M., E-mail: neekamal@srttu.edu [Department of Physics, University of Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16788 (Iran, Islamic Republic of)

    2014-02-21

    The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C{sub N{sub c}} X{sub N{sub x}} (X = F or H). We studied GNFs with 10 < N{sub c} < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference ? between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with N{sub c}, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.

  18. Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles.

    PubMed

    Pop, Ioan M; Geerlings, Kurtis; Catelani, Gianluigi; Schoelkopf, Robert J; Glazman, Leonid I; Devoret, Michel H

    2014-04-17

    Owing to the low-loss propagation of electromagnetic signals in superconductors, Josephson junctions constitute ideal building blocks for quantum memories, amplifiers, detectors and high-speed processing units, operating over a wide band of microwave frequencies. Nevertheless, although transport in superconducting wires is perfectly lossless for direct current, transport of radio-frequency signals can be dissipative in the presence of quasiparticle excitations above the superconducting gap. Moreover, the exact mechanism of this dissipation in Josephson junctions has never been fully resolved experimentally. In particular, Josephson's key theoretical prediction that quasiparticle dissipation should vanish in transport through a junction when the phase difference across the junction is ? (ref. 2) has never been observed. This subtle effect can be understood as resulting from the destructive interference of two separate dissipative channels involving electron-like and hole-like quasiparticles. Here we report the experimental observation of this quantum coherent suppression of quasiparticle dissipation across a Josephson junction. As the average phase bias across the junction is swept through ?, we measure an increase of more than one order of magnitude in the energy relaxation time of a superconducting artificial atom. This striking suppression of dissipation, despite the presence of lossy quasiparticle excitations above the superconducting gap, provides a powerful tool for minimizing decoherence in quantum electronic systems and could be directly exploited in quantum information experiments with superconducting quantum bits. PMID:24740067

  19. High-Energy Emission From the Polar Cap and Slot Gap

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2006-01-01

    Thirty-five years after the discovery of rotation-powered pulsars, we still do not understand the fundamentals of their pulsed emission at any wavelength. I will review the latest developments in understanding the high-energy emission of rotation-powered pulsars, with particular emphasis on the polar cap and slot gap models. Special and general relativistic effects play important roles in pulsar emission, from inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics. I will discuss how the next generation of gamma-ray detectors, AGILE and GLAST, will test prediction of these models.

  20. Magnesium diboride superconducting RF resonant cavities for high energy particle acceleration

    Microsoft Academic Search

    E W Collings; M D Sumption; T Tajima

    2004-01-01

    Arguments in support of any particular superconducting coating must be framed in terms of its fundamental thermodynamic properties. The superconducting transition temperature, Tc, determines the surface resistance, and thus the Q of the cavity. This must remain sufficiently high that the system can be driven at the required field gradients and frequencies without leading to excessive power loss. In this

  1. Rapidity gaps and jets as a new-physics signature in very-high-energy hadron-hadron collisions

    SciTech Connect

    Bjorken, J.D. (Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States))

    1993-01-01

    In hadron-hadron collisions, production of Higgs bosons and other color-singlet systems can occur via fusion of electroweak bosons, occasionally leaving a rapidity gap'' in the underlying-event structure. This observation, due to Dokshitzer, Khoze, and Troyan, is studied to see whether it serves as a signature for detection of the Higgs bosons, etc. We find it is a very strong signature at subprocess c.m. energies in excess of a few TeV. The most serious problem with this strategy is the estimation of the fraction of events containing the rapidity gap; most of the time the gap is filled by soft interactions of spectator degrees of freedom. We also study this question and estimate this survival probability of the rapidity gap'' to be of order 5%, with an uncertainty of a factor 3. Ways of testing this estimate and further discussion of the underlying hard-diffraction physics are presented.

  2. Renewable Energy Desalination: An Emerging Solution to Close MENA's Water Gap 56th Annual NM Water Conf., New Water New Energy: A Conference Linking Desalination and Renewable Energy

    E-print Network

    Johnson, Eric E.

    , Africa, and Middle East and North Africa. He has worked on, and led, many technical and policy oriented Desalination: An Emerging Solution to Close Middle East and North Africa's Water Gap (http://wrri.nmsu.edu/conf/conf11/re-desal.pdf) MENA Regional Water Outlook, Part II, Desalination Using Renewable Energy, Final

  3. Texture improvements in the high-temperature superconducting Bi?Sr?Ca?Cu?Ox̳/Ag system via surface energy driven grain alignment

    E-print Network

    Vodhanel, Mark E

    2005-01-01

    The relation between processing, microstructure, and material property was investigated in the high-temperature superconducting Bi?Sr?Ca?Cu?Ox̳/Ag system. Experiments were based on a theoretical surface energy model ...

  4. Enhanced spin polarization in graphene with spin energy gap induced by spin-orbit coupling and strain

    SciTech Connect

    Liu, Zheng-Fang; Wu, Qing-Ping, E-mail: wuqingping78519@163.com, E-mail: aixichen@ecjtu.jx.cn; Chen, Ai-Xi, E-mail: wuqingping78519@163.com, E-mail: aixichen@ecjtu.jx.cn [Department of Applied Physics, East China Jiaotong University, Nanchang 330013 (China); Xiao, Xian-Bo [School of Computer, Jiangxi University of Traditional Chinese Medicine, Nanchang 330004 (China); Liu, Nian-Hua [Institute for Advanced Study, Nanchang University, Nanchang 330031 (China)

    2014-05-28

    We investigate the possibility of spin polarization in graphene. The result shows that a spin energy gap can be opened in the presence of both spin-orbit coupling and strain. We find that high spin polarization with large spin-polarized current is achieved in the spin energy gap. However, only one of the two modulations is present, no spin polarization can be generated. So the combination of the two modulations provides a way to design tunable spin polarization without need for a magnetic element or an external magnetic field.

  5. Operation of the 30 MJ superconducting magnetic energy storage system in the Bonneville Power Administration Electrical Grid

    SciTech Connect

    Rogers, J.D.; Boenig, H.J.; Schermer, R.I.; Hauer, J.F.

    1984-01-01

    The 30 MJ superconducting magnetic energy storage (SMES) system was installed in the Bonneville Power Administration (BPA) Tacoma Substation in 1982 to 1983. Operation of the unit since that time has been for over 1200 hours. Specific tests to explore the SMES system's thermal and electrical characteristics and the control functions were conducted. The coil heat load with current modulation was determined. A converter with two 6-pulse bridges interfaces the superconducting coil to the power bus. Equal bridge voltage amplitude and constant reactive power modes of operation of the system were run with computer control of the SCR bridge firing angles. Coil energy dump tests were performed. Electrical grid system response to SMES modulation was observed, and full power SMES modulation was undertaken.

  6. Ultrasonic investigation of the superconducting properties of the Nb-Mo system

    NASA Technical Reports Server (NTRS)

    Lacy, L. L.

    1972-01-01

    The superconducting properties of single crystals of Nb and two alloys of Nb with Mo were investigated by ultrasonic techniques. The results of measurements of the ultrasonic attenuation and velocities as a function of temperature, Mo composition, crystallographic direction, and ultrasonic frequency are reported. The attenuation and small velocity changes associated with the superconductivity of the samples are shown to be dependent on the sample resistivity ratio which varied from 4.3 for Nb-9% Mo to 6500 for pure Nb. The ultrasonic attenuation data are analyzed in terms of the superconducting energy gap term of the BCS theory. A new model is proposed for the analysis of ultrasonic attenuation in pure superconductors with two partially decoupled energy bands. To analyze the attenuation in pure superconducting Nb, the existence of two energy gaps was assumed to be associated with the two partially decoupled energy bands. One of the gaps was found to have the normal BCS value of 3.4 and the other gap was found to have the anomalously large value of 10. No experimental evidence was found to suggest that the second energy gap had a different transition temperature. The interpretation of the results for the Nb-Mo alloys is shown to be complicated by the possible existence of a second superconducting phase in Nb-Mo alloys with a transition temperature of 0.35 of the transition temperature of the first phase. The elastic constants of Nb and Nb-Mo alloys are shown to be approximately independent of Mo composition to nine atomic percent Mo. These results do not agree with the current microscopic theory of transition temperature for the transition elements.

  7. Calculations of the electronic structure of silicon quantum dots: oxidation-induced redshifts in the energy gap

    NASA Astrophysics Data System (ADS)

    Nishida, Masahiko

    2006-04-01

    We study oxidation-induced redshifts in the energy gap for spherical Si30, Si42, Si87, Si99, Si167 and Si191 dots (of 1-2 nm in diameter) passivated with hydrogen by self-consistent calculations using the extended Hückel-type nonorthogonal tight-binding method for three different oxygen configurations (double-bonded, backbonded and inserted). While the nature of the lowest unoccupied molecular orbital (LUMO) state does not depend significantly on the dot size, the highest occupied molecular orbital (HOMO) state is associated closely with oxygen in the Si167 or smaller Si dots, and has a much larger Si contribution in the largest Si191 dot, so that the HOMO energy in the Si167 or smaller Si dots depends significantly on the oxygen configuration, while that in the Si191 dot does not. We find that the HOMO-LUMO energy gaps calculated for these Si dots double-bonded to oxygen are all dipole allowed, but gradually decrease from 2.2 eV to about 1.7 eV with increasing dot size, while the inserted oxygen configuration does not cause a significant energy-gap redshift even in the smallest Si dot. Finally, it is found that the energy gaps calculated for the Si dots backbonded to oxygen coincide well with luminescence redshifts observed in porous Si.

  8. Second-generation high-temperature superconducting coils and their applications for energy storage

    E-print Network

    Yuan, Weijia

    2010-11-16

    it still maintains superconductivity with a bigger transport current or in a bigger magnetic field. In 1960s, the first commercial superconducting wire, a niobium-titanium(NbTi) alloy and niobium-tin(Nb3Sn) alloy, was developed by researchers, allowing... and experimental anal- ysis of Ic and AC loss for bent 2G HTS wires used in an electric machine, IEEE transaction on applied superconductivity, vol. 19, issue 3, pp. 3356-3360, 2009 12. M. D. Ainslie, Y. Jiang, W. Xian, Z. Hong, W. Yuan, R. Pei, T. J. Flack, T...

  9. Superconductivity, magnetism, and pairing symmetry in Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Eremin, Ilya

    2009-03-01

    We analyze antiferromagnetism and superconductivity within the renormalization group(RG) technique in novel Fe-based superconductors using the itinerant model of small electron and hole pockets near (0; 0) and (?,?), respectively, originating from the two strongly hybridized orbitals. We find that, for this model, the bare interactions in the Cooper channel are repulsive, and superconductivity does not occur at the mean-field level. However, under RG the effective interaction in the superconducting channel changes sign and becomes attractive. Furthermore, the effective interactions in antiferromagnetic and superconducting channels logarithmically flow towards the same absolute values at low energies, i.e., both must be treated on equal footings. The magnetic instability comes first for equal sizes of the two pockets, but looses to superconductivity upon doping. The superconducting gap has no nodes, but changes sign between the two Fermi surfaces (extended s-wave symmetry). We argue that the T dependencies of the spin susceptibility and NMR relaxation rate for such state are exponential only at very low T, and can be well fitted by power-laws over a wide T range below Tc. We further show that below Tc excitonic resonance appears in the spin excitations spectrum. [4pt] [1] M. Korshunov, and I. Eremin, Phys. Rev. B 78, 140509(R) (2008) [0pt] [2] A.V. Chubukov, D. Efremov, I. Eremin, Phys. Rev. B 78, 134512 (2008). [0pt] [3] M.M. Korshunov and I. Eremin, Europhys. Lett. 83, 67003 (2008).

  10. Topological superconductivity at the edge of transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Xu, Gang; Wang, Jing; Yan, Binghai; Qi, Xiao-Liang

    2014-09-01

    Time-reversal breaking topological superconductors are new states of matter which can support Majorana zero modes at the edge. In this Rapid Communication, we propose a different realization of one-dimensional topological superconductivity and Majorana zero modes. The proposed system consists of a monolayer of transition-metal dichalcogenides MX2 (M =Mo,W; X =S,Se) on top of a superconducting substrate. Based on first-principles calculations, we show that a zigzag edge of the monolayer MX2 terminated by a metal atom M has edge states with strong spin-orbit coupling and spontaneous magnetization. By proximity coupling with a superconducting substrate, topological superconductivity can be induced at such an edge. We propose NbS2 as a natural choice of substrate, and estimate the proximity induced superconducting gap based on first-principles calculation and a low energy effective model. As an experimental consequence of our theory, we predict that Majorana zero modes can be detected at the 120° corner of a MX2 flake in proximity to a superconducting substrate.

  11. Superconductivity and ferromagnetism in topological insulators

    NASA Astrophysics Data System (ADS)

    Zhang, Duming

    Topological insulators, a new state of matter discovered recently, have attracted great interest due to their novel properties. They are insulating inside the bulk, but conducting at the surface or edges. This peculiar behavior is characterized by an insulating bulk energy gap and gapless surface or edge states, which originate from strong spin-orbit coupling and time-reversal symmetry. The spin and momentum locked surface states not only provide a model system to study fundamental physics, but can also lead to applications in spintronics and dissipationless electronics. While topological insulators are interesting by themselves, more exotic behaviors are predicted when an energy gap is induced at the surface. This dissertation explores two types of surface state gap in topological insulators, a superconducting gap induced by proximity effect and a magnetic gap induced by chemical doping. The first three chapters provide introductory theory and experimental details of my research. Chapter 1 provides a brief introduction to the theoretical background of topological insulators. Chapter 2 is dedicated to material synthesis principles and techniques. I will focus on two major synthesis methods: molecular beam epitaxy for the growth of Bi2Se3 thin films and chemical vapor deposition for the growth of Bi2Se3 nanoribbons and nanowires. Material characterization is discussed in Chapter 3. I will describe structural, morphological, magnetic, electrical, and electronic characterization techniques used to study topological insulators. Chapter 4 discusses the experiments on proximity-induced superconductivity in topological insulator (Bi2Se3) nanoribbons. This work is motivated by the search for the elusive Majorana fermions, which act as their own antiparticles. They were proposed by Ettore Majorara in 1937, but have remained undiscovered. Recently, Majorana's concept has been revived in condensed matter physics: a condensed matter analog of Majorana fermions is predicted to exist when topological insulators are interfaced with superconductors. The observation of Majorana fermions would not only be fundamentally important, but would also lead to applications in fault-tolerant topological quantum computation. By interfacing topological insulator nanoribbons with superconducting electrodes, we observe distinct signatures of proximity-induced superconductivity, which is found to be present in devices with channel lengths that are much longer than the normal transport characteristic lengths. This might suggest preferential coupling of the proximity effect to a ballistic surface channel of the topological insulator. In addition, when the electrodes are in the superconducting state, we observe periodic magnetoresistance oscillations which suggest the formation of vortices in the proximity-induced region of the nanoribbons. Our results demonstrate that proximity-induced superconductivity and vortices can be realized in our nanoribbon geometry, which accomplishes a first important step towards the search for Majorana fermions in condensed matter. In Chapter 5, I will discuss experiments on a magnetically-doped topological insulator (Mn-doped Bi2Se3) to induce a surface state gap. The metallic Dirac cone surface states of a topological insulator are expected to be protected against small perturbations by time-reversal symmetry. However, these surface states can be dramatically modified and a finite energy gap can be opened at the Dirac point by breaking the time-reversal symmetry via magnetic doping. The interplay between magnetism and topological surface states is predicted to yield novel phenomena of fundamental interest such as a topological magneto-electric effect, a quantized anomalous Hall effect, and the induction of magnetic monopoles. Our systematic measurements reveal a close correlation between the onset of ferromagnetism and quantum corrections to diffusive transport, which crosses over from the symplectic (weak anti-localization) to the unitary (weak localization) class. A comprehensive interpretation of data obtained from elec

  12. Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling.

    PubMed

    Zhou, Miao; Ming, Wenmei; Liu, Zheng; Wang, Zhengfei; Yao, Yugui; Liu, Feng

    2014-01-01

    For potential applications in spintronics and quantum computing, it is desirable to place a quantum spin Hall insulator [i.e., a 2D topological insulator (TI)] on a substrate while maintaining a large energy gap. Here, we demonstrate a unique approach to create the large-gap 2D TI state on a semiconductor surface, based on first-principles calculations and effective Hamiltonian analysis. We show that when heavy elements with strong spin orbit coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111) surface into a hexagonal lattice, they exhibit a 2D TI state with a large energy gap of ? 0.5 eV. The TI state arises from an intriguing substrate orbital filtering effect that selects a suitable orbital composition around the Fermi level, so that the system can be matched onto a four-band effective model Hamiltonian. Furthermore, it is found that within this model, the SOC gap does not increase monotonically with the increasing strength of SOC. These interesting results may shed new light in future design and fabrication of large-gap topological quantum states. PMID:25407432

  13. Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling

    PubMed Central

    Zhou, Miao; Ming, Wenmei; Liu, Zheng; Wang, Zhengfei; Yao, Yugui; Liu, Feng

    2014-01-01

    For potential applications in spintronics and quantum computing, it is desirable to place a quantum spin Hall insulator [i.e., a 2D topological insulator (TI)] on a substrate while maintaining a large energy gap. Here, we demonstrate a unique approach to create the large-gap 2D TI state on a semiconductor surface, based on first-principles calculations and effective Hamiltonian analysis. We show that when heavy elements with strong spin orbit coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111) surface into a hexagonal lattice, they exhibit a 2D TI state with a large energy gap of ?0.5?eV. The TI state arises from an intriguing substrate orbital filtering effect that selects a suitable orbital composition around the Fermi level, so that the system can be matched onto a four-band effective model Hamiltonian. Furthermore, it is found that within this model, the SOC gap does not increase monotonically with the increasing strength of SOC. These interesting results may shed new light in future design and fabrication of large-gap topological quantum states. PMID:25407432

  14. Biological effects of magnetic fields from superconducting magnetic energy storage systems

    SciTech Connect

    Tenforde, T.S.

    1989-12-01

    Physical interaction mechanisms and potential biological effects of static and slowly time-varying magnetic fields are summarized. The results of laboratory and human health studies on this topic are related to the fringe magnetic field levels anticipated to occur in the proximity of superconducting magnetic energy storage (SMES) systems. The observed biological effects of magnetic fields include: (1) magnetic induction of electrical potentials in the circulatory system and other tissues, (2) magneto-orientation of macromolecules and membranes in strong magnetic fields, and (3) Zeeman interactions with electronic spin states in certain classes of charge transfer reactions. In general, only the first of these interactions is relevant to the establishment of occupational exposure guidelines. Physical hazards posed by the interactions of magnetic fields with cardiac pacemakers and other implanted medical devices, e.g., aneurysm clips and prostheses, are important factors that must also be considered in establishing exposure guidelines. Proposed guidelines for limiting magnetic field exposure are discussed. 50 refs., 1 fig.

  15. PHYSICAL REVIEW B 84, 024501 (2011) Measurement of energy decay in superconducting qubits from nonequilibrium quasiparticles

    E-print Network

    Martinis, John M.

    . N. Cleland,1 and John M. Martinis1 1 Department of Physics, University of California, Santa Barbara in superconducting qubits, and can be described with a complex admittance that is a generalization of the Mattis-Bardeen

  16. Superconductivity in the system of p electrons

    SciTech Connect

    Zaitsev, R. O., E-mail: Zaitsev_rogdai@mail.ru [Moscow State Institute of Physics and Technology (Russian Federation)

    2012-10-15

    The problem of superconductivity in an electron system with partly filled sp shell is studied. The scattering amplitudes are determined and the equations of superconductivity are derived from the assumption that the Hubbard energy is the largest energy parameter.

  17. Superconducting pairing mediated by spin fluctuations from first principles

    NASA Astrophysics Data System (ADS)

    Essenberger, F.; Sanna, A.; Linscheid, A.; Tandetzky, F.; Profeta, G.; Cudazzo, P.; Gross, E. K. U.

    2014-12-01

    We present the derivation of an ab initio and parameter-free effective electron-electron interaction that goes beyond the screened random phase approximation and accounts for superconducting pairing driven by spin fluctuations. The construction is based on many-body perturbation theory and relies on the approximation of the exchange-correlation part of the electronic self-energy within time-dependent density functional theory. This effective interaction is included in an exchange-correlation kernel for superconducting density functional theory in order to achieve a completely parameter free superconducting gap equation. First results from applying the new functional to a simplified two-band electron gas model are consistent with experiments.

  18. Superconducting quantum bits.

    PubMed

    Clarke, John; Wilhelm, Frank K

    2008-06-19

    Superconducting circuits are macroscopic in size but have generic quantum properties such as quantized energy levels, superposition of states, and entanglement, all of which are more commonly associated with atoms. Superconducting quantum bits (qubits) form the key component of these circuits. Their quantum state is manipulated by using electromagnetic pulses to control the magnetic flux, the electric charge or the phase difference across a Josephson junction (a device with nonlinear inductance and no energy dissipation). As such, superconducting qubits are not only of considerable fundamental interest but also might ultimately form the primitive building blocks of quantum computers. PMID:18563154

  19. Design and construction of the main linac module for the superconducting energy recovery linac project at Cornell

    NASA Astrophysics Data System (ADS)

    Eichhorn, R.; Bullock, B.; He, Y.; Hoffstaetter, G.; Liepe, M.; O'Connell, T.; Quigley, P.; Sabol, D.; Sears, J.; Smith, E.; Veshcherevich, V.

    2014-01-01

    Cornell University has been designing and building superconducting accelerators for various applications for more than 50 years. Currently, an energy-recovery linac (ERL) based synchrotron-light facility is proposed making use of the existing CESR facility. As part of the phase 1 R&D program funded by the NSF, critical challenges in the design were addressed, one of them being a full linac cryo-module. It houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. Pushing the limits, a high quality factor of the cavities (2?1010) and high beam currents (100 mA accelerated plus 100 mA decelerated) are targeted. We will present the design of the main linac cryo-module (MLC) being finalized recently, its cryogenic features and report on the status of the fabrication which started in late 2012.

  20. Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata.

    PubMed

    Som, Sumit; Ghosh, Surajit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Roy, Suprakash

    2013-11-01

    Variable Energy Cyclotron Centre (VECC) has commissioned K500 Superconducting cyclotron (SCC) based on MSU and Texas A&M university cyclotrons. The radio frequency (RF) system of SCC has been commissioned with the stringent requirement of various RF parameters. The three-phase RF system of Superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.1°, respectively. The phase control system has the option to change the relative phase difference between any two RF cavities and maintain the phase stability within ±0.1° during round-the-clock cyclotron operation. The said precision phase loop consists of both analogue In-phase?Quadrature modulator to achieve faster response and also Direct Digital Synthesis based phase shifter to achieve wide dynamic range as well. This paper discusses detail insights into the various issues of phase control for the K500 SCC at VECC, Kolkata. PMID:24289392

  1. Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata

    NASA Astrophysics Data System (ADS)

    Som, Sumit; Ghosh, Surajit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Roy, Suprakash

    2013-11-01

    Variable Energy Cyclotron Centre (VECC) has commissioned K500 Superconducting cyclotron (SCC) based on MSU and Texas A&M university cyclotrons. The radio frequency (RF) system of SCC has been commissioned with the stringent requirement of various RF parameters. The three-phase RF system of Superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.1°, respectively. The phase control system has the option to change the relative phase difference between any two RF cavities and maintain the phase stability within ±0.1° during round-the-clock cyclotron operation. The said precision phase loop consists of both analogue In-phase/Quadrature modulator to achieve faster response and also Direct Digital Synthesis based phase shifter to achieve wide dynamic range as well. This paper discusses detail insights into the various issues of phase control for the K500 SCC at VECC, Kolkata.

  2. Design and construction of the main linac module for the superconducting energy recovery linac project at Cornell

    SciTech Connect

    Eichhorn, R.; Bullock, B.; He, Y.; Hoffstaetter, G.; Liepe, M.; O'Connell, T.; Quigley, P.; Sabol, D.; Sears, J.; Smith, E.; Veshcherevich, V. [Cornell Laboratory for Accelerator-based Science and Education (CLASSE), Cornell University, 161 Synchrotron Drive, Ithaca, NY 14853 (United States)

    2014-01-29

    Cornell University has been designing and building superconducting accelerators for various applications for more than 50 years. Currently, an energy-recovery linac (ERL) based synchrotron-light facility is proposed making use of the existing CESR facility. As part of the phase 1 R and D program funded by the NSF, critical challenges in the design were addressed, one of them being a full linac cryo-module. It houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. Pushing the limits, a high quality factor of the cavities (2?10{sup 10}) and high beam currents (100 mA accelerated plus 100 mA decelerated) are targeted. We will present the design of the main linac cryo-module (MLC) being finalized recently, its cryogenic features and report on the status of the fabrication which started in late 2012.

  3. Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata

    SciTech Connect

    Som, Sumit; Ghosh, Surajit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Roy, Suprakash [Variable Energy Cyclotron Centre, Kolkata (India)] [Variable Energy Cyclotron Centre, Kolkata (India)

    2013-11-15

    Variable Energy Cyclotron Centre (VECC) has commissioned K500 Superconducting cyclotron (SCC) based on MSU and Texas A and M university cyclotrons. The radio frequency (RF) system of SCC has been commissioned with the stringent requirement of various RF parameters. The three-phase RF system of Superconducting cyclotron has been developed in the frequency range 9–27 MHz with amplitude and phase stability of 100 ppm and ±0.1°, respectively. The phase control system has the option to change the relative phase difference between any two RF cavities and maintain the phase stability within ±0.1° during round-the-clock cyclotron operation. The said precision phase loop consists of both analogue In-phase/Quadrature modulator to achieve faster response and also Direct Digital Synthesis based phase shifter to achieve wide dynamic range as well. This paper discusses detail insights into the various issues of phase control for the K500 SCC at VECC, Kolkata.

  4. The microstructures and superconducting properties of MgB 2 bulks prepared by a high-energy milling method

    NASA Astrophysics Data System (ADS)

    Wu, Y. F.; Lu, Y. F.; Li, J. S.; Chen, S. K.; Yan, G.; Pu, M. H.; Li, C. S.; Zhang, P. X.

    2007-12-01

    We succeeded in the synthesis of high- Jc MgB 2 bulks via high energy ball-milling of elemental Mg and B powder at ambient temperatures. The mixed powder was ball-milled for 1-10 h and the completed reaction was achieved by subsequent annealing. The correlations among synthesis parameters, microstructures and superconducting properties in MgB 2 bulks were investigated. Samples were characterized by X-ray diffraction and scanning electron microscope, and the magnetization properties were examined by a superconducting quantum interfere device magnetometer. The highest Jc, approximately 2.3 × 10 5 A/cm 2 (15 K, 3 T), was obtained for samples milled for 5 h and sintered at 750 °C for 1 h. It is even comparable with SiC-doped MgB 2 bulks made by Dou’s group, which had exhibited the strongest reported flux pinning and the highest Jc in high field to date.

  5. Energy-Gap Opening in a Bi(110) Nanoribbon Induced by Edge

    E-print Network

    Chaudhuri, Sanjay

    mass and long Fermi wavelength (~40 nm at room temperature). Due to quantum and finite size effects, Bi thermoelectric efficiency, superconductivity, and strong spin-orbit coupling. In this work, the initial growth of Bi on epitaxial graphene (EG) on SiC(0001) is investigated using low temperature scanning tunneling

  6. Photoexcitations in La2CuO4: 2eV energy gap and long-lived defect states

    Microsoft Academic Search

    J. M. Ginder; M. G. Roe; Y. Song; R. P. McCall; J. R. Gaines; E. Ehrenfreund; A. J. Epstein

    1988-01-01

    We report the photoinduced optical-absorption spectrum of La2CuO4. Two photoinduced absorptions are observed, peaking at 0.5 and at 1.4 eV, with a crossover to photoinduced bleaching above 2.0 eV. These data, together with observed luminescence at ~2 eV, confirm the presence of an energy gap at or above this energy, as well as the existence of long-lived stable electronic defect

  7. Photoexcitations in LaâCuOâ: 2eV energy gap and long-lived defect states

    Microsoft Academic Search

    J. M. Ginder; M. G. Roe; Y. Song; R. P. McCall; J. R. Gaines; E. Ehrenfreund; A. J. Epstein

    1988-01-01

    We report the photoinduced optical-absorption spectrum of LaâCuOâ. Two photoinduced absorptions are observed, peaking at 0.5 and at 1.4 eV, with a crossover to photoinduced bleaching above 2.0 eV. These data, together with observed luminescence at approx.2 eV, confirm the presence of an energy gap at or above this energy, as well as the existence of long-lived stable electronic defect

  8. Edge singularities in high-energy spectra of gapped one-dimensional magnets in strong magnetic fields

    Microsoft Academic Search

    A. Friedrich; A. K. Kolezhuk; I. P. McCulloch; U. Schollwöck

    2007-01-01

    We use the dynamical density matrix renormalization group technique to show that the high-energy part of the spectrum of an S=1 Heisenberg chain, placed in a strong external magnetic field H exceeding the Haldane gap Delta , contains edge singularities, similar to those known to exist in the low-energy spectral response. It is demonstrated that in the frequency range omega≳Delta

  9. Edge singularities in high-energy spectra of gapped one-dimensional magnets in strong magnetic fields

    Microsoft Academic Search

    A. Friedrich; A. K. Kolezhuk; I. P. McCulloch; U. Schollwöck

    2007-01-01

    We use the dynamical density matrix renormalization group technique to show\\u000athat the high-energy part of the spectrum of a S=1 Haldane chain, placed in a\\u000astrong external magnetic field $H$ exceeding the Haldane gap $\\\\Delta$, contains\\u000aedge singularities, similar to those known to exist in the low-energy spectral\\u000aresponse. It is demonstrated that in the frequency range $\\\\omega\\\\gtrsim \\\\Delta$

  10. Experimental Indications of a BCS Behaviour in Superconducting Diamond

    NASA Astrophysics Data System (ADS)

    Sacépé, B.; Chapelier, C.; Marcenat, C.; Kamarik, J.; Klein, T.; Omnès, F.; Bustarret, E.

    2006-10-01

    This special issue of physica status solidi which was guest-edited by Satoshi Koizumi (National Institute for Materials Science, Tsukuba, Japan), Christoph E. Nebel (Diamond Research Center, Tsukuba, Japan), and Milos Nesladek (CEA-LIST, Gif sur Yvette, France) presents 10 Review Articles covering different areas of CVD Diamond research.The cover picture was taken from the article by Sacépé et al. [1]. The authors present a scanning tunneling spectroscopy study of superconducting single-crystalline heavily boron-doped diamond providing an experimental evidence for BCS behaviour. When a perpendicular magnetic field is applied to a superconducting boron-doped diamond film, vortices penetrate the sample, each carrying one quantum flux. In their centre, the superconductivity is washed out on a length scale equal to the superconducting coherence length s. The figures show the electronic Density of States (DOS) measured with a scanning tunnelling microscope at 50 mK along a line crossing the centre of a such a vortex. Outside the vortex core which extends between the two arrows, the DOS presents a gap at the Fermi level (V = 0) and two coherence peaks characteristic of a superconducting DOS. The measured DOS inside the vortex core reveals in addition numerous localized resonances, at positions pointed out by the black arrows on the two-dimensional view. For clean superconductors, quasi-particles are expected to form localized states inside the vortex cores at energies close to the Fermi level. Here, although boron-doped diamond films are in the dirty limit, localized resonances are still visible but at non zero energies inside the superconducting gap.

  11. Synthesis, characterization and band gap energy of poly(?-caprolactone)/Sr-MSA nano-composite

    NASA Astrophysics Data System (ADS)

    Kannammal, L.; Palanikumar, S.; Meenarathi, B.; Yelilarasi, A.; Anbarasan, R.

    2014-04-01

    A mercaptosuccinic acid (MSA) decorated Sr nano-particle (NP) was prepared and characterized by using various analytical techniques and was used as a chemical initiator for the ring opening polymerization (ROP) of ?-caprolactone (CL). The ROP of CL was carried out at various experimental conditions under N2 atmosphere with mild stirring. The initiating efficiency of MSA-decorated Sr NP was tested in terms of Fourier transform infrared-relative intensity, melting temperature (Tm), degradation temperature (Td) and molecular weight (Mw) of poly(?-caprolactone) (PCL), differential scanning calorimetry, UV-visible spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis and gel permeation chromatography analytical techniques. The nuclear magnetic resonance spectrum confirms the chemical structure of PCL. While increasing the [M/I] ratio, the Mw of PCL was linearly increased. The band gap energy of Sr was determined from the UV-visible spectrum. The reflectance study proves the hydrophobic nature of the Sr-hybrid and its nano-composite formation with PCL.

  12. Elevated temperature dependence of energy band gap of ZnO thin films grown by e-beam deposition

    SciTech Connect

    Rai, R. C.; Guminiak, M.; Wilser, S. [Department of Physics, SUNY College at Buffalo, Buffalo, New York 14222 (United States); Cai, B.; Nakarmi, M. L. [Department of Physics, Brooklyn College of the CUNY, Brooklyn, New York 11210 (United States)

    2012-04-01

    We report the surface, structural, electronic, and optical properties of the epitaxial ZnO thin films grown on (0001) sapphire substrate at 600 deg. C by an electron-beam deposition technique. ZnO thin films have been deposited in an oxygen environment and post-deposition annealed to improve the stoichiometry and the crystal quality. In order to investigate the free exciton binding energy and the temperature dependence of the energy bandgap, we carried out variable temperature (78-450 K) transmittance measurements on ZnO thin films. The absorption data below the energy bandgap have been modeled with the Urbach tail and a free exciton, while the data above the gap have been modeled with the charge transfer excitations. The exciton binding energy is measured to be E{sub 0}= 64 {+-} 7 meV, and the energy band gaps of the ZnO film are measured to be E{sub g}-tilde 3.51 and 3.48 eV at 78 and 300 K, respectively. The temperature dependence of the energy gap has been fitted with the Varshni model to extract the fitting parameters {alpha}= 0.00020 {+-} 0.00002 eV/K, {beta}= 325 {+-} 20 K, and E{sub g} (T = 0 K) = 3.516 {+-} 0.0002 eV.

  13. Quasiparticle properties of the superconducting state of the two-dimensional Hubbard model

    NASA Astrophysics Data System (ADS)

    Gull, E.; Millis, A. J.

    2015-02-01

    Cluster dynamical mean field methods are used to calculate the normal and anomalous components of the electron self-energy of the two-dimensional Hubbard model. Issues associated with the analytical continuation of the normal and anomalous parts of the gap function are discussed. Methods of minimizing the uncertainties associated with the pseudogap-related pole in the self-energy are discussed. From these the evolution of the superconducting gap and the momentum-dependent electron spectral function across the phase diagram are determined. In the pseudogap regime, decreasing the temperature into the superconducting state leads to a decrease in the energy gap and the formation of a "peak-dip-hump" structure in the electronic density of states. The peak feature disperses very weakly. The calculated spectral functions are in good qualitative agreement with published data. The mathematical origin of the behavior is found to be the effect of the superconductivity on the pole structure giving rise to the normal state pseudogap. In particular the "hump" feature is found to arise from a zero crossing of the real part of the electron self-energy rather than from an onset of scattering. The effect of superconductivity on the zone diagonal spectra is presented.

  14. Superconducting properties of Ca3Ir4Sn13: a ?SR study

    NASA Astrophysics Data System (ADS)

    Biswas, P. K.; Amato, A.; Wang, Kefeng; Petrovic, C.; Khasanov, R.; Luetkens, H.; Morenzoni, E.

    2014-12-01

    Muon spin relaxation and rotation (?SR) measurements have been performed to study the superconducting properties of Ca3Ir4Sn13. Zero-field ?SR data shows no sign of any magnetic anomaly in Ca3Ir4Sn13 at the superlattice transition temperature, T* or in the superconducting ground state. Transverse-field ?SR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth ?. The dependence of ??2 with temperature is consistent with the existence of a single s-wave energy gap in the superconducting state of Ca3Ir4Sn13 with a gap value of 1.51(5) meV at absolute zero temperature. The magnetic penetration depth at zero temperature ?(0) is 351(4) nm. The ratio ?(0)/kBTc = 2.41(8) indicates that Ca3Ir4Sn13 is a strong-coupling superconductor.

  15. Superconducting PM undiffused machines with stationary superconducting coils

    DOEpatents

    Hsu, John S.; Schwenterly, S. William

    2004-03-02

    A superconducting PM machine has a stator, a rotor and a stationary excitation source without the need of a ferromagnetic frame which is cryogenically cooled for operation in the superconducting state. PM material is placed between poles on the rotor to prevent leakage or diffusion of secondary flux before reaching the main air gap, or to divert PM flux where it is desired to weaken flux in the main air gap. The PM material provides hop-along capability for the machine in the event of a fault condition.

  16. Superconductive wire

    DOEpatents

    Korzekwa, D.A.; Bingert, J.F.; Peterson, D.E.; Sheinberg, H.

    1995-07-18

    A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity. 2 figs.

  17. Superconductive wire

    DOEpatents

    Korzekwa, David A. (Los Alamos, NM); Bingert, John F. (Jemez Springs, NM); Peterson, Dean E. (Los Alamos, NM); Sheinberg, Haskell (Santa Fe, NM)

    1995-01-01

    A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity.

  18. Effects of Ca and Sr chemical doping on the average superconducting kinetic energy of YBa2Cu3O7-?

    NASA Astrophysics Data System (ADS)

    Vieira, V. N.; Mendonça, A. P. A.; Dias, F. T.; Hneda, M. L.; Pureur, P.; Schaf, J.; Mesquita, F.

    2015-03-01

    In this brief communication we applied the MZFC(T) and MFCC(T) reversible dc magnetizations to get the average superconducting kinetic energy density, kS(T,B) of YBa2Cu3O7-?, Y0.95Ca0.05Ba2Cu3O7-? and YBa1.75Sr0.25Cu3O7-? ceramic samples with the aim of study the effects of Ca and Sr doping on the kS(T,B). The MZFC(T) and MFCC(T) measurements were performed with a SQUID magnetometer from quantum design to dc magnetic fields up to 50kOe. The determination of the kS(T,B) from reversible dc magnetization is supported by virial theorem of superconductivity [kS(T,B) = – MB]. The kS(T,B) results show an common temperature profile for all the samples which is smoothly affected by the magnetic field. On the other hand the kS(T,B) results to T > Tc could not be associated to the pseudogap phenomenon. The Ca doping affects more effectively the kS(T,B) behaviour then Sr doping. A possible explanation to this feature could be associated to the fact that the hole doping promoted by Ca doping depress more considerably the superconducting state and enhances the granular character of the YBa2Cu3O7-? superconductor than the chemical pressure effect promoted by Sr doping.

  19. Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates

    PubMed Central

    Giannetti, Claudio; Cilento, Federico; Conte, Stefano Dal; Coslovich, Giacomo; Ferrini, Gabriele; Molegraaf, Hajo; Raichle, Markus; Liang, Ruixing; Eisaki, Hiroshi; Greven, Martin; Damascelli, Andrea; van der Marel, Dirk; Parmigiani, Fulvio

    2011-01-01

    In strongly correlated systems the electronic properties at the Fermi energy (EF) are intertwined with those at high-energy scales. One of the pivotal challenges in the field of high-temperature superconductivity (HTSC) is to understand whether and how the high-energy scale physics associated with Mott-like excitations (|E?EF|>1 eV) is involved in the condensate formation. Here, we report the interplay between the many-body high-energy CuO2 excitations at 1.5 and 2 eV, and the onset of HTSC. This is revealed by a novel optical pump-supercontinuum-probe technique that provides access to the dynamics of the dielectric function in Bi2Sr2Ca0.92Y0.08Cu2O8+? over an extended energy range, after the photoinduced suppression of the superconducting pairing. These results unveil an unconventional mechanism at the base of HTSC both below and above the optimal hole concentration required to attain the maximum critical temperature (Tc). PMID:21673674

  20. Position-dependent effect of non-magnetic impurities on superconducting properties of nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, L.-F.; Covaci, L.; Peeters, F. M.

    2015-01-01

    Anderson's theorem states that non-magnetic impurities do not change the bulk properties of conventional superconductors. However, as the dimensionality is reduced, the effect of impurities becomes more significant. Here we investigate superconducting nanowires with diameter comparable to the Fermi wavelength ?F (which is less than the superconducting coherence length) by using a microscopic description based on the Bogoliubov-de Gennes method. We find that: 1) impurities strongly affect the superconducting properties, 2) the effect is impurity position dependent, and 3) it exhibits opposite behavior for resonant and off-resonant wire widths. We show that this is due to the interplay between the shape resonances of the order parameter and the subband energy spectrum induced by the lateral quantum confinement. These effects can be used to manipulate the Josephson current, filter electrons by subband and investigate the symmetries of the superconducting subband gaps.

  1. Procedures for Filling Short Gaps in Energy Use and Weather Data

    E-print Network

    Chen, H.; Claridge, D. E.

    2000-01-01

    data. Single variable regression, polynomial models, Lagrange interpolation, and linear interpolation models are developed, demonstrated, and used to fill 1-6 hour gaps in weather data, heating data and cooling data for commercial buildings...

  2. Band gap energy and bowing parameter of In-rich InAlN films grown by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    He, Hong; Cao, Yongge; Fu, Renli; Guo, Wang; Huang, Zhi; Wang, Meili; Huang, Changgang; Huang, Jiquan; Wang, Hai

    2010-01-01

    The crystal structure, band gap energy and bowing parameter of In-rich In xAl 1- xN (0.7 < x < 1.0) films grown by magnetron sputtering were investigated. Band gap energies of In xAl 1- xN films were obtained from absorption spectra. Band gap tailing due to compositional fluctuation in the films was observed. The band gap of the as-grown InN measured by optical absorption method is 1.34 eV, which is larger than the reported 0.7 eV for pure InN prepared by molecular beam epitaxy (MBE) method. This could be explained by the Burstein-Moss effect under carrier concentration of 10 20 cm -3 of our sputtered films. The bowing parameter of 3.68 eV is obtained for our In xAl 1- xN film which is consistent with the previous experimental reports and theoretical calculations.

  3. Ten questions and answers about superconductivity

    E-print Network

    Tian De Cao

    2012-11-13

    This work answers the basic questions of superconductivity in a question-and-answer format. We extend a basic hypothesis to various superconductors. This hypothesis is that superconductivity requires that the pairing gap locates around the Fermi level. On the basis of this hypothesis our calculations give the so-called three factor theory with which some key problems of the high temperature superconductivity are explained.

  4. Prospects for the medium- and long-term development of China`s electric power industry and analysis of the potential market for superconductivity technology

    SciTech Connect

    Li, Z. [Bob Lawrence and Associates, Inc., Alexandria, VA (United States)

    1998-05-01

    First of all, overall economic growth objectives in China are concisely and succinctly specified in this report. Secondly, this report presents a forecast of energy supply and demand for China`s economic growth for 2000--2050. In comparison with the capability of energy construction in China in the future, a gap between supply and demand is one of the important factors hindering the sustainable development of Chain`s economy. The electric power industry is one of China`s most important industries. To adopt energy efficiency through high technology and utilizing energy adequately is an important technological policy for the development of China`s electric power industry in the future. After briefly describing the achievements of China`s electric power industry, this report defines the target areas and policies for the development of hydroelectricity and nuclear electricity in the 2000s in China, presents the strategic position of China`s electric power industry as well as objectives and relevant plans of development for 2000--2050. This report finds that with the discovery of superconducting electricity, the discovery of new high-temperature superconducting (HTS) materials, and progress in materials techniques, the 21st century will be an era of superconductivity. Applications of superconductivity in the energy field, such as superconducting storage, superconducting transmission, superconducting transformers, superconducting motors, its application in Magneto-Hydro-Dynamics (MHD), as well as in nuclear fusion, has unique advantages. Its market prospects are quite promising. 12 figs.

  5. Superconducting Magnets for Particle Accelerators

    E-print Network

    Rossi, L

    2012-01-01

    Superconductivity has been the most influential technology in the field of accelerators in the last 30 years. Since the commissioning of the Tevatron, which demonstrated the use and operability of superconductivity on a large scale, superconducting magnets and rf cavities have been at the heart of all new large accelerators. Superconducting magnets have been the invariable choice for large colliders, as well as cyclotrons and large synchrotrons. In spite of the long history of success, superconductivity remains a difficult technology, requires adequate R&D and suitable preparation, and has a relatively high cost. Hence, it is not surprising that the development has also been marked by a few setbacks. This article is a review of the main superconducting accelerator magnet projects; it highlights the main characteristics and main achievements, and gives a perspective on the development of superconducting magnets for the future generation of very high energy colliders.

  6. Model for an Exciton Mechanism of Superconductivity

    Microsoft Academic Search

    David Allender; John Bardeen

    1973-01-01

    The exciton mechanism of superconductivity is discussed with respect to a particular model, a thin metal layer on a semiconductor surface. In this model, the metal electrons at the Fermi surface tunnel into the semiconductor gap where they interact with virtual excitons, producing a net attractive interaction among the electrons in direct analogy with the phonon mechanism of superconductivity. The

  7. SUPERCONDUCTING RF ACTIVITIES AT FZ-JUELICH

    Microsoft Academic Search

    R. Stassen; W. Bräutigam; R. Eichhorn; F. M. Esser; B. Laatsch; R. Maier; G. Schug; R. Tölle; LIGHT-ION LINAC

    Two types of superconducting cavities are currently under investigation at the research centre FZJ in Juelich. The niobium prototype of a four-gap spoke cavity is already under fabrication at the central workshop after analysing and tests of copper models. As a second activity, a new pulsed linac for the cooler synchrotron COSY has been designed based on superconductive half-wave resonators

  8. Enhancement of magnetic flux distribution in a DC superconducting electric motor

    NASA Astrophysics Data System (ADS)

    Hamid, N. A.; Ewe, L. S.; Chin, K. M.

    2013-06-01

    Most motor designs require an air gap between the rotor and stator to enable the armature to rotate freely. The interaction of magnetic flux from rotor and stator within the air gap will provide the thrust for rotational motion. Thus, the understanding of magnetic flux in the vicinity of the air gap is very important to mathematically calculate the magnetic flux generated in the area. In this work, a finite element analysis was employed to study the behavior of the magnetic flux in view of designing a synchronous DC superconducting electric motor. The analysis provides an ideal magnetic flux distribution within the components of the motor. From the flux plot analysis, it indicates that flux losses are mainly in the forms of leakage and fringe effect. The analysis also shows that the flux density is high at the area around the air gap and the rotor. The high flux density will provide a high force area that enables the rotor to rotate. In contrast, the other parts of the motor body do not show high flux density indicating low distribution of flux. Consequently, a bench top model of a DC superconducting motor was developed where by motor with a 2-pole type winding was chosen. Each field coil was designed with a racetrack-shaped double pancake wound using DI-BSCCO Bi-2223 superconducting tapes. The performance and energy efficiency of the superconducting motor was superior when compared to the conventional motor with similar capacity.

  9. Experimental study of high energy electron interactions in a superconducting aluminum alloy resonant bar

    E-print Network

    M. Barucci; M. Bassan; B. Buonomo; G. Cavallari; E. Coccia; S. D'Antonio; V. Fafone; C. Ligi; L. Lolli; A. Marini; G. Mazzitelli; G. Modestino; G. Pizzella; L. Quintieri; L. Risegari; A. Rocchi; F. Ronga; P. Valente; G. Ventura; S. M. Vinko

    2009-01-09

    Peak amplitude measurements of the fundamental mode of oscillation of a suspended aluminum alloy bar hit by an electron beam show that the amplitude is enhanced by a factor ~3.5 when the material is in the superconducting state. This result is consistent with the cosmic ray observations made by the resonant gravitational wave detector NAUTILUS, made of the same alloy, when operated in the superconducting state. A comparison of the experimental data with the predictions of the model describing the underlying physical process is also presented.

  10. Potential for Precision Measurement of Low-Energy Antiprotons with GAPS for Dark Matter and Primordial Black Hole Physics

    E-print Network

    T. Aramaki; S. E. Boggs; P. von Doetinchem; H. Fuke; C. J. Hailey; S. A. I. Mognet; R. A. Ong; K. M. Perez; J. Zweerink

    2014-04-02

    The general antiparticle spectrometer (GAPS) experiment is a proposed indirect dark matter search focusing on antiparticles produced by WIMP (weakly interacting massive particle) annihilation and decay in the Galactic halo. In addition to the very powerful search channel provided by antideuterons, GAPS has a strong capability to measure low-energy antiprotons (0.07 $\\le$ E $\\le$ 0.25 GeV) as dark matter signatures. This is an especially effective means for probing light dark matter, whose existence has been hinted at in the direct dark matter searches, including the recent result from the CDMS-II experiment. While severely constrained by LUX and other direct dark matter searches, light dark matter candidates are still viable in an isospin-violating dark matter scenario and halo-independent analysis. Along with the excellent antideuteron sensitivity, GAPS will be able to detect an order of magnitude more low-energy antiprotons, compared to BESS, PAMELA and AMS-02, providing a precision measurement of low-energy antiproton flux and a unique channel for probing light dark matter models. Additionally, dark matter signatures from gravitinos and Kaluza-Klein right-handed neutrinos as well as evidence of primordial black hole evaporation can be observed through low-energy antiproton search.

  11. Critical couplings in Crystalline Color superconductivity

    E-print Network

    Deog Ki Hong; Y. J. Sohn

    2001-06-30

    Solving the Schwinger-Dyson equations, we analyze the pairing of quarks in asymmetric quark matter where quarks have different chemical potentials. We show that in the asymmetric quark matter a crystalline color-superconducting gap opens when the quark coupling is stronger than a critical value. The critical coupling is nonzero, since the infrared divergence is lessened when the momenta of pairing quarks are not opposite. The superconducting gaps and the critical couplings are calculated both at high and intermediate densities.

  12. Superconducting Magnets in High-Energy Physics: Large-scale magnets that dissipate no electrical power are under construction for high-energy physics research.

    PubMed

    Derrick, M

    1967-10-20

    The promise of superconductivity making possible large magnets that dissipate no power is now being realized. Most of the early difficulties have been overcome; hence it is now a straight-forward engineering problem to design and build a large stable supermagnet. The application of such magnets to research in high-energy physics can be expected to grow rapidly in the next few years. PMID:17794314

  13. Formation Energies of Antiphase Boundaries in GaAs and GaP: An ab Initio Study

    PubMed Central

    Rubel, Oleg; Baranovskii, Sergei D.

    2009-01-01

    Electronic and structural properties of antiphase boundaries in group III-V semiconductor compounds have been receiving increased attention due to the potential to integration of optically-active III-V heterostructures on silicon or germanium substrates. The formation energies of {110}, {111}, {112}, and {113} antiphase boundaries in GaAs and GaP were studied theoretically using a full-potential linearized augmented plane-wave density-functional approach. Results of the study reveal that the stoichiometric {110} boundaries are the most energetically favorable in both compounds. The specific formation energy ? of the remaining antiphase boundaries increases in the order of ?{113} ? ?{112} < ?{111}, which suggests {113} and {112} as possible planes for faceting and annihilation of antiphase boundaries in GaAs and GaP. PMID:20054465

  14. Effect of electron divergence in air gaps on the measurement of the energy of cascades in emulsion chambers

    NASA Technical Reports Server (NTRS)

    Apanasenko, A. V.; Baradzey, L. T.; Kanevskaya, Y. A.; Smorodin, Y. A.

    1975-01-01

    The effect of an increase in electron density in the vicinity of the cascade axis caused by an avalanche passing through the gap between lead filters of the emulsion chamber was investigated experimentally. Optical densities were measured in three X-ray films spaced at 400, 800 and 1200 micrometer from the filter surface having a thickness of 6 cascade units. The optical densities of blackening spots caused by electron photon cascades of 1 to 2, 2 to 7 and greater than 7 BeV energies were measured. The results prove the presence of a gap between the filter and the nuclear emulsion which results in the underestimation of energy by several tenths of a percent.

  15. Modeling and simulation of energy-removal system for superconducting magnets

    Microsoft Academic Search

    J. M. Bailey; J. M. Googe; R. J. Wood

    1983-01-01

    The Large Coil Test Facility at the Oak Ridge National Laboratory employs six D shaped superconducting coils. The coil current ranges from 10 to 20 kA. The protection scheme of these coils requires the coil current to be interrupted. This interruption will generate high-voltage transients in the coil. To prevent destruction of the coil isolation, these transients have to be

  16. Progress in superconducting metamaterials

    NASA Astrophysics Data System (ADS)

    Jung, Philipp; Ustinov, Alexey V.; Anlage, Steven M.

    2014-07-01

    We review progress in the development and applications of superconducting metamaterials. The review is organized in terms of several distinct advantages and unique properties brought to the metamaterials field by superconductivity. These include the low-loss nature of the meta-atoms, their compact structure, their extraordinary degree of nonlinearity and tunability, magnetic flux quantization and the Josephson effect, quantum effects in which photons interact with quantized energy levels in the meta-atom, as well as strong diamagnetism.

  17. Progress in Superconducting Metamaterials

    E-print Network

    Philipp Jung; Alexey V. Ustinov; Steven M. Anlage

    2014-03-25

    We review progress in the development and applications of superconducting metamaterials. The review is organized in terms of several distinct advantages and unique properties brought to the metamaterials field by superconductivity. These include the low-loss nature of the meta-atoms, their compact structure, their extraordinary degree of nonlinearity and tunability, magnetic flux quantization and the Josephson effect, quantum effects in which photons interact with quantized energy levels in the meta-atom, as well as strong diamagnetism.

  18. Dynamical Model of Elementary Particles Based on an Analogy with Superconductivity. I

    Microsoft Academic Search

    Y. Nambu; G. Jona-Lasinio

    1961-01-01

    It is suggested that the nucleon mass arises largely as a self-energy of some primary fermion field through the same mechanism as the appearance of energy gap in the theory of superconductivity. The idea can be put into a mathematical formulation utilizing a generalized Hartree-Fock approximation which regards real nucleons as quasi-particle excitations. We consider a simplified model of nonlinear

  19. Superconductivity, the Structure Scale of the Universe, Tenth Edition (Elastic Resonant Symmetric Medium by Self-Energy)

    E-print Network

    Richard D. Saam

    2007-01-09

    A theoretical framework supported by literature reported experimental evidence (Homes, Harshman along with Voyager, Hubble and EGRET space platforms and others) is presented which indicates that superconductivity is a self energy phenomenon and congruent with the concept of the Charge Conjugation, Parity Change and Time Reversal (CPT) theorem. A resonant symmetric structure is proposed as an extension of Bardeen Cooper and Schrieffer (BCS) theory, which suspends Lorentz transforms at superluminal velocities in the context of the de Broglie hypothesis. A momentum and energy conserving (elastic) CPT resonant structural lattice scalable over 15 orders of magnitude from nuclear to universe dimensions and associated superconducting theory is postulated whereby nuclear (quark) weak and strong forces, electromagnetic and gravitational forces are mediated by a particle of resonant velocity transformed mass (mt) (110.123 x electron mass or 56 Mev/c2), The universe mass and density are based on an isotropic homogeneous media filling the vacuum of and could be considered a candidate for dark matter/energy. The model predicts a deceleration value consistent with observed Pioneer 10 and 11 deep space translational and rotational deceleration and consistent with the notion that, An object moving through momentum space will slow down.

  20. Magnetic-field dependence of energy levels of superconducting nano-scale mettalic grains with strong spin-orbit scattering

    NASA Astrophysics Data System (ADS)

    Nesterov, Konstantin; Alhassid, Yoram

    2012-02-01

    We study the Zeeman splitting of discrete energy levels of superconducting nano-scale metallic grains whose single-electron dynamics is chaotic [1]. In the absence of spin-orbit scattering the Zeeman splitting of a single-electron level is trivial; it is the same for all levels and linear in magnetic field. Spin-orbit coupling suppresses this splitting, induces level-to-level fluctuations and non-linear corrections to the energies. We investigate the combined effect of pairing correlations, which lead to superconductivity in the bulk limit, and spin-orbit scattering on the many-electron energy levels in a weak magnetic field. In particular, we focus our studies on the linear (g-factor) and quadratic (zero-field level curvature) corrections and their mesoscopic fluctuations. The single-electron part of the Hamiltonian follows the statistics of the Gaussian symplectic ensemble of random matrix theory, which is applicable in the limit of strong spin-orbit scattering and a large dimensionless Thouless conductance. The interaction is given by a BCS-like pairing term and the magnetic field coupling is described by a Zeeman term. [1] K. Nesterov and Y. Alhassid, to be published.

  1. ARPES Studies of Cuprate Fermiology: Superconductivity, Pseudogap and Quasiparticle Dynamics

    SciTech Connect

    Vishik, Inna

    2011-06-23

    We present angle-resolved photoemission spectroscopy (ARPES) studies of the cuprate high-temperature superconductors which elucidate the relation between superconductivity and the pseudogap and highlight low-energy quasiparticle dynamics in the superconducting state. Our experiments suggest that the pseudogap and superconducting gap represent distinct states, which coexist below T{sub c}. Studies on Bi-2212 demonstrate that the near-nodal and near-antinodal regions behave differently as a function of temperature and doping, implying that different orders dominate in different momentum-space regions. However, the ubiquity of sharp quasiparticles all around the Fermi surface in Bi-2212 indicates that superconductivity extends into the momentum-space region dominated by the pseudogap, revealing subtlety in this dichotomy. In Bi-2201, the temperature dependence of antinodal spectra reveals particle-hole asymmetry and anomalous spectral broadening, which may constrain the explanation for the pseudogap. Recognizing that electron-boson coupling is an important aspect of cuprate physics, we close with a discussion of the multiple 'kinks' in the nodal dispersion. Understanding these may be important to establishing which excitations are important to superconductivity.

  2. Magnetic hourglass dispersion and its relation to high-temperature superconductivity in iron-tuned Fe1+yTe0.7Se0.3

    NASA Astrophysics Data System (ADS)

    Tsyrulin, N.; Viennois, R.; Giannini, E.; Boehm, M.; Jimenez-Ruiz, M.; Omrani, A. A.; Dalla Piazza, B.; Rønnow, H. M.

    2012-07-01

    High-temperature superconductivity remains arguably the greatest enigma of condensed matter physics. The discovery of iron-based high-temperature superconductors [1, 2] has renewed the importance of understanding superconductivity in materials susceptible to magnetic order and fluctuations. Intriguingly, they show magnetic fluctuations reminiscent of superconducting (SC) cuprates [3], including a ‘resonance’ and an ‘hourglass’-shaped dispersion [4], which provides an opportunity to gain new insights into the coupling between spin fluctuations and superconductivity. In this paper, we report inelastic neutron scattering data on Fe1+yTe0.7Se0.3 using excess iron concentration to tune between an SC (y = 0.02) and a non-SC (y = 0.05) ground state. We find incommensurate spectra in both the samples but discover that in the one that becomes SC, a constriction toward a commensurate hourglass-shape develops well above Tc. Conversely, a spin gap and a concomitant spectral weight shift happen below Tc. Our results imply that the hourglass-shaped dispersion is most likely a prerequisite for superconductivity, whereas the spin gap and shift of spectral weight are the consequences of superconductivity. We explain this observation by pointing out that an inward dispersion toward the commensurate wave vector is needed for the opening of a spin gap to lower the magnetic exchange energy and hence provide the necessary condensation energy for the SC state to emerge.

  3. Band-gap energies and structural properties of doped Ba0.5Sr0.5TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Zheng, Y. B.; Wang, S. J.; Huan, A. C. H.; Tripathy, S.; Chai, J. W.; Kong, L. B.; Ong, C. K.

    2006-01-01

    We have investigated the effect of Ti and Mg dopants on the structural properties and band-gap energies of Ba0.5Sr0.5TiO3 (BST) thin films grown on LaAlO3 substrates. The transmission spectra of these BST thin films measured by ultraviolet-visible spectrophotometer show that the band-gap energies are strongly dependent on the dopant concentration. Based on the structural analyses and theoretical calculation, the variation of the band-gap energies can be attributed to the combined effects of stress, grain size, and phase transformation in Ti- and Mg-doped BST thin films.

  4. Large energy band-gap tuning of 980 nm InGaAs/InGaAsP quantum well structure via quantum well intermixing

    NASA Astrophysics Data System (ADS)

    Zhongliang, Qiao; Xiaohong, Tang; Kenneth, Lee Eng Kian; Huei, Lim Peng; BaoXue, Bo

    2013-01-01

    Quantum well (QW) inter-mixing based post-growth energy band gap turning of 980 nm InGaAs/InGaAsP QW-structures for high power semi-conductor lasers has been investigated. The QW intermixing was carried out by depositing SiO2 thin film on the samples and followed by high temperature annealing. The band gap energy blue shift of the QWs after the intermixing under various conditions has been studied. The largest band gap energy blue shift of the QWs reaches exceeds 220 nm.

  5. Energy Dependence of the Contribution of Pion Exchange to Large-Rapidity-Gap Events in Deep Inelastic Scattering

    E-print Network

    Chun-xiu Liu; Zuo-tang Liang

    2001-03-25

    We study the energy dependence of the contribution of pion exchange to large-rapidity-gap events in deep inelastic scattering. The results show that this contribution can be quite significant at low energy and that the LRG events observed by E665 collaboration in \\mu Xe and \\mu D interactions at 490 $GeV$ can be reasonably well described in terms of meson exchange. We also show that the distribution of the maximum rapidity for all hadrons is quite different from that for charged hadrons only and that the former exhibits also shoulder-like structure for events at 490 $GeV$ similar to that at HERA.

  6. Coexistence of antiferromagnetism and d+id superconducting correlations in the graphene bilayer

    NASA Astrophysics Data System (ADS)

    Milovanovi?, M. V.; Predin, S.

    2012-11-01

    We discuss the t-J-U model on a honeycomb monolayer that has the same low-energy description of the kinetic term as the graphene bilayer, and in particular study coexistence of antiferromagnetism and superconducting correlations that originate from Cooper pairs without phase coherence. We show that the model is relevant for the description of the graphene bilayer and that the presence of the d+id superconducting correlations with antiferromagnetism can lead to quadratic dependence in small magnetic fields of the gap of the effective monolayer consistent with the transport measurements of Velasco on the graphene bilayer.

  7. Superconducting thermoelectric generator

    DOEpatents

    Metzger, John D. (Eaton's Neck, NY); El-Genk, Mohamed S. (Albuquerque, NM)

    1998-01-01

    An apparatus and method for producing electricity from heat. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device.

  8. Superconducting thermoelectric generator

    DOEpatents

    Metzger, J.D.; El-Genk, M.S.

    1998-05-05

    An apparatus and method for producing electricity from heat is disclosed. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device. 4 figs.

  9. Superconducting thermoelectric generator

    DOEpatents

    Metzger, J.D.; El-Genk, M.S.

    1996-01-01

    An apparatus and method for producing electricity from heat. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device.

  10. Electronic Characterization of Defects in Narrow Gap Semiconductors-Comparison of Electronic Energy Levels and Formation Energies in Mercury Cadmium Telluride, Mercury Zinc Telluride, and Mercury Zinc Selenide

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1996-01-01

    We have used a Green's function technique to calculate the energy levels and formation energy of deep defects in the narrow gap semiconductors mercury cadmium telluride (MCT), mercury zinc telluride (MZT) and mercury zinc selenide (MZS). The formation energy is calculated from the difference between the total energy with an impurity cluster and the total energy for the perfect crystal. Substitutional (including antisite), interstitial (self and foreign), and vacancy deep defects are considered. Relaxation effects are calculated (with molecular dynamics). By use of a pseudopotential, we generalize the ideal vacancy model so as to be able to consider relaxation for vacancies. Different charge states are considered and the charged state energy shift (as computed by a modified Haldane-Anderson model) can be twice that due to relaxation. Different charged states for vacancies were not calculated to have much effect on the formation energy. For all cases we find deep defects in the energy gap only for cation site s-like orbitals or anion site p-like orbitals, and for the substitutional case only the latter are appreciably effected by relaxation. For most cases for MCT, MZT, MZS, we consider x (the concentration of Cd or Zn) in the range appropriate for a band gap of 0.1 eV. For defect energy levels, the absolute accuracy of our results is limited, but the precision is good, and hence chemical trends are accurately predicted. For the same reason, defect formation energies are more accurately predicted than energy level position. We attempt, in Appendix B, to calculate vacancy formation energies using relatively simple chemical bonding ideas due to Harrison. However, these results are only marginally accurate for estimating vacancy binding energies. Appendix C lists all written reports and publications produced for the grant. We include abstracts and a complete paper that summarizes our work which is not yet available.

  11. Perturbation theory of a superconducting 0 - ? impurity quantum phase transition

    NASA Astrophysics Data System (ADS)

    Žonda, M.; Pokorný, V.; Janiš, V.; Novotný, T.

    2015-03-01

    A single-level quantum dot with Coulomb repulsion attached to two superconducting leads is studied via the perturbation expansion in the interaction strength. We use the Nambu formalism and the standard many-body diagrammatic representation of the impurity Green functions to formulate the Matsubara self-consistent perturbation expansion. We show that at zero temperature second order of the expansion in its spin-symmetric version yields a nearly perfect agreement with the numerically exact calculations for the position of the 0 - ? phase boundary at which the Andreev bound states reach the Fermi energy as well as for the values of single-particle quantities in the 0-phase. We present results for phase diagrams, level occupation, induced local superconducting gap, Josephson current, and energy of the Andreev bound states with the precision surpassing any (semi)analytical approaches employed thus far.

  12. Perturbation theory of a superconducting 0 - ? impurity quantum phase transition.

    PubMed

    Žonda, M; Pokorný, V; Janiš, V; Novotný, T

    2015-01-01

    A single-level quantum dot with Coulomb repulsion attached to two superconducting leads is studied via the perturbation expansion in the interaction strength. We use the Nambu formalism and the standard many-body diagrammatic representation of the impurity Green functions to formulate the Matsubara self-consistent perturbation expansion. We show that at zero temperature second order of the expansion in its spin-symmetric version yields a nearly perfect agreement with the numerically exact calculations for the position of the 0 - ? phase boundary at which the Andreev bound states reach the Fermi energy as well as for the values of single-particle quantities in the 0-phase. We present results for phase diagrams, level occupation, induced local superconducting gap, Josephson current, and energy of the Andreev bound states with the precision surpassing any (semi)analytical approaches employed thus far. PMID:25744137

  13. Perturbation theory of a superconducting 0 ? ? impurity quantum phase transition

    PubMed Central

    Žonda, M.; Pokorný, V.; Janiš, V.; Novotný, T.

    2015-01-01

    A single-level quantum dot with Coulomb repulsion attached to two superconducting leads is studied via the perturbation expansion in the interaction strength. We use the Nambu formalism and the standard many-body diagrammatic representation of the impurity Green functions to formulate the Matsubara self-consistent perturbation expansion. We show that at zero temperature second order of the expansion in its spin-symmetric version yields a nearly perfect agreement with the numerically exact calculations for the position of the 0 ? ? phase boundary at which the Andreev bound states reach the Fermi energy as well as for the values of single-particle quantities in the 0-phase. We present results for phase diagrams, level occupation, induced local superconducting gap, Josephson current, and energy of the Andreev bound states with the precision surpassing any (semi)analytical approaches employed thus far. PMID:25744137

  14. NLO Vertex for a Forward Jet plus a Rapidity Gap at High Energies

    E-print Network

    Martin Hentschinski; José Daniel Madrigal Martínez; Beatrice Murdaca; Agustín Sabio Vera

    2014-09-26

    We present the calculation of the forward jet vertex associated to a rapidity gap (coupling of a hard pomeron to the jet) in the BFKL formalism at next-to-leading order (NLO). Real emission contributions are computed via Lipatov's effective action. The NLO jet vertex turns out to be finite within collinear factorization and allows, together with the NLO non-forward gluon Green's function, to perform NLO studies of jet production in diffractive events (e.g. Mueller-Tang dijets).

  15. NLO Vertex for a Forward Jet plus a Rapidity Gap at High Energies

    E-print Network

    Hentschinski, Martin; Murdaca, Beatrice; Vera, Agustín Sabio

    2014-01-01

    We present the calculation of the forward jet vertex associated to a rapidity gap (coupling of a hard pomeron to the jet) in the BFKL formalism at next-to-leading order (NLO). Real emission contributions are computed via Lipatov's effective action. The NLO jet vertex turns out to be finite within collinear factorization and allows, together with the NLO non-forward gluon Green's function, to perform NLO studies of jet production in diffractive events (e.g. Mueller-Tang dijets).

  16. Effect of oxidation on the electronic structure of a Si29 quantum dot: Calculations of redshifts in energy gap

    NASA Astrophysics Data System (ADS)

    Nishida, Masahiko

    2006-03-01

    We calculate the electronic structure of the H-covered Si29 quantum dot (~1 nm across) for four different oxygen configurations self-consistently using the extended Hückel-type nonorthogonal tight-binding method. The redshift in energy gap can occur in all oxygen configurations studied, but the size of the redshift depends on the oxygen configuration and also on the oxidation level. The energy-gap redshifts calculated for both backbonded and double-bonded oxygen configurations are large enough to explain the ones observed in the photoluminescence (PL) spectra from porous Si. For bridge-bonded and inserted oxygen configurations, the calculated redshifts are too small to explain the observed ones. The lifetimes calculated for the double-bonded oxygen configuration are around 2 ?s independent of oxidation level and photon energy. In contrary, for the backbonded oxygen configuration the calculated lifetime increases with an increasing level of oxidation and with decreasing photon energy (from several to a hundred micro seconds), being on the same order of magnitude as lifetimes measured for PL in porous Si.

  17. Mechanical Design of a High Energy Beam Absorber for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab

    SciTech Connect

    Baffes, C.; Church, M.; Leibfritz, J.; Oplt, S.; Rakhno, I.; /Fermilab

    2012-05-10

    A high energy beam absorber has been built for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. In the facility's initial configuration, an electron beam will be accelerated through 3 TTF-type or ILC-type SRF cryomodules to an energy of 750MeV. The electron beam will be directed to one of multiple downstream experimental and diagnostic beam lines and then deposited in one of two beam absorbers. The facility is designed to accommodate up to 6 cryomodules, which would produce a 75kW beam at 1.5GeV; this is the driving design condition for the beam absorbers. The beam absorbers consist of water-cooled graphite, aluminum and copper layers contained in a helium-filled enclosure. This paper describes the mechanical implementation of the beam absorbers, with a focus on thermal design and analysis. The potential for radiation-induced degradation of the graphite is discussed.

  18. The Cost of Superconducting Magnets as a Function of Stored Energy and Design Magnetic Induction Times the Field Volume

    SciTech Connect

    Green, Mike; Green, M.A.; Strauss, B.P.

    2007-08-27

    By various theorems one can relate the capital cost of superconducting magnets to the magnetic energy stored within that magnet. This is particularly true for magnet where the cost is dominated by the structure needed to carry the magnetic forces. One can also relate the cost of the magnet to the product of the magnetic induction and the field volume. The relationship used to estimate the cost the magnet is a function of the type of magnet it is. This paper updates the cost functions given in two papers that were published in the early 1990 s. The costs (escalated to 2007 dollars) of large numbers of LTS magnets are plotted against stored energy and magnetic field time field volume. Escalated costs for magnets built since the early 1990 s are added to the plots.

  19. Absence of a {open_quote}{open_quote}Threshold Effect{close_quote}{close_quote} in the Energy Loss of Slow Protons Traversing Large-Band-Gap Insulators

    Microsoft Academic Search

    K. Eder; D. Semrad; P. Bauer; R. Golser; P. Maier-Komor; F. Aumayr; M. Penalba; A. Arnau; J. M. Ugalde; P. M. Echenique

    1997-01-01

    The electronic stopping cross section {var_epsilon} of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV. Even at velocities as low as vâ\\/3 (vâ=c\\/137) , we find no influence of the band gap on the velocity dependence of {var_epsilon} , contrary to the case of gaseous targets with similar minimum excitation energy. The magnitude

  20. Restoration of the derivative discontinuity in Kohn-Sham density functional theory: an efficient scheme for energy gap correction.

    PubMed

    Chai, Jeng-Da; Chen, Po-Ta

    2013-01-18

    From the perspective of perturbation theory, we propose a systematic procedure for the evaluation of the derivative discontinuity (DD) of the exchange-correlation energy functional in Kohn-Sham (KS) density functional theory, wherein the exact DD can in principle be obtained by summing up all the perturbation corrections to infinite order. Truncation of the perturbation series at low order yields an efficient scheme for obtaining the approximate DD. While the zeroth-order theory yields a vanishing DD, the first-order correction to the DD can be expressed as an explicit universal functional of the ground-state density and the KS lowest unoccupied molecular orbital density, allowing the direct evaluation of the DD in the standard KS method without extra computational cost. The fundamental gap can be predicted by adding the estimated DD to the KS gap. This scheme is shown to be accurate in the prediction of the fundamental gaps for a wide variety of atoms and molecules. PMID:23373919

  1. Color Superconductivity in High Density Effective Theory

    E-print Network

    Deog Ki Hong

    2000-03-22

    In this talk, I discuss the recent development in color superconductivity in terms of effective field theory. By investigating the Cooper pair gap equations at high density, we see that the effective theory simplifies the gap analysis very much, especially in finding the ground state, the precise form of the gap, and the critical temperature. Furthermore, the effective theory enables us to estimate the critical density for color superconductivity, which is found to be around $230~{\\rm MeV}$ in the hard-dense-loop approximation. Finally, I briefly mention the low-lying spectra of color superconductor at high density.

  2. Coexistence of the spini-density-wave and superconductivity in the Ba1-xKxFe2As2

    SciTech Connect

    Bao, Wei [Los Alamos National Laboratory; Chen, H [HEFEI NAT. LAB; Ren, Y [ANL; Qiu, Y [NIST CENTER FOR NEUTRON; Liu, R [HEFEI NAT. LAB.; Wu, G H [HEFEI NAT. LAB; Wu, T [HEFEI NAT. LAB.; Xie, Y L [HEFEI NAT. LAB; Wang, F [HEFEI NAT. LAB.; Huang, Q [NIST CENTER FOR NEUTRON; Chen, X H [HEFEI NAT. LAB

    2008-01-01

    The relation between the spin-density-wave (SDW) and superconducting order is a central topic in current research on the FeAs-based high T{sub c} superconductors. Conflicting results exist in the LaFeAs(O,F)-class of materials, for which whether the SDW and superconductivity are mutually exclusive or they can coexist has not been settled. Here we show that for the (Ba,K)Fe{sub 2}As{sub 2} system, the SDW and superconductivity can coexist in an extended range of compositions. The availability of single crystalline samples and high value of the energy gaps would make the materials a model system to investigate the high T{sub c} ferropnictide superconductivity.

  3. Color superconductivity with determinant interaction in strange quark matter

    E-print Network

    Amruta Mishra; Hiranmaya Mishra

    2006-08-28

    We investigate the effect of six fermion determinant interaction on color superconductivity as well as on chiral symmetry breaking. Coupled mass gap equations and the superconducting gap equation are derived through the minimisation of the thermodynamic potential. The effect of nonzero quark -- antiquark condensates on the superconducting gap is derived. This becomes particularly relevant for the case of 2-flavor superconducting matter with unpaired strange quarks in the diquark channel. While the effect of six fermion interaction leads to an enhancement of u-d superconductivity, due to nonvanishing strange quark--antiquark condensates, such an enhancement will be absent at higher densities for u-s or d-s superconductivity due to early (almost) vanishing of light quark-- antiquark condensates.

  4. Suppression of activation energy and superconductivity by the addition of Al2O3 nanoparticles in CuTl-1223 matrix

    NASA Astrophysics Data System (ADS)

    Jabbar, Abdul; Qasim, Irfan; Mumtaz, M.; Zubair, M.; Nadeem, K.; Khurram, A. A.

    2014-05-01

    Low anisotropic (Cu0.5Tl0.5)Ba2Ca2Cu3O10-? (CuTl-1223) high Tc superconducting matrix was synthesized by solid-state reaction and Al2O3 nanoparticles were prepared separately by co-precipitation method. Al2O3 nanoparticles were added with different concentrations during the final sintering cycle of CuTl-1223 superconducting matrix to get the required (Al2O3)y/CuTl-1223, y = 0.0, 0.5, 0.7, 1.0, and 1.5 wt. %, composites. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray, and dc-resistivity (?) measurements. The activation energy and superconductivity were suppressed with increasing concentration of Al2O3 nanoparticles in (CuTl-1223) matrix. The XRD analysis showed that the addition of Al2O3 nanoparticles did not affect the crystal structure of the parent CuTl-1223 superconducting phase. The suppression of activation energy and superconducting properties is most probably due to weak flux pinning in the samples. The possible reason of weak flux pinning is reduction of weak links and enhanced inter-grain coupling due to the presence of Al2O3 nanoparticles at the grain boundaries. The presence of Al2O3 nanoparticles at the grain boundaries possibly reduced the number of flux pinning centers, which were present in the form of weak links in the pure CuTl-1223 superconducting matrix. The increase in the values of inter-grain coupling (?) deduced from the fluctuation induced conductivity analysis with the increased concentration of Al2O3 nanoparticles is a theoretical evidence of improved inter-grain coupling.

  5. Superconducting Microelectronics.

    ERIC Educational Resources Information Center

    Henry, Richard W.

    1984-01-01

    Discusses superconducting microelectronics based on the Josephson effect and its advantages over conventional integrated circuits in speed and sensitivity. Considers present uses in standards laboratories (voltage) and in measuring weak magnetic fields. Also considers future applications in superfast computer circuitry using Superconducting

  6. The next-to-leading order vertex for a forward jet plus a rapidity gap at high energies

    E-print Network

    Hentschinski, M.; Murdaca, B.; Vera, A. Sabio

    2014-01-01

    We present the results for the calculation of the forward jet vertex associated to a rapidity gap (coupling of a hard pomeron to the jet) in the Balitsky-Fadin-Kuraev-Lipatov (BFKL) formalism at next-to-leading order (NLO). We handle the real emission contributions making use of the high energy effective action proposed by Lipatov, valid for multi-Regge and quasi-multi-Regge kinematics. This result is important since it allows, together with the NLO non-forward gluon Green function, to perform NLO studies of jet production in diffractive events (Mueller-Tang dijets, as a well-known example).

  7. HOM damping properties of fundamental power couplers in the superconducting electron gun of the energy recovery LINAC at Brookhaven National Laboratory

    SciTech Connect

    Hammons, L.; Hahn, H.

    2011-03-28

    Among the accelerator projects under construction at the Relativistic Heavy Ion Collider (RHIC) is an R and D energy recovery LINAC (ERL) test facility. The ERL includes both a five-cell superconducting cavity as well as a superconducting, photoinjector electron gun. Because of the high-charge and high-current demands, effective higher-order mode (HOM) damping is essential, and several strategies are being pursued. Among these is the use of the fundamental power couplers as a means for damping some HOMs. Simulation studies have shown that the power couplers can play a substantial role in damping certain HOMs, and this presentation discusses these studies along with measurements.

  8. Direct Evidence for Cage Conduction Band in Superconducting Cement 12CaO\\cdot7Al2O3 by Low-Energy High-Resolution Photoemission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Souma, Seigo; Arakane, Toshiyuki; Sato, Takafumi; Takahashi, Takashi; Kim, Sung Wng; Matsuishi, Satoru; Hosono, Hideo

    2010-10-01

    We have performed low-energy high-resolution photoemission spectroscopy of a superconducting cement 12CaO\\cdot7Al2O3 (C12A7). By using the bulk-sensitive xenon-plasma light, we clearly observed a small but well-defined peak at the Fermi level (EF). Comparison with the band calculations suggests that the observed near-EF peak is ascribed to the conduction electrons distributed over the crystal cages responsible for the metallic nature and superconductivity of C12A7.

  9. Modeling and simulation of energy-removal system for superconducting magnets

    SciTech Connect

    Bailey, J.M.; Googe, J.M.; Wood, R.J.

    1983-01-01

    The Large Coil Test Facility at the Oak Ridge National Laboratory employs six D shaped superconducting coils. The coil current ranges from 10 to 20 kA. The protection scheme of these coils requires the coil current to be interrupted. This interruption will generate high-voltage transients in the coil. To prevent destruction of the coil isolation, these transients have to be reduced. Two types of suppressor networks, one a varistor and the other an R-C network, were reviewed. Then each suppressor circuit was simulated to determine the effectiveness of each suppressor. The modelling used the Super Sceptre computer program to simulate these transients.

  10. Superconducting structure

    DOEpatents

    Kwon, Chuhee (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM); Foltyn, Stephen R. (Los Alamos, NM)

    2003-04-01

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  11. Superconducting Structure

    DOEpatents

    Kwon, Chuhee (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM); Foltyn, Stephen R. (Los Alamos, NM)

    2005-09-13

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  12. Superconducting terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong [Los Alamos National Laboratory; Singh, Ranjan [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Azad, Abul K [Los Alamos National Laboratory; Trugman, Stuart A [Los Alamos National Laboratory; Jia, Quanxi [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory

    2010-01-01

    During the past ten years subwavelength metallic structures have enabled metamaterials exhibiting exotic physical properties that are not possible or difficult to realize using naturally occurring materials, This bottom-up metamaterial approach is particularly attractive in the terahertz (THz) frequency range, where the THz gap is inherently associated with the lack of materials with appropriate reponse. In fact THz metamaterial devices have accomplished unprecedented performance towards practical applications. In these devices, the key is to incorporate natural materials, e,g, semiconductors, as the metamaterial substrates or integration parts of metamaterial structures. The active or dynamic tunability of metamaterials is through the application of external stimuli such as temperature, photoexcitation, or electric field. to modify the capacitive gaps in split-ring resonators (SRRs), It becomes clear that we would not be able to do much on the metallic SRRs, i.e. the metal conductivity and therefore the inductance largely remain constant not affected by external stimuli. Recently, there has been increasing interest in superconducting metamaterials towards loss reduction. Significant Joule losses have often prevented resonant metal metamaterials from achieving proposed applications. particularly in the optical frequency range. At low temperatures, superconducting materials possess superior conductivity than metals at frequencies up to THz. and therefore it is expected that superconducting melamaterials will have a lower loss than metal metamatetials, More interestingly, superconductors exhibit tunable complex conductivity over a wide range of values through change of temperature and application of photoexcitation, electrical currents and magnetic fields. Therefore, we would expect correspondingly tunable metamaterials. which originate from the superconducting materials composing the metamaterial, in contrast to tuning the metamaterial embedded environment.

  13. Prototype of the accelerating resonator for the superconducting sector deuteron cyclotron

    Microsoft Academic Search

    N. V. Vasiliev; A. A. Glazov; E. N. Zaplatin; V. A. Kochkin; D. L. Novikov

    1991-01-01

    A full-scale prototype of the accelerating cavity for the superconducting deuteron sector cyclotron at the energy of 100 MeV is described. The fundamental frequency and the distribution of the radio frequency voltage along the accelerating gap were calculated by the RFC3D program for computing 3D components of the electromagnetic field. The RF measurements proved the validity of the calculations with

  14. Long distance renewable-energy-sources power transmission using hydrogen-cooled MgB 2 superconducting line

    NASA Astrophysics Data System (ADS)

    Trevisani, L.; Fabbri, M.; Negrini, F.

    2007-02-01

    Renewable Energy Sources (RES) exploitation for electric energy and hydrogen production has been identified as one of the leading ways towards a future sustainable energy system. Hydrogen can be stored and transported in gaseous (GH 2) or liquid form (LH 2). When large hydrogen storage is required, liquefaction can be convenient with respect to compression, because of its higher storage density. LH 2 can also be used as a coolant for superconducting lines, acting at the same time as energy vector and cryogen. In particular, in this paper we focus on the MgB 2 material mainly due to economic considerations and working temperature match with LH 2. A system for large scale RES exploitation allowing flexible and controlled delivery of electric energy and LH 2 is presented. For the thermo-hydraulic design, a method is proposed which resorts to compressible fluid equations put in a convenient simplified form. A case application with 20 km distance between cooling stations is considered, and the need of taking into account LH 2 compressibility for pipeline design is shown.

  15. Superconducting magnet development in Japan

    SciTech Connect

    Yasukochi, K.

    1983-05-01

    The present state of R and D works on the superconducting magnet and its applications in Japan are presented. On electrical rotating machines, 30 MVA superconducting synchronous rotary condenser (Mitsubishi and Fuji) and 50 MVA generator are under construction. Two ways of ship propulsion by superconducting magnets are developing. A superconducting magnetically levitated and linear motor propelled train ''MAGLEV'' was developed by the Japan National Railways (JNR). The superconducting magnet development for fusion is the most active field in Japan. The Cluster Test program has been demonstrated on a 10 T Nb/sub 3/Sn coil and the first coil of Large Coil Task in IEA collaboration has been constructed and the domestic test was completed in JAERI. These works are for the development of toroidal coils of the next generation tokamak machine. R and D works on superconducting ohmic heating coil are in progress in JAERI and ETL. The latter group has constructed 3.8 MJ pulsed coil. A high ramp rate of changing field in pulsed magnet, 200 T/s, has been tested successfully. High Energy Physics Laboratory (KEK) are conducting active works. The superconducting ..mu.. meson channel and ..pi.. meson channel have been constructed and are operating successfully. KEK has also a project of big accelerator named ''TRISTAN'', which is similar to ISABELLE project of BNL. Superconducting synchrotron magnets are developed for this project. The development of superconducting three thin wall solenoid has been started. One of them, CDF, is progressing under USA-Japan collaboration.

  16. Attenuation in Superconducting Rectangular Waveguides

    NASA Astrophysics Data System (ADS)

    Yeap, Kim Ho; Mei Teh, Joyce Shu; Nisar, Humaira; Yeong, Kee Choon; Hirasawa, Kazuhiro

    2015-03-01

    We present an accurate analysis on the attenuation of waves, propagating in rectangular waveguides with superconducting walls. The wavenumbers kx and ky in the x and y directions, respectively, are first obtained as roots of a set of transcendental equations developed by matching the tangential fields at the surface of the wall with the electrical properties of the wall material. The complex conductivity of the superconducting waveguide is obtained from the extended Mattis-Bardeen theory. The propagation constant kz is found by substituting the values of kx and ky into the dispersion relation. We have computed and compared the loss in the waveguides below and above the critical temperature. At frequencies above the cutoff frequency fc but below the gap frequency fg, the loss in the superconducting waveguide is significantly lower than that in a normal conducting waveguide. Above the gap frequency, however, the result indicates that the attenuation in the waveguide below the critical temperature is higher than that at room temperature. We attribute the higher loss as due to the higher surface resistance and field penetration for superconducting waveguides operating above the gap frequency.

  17. Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius

    E-print Network

    Lacomba-Perales, R; Errandonea, D; Martinez-Garcia, D; Segura, A

    2008-01-01

    We have carried out optical-absorption and reflectance measurements at room temperature in single crystals of AWO4 tungstates (A = Ba, Ca, Cd, Cu, Pb, Sr, and Zn). From the experimental results their band-gap energy has been determined to be 5.26 eV (BaWO4), 5.08 eV (SrWO4), 4.94 eV (CaWO4), 4.15 eV (CdWO4), 3.9-4.4 eV (ZnWO4), 3.8-4.2 eV (PbWO4), and 2.3 eV (CuWO4). The results are discussed in terms of the electronic structure of the studied tungstates. It has been found that those compounds where only the s electron states of the A2+ cation hybridize with the O 2p and W 5d states (e.g BaWO4) have larger band-gap energies than those where also p, d, and f states of the A2+ cation contribute to the top of the valence band and the bottom of the conduction band (e.g. PbWO4). The results are of importance in view of the large discrepancies existent in prevoiusly published data.

  18. Superconducting accelerating structures for very low velocity ion beams.

    SciTech Connect

    Xu, J.; Shepard, K. W.; Ostroumov, P. N.; Fuerst, J. D.; Waldschmidt, G.; Gonin, I. V.; FNAL

    2008-03-01

    This paper presents designs for four types of very-low-velocity superconducting (SC) accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006Superconducting TEM-class cavities have been widely applied to cw acceleration of ion beams. SC linacs can be formed as an array of independently phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the U.S. and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front end of such linacs, particularly for the postacceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008<{beta}=v/c<0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication, and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

  19. Superconducting accelerating structures for very low velocity ion beams

    NASA Astrophysics Data System (ADS)

    Xu, J.; Shepard, K. W.; Ostroumov, P. N.; Fuerst, J. D.; Waldschmidt, G.; Gonin, I. V.

    2008-03-01

    This paper presents designs for four types of very-low-velocity superconducting (SC) accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006Superconducting TEM-class cavities have been widely applied to cw acceleration of ion beams. SC linacs can be formed as an array of independently phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the U.S. and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front end of such linacs, particularly for the postacceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

  20. Superconducting accelerating structures for very low velocity ion beams

    SciTech Connect

    Xu, J.; Shepard, K.W.; Ostroumov, P.N.; Fuerst, J.D.; Waldschmidt, G.; /Argonne; Gonin, I.V.; /Fermilab

    2008-01-01

    This paper presents designs for four types of very-low-velocity superconducting accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006 < v/c < 0.06. Superconducting TEM-class cavities have been widely applied to CW acceleration of ion beams. SC linacs can be formed as an array of independently-phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the US and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front-end of such linacs, particularly for the post-acceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008 < {beta} = v/c < 0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

  1. Investigation of Nonequilibrium Superconductivity Using Terahertz Pulse Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cooke, David; Hegmann, Frank A.

    2003-03-01

    The nonequilibrium response of both conventional and high-Tc superconductors is investigated using terahertz pulse spectroscopy. This technique has gained popularity in recent years and is now widely accepted as a useful spectroscopic tool for examining carrier dynamics of materials. A near single-cycle, picosecond width electromagnetic transient centered in the THz region is used as the probe in a typical pump-probe fashion along with an optical pump pulse. This THz pulse is ideal for the measurement of superconducting systems, being on the same energy scale as the gap. The time resolved response of various samples after optical excitation by a femtosecond laser pulse is reported as a function of pump fluence and temperature. Linear spectroscopy will also be used, where the ratio of the transmission coefficient in the superconducting state to that in the normal state Ts/Tn is used to monitor the superconducting gap in conventional samples. *We acknowledge financial support from NSERC, CFI, iCORE and CIPI.

  2. Superconductivity from repulsion in LiFeAs: Novel s-wave symmetry and potential time-reversal symmetry breaking

    NASA Astrophysics Data System (ADS)

    Ahn, F.; Eremin, I.; Knolle, J.; Zabolotnyy, V. B.; Borisenko, S. V.; Büchner, B.; Chubukov, A. V.

    2014-04-01

    We analyze the structure of the pairing interaction and superconducting gap in LiFeAs by decomposing the pairing interaction for various kz cuts into s- and d-wave components and by studying the leading superconducting instabilities. We use the ten-orbital tight-binding model, derived from ab initio LDA calculations with hopping parameters extracted from the fit to ARPES experiments. We find that the pairing interaction almost decouples between two subsets; one consists of the outer hole pocket and two electron pockets, which are quasi-2D and are made largely out of the dxy orbital, and the other consists of the two inner hole pockets, which are quasi-3D and are made mostly out of dxz and dyz orbitals. Furthermore, the bare interpocket and intrapocket interactions within each subset are nearly equal. In this situation, small changes in the intrapocket and interpocket interactions due to renormalizations by high-energy fermions give rise to a variety of different gap structures. We focus on s-wave pairing which, as experiments show, is the most likely pairing symmetry in LiFeAs. We find four different configurations of the s-wave gap immediately below Tc: one in which the superconducting gap changes sign between two inner hole pockets and between the outer hole pocket and two electron pockets, one in which the gap changes sign between two electron pockets and three hole pockets, one in which the gap on the outer hole pocket differs in sign from the gaps on the other four pockets, and one in which the gaps on two inner hole pockets have one sign and the gaps on the outer hole pockets and on electron pockets have different sign. Different s-wave gap configurations emerge depending on whether the renormalized interactions increase attraction within each subset or increase the coupling between particular components of the two subsets. We discuss the phase diagram and experimental probes to determine the structure of the superconducting gap in LiFeAs. We argue that the state with opposite sign of the gaps on the two inner hole pockets has the best overlap with ARPES data. We also argue that at low T, the system may enter into a "mixed" s +is state, in which the phases of the gaps on different pockets differ by less than ? and time-reversal symmetry is spontaneously broken.

  3. Hard-gapped Holographic Superconductors

    E-print Network

    Pallab Basu; Jianyang He; Anindya Mukherjee; Hsien-Hang Shieh

    2009-12-05

    In this work we discuss the zero temperature limit of a "p-wave" holographic superconductor. The bulk description consists of a non-Abelian SU(2) gauge fields minimally coupled to gravity. We numerically construct the zero temperature solution which is the gravity dual of the superconducting ground state of the "p-wave" holographic superconductors. The solution is a smooth soliton with zero horizon size and shows an emergent conformal symmetry in the IR. We found the expected superconducting behavior. Using the near horizon analysis we show that the system has a "hard gap" for the relevant gauge field fluctuations. At zero temperature the real part of the conductivity is zero for an excitation frequency less than the gap frequency. This is in contrast with what has been observed in similar scalar- gravity-gauge systems (holographic superconductors). We also discuss the low but finite temperature behavior of our solution.

  4. Method for obtaining large levitation pressure in superconducting magnetic bearings

    DOEpatents

    Hull, John R. (Hinsdale, IL)

    1997-01-01

    A method and apparatus for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap.

  5. Method for obtaining large levitation pressure in superconducting magnetic bearings

    DOEpatents

    Hull, John R. (Hinsdale, IL)

    1996-01-01

    A method and apparatus for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap.

  6. Method for obtaining large levitation pressure in superconducting magnetic bearings

    DOEpatents

    Hull, J.R.

    1997-08-05

    A method and apparatus are disclosed for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap. 4 figs.

  7. Superconducting materials

    NASA Astrophysics Data System (ADS)

    Baron, V. V.

    The papers contained in this volume deal with the structure and properties of superconducting compounds and alloys, methods of their production, and principal applications of superconducting materials. Particular attention is given to superconductors based on phases of the A15 type. Ways to increase the critical temperature and the critical current of this group of materials are discussed. Another type of superconducting compounds discussed is molybdenum trisulfides and Laves phases. Alloys based on solid solutions and pure metals are also discussed, with particular reference to niobium-titanium and lead alloys. No individual items are abstracted in this volume

  8. Temperature dependence of the optical energy band gap in CuIn3Se5 and CuGa3Se5

    NASA Astrophysics Data System (ADS)

    Rincón, C.; Wasim, S. M.; Marín, G.; Molina, I.

    2003-01-01

    The temperature dependence of the optical band gap EG in bulk crystals of CuIn3Se5 and CuGa3Se5 has been analyzed by separately considering the contributions due to electron-phonon interaction and thermal expansion. For the former contribution, we use an expression related to the mean frequency of phonons, defined by a temperature ?, that participate in the shift of the fundamental energy gap with temperature. For the latter, a term that explicitly takes into account the temperature variation of the thermal expansion coefficient and the pressure dependence of the band gap is employed.

  9. Hard gap in epitaxial semiconductor–superconductor nanowires

    NASA Astrophysics Data System (ADS)

    Chang, W.; Albrecht, S. M.; Jespersen, T. S.; Kuemmeth, F.; Krogstrup, P.; Nygård, J.; Marcus, C. M.

    2015-03-01

    Many present and future applications of superconductivity would benefit from electrostatic control of carrier density and tunnelling rates, the hallmark of semiconductor devices. One particularly exciting application is the realization of topological superconductivity as a basis for quantum information processing. Proposals in this direction based on the proximity effect in semiconductor nanowires are appealing because the key ingredients are currently in hand. However, previous instances of proximitized semiconductors show significant tunnelling conductance below the superconducting gap, suggesting a continuum of subgap states—a situation that nullifies topological protection. Here, we report a hard superconducting gap induced by the proximity effect in a semiconductor, using epitaxial InAs–Al semiconductor–superconductor nanowires. The hard gap, together with favourable material properties and gate-tunability, makes this new hybrid system attractive for a number of applications, as well as fundamental studies of mesoscopic superconductivity.

  10. Hard gap in epitaxial semiconductor-superconductor nanowires.

    PubMed

    Chang, W; Albrecht, S M; Jespersen, T S; Kuemmeth, F; Krogstrup, P; Nygård, J; Marcus, C M

    2015-03-01

    Many present and future applications of superconductivity would benefit from electrostatic control of carrier density and tunnelling rates, the hallmark of semiconductor devices. One particularly exciting application is the realization of topological superconductivity as a basis for quantum information processing. Proposals in this direction based on the proximity effect in semiconductor nanowires are appealing because the key ingredients are currently in hand. However, previous instances of proximitized semiconductors show significant tunnelling conductance below the superconducting gap, suggesting a continuum of subgap states-a situation that nullifies topological protection. Here, we report a hard superconducting gap induced by the proximity effect in a semiconductor, using epitaxial InAs-Al semiconductor-superconductor nanowires. The hard gap, together with favourable material properties and gate-tunability, makes this new hybrid system attractive for a number of applications, as well as fundamental studies of mesoscopic superconductivity. PMID:25581886

  11. Superconductivity in the Einstein solid VAl(10.1).

    PubMed

    Klimczuk, T; Szlawska, M; Kaczorowski, D; O'Brien, J R; Safarik, D J

    2012-09-12

    We used magnetic susceptibility, resistivity and heat capacity measurements to characterize the superconducting state in the Einstein solid VAl(10.1). We find that VAl(10.1) is a weak-coupling, type-II superconductor with T(c) = 1.53 K and an upper critical field of H(c2)(0) = 800 Oe. The heat capacity data in the range 0.07 K < T < 1.53 K are consistent with an isotropic energy gap of ?(0) = 0.23 meV. PMID:22892873

  12. Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide

    NASA Technical Reports Server (NTRS)

    Patterson, James D.; Li, Wei-Gang

    1995-01-01

    The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

  13. Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit

    NASA Astrophysics Data System (ADS)

    Löptien, P.; Zhou, L.; Khajetoorians, A. A.; Wiebe, J.; Wiesendanger, R.

    2014-10-01

    The thickness dependence of the superconducting energy gap ?La of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ?La and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

  14. Effect of disorder on superconductivity in the presence of spin-density wave order

    NASA Astrophysics Data System (ADS)

    Mishra, Vivek

    2015-03-01

    The majority of unconventional superconductors has close proximity to a magnetic phase. In many cases, the magnetic phase coexists with superconductivity in some fraction of the phase diagram. The response of these two competing phases to disorder can be used as a tool to gain a better understanding of these complex systems. Here I consider the effect of disorder on a multiband superconductor appropriate for the ferro-pnictide superconductors. I consider both interband and intraband scattering for a two-band model consisting of a hole pocket and an electron pocket. The scattering from pointlike impurities is treated within the self-consistent Born approximation. I calculate the effect of disorder on the transition temperature to the superconducting state. The influence of impurity scattering on the low-energy excitation spectrum in the superconducting state is also studied for different kinds of gap structures.

  15. Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit.

    PubMed

    Löptien, P; Zhou, L; Khajetoorians, A A; Wiebe, J; Wiesendanger, R

    2014-10-22

    The thickness dependence of the superconducting energy gap ?La of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ?La and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here. PMID:25272968

  16. Modulating Sub-THz Radiation with Current in Superconducting Metamaterial

    NASA Astrophysics Data System (ADS)

    Savinov, V.; Fedotov, V. A.; Anlage, S. M.; de Groot, P. A. J.; Zheludev, N. I.

    2012-12-01

    We show that subterahertz transmission of the superconducting metamaterial, an interlinked two-dimensional network of subwavelength resonators connected by a continuous superconducting wire loop, can be dynamically modulated by passing electrical current through it. We have identified the main mechanisms of modulation that correspond to the suppression of the superconductivity in the network by magnetic field and heat dissipation. Using the metamaterial fabricated from thin niobium film, we were able to demonstrate a transmission modulation depth of up to 45% and a bandwidth of at least 100 kHz. The demonstrated approach may be implemented with other superconducting materials at frequencies below the superconducting gap in the THz and subterahertz bands.

  17. Evidence of multiband superconductivity in the ?-phase Mo1-xRex alloys.

    PubMed

    Sundar, Shyam; Sharath Chandra, L S; Chattopadhyay, M K; Roy, S B

    2015-02-01

    We present a detailed study of the superconducting properties in the ?-phase Mo(1-x)Re(x) (x = 0.25 and 0.4) solid solution alloys pursued through magnetization and heat capacity measurements. The temperature dependence of the upper critical field H(C2)(T) in these binary alloys shows a deviation from the prediction of the Werthamer-Helfand-Hohenberg (WHH) theory. The temperature dependence of superfluid density estimated from the variation of lower critical field H(C1) with temperature, cannot be explained within the framework of a single superconducting energy gap. The heat capacity also shows an anomalous feature in its temperature dependence. All these results can be reasonably explained by considering the existence of two superconducting energy gaps in these Mo(1-x)Re(x) alloys. Initial results of electronic structure calculations and resonant photoelectron spectroscopy measurements support this possibility and suggest that the Re-5d like states at the Fermi level may not intermix with the Mo-5p and 5s like states in the ?-phase Mo(1-x)Re(x) alloys and contribute quite distinctly to the superconductivity of these alloys. PMID:25563211

  18. Study of the superconducting phase in silicene under biaxial tensile strain

    NASA Astrophysics Data System (ADS)

    Durajski, A. P.; Szcz??niak, D.; Szcz??niak, R.

    2014-12-01

    The electron-doped silicene under the influence of the biaxial tensile strain is predicted to be the phonon-mediated superconductor. By using the Eliashberg formalism, we investigate the thermodynamic properties of the superconducting silicene in the case when the tension is 5% and the electron doping equals 3.5×1014 cm-2. Under such conditions, silicene monolayer is expected to exhibit the highest superconducting transition temperature (TC). In particular, based on the electron-phonon spectral function and assuming a wide range of the Coulomb pseudopotential values (???<0.1,0.3>) it is stated that the superconducting transition temperature decreases from 18.7 K to 11.6 K. Similar behavior is observed in the case of the zeroth temperature superconducting energy gap at the Fermi level: 2?(0)?<6.68,3.88> meV. Other thermodynamic parameters differ from the predictions of the Bardeen-Cooper-Schrieffer theory. In particular, the ratio of the energy gap to the critical temperature changes in the range from 4.14 to 3.87. The ratio of the specific heat jump to the specific heat in the normal state takes the values from 2.19 to 2.05, and the ratio of the critical temperature and specific heat in the normal state to the thermodynamic critical field increases from 0.143 to 0.155. It is also determined that the maximum value of the electron effective mass equals 2.11 of the electron band mass.

  19. Evidence of multiband superconductivity in the ?-phase Mo1?xRex alloys

    NASA Astrophysics Data System (ADS)

    Sundar, Shyam; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Roy, S. B.

    2015-02-01

    We present a detailed study of the superconducting properties in the ?-phase Mo1?xRex (x = 0.25 and 0.4) solid solution alloys pursued through magnetization and heat capacity measurements. The temperature dependence of the upper critical field HC2(T) in these binary alloys shows a deviation from the prediction of the Werthamer–Helfand–Hohenberg (WHH) theory. The temperature dependence of superfluid density estimated from the variation of lower critical field HC1 with temperature, cannot be explained within the framework of a single superconducting energy gap. The heat capacity also shows an anomalous feature in its temperature dependence. All these results can be reasonably explained by considering the existence of two superconducting energy gaps in these Mo1?xRex alloys. Initial results of electronic structure calculations and resonant photoelectron spectroscopy measurements support this possibility and suggest that the Re-5d like states at the Fermi level may not intermix with the Mo-5p and 5s like states in the ?-phase Mo1?xRex alloys and contribute quite distinctly to the superconductivity of these alloys.

  20. Aspects of Color Superconductivity

    E-print Network

    Deog Ki Hong

    2001-01-03

    I discuss some aspects of recent developments in color superconductivity in high density quark matter. I calculate the Cooper pair gap and the critical points at high density, where magnetic gluons are not screened. The ground state of high density QCD with three light flavors is shown to be a color-flavor locking state, which can be mapped into the low-density hadronic phase. The meson mass at the CFL superconductor is also calculated. The CFL color superconductor is bosonized, where the Fermi sea is identified as a $Q$-matter and the gapped quarks as topological excitations, called superqualitons, of mesons. Finally, as an application of color supercoductivity, I discuss the neutrino interactions in the CFL color superconductor.

  1. Superconducting cosmic strings

    NASA Astrophysics Data System (ADS)

    Sabancilar, Eray

    2013-10-01

    Superconducting cosmic strings produce a variety of effects, such as spectral distortion of the cosmic microwave background (CMB), early reionization, linearly polarized radio transients and ultra high energy cosmic ray bursts, in addition to the well known gravitational wave signals and CMB anisotropies. I will argue that these effects can be seen in the CMB distortion (PIXIE), radio transient experiments (LOFAR, SKA) and at the future neutrino telescopes (JEM-EUSO, LOFAR, SKA), and can be complimentary to the gravitational wave experiments (LIGO, eLISA) and CMB anisotropy observations. If none of these effects are seen within a few years, very stringent constraints can be put on superconducting cosmic strings.

  2. Effect of surface viscosity, anchoring energy, and cell gap on the response time of nematic liquid crystals

    SciTech Connect

    Souza, R.F. de [Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo 5790, 87020 - 900 Maringá –PR (Brazil); Yang, D.-Ke [Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH 44242 (United States); Lenzi, E.K.; Evangelista, L.R. [Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo 5790, 87020 - 900 Maringá –PR (Brazil); Zola, R.S., E-mail: rzola@utfpr.edu.br [Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo 5790, 87020 - 900 Maringá –PR (Brazil); Universidade Tecnologica Federal do Paraná, Rua Marcilio Dias 635, 86812-460 Apucarana, Paraná (Brazil)

    2014-07-15

    An analytical expression for the relaxation time of a nematic liquid crystal is obtained for the first time by considering the influence of surface viscosity, anchoring energy strength and cell gap, validated numerically by using the so-called relaxation method. This general equation for the molecular response time (?{sub 0}) was derived for a vertical aligned cell and by solving an eigenvalue equation coming from the usual balance of torque equation in the Derzhanskii and Petrov formulation, recovering the usual equations in the appropriate limit. The results show that ??d{sup b}, where b=2 is observed only for strongly anchored cells, while for moderate to weak anchored cells, the exponent lies between 1 and 2, depending on both, surface viscosity and anchoring strength. We found that the surface viscosity is important when calculating the response time, specially for thin cells, critical for liquid crystal devices. The surface viscosity’s effect on the optical response time with pretilt is also explored. Our results bring new insights about the role of surface viscosity and its effects in applied physics. - Highlights: • The relaxation of nematic liquid crystals is calculated by taking the surface viscosity into account. • An analytical expression for the relaxation time depending on surface viscosity, anchoring strength and cell gap is obtained. • The results are numerically verified. • Surface viscosity is crucial for thin and weak anchored cells. • The effect on optical time and pretilt angle is also studied.

  3. Introducing the prebound effect: the gap between performance and actual energy consumption

    Microsoft Academic Search

    Minna Sunikka-Blank; Ray Galvin

    2012-01-01

    German regulations for the thermal renovation of existing homes demand high thermal standards, which the government claims are technically and economically feasible. This paper examines existing data on 3400 German homes; their calculated energy performance ratings (EPR) are then plotted against the actual measured consumption. The results indicate that occupants consume, on average, 30% less heating energy than the calculated

  4. Pairing gaps and Fermi energies at scission for 296Lv alpha-decay

    E-print Network

    M. Mirea

    2014-11-12

    The pairing corrections, the single particle occupation numbers, are investigated within density-dependent delta interaction formalism for pairing residual interactions. The potential barrier is computed in the framework of the macroscopic-microscopic model. The microscopic part is based on the Woods-Saxon two center shell model. The alpha-decay of a superheavy element is treated, by paying a special attention to the region of the scission configurations. The sequence of nuclear shapes follows the superasymmetric fission path for alpha decay. It was found that the pairing gaps of the states that reach asymptotically the potential well of the alpha particle have large values at scission but become zero after scission. The 1s1/2 single particle levels of the nascent alpha particle are fully occupied while the superior levels are empties in the scission region and remains in the same states during the penetration of the Coulomb barrier. The projection of the numbers of particle on the two fragments are obtained naturally. At scission, the nascent alpha particle forms a very bound cluster.

  5. Attempting to bridge the gap between laboratory and seismic estimates of fracture energy

    USGS Publications Warehouse

    McGarr, A.; Fletcher, Joe B.; Beeler, N.M.

    2004-01-01

    To investigate the behavior of the fracture energy associated with expanding the rupture zone of an earthquake, we have used the results of a large-scale, biaxial stick-slip friction experiment to set the parameters of an equivalent dynamic rupture model. This model is determined by matching the fault slip, the static stress drop and the apparent stress. After confirming that the fracture energy associated with this model earthquake is in reasonable agreement with corresponding laboratory values, we can use it to determine fracture energies for earthquakes as functions of stress drop, rupture velocity and fault slip. If we take account of the state of stress at seismogenic depths, the model extrapolation to larger fault slips yields fracture energies that agree with independent estimates by others based on dynamic rupture models for large earthquakes. For fixed stress drop and rupture speed, the fracture energy scales linearly with fault slip.

  6. Proximity-induced superconductivity effect in a double-stranded DNA

    SciTech Connect

    Simchi, Hamidreza, E-mail: simchi@iust.ac.ir [Department of Physics, Iran University of Science and Technology, Narrmak, Tehran 16844 (Iran, Islamic Republic of); Semiconductor Technology Center, Tehran (Iran, Islamic Republic of); Esmaeilzadeh, Mahdi, E-mail: mahdi@iust.ac.ir; Mazidabadi, Hossein [Department of Physics, Iran University of Science and Technology, Narrmak, Tehran 16844 (Iran, Islamic Republic of)

    2014-02-07

    We study the proximity-induced superconductivity effect in a double-stranded DNA by solving the Bogoliubov-de Gennes equations and taking into account the effect of thermal fluctuations of the twist angle between neighboring base pairs. We show that the electron conductance is spin-dependent and the conductance of spin up (down) increases (decreases) due to the spin-orbit coupling (SOC). It is found that, for T?gap energy is temperature-independent and it decreases due to the SOC. In addition, by solving the Bogoliubov-de Gennes equations and local gap parameter equation self-consistently, we find the critical temperature at which transition to superconductivity can take place.

  7. Gap Winds

    NSDL National Science Digital Library

    2014-09-14

    This module provides a basic understanding of why gap winds occur, their typical structures, and how gap wind strength and extent are controlled by larger-scale, or synoptic, conditions. You will learn about a number of important gap flows in coastal regions around the world, with special attention given to comprehensively documented gap wind cases in the Strait of Juan de Fuca and the Columbia River Gorge. Basic techniques for evaluating and predicting gap flows are presented. The module reviews the capabilities and limitations of the current generation of mesoscale models in producing realistic gap winds. By the end of this module, you should have sufficient background to diagnose and forecast gap flows around the world, and to use this knowledge to understand their implications for operational decisions. Other features in this module include a concise summary for quick reference and a final exam to test your knowledge. Like other modules in the Mesoscale Meteorology Primer, this module comes with audio narration, rich graphics, and a companion print version.

  8. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  9. Basis Set Effects on Frontier Molecular Orbital Energies and Energy Gaps: A comparative study between plane waves and localized basis functions in molecular systems

    SciTech Connect

    Matus, Myrna H.; Garza, Jorge; Galvan, Marcelo

    2004-06-08

    In order to study the KohnSham frontier molecular orbital energies in the complete basis limit, a comparative study between localized functions and plane waves, obtained with the local density approximation exchange-correlation functional is made. The analyzed systems are ethylene and butadiene, since they are theoretical and experimentally well characterized. The localized basis sets used are those developed by Dunning. For the plane-waves method, the pseudopotential approximation is employed. The results obtained by the localized basis sets suggest that it is possible to get an estimation of the orbital energies in the limit of the complete basis set, when the basis set size is large. It is shown that the frontier molecular orbital energies and the energy gaps obtained with plane waves are similar to those obtained with a large localized basis set, when the size of the supercell and the plane-wave expansion have been appropriately calibrated.

  10. Flavor Superconductivity & Superfluidity

    E-print Network

    Matthias Kaminski

    2010-02-25

    In these lecture notes we derive a generic holographic string theory realization of a p-wave superconductor and superfluid. For this purpose we also review basic D-brane physics, gauge/gravity methods at finite temperature, key concepts of superconductivity and recent progress in distinct realizations of holographic superconductors and superfluids. Then we focus on a D3/D7-brane construction yielding a superconducting or superfluid vector-condensate. The corresponding gauge theory is 3+1-dimensional N=2 supersymmetric Yang-Mills theory with SU(N) color and SU(2) flavor symmetry. It shows a second order phase transition to a phase in which a U(1) subgroup of the SU(2) symmetry is spontaneously broken and typical superconductivity signatures emerge, such as a conductivity (pseudo-)gap and the Meissner-Ochsenfeld effect. Condensates of this nature are comparable to those recently found experimentally in p-wave superconductors such as a ruthenate compound. A string picture of the pairing mechanism and condensation is given using the exact knowledge of the corresponding field theory degrees of freedom.

  11. Gain-assisted propagation of electromagnetic energy in subwavelength surface plasmon polariton gap waveguides

    Microsoft Academic Search

    Stefan A Maier

    2006-01-01

    The propagation of electromagnetic energy via coupled surface plasmon polariton modes in a metal–insulator–metal heterostructure is analyzed analytically for a core material exhibiting optical gain. It is shown that a sufficiently large gain can completely compensate for the absorption losses due to energy dissipation in the metallic boundaries, enabling long-range transport with a confinement below the diffraction limit for on-chip

  12. Photoexcitation and Photoionization of Irradiated Large-gap Thermionic Energy Converter by Xenon Lamp

    Microsoft Academic Search

    Wei Zheng; Akihisa Ogino; Masashi Kando

    1998-01-01

    This study is concerned with low temperature operated thermionic energy converter (TEC). To reduce the negative space charge, an auxiliary discharge by photo irradiation is proposed to produce cesium ions for space charge neutralization. Cesium has not only the lowest ionization potential of 3.89eV among all materials, but also low excitation potentials about 1.4eV. Excited cesium atoms with low energy

  13. Temperature and Spatial Dependence of the Superconducting and Pseudogap of NdFeAsO0.86F0.14.

    NASA Astrophysics Data System (ADS)

    He, X. B.; Pan, M. H.; Li, G. R.; Wendelken, J. F.; Jin, R. Y.; Sefat, A. S.; McGuire, M. A.; Sales, B. C.; Mandrus, D.; Plummer, E. W.

    2009-03-01

    Scanning tunneling microscopy/spectroscopy are used to investigate the superconducting gap and pseudogap of Fe based high-Tc superconducting material NdFeAsO0.86F0.14 at various temperatures from 17 K to 150 K. The superconducting gap (SG) in the tunneling spectra follows the BCS prediction and closes at Tc of the bulk material. Surprisingly, a pseudogap (PG) opens abruptly just above Tc and closes at 120 K, strongly suggesting that the SG and PG states have competing order parameters in contrast to the cuprates. The PG state may be related to spin fluctuations in the doped materials. Research was supported in part at ORNL by Laboratory Directed Research and Development funds and by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, US DOE.

  14. Design of 57.5 MHz CW RFQ for medium energy heavy ion superconducting linac.

    SciTech Connect

    Ostroumov, P. N.; Kolomiets, A. A.; Kashinsky, D. A.; Minaev, S. A.; Pershin, V. I.; Tretyakova, T. E.; Yaramishev, S. G.; Physics; Inst. of Theoretical and Experimental Physics

    2002-06-01

    The nuclear science community considers the construction of the Rare Isotope Accelerator (RIA) facility as a top priority. The RIA includes a 1.4 GV superconducting linac for production of 400 kW cw heavy ion beams. The initial acceleration of heavy ions delivered from an electron cyclotron resonance ion source can be effectively performed by a 57.5 MHz 4-m long room temperature RFQ. The principal specifications of the RFQ are (i) formation of extremely low longitudinal emittance, (ii) stable operation over a wide range of voltage for acceleration of various ion species needed for RIA operation, and (iii) simultaneous acceleration of two-charge states of uranium ions. cw operation of an accelerating structure leads to a number of requirements for the resonators such as high shunt impedance, efficient water cooling of all parts of the resonant cavity, mechanical stability together with precise alignment, reliable rf contacts, a stable operating mode, and fine tuning of the resonant frequency during operation. To satisfy these requirements a new resonant structure has been developed. This paper discusses the beam dynamics and electrodynamics design of the RFQ cavity, as well as some aspects of the mechanical design of the low-frequency cw RFQ.

  15. Superconducting Storage Cavity for RHIC

    SciTech Connect

    Ben-Zvi,I.

    2009-01-02

    This document provides a top-level description of a superconducting cavity designed to store hadron beams in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It refers to more detailed documents covering the various issues in designing, constructing and operating this cavity. The superconducting storage cavity is designed to operate at a harmonic of the bunch frequency of RHIC at a relatively low frequency of 56 MHz. The current storage cavities of RHIC operate at 197 MHz and are normal-conducting. The use of a superconducting cavity allows for a high gap voltage, over 2 MV. The combination of a high voltage and low frequency provides various advantages stemming from the resulting large longitudinal acceptance bucket.

  16. Making Superconducting Welds between Superconducting Wires

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin I.; Eom, Byeong Ho

    2008-01-01

    A technique for making superconducting joints between wires made of dissimilar superconducting metals has been devised. The technique is especially suitable for fabrication of superconducting circuits needed to support persistent electric currents in electromagnets in diverse cryogenic applications. Examples of such electromagnets include those in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) systems and in superconducting quantum interference devices (SQUIDs). Sometimes, it is desirable to fabricate different parts of a persistent-current-supporting superconducting loop from different metals. For example, a sensory coil in a SQUID might be made of Pb, a Pb/Sn alloy, or a Cu wire plated with Pb/Sn, while the connections to the sensory coil might be made via Nb or Nb/Ti wires. Conventional wire-bonding techniques, including resistance spot welding and pressed contact, are not workable because of large differences between the hardnesses and melting temperatures of the different metals. The present technique is not subject to this limitation. The present technique involves the use (1) of a cheap, miniature, easy-to-operate, capacitor-discharging welding apparatus that has an Nb or Nb/Ti tip and operates with a continuous local flow of gaseous helium and (2) preparation of a joint in a special spark-discharge welding geometry. In a typical application, a piece of Nb foil about 25 m thick is rolled to form a tube, into which is inserted a wire that one seeks to weld to the tube (see figure). The tube can be slightly crimped for mechanical stability. Then a spark weld is made by use of the aforementioned apparatus with energy and time settings chosen to melt a small section of the niobium foil. The energy setting corresponds to the setting of a voltage to which the capacitor is charged. In an experiment, the technique was used to weld an Nb foil to a copper wire coated with a Pb/Sn soft solder, which is superconducting. The joint was evaluated as part of a persistent-current circuit having an inductance of 1 mH. A current was induced in a loop, and no attenuation of the current after a time interval 1,000 s was discernible in a measurement having a fractional accuracy of 10(exp -4): This observation supports the conclusion that the weld had an electrical resistance <10(exp -10) omega.

  17. Non-Empirical Nuclear Energy Functionals, Pairing Gaps, and Odd-Even Mass Differences

    SciTech Connect

    Duguet, T. [CEA, Saclay, France; Lesinski, Thomas [ORNL

    2009-01-01

    First, we briefly outline some aspects of the starting project to design non-empirical energy functionals based on low-momentum vacuum interactions and many-body perturbation theory. Second, we present results obtained within an approximation of such a scheme where the pairing part of the energy density functional is constructed at first order in the nuclear plus Coulomb two-body interaction. We discuss in detail the physics of the odd-even mass staggering and the necessity to compute actual odd-even mass differences to analyze it meaningfully.

  18. Electron Energy Distribution in Hotspots of Cygnus A:Filling the Gap with Spitzer Space Telescope

    SciTech Connect

    Stawarz, L.; Cheung, C.C.; Harris, D.E.; Ostrowski, M.

    2007-03-06

    Here we present Spitzer Space Telescope imaging of Cyg A with the Infrared Array Camera at 4.5 {micro}m and 8.0 {micro}m, resulting in the detection of the high-energy tails or cut-offs in the synchrotron spectra for all four hotspots of this archetype radio galaxy. When combined with the other data collected (and re-analyzed) from the literature, our observations allow for detailed modeling of the broad-band (radio-to-X-ray) emission for the brightest spots A and D. We confirm that the X-ray flux detected previously from these features is consistent with the synchrotron self-Compton radiation for the magnetic field intensity B {approx} 170 {micro}G in spot A, and B {approx} 270 {micro}G in spot D. We also find that the energy density of the emitting electrons is most likely larger by a factor of a few than the energy density of the hotspots magnetic field. We construct energy spectra of the radiating ultrarelativistic electrons. We find that for both hotspots A and D these spectra are consistent with a broken power-law extending from at least 100MeV up to {approx} 100GeV, and that the spectral break corresponds almost exactly to the proton rest energy of {approx} 1GeV. We argue that the shape of the electron continuum most likely reflects two different regimes of the electron acceleration process taking place at mildly relativistic shocks, rather than resulting from radiative cooling and/or absorption e.ects. In this picture the protons inertia defines the critical energy for the hotspot electrons above which Fermi-type acceleration processes may play a major role, but below which the operating acceleration mechanism has to be of a different type. At energies {approx}> 100 GeV, the electron spectra cut-off/steepen again, most likely as a result of spectral aging due to radiative loss effects. We discuss several implications of the presented analysis for the physics of extragalactic jets.

  19. Athermal Energy Loss from X-Rays Deposited in Thin Superconducting Bilayers on Solid Substrates

    NASA Technical Reports Server (NTRS)

    Bandler, Simon R.; Kozorezov, Alexander; Balvin, Manuel A.; Busch, Sarah E.; Nagler, Peter N.; Porst, Jan-Patrick; Smith, Stephen J.; Stevenson, Thomas R.; Sadleir, John E.; Seidel, George M.

    2012-01-01

    An important feature that determines the energy resolution of any type of thin film microcalorimeter is the fraction of athermal energy that can be lost to the heat bath prior to the device coming into thermal equilibrium.

  20. Suppression of geometric barrier in type-II superconducting strips

    NASA Astrophysics Data System (ADS)

    Willa, R.; Geshkenbein, V. B.; Blatter, G.

    2014-03-01

    We study the magnetic response of a superconducting double strip, i.e., two parallel coplanar thin strips of width 2w, thickness d ?w, and infinite length, separated by a gap of width 2s and subject to a perpendicular magnetic field H. The magnetic properties of this system are governed by the presence of a geometric energy barrier for vortex penetration which we investigate as a function of applied field H and gap parameter s. The new results deal with the case of a narrow gap s ?w, where the field penetration from the inner edges is facilitated by large flux focusing. Upon reducing the gap width 2s, we observe a considerable rearrangement of the screening currents, leading to a strong reduction of the penetration field and the overall magnetization loop, with a suppression factor reaching ˜(d/w)1/2 as the gap drops below the sample thickness, 2s

  1. Power-flow control and transient-stability enhancement of a large-scale wind power generation system using a superconducting magnetic energy storage (SMES) unit

    Microsoft Academic Search

    Shiang-Shong Chen; Li Wang; Zhe Chen; Wei-Jen Lee

    2008-01-01

    This paper proposes a novel scheme using a superconducting magnetic energy-storage (SMES) unit to simultaneously perform both power-flow control and transient stability improvement of a large-scale wind power generation system (WPGS) subject to severe wind fluctuations. A complete system model based on a synchronously rotating reference frame for the studied WPGS combined with the proposed SMES unit is derived and

  2. Superconductivity and magnetism and their interplay in quaternary borocarbides RNi2B2C

    NASA Astrophysics Data System (ADS)

    Gupta, L. C.

    2006-12-01

    Since 1986, most of the interest in superconductivity became focused on high-Tc cuprates. The discovery of the superconducting quaternary borocarbide system Y Ni B C with Tc as high as?˜12?K inspired research into intermetallic superconductors (IMS) once again. Several reasons can be attributed to this revival of interest in IMS: (i) In the tetragonal quaternary magnetic superconductors RNi2B2C, superconductivity and magnetism occur with Tc and TN?˜?10?K, thereby allowing studies of exotic phenomena associated with, and arising from, the interplay of superconductivity and magnetism. (ii) High TN's and a variety of commensurate and incommensurate magnetic structures in RNi2B2C (Fermi surface nesting playing a central role) strongly suggest that R-spins are coupled via the RKKY-exchange interaction. Hence, unlike in most other magnetic superconductors known so far, conduction electrons take part in superconductivity and magnetism. (iii) Quaternary borocarbides open up new pathways to try and synthesize multicomponent intermetallic superconductors. Their remarkable intrinsic superconducting and magnetic properties and the availability of high quality samples (bulk polycrystalline, large single crystals and thin films) make RNi2B2C particularly special to investigate. Several unusual phenomena have been reported, such as, to name a few, dramatic phonon mode softening at Tc, Hc2(T) exhibiting a positive curvature near Tc and a four-fold anisotropy in the basal plane; a variety of exceptional and fascinating flux line lattice (FLL) related effects — FLL-symmetry transformations and alignments with the underlying crystal lattice as a function of applied field (manifestation of nonlocal electrodynamics despite high ??˜?10, and thermal fluctuation effects even though Tc,?˜?16?K, is not too high) and a four-fold symmetric star-shaped (in real space) vortex core. RNi2B2C are strong coupling s-wave BCS superconductors and, remarkably, have a superconducting gap with extreme anisotropy. Strong experimental evidence shows that the four-fold symmetric superconducting gap has point nodes along the 100- and 10-directions, a feature that has been shown consistent with (s?+?g)-Cooper pairing. An energy gap with such strong anisotropy is unusual for an s-wave superconductor and, hence, calls for a pairing mechanism different from conventional electron phonon coupling. Antiferromagnetic fluctuations possibly play an important role in the mechanism. Magnetic superconductors RNi2B2C (R?=?Dy, Ho, Er, Tm) reveal several phenomena, not observed earlier, associated with the interplay of superconductivity and magnetism. Microscopic evidence (via square FLL interacting with magnetism) of the coexistence of magnetism and superconductivity; intrinsic FLL-pinning by magnetic ions; weak ferromagnetism (local moment) coexisting with superconductivity (down to the lowest temperature) and the spontaneous vortex phase (ErNi2B2C); superconductivity setting in an already magnetically ordered lattice (DyNi2B2C) and pair-breaking by nonmagnetic ions in such materials; rich and complex magnetic structures and double (nearly) re-entrant superconductivity (HoNi2B2C) and changes in the FLL-symmetry in the vicinity of magnetic transition (TmNi2B2C) and 4f-quadrupole ordering (TmNi2B2C) are several exciting phenomena that magnetic superconductors RNi2B2C exhibit.

    At the end of this review are indicated some possible further studies in quaternary borocarbide superconductors. These studies may turn out to be important not only with respect to borocarbides themselves but also from the standpoint of superconductivity in general.

  3. Superconducting thermoelectric generator

    DOEpatents

    Metzger, J.D.; El-Genk, M.S.

    1994-01-01

    Thermoelectricity is produced by applying a temperature differential to dissimilar electrically conducting or semiconducting materials, thereby producing a voltage that is proportional to the temperature difference. Thermoelectric generators use this effect to directly convert heat into electricity; however, presently-known generators have low efficiencies due to the production of high currents which in turn cause large resistive heating losses. Some thermoelectric generators operate at efficiencies between 4% and 7% in the 800{degrees} to 1200{degrees}C range. According to its major aspects and bradly stated, the present invention is an apparatus and method for producing electricity from heat. In particular, the invention is a thermoelectric generator that juxtaposes a superconducting material and a semiconducting material - so that the superconducting and the semiconducting materials touch - to convert heat energy into electrical energy without resistive losses in the temperature range below the critical temperature of the superconducting material. Preferably, an array of superconducting material is encased in one of several possible configurations within a second material having a high thermal conductivity, preferably a semiconductor, to form a thermoelectric generator.

  4. A Study of Higher-Order Mode Damping in the Superconducting Energy Recovery LINAC at Brookhaven National Laboratory

    NASA Astrophysics Data System (ADS)

    Hammons, Lee Reginald, III

    An energy recovery LINAC (ERL) is being constructed at Brookhaven National Laboratory that will involve a superconducting LINAC along with a superconducting electron gun, all operating at 703.75 MHz. The ERL will serve as a testbed for the concepts and technologies required to implement future upgrades in the Relativistic Heavy Ion Collider (RHIC). Because of the high current and high charge requirements of the ERL, effective higher-order mode (HOM) damping is an essential component of the ERL research and development program. This thesis focuses on three areas of HOM characterization and damping development: damping of HOMs in the five-cell LINAC, use of the electron gun fundamental power couplers (FPCs) to damp HOMs, and the development of a ceramic/ferrite damper for the electron gun. The five-cell LINAC uses an HOM load lined with ferrite and attached to the beampipe on either side of the cavity. These studies characterized the frequency-dependent nature of the ferrite absorbing material and derived a set of "portable" ferrite parameters that simplified simulation work. Using these "portable" parameters, it was determined that the ferrite absorber is effective in damping the HOMs of the five-cell cavity over a range of frequencies. In addition, higher-order mode damping in the electron gun was studied using the fundamental power couplers. The gun cavity is a superconducting half-cell structure designed to accelerate electrons to an energy of 2.5 MeV and features dual fundamental power couplers. The HOMs of the gun cavity were studied along with the damping capabilities of the FPCs. Simulation studies determined that the FPCs couple strongly to many of the HOMs studied. However, the transition between the coaxial FPCs and the waveguide that feeds power to the FPCs is a "doorknob" type transition, and it was found that this component shows the best transmission qualities between 1 and 2 GHz, thus limiting the damping capabilities of the FPCs to this bandwidth. It remains to be seen how the FPCs will perform under actual conditions. Finally, the development of a ceramic/ferrite damper was described for the electron gun. The damper features a lossless alumina ceramic break surrounded by a ferrite load and was designed to isolate the vacuum chamber from the ferrite tiles. Various studies were conducted using simulation and prototype designs, and it was determined that the ceramic/ferrite load can be effective in damping higher-order modes of the gun cavity. Analytical calculations along with simulation show that the ceramic tends to alter the field distribution of higher-order modes and change the damping qualities depending on the frequency. The effectiveness of the damping for a given mode depends on a variety of factors including the thickness of the ceramic, the spacing between the ceramic and ferrite layers, and the diameter of the inner ceramic surface.

  5. Nodeless superconductivity in quasi-one-dimensional Nb2PdS5 : A ? SR study

    NASA Astrophysics Data System (ADS)

    Biswas, P. K.; Luetkens, H.; Xu, Xiaofeng; Yang, J. H.; Baines, C.; Amato, A.; Morenzoni, E.

    2015-03-01

    Muon spin relaxation and rotation (? SR ) measurements have been performed to study the superconducting and magnetic properties of Nb2PdS5 . Zero-field ? SR data show that no sizable spontaneous magnetization arises with the onset of superconductivity in Nb2PdS5 , which indicates that the time-reversal symmetry is probably preserved in the superconducting state of this system. A strong diamagnetic shift is observed in the transverse-field ? SR data practically ruling out a dominant triplet-pairing superconducting state in Nb2PdS5 . The temperature dependence of magnetic penetration depth evidences the existence of a single s -wave energy gap ? (0 ) with a gap value of 1.07(4) meV at zero temperature. The ratio ? (0 ) /kBTc=2.02 (9 ) indicates that Nb2PdS5 should be considered as a moderately strong-coupling superconductor. The magnetic penetration depth at zero temperature is 785(20) nm, indicating a very low superfluid density consistent with the quasi-one-dimensional nature of this system.

  6. Superconducting frustration bit

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.

    2014-10-01

    A basic design is proposed for a classical bit element of a superconducting circuit that mimics a frustrated multiband superconductor and is composed of an array of ?-Josephson junctions (?-junction). The phase shift of ? provides the lowest energy for one ?-junction, but neither a ? nor a zero phase shift gives the lowest energy for an assembly of ?-junctions. There are two chiral states that can be used to store one bit information. The energy scale for reading and writing to memory is of the same order as the junction energy, and is thus in the same order of the driving energy of the circuit. In addition, random access is also possible.

  7. Superconducting magnets

    SciTech Connect

    Willen, E.; Dahl, P.; Herrera, J.

    1985-01-01

    This report provides a self-consistent description of a magnetic field in the aperture of a superconducting magnet and details how this field can be calculated in a magnet with cos theta current distribution in the coils. A description of an apparatus that can be used to measure the field uniformity in the aperture has been given. Finally, a detailed description of the magnet being developed for use in the Superconducting Super Collider is given. When this machine is built, it will be by far the largest application of superconductivity to date and promises to make possible the experimental discoveries needed to understand the basic laws of nature governing the world in which we live.

  8. Pseudogap The underdoped region of the temperature doping phase diagram from which cuprate superconductivity

    E-print Network

    Weston, Ken

    superconductivity emerges is referred to as the `pseudogap' because evidence exists for partial gapping the masking effects of superconductivity. Quantum Critical Point ­ This identifies the pseudogap in YBa2Cu3O6 is such that it terminates at zero temperature inside the superconducting dome. This indicates that quantum criticality

  9. Raman spectroscopy on the zigzag graphene nanoribbon Interplay of Antiferromagnetsm and Superconductivity

    E-print Network

    and Superconductivity in Bilayer Superconductors Optimal observation time window for forecasting the next earthquake description by two phase variables #12;Topological interference of superconductivity in Pb/Ru/Sr2RuO4-universal superconducting gap structure in iron-pnictides revealed by magnetic penetration depth measurements Quantum

  10. Superconducting super collider magnet cryostat

    SciTech Connect

    Niemann, R.C.; Craddock, W.W.; Engler, N.H.; Gonczy, J.D.; Nicol, T.H.; Powers, R.J.; Rode, C.H.

    1986-07-01

    The proposed Superconducting Super Collider high energy physics research facility will entail one of the major cryogenic system undertakings of the next decade. The two 30 Km diameter accelerator rings contain an integrated system of approx. = 10,000 superconducting devices that must have low capital cost and operate reliably and efficiently over the lifetime of the machine. The design for the approx. = 8000 superconducting dipole magnet cryostats has been developed and evaluated by both component and systems tests. The details of the design are presented along with summaries of the experimental evaluations of the suspension system, insulation, transient phenomena, systems' performance, etc.

  11. Suppression of activation energy and superconductivity by the addition of Al{sub 2}O{sub 3} nanoparticles in CuTl-1223 matrix

    SciTech Connect

    Jabbar, Abdul; Qasim, Irfan; Mumtaz, M.; Zubair, M.; Nadeem, K. [Materials Research Laboratory, Department of Physics, FBAS, International Islamic University (IIU) Islamabad, Islamabad 44000 (Pakistan); Khurram, A. A. [Experimental Physics Labs, National Centre for Physics, Islamabad (Pakistan)

    2014-05-28

    Low anisotropic (Cu{sub 0.5}Tl{sub 0.5})Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10??} (CuTl-1223) high T{sub c} superconducting matrix was synthesized by solid-state reaction and Al{sub 2}O{sub 3} nanoparticles were prepared separately by co-precipitation method. Al{sub 2}O{sub 3} nanoparticles were added with different concentrations during the final sintering cycle of CuTl-1223 superconducting matrix to get the required (Al{sub 2}O{sub 3}){sub y}/CuTl-1223, y?=?0.0, 0.5, 0.7, 1.0, and 1.5?wt.?%, composites. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray, and dc-resistivity (?) measurements. The activation energy and superconductivity were suppressed with increasing concentration of Al{sub 2}O{sub 3} nanoparticles in (CuTl-1223) matrix. The XRD analysis showed that the addition of Al{sub 2}O{sub 3} nanoparticles did not affect the crystal structure of the parent CuTl-1223 superconducting phase. The suppression of activation energy and superconducting properties is most probably due to weak flux pinning in the samples. The possible reason of weak flux pinning is reduction of weak links and enhanced inter-grain coupling due to the presence of Al{sub 2}O{sub 3} nanoparticles at the grain boundaries. The presence of Al{sub 2}O{sub 3} nanoparticles at the grain boundaries possibly reduced the number of flux pinning centers, which were present in the form of weak links in the pure CuTl-1223 superconducting matrix. The increase in the values of inter-grain coupling (?) deduced from the fluctuation induced conductivity analysis with the increased concentration of Al{sub 2}O{sub 3} nanoparticles is a theoretical evidence of improved inter-grain coupling.

  12. PREFACE: Superconducting materials Superconducting materials

    NASA Astrophysics Data System (ADS)

    Charfi Kaddour, Samia; Singleton, John; Haddad, Sonia

    2011-11-01

    The discovery of superconductivity in 1911 was a great milestone in condensed matter physics. This discovery has resulted in an enormous amount of research activity. Collaboration among chemists and physicists, as well as experimentalists and theoreticians has given rise to very rich physics with significant potential applications ranging from electric power transmission to quantum information. Several superconducting materials have been synthesized. Crucial progress was made in 1987 with the discovery of high temperature superconductivity in copper-based compounds (cuprates) which have revealed new fascinating properties. Innovative theoretical tools have been developed to understand the striking features of cuprates which have remained for three decades the 'blue-eyed boy' for researchers in superconductor physics. The history of superconducting materials has been notably marked by the discovery of other compounds, particularly organic superconductors which despite their low critical temperature continue to attract great interest regarding their exotic properties. Last but not least, the recent observation of superconductivity in iron-based materials (pnictides) has renewed hope in reaching room temperature superconductivity. However, despite intense worldwide studies, several features related to this phenomenon remain unveiled. One of the fundamental key questions is the mechanism by which superconductivity takes place. Superconductors continue to hide their 'secret garden'. The new trends in the physics of superconductivity have been one of the two basic topics of the International Conference on Conducting Materials (ICoCoM2010) held in Sousse,Tunisia on 3-7 November 2010 and organized by the Tunisian Physical Society. The conference was a nice opportunity to bring together participants from multidisciplinary domains in the physics of superconductivity. This special section contains papers submitted by participants who gave an oral contribution at ICoCoM2010 and by invited authors selected by the editor. We are grateful to IUPAP, ICTP and the European Office of Aerospace Research and Development, Air Force Office of Scientific Research, United States Air Force Laboratory. We would like to acknowledge the authors for their careful work, and finally we thank Dr L Smith the publisher of Journal of Physics: Condensed Matter for her patience and help. Superconducting materials contents Raman spectrum in the pseudogap phase of the underdoped cuprates: effect of phase coherence and the signature of the KT-type superconducting transitionTao Li and Haijun Liao Pressure effects on Dirac fermions in ?-(BEDT-TTF)2I3Takahiro Himura, Takao Morinari and Takami Tohyama Effect of Zn doping in hole-type 1111 phase (Pr, Sr)FeAsOXiao Lin, Chenyi Shen, Chen Lv, Jianjian Miao, Hao Tan, Guanghan Cao and Zhu-An Xu Superconductivity and ferromagnetism in EuFe2(As1 - xPx)2*Guanghan Cao, Shenggao Xu, Zhi Ren, Shuai Jiang, Chunmu Feng and Zhu'an Xu OInhomogeneous superconductivity in organic conductors: the role of disorder and magnetic fieldS Haddad, S Charfi-Kaddour and J-P Pouget

  13. Numerical simulation and analysis of energy loss in a nanosecond spark gap switch

    NASA Astrophysics Data System (ADS)

    Lavrinovich, I. V.; Oreshkin, V. I.

    2014-11-01

    A system of differential equations for the RLC circuit of a capacitor-switch assembly was derived being supplemented with an equation for the spark resistance of the switch in accordance with the Braginsky model. The parameters that affect the solutions of equations for the circuit with parallel or series connection of several capacitor-switch assemblies to a common inductive load were determined. Based on numerical solution of the system of equations, a dependence of the energy ES released in the spark within the first halfperiod on the discharge circuit and switch parameters was found.

  14. Bridging the energy gap: Anadromous blueback herring feeding in the Hudson and Mohawk rivers, New York

    USGS Publications Warehouse

    Simonin, P.W.; Limburg, K.E.; Machut, L.S.

    2007-01-01

    Adult blueback herring Alosa aestivalis (N = 116) were collected during the 1999, 2000, and 2002-2004 spawning runs from sites on the Hudson and Mohawk rivers, and gut contents were analyzed. Thirty-four fish (33% of those examined) were found to contain food material. Food items were present in 41% of Mohawk River samples and 11% of Hudson River samples; all Hudson River fish containing food were captured in small tributaries above the head of tide. Hudson River fish predominantly consumed zooplankton, while Mohawk River fish consumed benthic aquatic insects in large quantities, including Baetidae, Ephemeridae, and Chironomidae. Using stable isotope analysis and a mixing model, we found that fish collected later in the season had significantly decreased marine-derived C. Condition indices of later-season fish were equal to or greater than those of fish collected earlier in the season. Blueback herring in this system may face increased energy requirements as they migrate farther upstream during spawning runs, and feeding may provide energy subsidies needed to maintain fitness over their expanded migratory range. ?? Copyright by the American Fisheries Society 2007.

  15. Mesoscopic superconductivity in ultrasmall metallic grains

    E-print Network

    Y. Alhassid; K. N. Nesterov

    2014-07-31

    A nano-scale metallic grain (nanoparticle) with irregular boundaries in which the single-particle dynamics are chaotic is a zero-dimensional system described by the so-called universal Hamiltonian in the limit of a large number of electrons. The interaction part of this Hamiltonian includes a superconducting pairing term and a ferromagnetic exchange term. Spin-orbit scattering breaks spin symmetry and suppresses the exchange interaction term. Of particular interest is the fluctuation-dominated regime, typical of the smallest grains in the experiments, in which the bulk pairing gap is comparable to or smaller than the single-particle mean-level spacing, and the Bardeen-Cooper-Schrieffer (BCS) mean-field theory of superconductivity is no longer valid. Here we study the crossover between the BCS and fluctuation-dominated regimes in two limits. In the absence of spin-orbit scattering, the pairing and exchange interaction terms compete with each other. We describe the signatures of this competition in thermodynamic observables, the heat capacity and spin susceptibility. In the presence of strong spin-orbit scattering, the exchange interaction term can be ignored. We discuss how the magnetic-field response of discrete energy levels in such a nanoparticle is affected by pairing correlations. We identify signatures of pairing correlations in this response, which are detectable even in the fluctuation-dominated regime.

  16. Majorana fermion states and fractional flux periodicity in mesoscopic d-wave superconducting loops with spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Zha, Guo-Qiao; Covaci, Lucian; Peeters, F. M.; Zhou, Shi-Ping

    2014-07-01

    We numerically investigate the spin-orbit (SO) coupling effect on the magnetic flux evolution of energy and supercurrent in mesoscopic d-wave superconducting loops by solving the spin-generalized Bogoliubov-de Gennes equations self-consistently. It is found that the energy spectrum splits when the SO interaction is involved and the Majorana zero mode can be realized in the [100] edges of square systems for an appropriate SO coupling strength. Superconducting phase transitions appear when the energy gap closes, accompanied by energy jumps between different energy parabolas in the ground state, which provides a possible mechanism to support fractional flux periodicity of supercurrent. Moreover, in the case of rectangular loops with SO coupling, the jumps of the ground-state energy gradually disappear by increasing the ratio of length to height of the sample, and a paramagnetic response with opposite direction of the screening current around zero flux value can occur in such systems.

  17. Operational Merits of Maritime Superconductivity

    NASA Astrophysics Data System (ADS)

    Ross, R.; Bosklopper, J. J.; van der Meij, K. H.

    The perspective of superconductivity to transfer currents without loss is very appealing in high power applications. In the maritime sector many machines and systems exist in the roughly 1-100 MW range and the losses are well over 50%, which calls for dramatic efficiency improvements. This paper reports on three studies that aimed at the perspectives of superconductivity in the maritime sector. It is important to realize that the introduction of superconductivity comprises two technology transitions namely firstly electrification i.e. the transition from mechanical drives to electric drives and secondly the transition from normal to superconductive electrical machinery. It is concluded that superconductivity does reduce losses, but its impact on the total energy chain is of little significance compared to the investments and the risk of introducing a very promising but as yet not proven technology in the harsh maritime environment. The main reason of the little impact is that the largest losses are imposed on the system by the fossil fueled generators as prime movers that generate the electricity through mechanical torque. Unless electric power is supplied by an efficient and reliable technology that does not involve mechanical torque with the present losses both normal as well as superconductive electrification of the propulsion will hardly improve energy efficiency or may even reduce it. One exception may be the application of degaussing coils. Still appealing merits of superconductivity do exist, but they are rather related to the behavior of superconductive machines and strong magnetic fields and consequently reduction in volume and mass of machinery or (sometimes radically) better performance. The merits are rather convenience, design flexibility as well as novel applications and capabilities which together yield more adequate systems. These may yield lower operational costs in the long run, but at present the added value of superconductivity rather seems more adequate than cheaper systems.

  18. Design of single-winding energy-storage reactors for dc-to-dc converters using air-gapped magnetic-core structures

    NASA Technical Reports Server (NTRS)

    Ohri, A. K.; Wilson, T. G.; Owen, H. A., Jr.

    1977-01-01

    A procedure is presented for designing air-gapped energy-storage reactors for nine different dc-to-dc converters resulting from combinations of three single-winding power stages for voltage stepup, current stepup and voltage stepup/current stepup and three controllers with control laws that impose constant-frequency, constant transistor on-time and constant transistor off-time operation. The analysis, based on the energy-transfer requirement of the reactor, leads to a simple relationship for the required minimum volume of the air gap. Determination of this minimum air gap volume then permits the selection of either an air gap or a cross-sectional core area. Having picked one parameter, the minimum value of the other immediately leads to selection of the physical magnetic structure. Other analytically derived equations are used to obtain values for the required turns, the inductance, and the maximum rms winding current. The design procedure is applicable to a wide range of magnetic material characteristics and physical configurations for the air-gapped magnetic structure.

  19. Superconducting Radio-Frequency Cavities

    NASA Astrophysics Data System (ADS)

    Padamsee, Hasan S.

    2014-10-01

    Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

  20. Superconductivity above 100 K in single-layer FeSe films on doped SrTiO3.

    PubMed

    Ge, Jian-Feng; Liu, Zhi-Long; Liu, Canhua; Gao, Chun-Lei; Qian, Dong; Xue, Qi-Kun; Liu, Ying; Jia, Jin-Feng

    2015-03-01

    Recent experiments on FeSe films grown on SrTiO3 (STO) suggest that interface effects can be used as a means to reach superconducting critical temperatures (Tc) of up to 80 K (ref. ). This is nearly ten times the Tc of bulk FeSe and higher than the record value of 56 K for known bulk Fe-based superconductors. Together with recent studies of superconductivity at oxide heterostructure interfaces, these results rekindle the long-standing idea that electron pairing at interfaces between two different materials can be tailored to achieve high-temperature superconductivity. Subsequent angle-resolved photoemission spectroscopy measurements of the FeSe/STO system revealed an electronic structure distinct from bulk FeSe (refs , ), with an energy gap vanishing at around 65 K. However, ex situ electrical transport measurements have so far detected zero resistance-the key experimental signature of superconductivity-only below 30 K. Here, we report the observation of superconductivity with Tc above 100 K in the FeSe/STO system by means of in situ four-point probe electrical transport measurements. This finding confirms FeSe/STO as an ideal material for studying high-Tc superconductivity. PMID:25419814

  1. Superconductivity above 100 K in single-layer FeSe films on doped SrTiO3

    NASA Astrophysics Data System (ADS)

    Ge, Jian-Feng; Liu, Zhi-Long; Liu, Canhua; Gao, Chun-Lei; Qian, Dong; Xue, Qi-Kun; Liu, Ying; Jia, Jin-Feng

    2015-03-01

    Recent experiments on FeSe films grown on SrTiO3 (STO) suggest that interface effects can be used as a means to reach superconducting critical temperatures (Tc) of up to 80 K (ref. ). This is nearly ten times the Tc of bulk FeSe and higher than the record value of 56 K for known bulk Fe-based superconductors. Together with recent studies of superconductivity at oxide heterostructure interfaces, these results rekindle the long-standing idea that electron pairing at interfaces between two different materials can be tailored to achieve high-temperature superconductivity. Subsequent angle-resolved photoemission spectroscopy measurements of the FeSe/STO system revealed an electronic structure distinct from bulk FeSe (refs , ), with an energy gap vanishing at around 65 K. However, ex situ electrical transport measurements have so far detected zero resistance—the key experimental signature of superconductivity—only below 30 K. Here, we report the observation of superconductivity with Tc above 100 K in the FeSe/STO system by means of in situ four-point probe electrical transport measurements. This finding confirms FeSe/STO as an ideal material for studying high-Tc superconductivity.

  2. Hall conductivity in the normal and superconducting phases of the Rashba system with Zeeman field

    NASA Astrophysics Data System (ADS)

    Chung, Suk Bum; Roy, Rahul

    2014-12-01

    We study the intrinsic Hall conductivity of the ordinary and topological superconducting phases of a Rashba metal in a perpendicular Zeeman field. In this system, the normal metal breaks time reversal symmetry while the superconducting order parameter does not, in contrast to the chiral p -wave superconducting state predicted in the monolayer strontium ruthenate (Sr2RuO4) whose Hall conductivity has been studied extensively. We study the effects of intraband and interband pairing and find there is qualitatively larger change in the intrinsic Hall conductivity when there is interband pairing, with the change in magnitude linear in the pairing gap. We argue that interband pairing leads in general to higher energy costs for the topological phase compared to the topologically trivial phase and thus that the qualitative behavior of the intrinsic Hall conductivity with superconductivity in these systems could provide important clues about the nature of pairing in the superconducting phase and even some hints of whether it is topological or not.

  3. Theory of novel and superconducting properties of Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Chubukov, Andrey

    2009-03-01

    I will discuss antiferromagnetism and superconductivity in novel Fe-based superconductors within the itinerant model of small electron and hole pockets near (0,0) and (,). I will argue that the effective interactions in both channels logarithmically flow towards the same values at low energies, i.e., antiferromagnetism and superconductivity must be treated on equal footings. The magnetic instability comes first for equal sizes of the two pockets, but looses to superconductivity upon doping. The superconducting gap has no nodes, but changes sign between the two Fermi surfaces (extended s-wave symmetry). I will argue that the T dependencies of the spin susceptibility, NMR relaxation rate, and the penetration depth for such state are exponential only at very low T, and can be well fitted by power-laws over a wide T range below Tc. I will also discuss the type of a transition between spin-density-wave and superconducting states at T=0 and at finite T, and the linear T dependence of the spin susceptibility in the normal state. Based on the works done with I. Eremin, D. Efremov, M. Korshunov, D. Maslov, M. Vavilov, and A. Vorontsov.

  4. Imaging the impact on cuprate superconductivity of varying the interatomic distances within individual crystal unit cells

    PubMed Central

    Slezak, J. A.; Lee, Jinho; Wang, M.; McElroy, K.; Fujita, K.; Andersen, B. M.; Hirschfeld, P. J.; Eisaki, H.; Uchida, S.; Davis, J. C.

    2008-01-01

    Many theoretical models of high-temperature superconductivity focus only on the doping dependence of the CuO2-plane electronic structure. However, such models are manifestly insufficient to explain the strong variations in superconducting critical temperature, Tc, among cuprates that have identical hole density but are crystallographically different outside of the CuO2 plane. A key challenge, therefore, has been to identify a predominant out-of-plane influence controlling the superconductivity, with much attention focusing on the distance dA between the apical oxygen and the planar copper atom. Here we report direct determination of how variations in interatomic distances within individual crystalline unit cells affect the superconducting energy-gap maximum ? of Bi2Sr2CaCu2O8+?. In this material, quasiperiodic variations of unit cell geometry occur in the form of a bulk crystalline “supermodulation.” Within each supermodulation period, we find ?9 ± 1% cosinusoidal variation in local ? that is anticorrelated with the associated dA variations. Furthermore, we show that phenomenological consistency would exist between these effects and the random ? variations found near dopant atoms if the primary effect of the interstitial dopant atom is to displace the apical oxygen so as to diminish dA or tilt the CuO5 pyramid. Thus, we reveal a strong, nonrandom out-of-plane effect on cuprate superconductivity at atomic scale. PMID:18287001

  5. Tuning the band structure and superconductivity in single-layer FeSe by interface engineering.

    PubMed

    Peng, R; Xu, H C; Tan, S Y; Cao, H Y; Xia, M; Shen, X P; Huang, Z C; Wen, C H P; Song, Q; Zhang, T; Xie, B P; Gong, X G; Feng, D L

    2014-01-01

    The interface between transition metal compounds provides a rich playground for emergent phenomena. Recently, significantly enhanced superconductivity has been reported for single-layer FeSe on Nb-doped SrTiO3 substrate. Yet it remains mysterious how the interface affects the superconductivity. Here we use in situ angle-resolved photoemission spectroscopy to investigate various FeSe-based heterostructures grown by molecular beam epitaxy, and uncover that electronic correlations and superconducting gap-closing temperature (Tg) are tuned by interfacial effects. Tg up to 75?K is observed in extremely tensile-strained single-layer FeSe on Nb-doped BaTiO3, which sets a record high pairing temperature for both Fe-based superconductor and monolayer-thick films, providing a promising prospect on realizing more cost-effective superconducting device. Moreover, our results exclude the direct correlation between superconductivity and tensile strain or the energy of an interfacial phonon mode, and highlight the critical and non-trivial role of FeSe/oxide interface on the high Tg, which provides new clues for understanding its origin. PMID:25256736

  6. Athermal Energy Loss from X-rays Deposited in Thin Superconducting Films on Solid Substrates

    NASA Technical Reports Server (NTRS)

    Kozorezov, Alexander G.; Lambert, Colin J.; Bandler, Simon R.; Balvin, Manuel A.; Busch, Sarah E.; Sagler, Peter N.; Porst, Jan-Patrick; Smith, Stephen J.; Stevenson, Thomas R.; Sadleir, John E.

    2013-01-01

    When energy is deposited in a thin-film cryogenic detector, such as from the absorption of an X-ray, an important feature that determines the energy resolution is the amount of athermal energy that can be lost to the heat bath prior to the elementary excitation systems coming into thermal equilibrium. This form of energy loss will be position-dependent and therefore can limit the detector energy resolution. An understanding of the physical processes that occur when elementary excitations are generated in metal films on dielectric substrates is important for the design and optimization of a number of different types of low temperature detector. We have measured the total energy loss in one relatively simple geometry that allows us to study these processes and compare measurements with calculation based upon a model for the various di.erent processes. We have modeled the athermal phonon energy loss in this device by finding an evolving phonon distribution function that solves the system of kinetic equations for the interacting system of electrons and phonons. Using measurements of device parameters such as the Debye energy and the thermal di.usivity we have calculated the expected energy loss from this detector geometry, and also the position-dependent variation of this loss. We have also calculated the predicted impact on measured spectral line-shapes, and shown that they agree well with measurements. In addition, we have tested this model by using it to predict the performance of a number of other types of detector with di.erent geometries, where good agreement is also found.

  7. Vacuum low-temperature superconductivity is the essence of superconductivity - Atomic New Theory

    NASA Astrophysics Data System (ADS)

    Yongquan, Han

    2010-10-01

    The universe when the temperature closest to the Big Bang the temperature should be nuclear. Because, after the big bang, instant formation of atoms, nuclei and electrons between the absolute vacuum, the nucleus can not emit energy. (Radioactive elements, except in fact, radiation Yuan Su limited power emitted) which causes atomic nuclei and external temperature difference are so enormous that a large temperature difference reasons, all external particles became closer to the nucleus, affect the motion of electrons. When the conductor conductivity and thus affect the conductivity, the formation of resistance. Assumption that no particles affect the motion of electrons (except outside the nucleus) to form a potential difference will not change after the vector form, is now talking about the phenomenon of superconductivity, and then to introduce general, the gap between atoms in molecules or between small, valence electron number of high temperature superconducting conductors. This theory of atomic nuclei, but also explain the atomic and hydrogen bombs can remain after an explosion Why can release enormous energy reasons. Can also explain the ``super flow'' phenomenon. natural world. Tel 13241375685

  8. Properties of Superconducting Mo, Mo2n and Trilayer Mo2n-Mo-Mo2n Thin Films

    NASA Technical Reports Server (NTRS)

    Barrentine, E. M.; Stevenson, T. R.; Brown, A. D.; Lowitz, A. E.; Noroozian, O.; U-Yen, K.; Eshan, N.; Hsieh, W. T.; Moseley, S. H.; Wollack, E. J.

    2014-01-01

    We present measurements of the properties of thin film superconducting Mo, Mo2N and Mo2N/Mo/Mo2N trilayers of interest for microwave kinetic inductance detector (MKID) applications. Using microwave resonator devices, we investigate the transition temperature, energy gaps, kinetic inductance, and internal quality factors of these materials. We present an Usadel-based interpretation of the trilayer transition temperature as a function of trilayer thicknesses, and a 2-gap interpretation to understand the change in kinetic inductance and internal resonance quality factor (Q) as a function of temperature.

  9. Probe-type of superconductivity by impurity in materials with short coherence length: the s-wave and ?-wave phases study

    NASA Astrophysics Data System (ADS)

    Ptok, Andrzej; Jerzy Kapcia, Konrad

    2015-04-01

    The effects of a single non-magnetic impurity on superconducting states in the Penson–Kolb–Hubbard model have been analyzed. The investigations have been performed within the Hartree–Fock mean field approximation in two steps: (i) the homogeneous system is analysed using the Bogoliubov transformation, whereas (ii) the inhomogeneous system is investigated by self-consistent Bogoliubov-de Gennes equations (with the exact diagonalization and the kernel polynomial method). We analysed both signs of the pair hopping, which correspond to s-wave and ?-wave superconductivity. Our results show that an enhancement of the local superconducting gap at the impurity-site occurs for both cases. We obtained that Cooper pairs are scattered (at the impurity site) into the states which are from the neighborhoods of the states, which are commensurate ones with the crystal lattice. Additionally, in the ?-phase there are peaks in the local-energy gap (in momentum space), which are connected with long-range oscillations in the spatial distribution of the energy gap, superconducting order parameter (SOP), as well as effective pairing potential. Our results can be contrasted with the experiment and predicts how to experimentally differentiate these two different symmetries of SOP by the scanning tunneling microscopy technique.

  10. Nanoscale phase separation of antiferromagnetic order and superconductivity in K0.75Fe1.75Se2

    PubMed Central

    Yuan, R. H.; Dong, T.; Song, Y. J.; Zheng, P.; Chen, G. F.; Hu, J. P.; Li, J. Q.; Wang, N. L.

    2012-01-01

    We report an in-plane optical spectroscopy study on the iron-selenide superconductor K0.75Fe1.75Se2. The measurement revealed the development of a sharp reflectance edge below Tc at frequency much smaller than the superconducting energy gap on a relatively incoherent electronic background, a phenomenon which was not seen in any other Fe-based superconductors so far investigated. Furthermore, the feature could be noticeably suppressed and shifted to lower frequency by a moderate magnetic field. Our analysis indicates that this edge structure arises from the development of a Josephson-coupling plasmon in the superconducting condensate. Together with the transmission electron microscopy analysis, our study yields compelling evidence for the presence of nanoscale phase separation between superconductivity and magnetism. The results also enable us to understand various seemingly controversial experimental data probed from different techniques. PMID:22355735

  11. Computer simulation of the energy gap in ZnO- and TiO{sub 2}-based semiconductor photocatalysts

    SciTech Connect

    Skorikov, N. A., E-mail: nskorikov@gmail.com; Korotin, M. A.; Kurmaev, E. Z. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Cholakh, S. O. [Ural Federal University (Russian Federation)

    2012-12-15

    Ab initio calculations of the electronic structures of binary ZnO- and TiO{sub 2}-based oxides are performed to search for optimum dopants for efficient absorption of the visible part of solar radiation. Light elements B, C, and N are chosen for anion substitution. Cation substitution is simulated by 3d elements (Cr, Mn, Fe, Co) and heavy metals (Sn, Sb, Pb, Bi). The electronic structures are calculated by the full-potential linearized augmented plane wave method using the modified Becke-Johnson exchange-correlation potential. Doping is simulated by calculating supercells Zn{sub 15}D{sub 1}O{sub 16}, Zn{sub 16}O{sub 15}D{sub 1}, Ti{sub 15}D{sub 1}O{sub 32}, and Ti{sub 8}O{sub 15}D{sub 1}, where one-sixteenth of the metal (Ti, Zn) or oxygen atoms is replaced by dopant atoms. Carbon and antimony are found to be most effective dopants for ZnO: they form an energy gap {Delta}E = 1.78 and 1.67 eV, respectively. For TiO{sub 2}, nitrogen is the most effective dopant ({Delta}E = 1.76 eV).

  12. The collective emission of electromagnetic waves from astrophysical jets - Luminosity gaps, BL Lacertae objects, and efficient energy transport

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Borovsky, Joseph E.; Benford, Gregory; Eilek, Jean A.

    1988-01-01

    A model of the inner portions of astrophysical jets is constructed in which a relativistic electron beam is injected from the central engine into the jet plasma. This beam drives electrostatic plasma wave turbulence, which leads to the collective emission of electromagnetic waves. The emitted waves are beamed in the direction of the jet axis, so that end-on viewing of the jet yields an extremely bright source (BL Lacertae object). The relativistic electron beam may also drive long-wavelength electromagnetic plasma instabilities (firehose and Kelvin-Helmholtz) that jumble the jet magnetic field lines. After a sufficient distance from the core source, these instabilities will cause the beamed emission to point in random directions and the jet emission can then be observed from any direction relative to the jet axis. This combination of effects may lead to the gap turn-on of astrophysical jets. The collective emission model leads to different estimates for energy transport and the interpretation of radio spectra than the conventional incoherent synchrotron theory.

  13. Equilibrium Distributions and Superconductivity

    E-print Network

    Ashot Vagharshakyan

    2011-06-07

    In this article two models for charges distributions are discussed. On the basis of our consideration we put different points of view for stationary state. We prove that only finite energy model for charges' distribution and well-known variation principle explain some well-known experimental results. A new model for superconductivity was suggested, too. In frame of that model some characteristic experimental results for superconductors is possible to explain.

  14. Understanding Superconducting Magnetic Energy Storage (SMES) technology, applications, and economics, for end-use workshop

    SciTech Connect

    Ferraro, R.J. [Ferraro, Oliver, and Associates, Inc., Knoxville, TN (United States); McConnell, B.W. [Oak Ridge National Lab., TN (United States)

    1993-06-01

    The overall objective of this project was to determine the state-of-the-art and to what extent existing SMES is a viable option in meeting the needs of utilities and their customers for improving electric service power quality. By defining and analyzing SMES electrical/mechanical performance characteristics, and comparing SMES application benefits with competitive stored energy systems, industry will be able to determine SMES unique applications and potential market penetration. Building on this information base, it would also be possible to evaluate the impact of high temperature superconductors (77 K and 20-35 K) on SMES technology applications. The authors of this report constructed a network of industry contacts and research consultants that were used to collect, update, and analyze ongoing SMES R&D and marketing activities in industries, utilities, and equipment manufacturers. These key resources were utilized to assemble performance characteristics on existing SMES, battery, capacitor, flywheel, and high temperature superconductor (HTS) stored energy technologies. From this information, preliminary stored energy system comparisons were accomplished. In this way, the electric load needs would be readily comparable to the potential solutions and applications offered by each aforementioned energy storage technology.

  15. Theory of spin-fluctuation induced superconductivity in iron-based superconductors

    SciTech Connect

    Zhang, Junhua

    2011-08-15

    In this dissertation we focus on the investigation of the pairing mechanism in the recently discovered high-temperature superconductor, iron pnictides. Due to the proximity to magnetic instability of the system, we considered short-range spin fluctuations as the major mediating source to induce superconductivity. Our calculation supports the magnetic fluctuations as a strong candidate that drives Cooper-pair formation in this material. We find the corresponding order parameter to be of the so-called ss-wave type and show its evolution with temperature as well as the capability of supporting high transition temperature up to several tens of Kelvin. On the other hand, our itinerant model calculation shows pronounced spin correlation at the observed antiferromagnetic ordering wave vector, indicating the underlying electronic structure in favor of antiferromagnetic state. Therefore, the electronic degrees of freedom could participate both in the magnetic and in the superconducting properties. Our work shows that the interplay between magnetism and superconductivity plays an important role to the understanding of the rich physics in this material. The magnetic-excitation spectrum carries important information on the nature of magnetism and the characteristics of superconductivity. We analyze the spin excitation spectrum in the normal and superconducting states of iron pnictides in the magnetic scenario. As a consequence of the sign-reversed gap structure obtained in the above, a spin resonance mode appears below the superconducting transition temperature. The calculated resonance energy, scaled with the gap magnitude and the magnetic correlation length, agrees well with the inelastic neutron scattering (INS) measurements. More interestingly, we find a common feature of those short-range spin fluctuations that are capable of inducing a fully gapped ss state is the momentum anisotropy with elongated span along the direction transverse to the antiferromagnetic momentum transfer. This calculated intrinsic anisotropy exists both in the normal and in the superconducting state, which naturally explains the elliptically shaped magnetic responses observed in INS experiments. Our detailed calculation further shows that the magnetic resonance mode exhibits an upward dispersion-relation pattern but anisotropic along the transverse and longitudinal directions. We also perform a qualitative analysis on the relationship between the anisotropic momentum structure of the magnetic fluctuations and the stability of superconducting phase by intraorbital but interband pair scattering to show the consistency of the magnetic mechanism for superconductivity. As discussed for cuprates, an important identification of the mediating boson is from the fermionic spectrum. We study the spectral function in the normal and superconducting state. Not only do we extract the gap magnitude on the electron- and hole-pockets to show the momentum structure of the gap, but also find a peak-dip-hump feature in the electron spectrum, which reflects the feedback from the spin excitations on fermions. This serves as an interpretation of the kink structure observed in ARPES measurements.

  16. ASC 84: applied superconductivity conference. Final program and abstracts

    SciTech Connect

    Not Available

    1984-01-01

    Abstracts are given of presentations covering: superconducting device fabrication; applications of rf superconductivity; conductor stability and losses; detectors and signal processing; fusion magnets; A15 and Nb-Ti conductors; stability, losses, and various conductors; SQUID applications; new applications of superconductivity; advanced conductor materials; high energy physics applications of superconductivity; electronic materials and characterization; general superconducting electronics; ac machinery and new applications; digital devices; fusion and other large scale applications; in-situ and powder process conductors; ac applications; synthesis, properties, and characterization of conductors; superconducting microelectronics. (LEW)

  17. Bridging the Generation Gap

    ERIC Educational Resources Information Center

    Johnson, Susan Moore; Kardos, Susan M.

    2005-01-01

    The lack of instructional continuity in schools negates every effort of principals to provide an environment where all students would be successful. One solution could be to bridge the gap between the professional knowledge and skills of experienced teachers and the energy and fresh ideas of new recruits so that the latter are provided support…

  18. Superconductivity, Superfluidity and Holography

    E-print Network

    Alberto Salvio

    2013-01-16

    This is a concise review of holographic superconductors and superfluids. We highlight some predictions of the holographic models and the emphasis is given to physical aspects rather than to the technical details, although some references to understand the latter are systematically provided. We include gapped systems in the discussion, motivated by the physics of high-temperature superconductivity. In order to do so we consider a compactified extra dimension (with radius R), or, alternatively, a dilatonic field. The first setup can also be used to model cylindrical superconductors; when these are probed by an axial magnetic field a universal property of holography emerges: while for large R (compared to the other scales in the problem) non-local operators are suppressed, leading to the so called Little-Parks periodicity, the opposite limit shows non-local effects, e.g. the uplifting of the Little-Parks periodicity. This difference corresponds in the gravity side to a Hawking-Page phase transition.

  19. Rapidity gap signals in Higgs production at the SSC

    Microsoft Academic Search

    R. S. Fletcher; T. Stelzer

    1993-01-01

    We examine the structure of the underlying event in neutral Higgs production\\u000aat the Superconducting-Supercollider (SSC). Gaps, regions of rapidity\\u000acontaining no soft particle production, can provide a clean signature for $W$\\u000aboson fusion to the heavy Higgs. We first examine the physical basis of gap\\u000aproduction and estimate the survival probability of gaps in the minijet model.\\u000aThen, using

  20. Superconducting magnet

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.