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1

Protection of excited spin states by a superconducting energy gap  

NASA Astrophysics Data System (ADS)

The latest concepts for quantum computing and data storage rely on the addressing and manipulation of single spins. A limitation for single atoms or molecules in contact with a metal surface is the short lifetime of excited spin states, typically picoseconds, due to the exchange of energy and angular momentum with the itinerant electrons of the substrate. Here we show that paramagnetic molecules on a superconducting substrate exhibit excited spin states with a lifetime of ?~10ns. We ascribe this increase in lifetime by orders of magnitude to the depletion of electronic states around the Fermi level in the superconductor. This prohibits pathways of energy relaxation into the substrate and allows the magnetic molecule to be electrically pumped into higher spin states, making superconducting substrates prime candidates for spin manipulation. We further show that the proximity of the scanning tunnelling microscope tip modifies the magnetic anisotropy.

Heinrich, B. W.; Braun, L.; Pascual, J. I.; Franke, K. J.

2013-12-01

2

Superconducting gap in the hubbard model and the two-gap energy scales of high-T{c} cuprate superconductors.  

PubMed

Recent experiments (angle-resolved photoemission spectroscopy and Raman) suggest the presence of two distinct energy gaps in high-temperature superconductors (HTSC), exhibiting different doping dependences. The results of a variational cluster approach to the superconducting state of the two-dimensional Hubbard model are presented which show that this model qualitatively describes this gap dichotomy. The antinodal gap increases with less doping, a behavior long considered as reflecting the general gap behavior of the HTSC. On the other hand, the near-nodal gap does even slightly decrease with underdoping. An explanation of this unexpected behavior is given which emphasizes the crucial role of spin fluctuations in the pairing mechanism. PMID:18233549

Aichhorn, M; Arrigoni, E; Huang, Z B; Hanke, W

2007-12-21

3

Superconducting energy gap and nodes in the doped BaFe2As2 system  

NASA Astrophysics Data System (ADS)

Angle resolved photoemission spectroscopy (ARPES) is very powerful to know the solid state properties. We have developed low-temperature high-resolution laser-based ARPES system and recently achieved the highest energy resolution of ˜ 100 ?eV and the lowest sample temperature of ˜ 1.0 K. We would like to show our recent results of superconducting-gap measurements on the iron-based superconductors by laser-ARPES, mainly for Ba1-xKxFe2As2 [1-3]. Little Fermi-surface dependent superconducting gap sizes are found for the Ba0.6K0.4Fe2As2 that has the maximum Tc around 40K [1]. Inter-orbital interaction is important as well as intra-orbital interaction. On the other hand, KFe2As2 is an extremely hole-doped compound in Ba1-xKxFe2As2 system and no longer has electron Fermi surfaces. Regardless of this, KFe2As2 still exhibits superconductivity with Tc of 3.4 K and the existence of nodes in its superconducting gap has been suggested by the several transport measurements. Our ultrahigh-resolution laser ARPES [2] unveils that KFe2As2 is a nodal s-wave superconductor with highly unusual FS-selective multi-gap structure: a nodeless gap on the inner FS, an unconventional gap with octet-line nodes on the middle FS, and an almost-zero gap on the outer FS. This gap structure may arise from the frustration between competing pairing interactions on the hole FSs causing the eightfold sign reversal. Our results suggest that the A1g superconducting symmetry is universal in iron-pnictides, in spite of the variety of gap functions.[4pt] [1] Shimojima et al., Science 332 (2011) 564.[0pt] [2] Okazaki et al., Science 337 1314 (2012).[0pt] [3] Malaeb et al., Phys. Rev.B86 (2012) 165117.

Shin, Shik

2013-03-01

4

PUBLISHED ONLINE: 9 NOVEMBER 2008 DOI: 10.1038/NPHYS1128 Fermi-surface-dependent superconducting gap  

E-print Network

-surface-dependent superconducting gap in C6Ca K. Sugawara1 , T. Sato1 * and T. Takahashi1,2 The discovery of superconductivity in C6 of superconductivity lies in the superconducting energy gap associated with the formation of superconducting pairs. Here, we report the first direct observation of a superconducting gap in C6Ca by high- resolution angle

Loss, Daniel

5

Model Evidence of a Superconducting State with a Full Energy Gap in Small Cuprate Islands  

NASA Astrophysics Data System (ADS)

We investigate subdominant order parameters stabilizing at low temperatures in nanoscale high-Tc cuprate islands, motivated by the recent observation of a fully gapped state in nanosized YBa2Cu3O7-? [D. Gustafsson et al., Nature Nanotech. 8, 25 (2013)]. Using complementary quasiclassical and tight-binding Bogoliubov-de Gennes methods, we show on distinctly different properties dependent on the symmetry being dx2-y2+is or dx2-y2+idxy. We find that a surface-induced dx2-y2+is phase creates a global spectroscopic gap which increases with an applied magnetic field, consistent with experimental observation.

Black-Schaffer, Annica M.; Golubev, Dmitri S.; Bauch, Thilo; Lombardi, Floriana; Fogelström, Mikael

2013-05-01

6

Evidence of Gap Anisotropy in Superconducting YNi2B2C Using Directional Point-Contact Spectroscopy  

E-print Network

Evidence of Gap Anisotropy in Superconducting YNi2B2C Using Directional Point-Contact Spectroscopy of the anisotropy in the superconducting energy gap in a single crystal of YNi2B2C (Tc 14:6 K) using directional point-contact spectroscopy. The superconducting energy gap at 2.7 K, when measured for Ijjc, is 4

Raychaudhuri, Pratap

7

Phonon-induced enhancements of the energy gap and critical current in superconducting aluminum  

SciTech Connect

8 to 10 GHz phonons were generated by piezoelectric transduction of a microwave and by means of a quartz delay line, were allowed to enter the aluminum only after the microwaves had long since disappeared. The maximum enhancements detected were (deltaT/T/sub c/) = -0.07, for i/sub c/ and (deltaT/T/sub c/) = -0.03 for ..delta... The power- and temperature-dependence (0.82 less than or equal to T/T/sub c/ less than or equal to 0.994) of the enhancements were compared with the prediction of a theory given by Eliashberg. The gap-enhancement was in good agreement with the theory only for low input lower. The critical current measurements are predicted to be in rough agreement with the ..delta.. measurements but this was not observed. The magnitude of the critical current enhancements was typically more than twice the observed gap enhancements. The measured critical current enhancement was relatively independent of temperature whereas the gap enhancement decreased rapidly as the temperature was lowered.

Seligson, D.

1983-05-01

8

Effect of Fermi surface evolution on superconducting gap in superconducting topological insulator  

NASA Astrophysics Data System (ADS)

We study the bulk electronic states of a superconducting topological insulator, which is a promising candidate topological superconductors. Recent experiments suggest that the three-dimensional Fermi surface evolves into two-dimensional one. We show that the superconducting energy gap structure on the Fermi surface systematically changes with this evolution. It is clarified that the bulk electronic properties, such as spin-lattice relaxation rate and specific heat, depend on the shape of the Fermi surface and the type of the energy gap function. These results serve as a guide to determine the pairing symmetry of CuxBi2Se3.

Hashimoto, Tatsuki; Yada, Keiji; Yamakage, Ai; Sato, Masatoshi; Tanaka, Yukio

2014-10-01

9

Temperature dependence of superconducting gap and penetration depth for MgB2  

NASA Astrophysics Data System (ADS)

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.

Karakaya, Seniye; Ozbas, Omer

2012-09-01

10

The origin of multiple superconducting gaps in MgB2.  

PubMed

Magnesium diboride, MgB2, has the highest transition temperature (T(c) = 39 K) of the known metallic superconductors. Whether the anomalously high T(c) can be described within the conventional BCS (Bardeen-Cooper-Schrieffer) framework has been debated. The key to understanding superconductivity lies with the 'superconducting energy gap' associated with the formation of the superconducting pairs. Recently, the existence of two kinds of superconducting gaps in MgB2 has been suggested by several experiments; this is in contrast to both conventional and high-T(c) superconductors. A clear demonstration of two gaps has not yet been made because the previous experiments lacked the ability to resolve the momentum of the superconducting electrons. Here we report direct experimental evidence for the two-band superconductivity in MgB2, by separately observing the superconducting gaps of the sigma and pi bands (as well as a surface band). The gaps have distinctly different sizes, which unambiguously establishes MgB2 as a two-gap superconductor. PMID:12721624

Souma, S; Machida, Y; Sato, T; Takahashi, T; Matsui, H; Wang, S-C; Ding, H; Kaminski, A; Campuzano, J C; Sasaki, S; Kadowaki, K

2003-05-01

11

Measurement of an Enhanced Superconducting Phase and a Pronounced Anisotropy of the Energy Gap of a Strained FeSe Single Layer in FeSe /Nb:SrTiO3/KTaO3 Heterostructures Using Photoemission Spectroscopy  

NASA Astrophysics Data System (ADS)

Single-layer FeSe films with an extremely expanded in-plane lattice constant of 3.99±0.02 Å are fabricated by epitaxially growing FeSe /Nb:SrTiO3/KTaO3 heterostructures and studied by in situ angle-resolved photoemission spectroscopy. Two elliptical electron pockets at the Brillouin zone corner are resolved with negligible hybridization between them, indicating that the symmetry of the low-energy electronic structure remains intact as a freestanding single-layer FeSe, although it is on a substrate. The superconducting gap closes at a record high temperature of 70 K for the iron-based superconductors. Intriguingly, the superconducting gap distribution is anisotropic but nodeless around the electron pockets, with minima at the crossings of the two pockets. Our results place strong constraints on current theories.

Peng, R.; Shen, X. P.; Xie, X.; Xu, H. C.; Tan, S. Y.; Xia, M.; Zhang, T.; Cao, H. Y.; Gong, X. G.; Hu, J. P.; Xie, B. P.; Feng, D. L.

2014-03-01

12

Measurement of an enhanced superconducting phase and a pronounced anisotropy of the energy gap of a strained FeSe single layer in FeSe/Nb:SrTiO3/KTaO3 heterostructures using photoemission spectroscopy.  

PubMed

Single-layer FeSe films with an extremely expanded in-plane lattice constant of 3.99±0.02??Å are fabricated by epitaxially growing FeSe/Nb:SrTiO3/KTaO3 heterostructures and studied by in situ angle-resolved photoemission spectroscopy. Two elliptical electron pockets at the Brillouin zone corner are resolved with negligible hybridization between them, indicating that the symmetry of the low-energy electronic structure remains intact as a freestanding single-layer FeSe, although it is on a substrate. The superconducting gap closes at a record high temperature of 70 K for the iron-based superconductors. Intriguingly, the superconducting gap distribution is anisotropic but nodeless around the electron pockets, with minima at the crossings of the two pockets. Our results place strong constraints on current theories. PMID:24679321

Peng, R; Shen, X P; Xie, X; Xu, H C; Tan, S Y; Xia, M; Zhang, T; Cao, H Y; Gong, X G; Hu, J P; Xie, B P; Feng, D L

2014-03-14

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)

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.

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

1999-01-01

14

PHYSICAL REVIEW B 83, 104511 (2011) Superconducting energy gap in MgCNi3 single crystals: Point-contact spectroscopy  

E-print Network

-contact spectroscopy and specific-heat measurements Z. Pribulov´a,1 J. Kacmarc´ik,1 C. Marcenat,2 P. Szab´o,1 T. Klein may play an important role. Energy band calculations2 have shown that the density of states

Boyer, Edmond

15

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

E-print Network

Point contacts are used to investigate the anisotropy of the superconducting energy gap in LuNi2B2C in the ab plane and along the c axis. It is shown that the experimental curves should be described assuming that the superconducting gap...

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

2005-01-01

16

Superconducting-to-Normal Switching and I-V Experiments showing Multiple Tunneling Channels in a Multi-Gap Superconductor  

NASA Astrophysics Data System (ADS)

Magnesium diboride is a BCS superconductor with many interesting properties, notably its two superconducting energy gaps associated with the disconnected sheets of its Fermi surface. A heterojunction, using the dual-gap MgB2 and a single-gap superconductor as its superconducting electrodes, provides a system well-suited for exploring the unique properties of MgB2, by exhibiting multiple tunneling channels. We present data from superconducting-to-normal state switching experiments and tunneling spectroscopy experiments to temperatures as low as 20mK that indicate multiple tunneling channels in this multiple-gap superconductor. We describe features of escape rates and I-V curves that may be consistent with recent published theoretical work on macroscopic quantum tunneling in multi-gap superconductors.

Carabello, Steve; Lambert, Joseph; Mlack, Jerome; Dai, Wenqing; Shen, Yi.; Li, Qi; Cunnane, Daniel; Zhuang, C. G.; Chen, Ke; Xi, X. X.; Ramos, Roberto

2012-02-01

17

Energy gaps in high-transition-temperature cuprate superconductors  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

18

An Abelian Ward identity and the vertex corrections to the color superconducting gap  

E-print Network

We derive an Abelian-like Ward identity in color superconducting phase and calculate vertex corrections to the color superconducting gap. Making use of the Ward identity, we show that subleading order contributions to the gap from vertices are absent for gapped excitations.

Hao-jie Xu; Qun Wang

2008-10-13

19

Analysis and performance of an axial-gap superconducting motor  

NASA Astrophysics Data System (ADS)

The performance of a variable-speed, ac, superconducting motor has been evaluated. A novel axial-gap geometry was chosen for four-pole, 1800-r/min operation, using a superconducting stator and normal armature. The pool-boiling cryostat contains four solenoidal field windings of filamentary niobium-titanium conductor and has a maximum field of 7 T and an air-gap field of 2-3 T. The armature windings are formed from copper Litz wire and are arranged in 48 radial slots. The wires inside diameter and outside diameter are 17.18 and 69.24 cm, respectively. The armature is driven by three-phase power supplied via slip rings and an adjustable-speed drive. The maximum design power is 100 hp, which can be doubled by using two armatures. Motor-performance data as a function of speed and air-gap flux density are presented for initial low-power tests with a drive capable of delivering 60 A per phase to the armature.

Hawsey, R. A.; Kahl, W. K.; Schwenterly, S. W.; Bailey, J. M.; Sohns, C. W.

1991-03-01

20

Possibility of large superconducting gaps in the presence of quantum fluctuations  

NASA Astrophysics Data System (ADS)

According to the BCS model, the probability vk2 of filling electronic states as a function of kinetic energy is smeared out. A modified mechanism for formation of vk2 that includes fluctuations near quantum phase transitions is proposed. The superconducting gap ? for materials with parameters close to those of HTSC materials is estimated when fluctuations are present and the result is comparable to actual observations. The major characteristics of the proposed model resemble those of the model used to describe HTSC materials.

Zhilyaev, I. N.

2012-11-01

21

Superconducting energy storage  

SciTech Connect

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.

Giese, R.F.

1993-10-01

22

Phonon imaging in superconducting Pb crystals: Absence of large gap anisotropy and spin-density waves  

NASA Astrophysics Data System (ADS)

We show that anisotropies in the electronic structure of a superconducting metal can be probed with ballistic acoustic phonons at low temperatures. We were motivated by the possibility that Pb has narrow valleys of lowered gap, possibly caused by the spin-density wave (SDW) postulated by Overhauser and Daemen [Phys. Rev. Lett. 61, 1885 (1988)]. Our experiments and analysis on crystals of different thickness, plus results with a phonon-frequency filter, do not support their idea of deep valleys in the superconducting gap parameter. For a spherical Fermi surface, phonon scattering would be isotropic but for the highly anisotropic Fermi surface of Pb, the scattering rate depends on the direction of the phonon wave vector, q . To observe this anisotropy, we perform phonon-imaging experiments on high-purity Pb crystals cooled between 1.45 and 2.1 K. At this low temperature the mean-free path of a phonon can extend to millimeter distances if its energy is less than the superconducting energy gap, 2?o . In this regime, phonons are absorbed by thermally excited quasiparticles on the Fermi surface. Phonon images show a striking pattern of phonon absorption that becomes stronger as the temperature is raised. The anisotropy is explained by a calculation of phonon scattering on the actual Fermi surface of Pb without recourse to SDWs. The preliminary temperature dependences reported in this paper, which assumes that the quasiparticles doing the scattering are in equilibrium at the lattice temperature, are much weaker than the low-temperature form exp(-?o/kBT) predicted by the BCS theory of superconductivity. Even accounting for the inherent scattering of phonons from isotopes in the crystal, we find a path-length dependence of phonon-absorption coefficient inconsistent with deep SDW valleys. A phonon filter experiment designed to attenuate phonons that would eject quasiparticles from such valleys clearly supports this conclusion. A resolution of the anomalous temperature and sample-length dependences, plus a measurement of the superconducting gap by phonon-imaging, is reported in the following paper.

Short, J. D.; Head, T. L.; Wolfe, J. P.

2008-08-01

23

Ultrafast quenching of electron–boson interaction and superconducting gap in a cuprate superconductor  

NASA Astrophysics Data System (ADS)

Ultrafast spectroscopy is an emerging technique with great promise in the study of quantum materials, as it makes it possible to track similarities and correlations that are not evident near equilibrium. Thus far, however, the way in which these processes modify the electron self-energy—a fundamental quantity describing many-body interactions in a material—has been little discussed. Here we use time- and angle-resolved photoemission to directly measure the ultrafast response of self-energy to near-infrared photoexcitation in high-temperature cuprate superconductor. Below the critical temperature of the superconductor, ultrafast excitations trigger a synchronous decrease of electron self-energy and superconducting gap, culminating in a saturation in the weakening of electron–boson coupling when the superconducting gap is fully quenched. In contrast, electron–boson coupling is unresponsive to ultrafast excitations above the critical temperature of the superconductor and in the metallic state of a related material. These findings open a new pathway for studying transient self-energy and correlation effects in solids.

Zhang, Wentao; Hwang, Choongyu; Smallwood, Christopher L.; Miller, Tristan L.; Affeldt, Gregory; Kurashima, Koshi; Jozwiak, Chris; Eisaki, Hiroshi; Adachi, Tadashi; Koike, Yoji; Lee, Dung-Hai; Lanzara, Alessandra

2014-09-01

24

Germany's green - energy gap  

Microsoft Academic Search

Germany stumbles in its move to replace coal and nuclear power with offshore wind energy. The six offshore wind turbines that REpower Systems began erecting near Germany's coast in 2004 make their older cousins look like pin wheels. Each one has three 61.5-meter blades, which in a good breeze make one revolution every 5 seconds, producing 5 megawatts of electric

P. Fairley

2009-01-01

25

Superconducting Gap and Valence Band of Mg10Ir19B16 Studied by Laser and Synchrotron Photoemission Spectroscopy  

NASA Astrophysics Data System (ADS)

We report the results of first photoemission spectroscopy on a newly discovered noncentrosymmetric superconductor Mg10Ir19B16. We measured the valence band structure of Mg10Ir19B16 using soft X-ray photoemission technique and found that the first principal calculation explains our observation well. In the bulk-sensitive laser-excited photoemission study, we observed that the intensity at the Fermi level decreases as we lower the sample temperature, indicative of the opening of superconducting energy gap. Using Dynes’ function, we performed fitting analysis on the spectra of superconducting state.

Yoshida, Rikiya; Okazaki, Hiroyuki; Iwai, Keisuke; Noami, Kengo; Muro, Takayuki; Okawa, Mario; Ishizaka, Kyoko; Shin, Shik; Li, Zheng; Luo, Jianlin; Zheng, Guo-qing; Oguchi, Tamio; Hirai, Masaaki; Muraoka, Yuji; Yokoya, Takayoshi

2009-03-01

26

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

27

Heat transport in Mo3Sb7 single crystal: Evidence for nodeless s-wave superconducting gap  

NASA Astrophysics Data System (ADS)

We investigate the superconducting gap structure of the intermetallic superconductor Mo3Sb7 single crystal by low-temperature thermal conductivity measurements. In zero field, the absence of a residual linear term ?0/T in the T?0 limit provides strong evidence for nodeless superconducting gap. The field dependence of ?0/T is very similar to that of InBi, a typical s-wave superconductor in the dirty limit. These results demonstrate that Mo3Sb7 has nodeless s-wave superconducting gap, despite the opening of a spin gap at 53 K and the possible interplay between superconductivity and magnetism.

Dong, W. N.; Pan, J.; Zhang, J.; Hong, X. C.; He, L. P.; Zhou, S. Y.; Dong, J. K.; Li, S. Y.

2014-10-01

28

Measurement of a sign-changing two-gap superconducting phase in electron-doped Ba(Fe(1-x)Co(x))2As2 single crystals using scanning tunneling spectroscopy.  

PubMed

Scanning tunneling spectroscopic studies of Ba(Fe(1-x)Co(x))(2)As(2) (x=0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition T(c). The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave vectors (±?, 0) and (0, ±?) are consistent with sign-changing s-wave superconductivity. The excess zero-bias conductance and the large gap-to-T(c) ratios suggest dominant unitary impurity scattering. PMID:21405593

Teague, M L; Drayna, G K; Lockhart, G P; Cheng, P; Shen, B; Wen, H-H; Yeh, N-C

2011-02-25

29

Development of the axial gap type motor\\/generator for the flywheel with superconducting magnetic bearings  

Microsoft Academic Search

Flywheel with superconducting magnetic bearings requires the characteristics for the motor\\/generator such as lower loss, higher efficiency, lower bearing load and more displacement tolerance of the radial directions. We developed an extremely flat shape axial gap type motor\\/generator which consists of a rotor with permanent magnets and slotless windings to satisfy these characteristics. We introduced the system for adjusting intensity

S. Nagaya; N. Kashima; H. Kawashima; Y. Kakiuchi; A. Hoshino; S. Isobe

2003-01-01

30

Superconducting Levitation Styles for Superconducting Energy Storage Flywheel  

Microsoft Academic Search

The flywheel comprising of magnetic and superconducting bearings, which will provide a stable levitation of rotor, is fit for energy storage. According to the HTS cooling mode, there are ZFC bearings and FC bearings. ZFC bearings produce a large levitation force, but they ensure only one direction suspension. FC bearings produce less level of levitation force, but they provide passive

Jiqiang Tang; Yanshun Zhang; Jiancheng Fang

2007-01-01

31

Two-gap superconductivity in heavily n-doped graphene: Ab initio Migdal-Eliashberg theory  

NASA Astrophysics Data System (ADS)

Graphene is the only member of the carbon family from zero- to three-dimensional materials for which superconductivity has not been observed yet. At this time, it is not clear whether the quest for superconducting graphene is hindered by technical challenges, or else by the fluctuation of the order parameter in two dimensions. In this area, ab initio calculations are useful to guide experimental efforts by narrowing down the search space. In this spirit, we investigate from first principles the possibility of inducing superconductivity in doped graphene using the fully anisotropic Migdal-Eliashberg theory powered by Wannier-Fourier interpolation. To address a best-case scenario, we consider both electron and hole doping at high carrier densities so as to align the Fermi level to a van Hove singularity. In these conditions, we find superconducting gaps of s-wave symmetry, with a slight anisotropy induced by the trigonal warping, and, in the case of n-doped graphene, an unexpected two-gap structure reminiscent of MgB2. Our Migdal-Eliashberg calculations suggest that the observation of superconductivity at low temperature should be possible for n-doped graphene at carrier densities exceeding 1015cm-2.

Margine, E. R.; Giustino, Feliciano

2014-07-01

32

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

NASA Astrophysics Data System (ADS)

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.

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

33

Fully gapped superconductivity in a nanometre-size YBa2Cu3O7-? island enhanced by a magnetic field  

NASA Astrophysics Data System (ADS)

The symmetry of Cooper pairs is central to constructing a superconducting state. The demonstration of a -wave order parameter with nodes represented a breakthrough for high critical temperature superconductors (HTSs). However, despite this fundamental discovery, the origin of superconductivity remains elusive, raising the question of whether something is missing from the global picture. Deviations from -wave symmetry, such as an imaginary admixture + is (or idxy), predict a ground state with unconventional properties exhibiting a full superconducting gap and time reversal symmetry breaking. The existence of such a state, until now highly controversial, can be proved by highly sensitive measurements of the excitation spectrum. Here, we present a spectroscopic technique based on an HTS nanoscale device that allows an unprecedented energy resolution thanks to Coulomb blockade effects, a regime practically inaccessible in these materials previously. We find that the energy required to add an extra electron depends on the parity (odd/even) of the excess electrons on the island and increases with magnetic field. This is inconsistent with a pure -wave symmetry and demonstrates a complex order parameter component that needs to be incorporated into any theoretical model of HTS.

Gustafsson, D.; Golubev, D.; Fogelström, M.; Claeson, T.; Kubatkin, S.; Bauch, T.; Lombardi, F.

2013-01-01

34

Directional dependence of a color superconducting gap in two-flavor QCD in a magnetic field  

NASA Astrophysics Data System (ADS)

We study the effect of a magnetic field on the pairing dynamics in two-flavor color superconducting dense quark matter. The study is performed in the weakly coupled regime of QCD at asymptotically high density, using the framework of the Schwinger-Dyson equation in the improved rainbow approximation. We show that the superconducting gap function develops a directional dependence in momentum space. Quasiparticles with momenta perpendicular to the direction of the magnetic field have the largest gaps, while quasiparticles with momenta parallel to the field have the smallest gaps. We argue that the directional dependence is a consequence of a long-range interaction in QCD. The quantitative measure of the ellipticity of the gap function is determined by a dimensionless ratio, proportional to the square of the magnetic field and inversely proportional to the fourth power of the quark chemical potential. For magnetic fields in stars, B?1018G, the corresponding ratio is estimated to be less than about 10-2, justifying the use of the weak magnetic field limit in all stellar applications.

Yu, Lang; Shovkovy, Igor A.

2012-04-01

35

Energy loss in spark gap switches  

NASA Astrophysics Data System (ADS)

The paper reports on numerical study of the energy loss in spark gap switches. The operation of the switches is analyzed using the Braginsky model which allows calculation of the time dependence of the spark channel resistance. The Braginsky equation is solved simultaneously with generator circuit equations for different load types. Based on the numerical solutions, expressions which determine both the energy released in a spark gap switch and the switching time are derived.

Oreshkin, V. I.; Lavrinovich, I. V.

2014-04-01

36

Photonic band gaps of a two-dimensional square lattice composed by superconducting hollow rods  

NASA Astrophysics Data System (ADS)

In this paper by means of the plane wave expansion method, we have calculated the photonic band structure of 2D photonic crystals consisting of high temperature superconducting hollow cylinders arranged in a square lattice. Band structures were obtained at low frequencies and assuming TM polarization of the incident wave, for different inner radii of the cylinders and for two different temperatures (5 K and 15 K), showing the tunability of photonic band gaps with respect to these parameters. Interesting features, such as the decreasing of cutoff frequency and separation of photonic modes were observed by increasing both the temperature and inner radius. Permittivity contrast and the difference between the inner and outer radius lead to the appearance of new band gaps when compared with the case of solid cylinders. These band gaps can be modulated by the width of the shell and temperature, which may be used for the development of novel optical devices.

Diaz-Valencia, B. F.; Calero, J. M.

2014-10-01

37

Superconducting RF for energy-recovery linacs  

NASA Astrophysics Data System (ADS)

Since superconducting RF for particle accelerators made its first appearance in the 1970s, it has found highly successful application in a variety of machines. Recent progress in this technology has made so-called Energy-Recovery Linacs (ERLs)—originally proposed in 1965—feasible, and interest in this type of machine has increased enormously. A superconducting linac is the driving heart of ERLs, and emittance preservation and cost efficiency is of utmost importance. The resulting challenges for the superconducting cavity technology and RF field control are manifold. In March 2005 the first international workshop on ERLs was held at Newport News, VA, to explore the potential of ERLs and to discuss machine-physics and technology challenges and their solutions. This paper reviews the state-of-the-art in superconducting RF and RF control for ERLs, and summarizes the discussions of the SRF working group on this technology during the ERL2005 workshop.

Liepe, M.; Knobloch, J.

2006-02-01

38

Flywheel energy storage using superconducting magnetic bearings  

Microsoft Academic Search

Storage of electrical energy on a utility scale is currently not practicable for most utilities, preventing the full utilization of existing base-load capacity. A potential solution to this problem is Flywheel Energy Storage (FES), made possible by technological developments in high-temperature superconducting materials. Commonwealth Research Corporation (CRC), the research arm of Commonwealth Edison Company, and Argonne National Laboratory are implementing

R. G. Abboud; K. Uherka; J. Hull; T. Mulcahy; R ABBOUD

1994-01-01

39

Multiple nodeless superconducting gaps in optimally doped SrTi1 -xNbxO3  

NASA Astrophysics Data System (ADS)

We present a study of thermal conductivity in superconducting SrTi1 -xNbxO3, sufficiently doped to be near its maximum critical temperature. The bulk critical temperature, determined by the jump in specific heat, occurs at a significantly lower temperature than the resistive Tc. Thermal conductivity, dominated by the electron contribution, deviates from its normal-state magnitude at bulk Tc, following a Bardeen-Rickayzen-Tewordt behavior, which is expected for thermal transport by Bogoliubov excitations. The absence of a T-linear term at very low temperatures rules out the presence of nodal quasiparticles. On the other hand, the field dependence of thermal conductivity points to the existence of at least two distinct superconducting gaps. We conclude that optimally doped strontium titanate is a multigap nodeless superconductor.

Lin, Xiao; Gourgout, Adrien; Bridoux, German; Jomard, François; Pourret, Alexandre; Fauqué, Benoît.; Aoki, Dai; Behnia, Kamran

2014-10-01

40

High temperature superconducting magnetic energy storage for future NASA missions  

NASA Technical Reports Server (NTRS)

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.

Faymon, Karl A.; Rudnick, Stanley J.

1988-01-01

41

Superconducting phase coherence and pairing gap in the three-dimensional attractive Hubbard model  

NASA Astrophysics Data System (ADS)

We consider a lattice version of the ``negative-U'' Hubbard model in three dimensions, to study the crossover from a superconducting phase transition (dominated by phase fluctuation) to a regime where the amplitude of the superconducting order parameter controls the critical temperature. Starting from a fermionic Hamiltonian, we give a microscopic derivation of the effective action in terms of the relevant physical fields: the modulus and phase of the superconducting order parameter. Furthermore, by employing to the resulting coarse-grained quantum XY model the phase fluctuation algebra between number and phase operators (given by the Euclidean group E2), we map the ``phase-only'' action onto a solvable quantum spherical model. We establish the self-consistent theory (involving both fermionic and bosonic degrees of freedom), and calculate the superconducting phase coherence transition temperature Tc as a function of the coupling strength \\|U\\|, exhibiting a maximum where the behavior crosses over from BCS to Bose-Einstein (BE) condensation. We examine a pseudogap in the normal state which emerges naturally as a precursor of superconductivity at the second characteristic temperature Tg due to a state with bound pairs but without long-range phase coherence. Furthermore, we demonstrate that the reduced gaps of the model 2?0/kBTg~4 is almost independent on the pairing strength \\|U\\|/t, whereas 2?0/kBTc increases with increasing \\|U\\|-in striking analogy with the phenomenology of the high-temperature cuprate superconductors when interpreted in terms of the BCS-BC crossover scenario.

Kope?, T. K.

2002-02-01

42

Impurity energy level in the Haldane gap.  

National Technical Information Service (NTIS)

An impurity bond J' in a periodic 1D antiferromagnetic spin 1 chain with exchange J is considered. Using the numerical density matrix renormalization group method, we find an impurity energy level in the Haldane gap, corresponding to a bound state near th...

Wang Wei Qin Shaojin Su Zhaobin Lu Zhongyi Lu Yu

1995-01-01

43

NMR Study of the Superconducting Gap Variation near the Mott Transition in Cs3C60  

NASA Astrophysics Data System (ADS)

Former extensive studies of superconductivity in the A3C60 compounds, where A is an alkali metal, have led one to consider that Bardeen-Cooper-Schrieffer electron-phonon pairing prevails in those compounds, though the incidence of electronic Coulomb repulsion has been highly debated. The discovery of two isomeric fulleride compounds Cs3C60 which exhibit a transition with pressure from a Mott insulator (MI) to a superconducting (SC) state clearly reopens that question. Using pressure (p) as a single control parameter of the C60 balls lattice spacing, one can now study the progressive evolution of the SC properties when the electronic correlations are increased towards the critical pressure pc of the Mott transition. We have used C13 and Cs133 NMR measurements on the cubic phase A15-Cs3C60 just above pc=5.0(3) kbar, where the SC transition temperature Tc displays a dome shape with decreasing cell volume. From the T dependence below Tc of the nuclear spin lattice relaxation rate (T1)-1 we determine the electronic excitations in the SC state, that is 2?, the gap value. The latter is found to be largely enhanced with respect to the Bardeen-Cooper-Schrieffer value established in the case of dense A3C60 compounds. It even increases slightly with decreasing p towards pc, where Tc decreases on the SC dome, so that 2? /kBTc increases regularly upon approaching the Mott transition. These results bring clear evidence that the increasing correlations near the Mott transition are not significantly detrimental to superconductivity. They rather suggest that repulsive electron interactions might even reinforce elecron-phonon superconductivity, being then partly responsible for the large Tc values, as proposed by theoretical models taking the electronic correlations as a key ingredient.

Wzietek, P.; Mito, T.; Alloul, H.; Pontiroli, D.; Aramini, M.; Riccò, M.

2014-02-01

44

Calculation of the Superconductivity Gap of Metal from Its Parameters in Normal State  

E-print Network

A previously considered model interpreted a superconductor as an electron gas immersed in a medium with the dielectric constant $\\epsilon$ and a certain elasticity, which could be determined by measured sonic speed in the metal. The obtained expression of effective electron-electron interaction (EEI) potential unambiguously implied that, contrary to the suggestions of BCS theory, it is its long-wave limit which is responsible for the emergence of bound two-electron states and, consequently, for gap formation in one-electron spectrum of the metal. However, the existence of singularities in the EEI potential expression continued to pose a problem, which did not allow a calculation of the gap value for specific superconducting materials, first of all, for metals belonging to periodic table (PT). In the present work, I suggest taking into account matrix elements traditionally attributed to electron scattering in EEI effective potential calculations. For superconductors that has been made on the basis of a semiconductor material by implanting electro-active defects into it, this inclusion results in the appearance of an uncertainty of electron momentum $\\delta p \\sim l^{- 1}$, where $l$ is the electron free path. When considering pure PT metals, Hamiltonian terms relating to creation and annihilaton of phonons should be taken into account, which also produces an uncertainty of electron momentum. This uncertainty results in a regularization of EEI potential expression and, therefore, in a possibility of examination of physical properties of specific superconductors. Results of calculation of superconductivity gap value for a range of simple metals (Al, Zn, Pb, Sn) confirm the consistency of the developed approach.

I. M. Yurin

2006-03-29

45

Spin gap and superconductivity in the three-dimensional attractive Hubbard model  

NASA Astrophysics Data System (ADS)

We study the phase diagram for the attractive (i.e., negative-U) Hubbard model on a simple-cubic lattice, through Monte Carlo simulations. We obtain the critical temperature Tc for superconductivity from a finite-size scaling analysis of the data for the pairing correlations. For fixed on-site attraction U, Tc displays a maximum near the filling factor 0.9, roughly independent of U. For fixed filling we estimate the crossover temperature T×(U), separating the normal states: metallic and spin gap. There is also a critical value Up for pair formation, the magnitude of which seems to be independent of doping. The relevance of these results to the high-Tc oxides is discussed.

Santos, Raimundo R.

1994-07-01

46

Pushing the Gradient Limitations of Superconducting Photonic Band Gap Structure Cells  

SciTech Connect

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.

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

47

Gap-Inhomogeneity-Induced Electronic States in Superconducting Bi2Sr2CaCu2O8+delta  

SciTech Connect

In this Letter, we analyze, using scanning tunneling spectroscopy, the density of electronic states in nearly optimally doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} in zero magnetic field. Focusing on the superconducting gap, we find patches of what appear to be two different phases in a background of some average gap, one with a relatively small gap and sharp large coherence peaks and one characterized by a large gap with broad weak coherence peaks. We compare these spectra with calculations of the local density of states for a simple phenomenological model in which a 2{zeta}{sub 0} x 2{zeta}{sub 0} patch with an enhanced or suppressed d-wave gap amplitude is embedded in a region with a uniform average d-wave gap.

Fang, A.C.

2010-02-25

48

Effect of antiferromagnetic ordering on temperature dependent superconducting gap in ErNi 2B 2C: Laser-photoemission spectroscopy  

NASA Astrophysics Data System (ADS)

We have performed temperature ( T)-dependent laser-photoemission spectroscopy of antiferromagnetic (AF) superconductor ErNi 2B 2C to study the electronic structure, especially the effect of AF ordering in T-dependent superconducting (SC) gap. To estimate the values of T-dependent SC gap, we fitted the experimental data by Dynes function having an anisotropic s-wave SC gap. From the fitting results, we find a sudden deviation from the BCS prediction just below TN. This observation can be well explained by the theoretical model, indicating that the origin of anomalous T-dependence is competition between rapid evolution of AF molecular field and SC condensation energy.

Baba, T.; Yokoya, T.; Tsuda, S.; Kiss, T.; Shimojima, T.; Ishizaka, K.; Takeya, H.; Hirata, K.; Nakai, N.; Machida, K.; Togashi, T.; Chen, C. T.; Zhang, C. Q.; Watanabe, S.; Shin, S.

2009-10-01

49

Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe0.55Se0.45  

NASA Astrophysics Data System (ADS)

We used angle-resolved photoemission spectroscopy to reveal directly the momentum distribution of the superconducting gap in FeTe1-xSex, which has the simplest structure of all Fe-based superconductors. We found isotropic superconducting gaps on all Fermi surfaces whose sizes can be fitted by a single gap function derived from a strong coupling approach, promoting local antiferromagnetic exchange interactions as a serious candidate for the pairing origin.

Miao, H.; Richard, P.; Tanaka, Y.; Nakayama, K.; Qian, T.; Umezawa, K.; Sato, T.; Xu, Y.-M.; Shi, Y. B.; Xu, N.; Wang, X.-P.; Zhang, P.; Yang, H.-B.; Xu, Z.-J.; Wen, J. S.; Gu, G.-D.; Dai, X.; Hu, J.-P.; Takahashi, T.; Ding, H.

2012-03-01

50

Superconducting condensation energy of CeCu2Si2 and theoretical implications  

NASA Astrophysics Data System (ADS)

Unconventional superconductivity occurs in a broad range of strongly correlated electron systems including the newly discovered iron pnictides and chalcogenides, various intermetallic rare earth metals, the cuprates and the organic superconductors. These systems are not only of varying effective dimensionality but their parent compounds out of which superconductivity emerges ranges from metals to bad metals and Mott insulators. The only unifying characteristic features seems that unconventional superconductivity occurs in close vicinity of zero-temperature instabilities which are most often magnetic in nature. Heavy fermion compounds represent prototype systems to address the interplay between quantum criticality and unconventional superconductivity [1]. In CeCu2Si2, the magnetic quantum phase transition and superconductivity occur at ambient pressure which allows for a detailed study of the energetics across the superconducting transition. Based on an in-depth study of the magnetic excitation spectrum of CeCu2Si2 in the normal and superconducting state we obtain a lower bound for the change in exchange energy [2]. The comparison with the superconducting condensation energy demonstrates that the built-up of magnetic correlations near the quantum critical point does drive superconductivity in CeCu2Si2. In addition, our comparison establishes a huge kinetic energy loss which we relate to the competition of Kondo screening and superconductivity as the opening of the gap weakens the Kondo effect [2,3]. We discuss the relation between kinetic energy loss and the nature of the underlying quantum critical point [1,3]. Our unexpected findings sheds further light on the emerging global phase diagram of heavy fermion compounds [4] and are believed to be relevant to other families of superconductivity which are also located in close proximity to magnetism.[4pt] [1] O. Stockert, S. Kirchner, F. Steglich, Q. Si, ``Superconductivity in Ce- and U-based 122 heavy-fermion compounds,'' to be published in JPSJ (invited review paper).[0pt] [2] O. Stockert, J. Arndt, E. Faulhaber, C. Geibel, H. S. Jeevan, S. Kirchner, M. Loewenhaupt, K. Schmalzl, W. Schmidt, Q. Si, F. Steglich, ``Magnetically driven superconductivity in CeCu2Si2,'' Nature Physics, 7, 119-124 (2011).[0pt] [3] S. Kirchner and Q. Si, to be published.[0pt] [4] Q. Si, ``Quantum Criticality and Global Phase Diagram of Magnetic Heavy Fermions,'' Phys. Status Solidi B247, 476 (2010).

Kirchner, Stefan

2012-02-01

51

Two-gap superconductivity in R2Fe3Si5 (R=Lu, Sc) and Sc5Ir4Si10  

NASA Astrophysics Data System (ADS)

R2Fe3Si5 (R= Sc, Y, Lu) contains nonmagnetic iron and has a relatively high superconducting transition temperature Tc among iron-containing superconductors. An anomalous temperature dependence of specific heat C(T) has been reported for polycrystalline samples down to 1 K. We have grown R2Fe3Si5 single crystals, confirmed the anomalous C(T) dependence, and found a second drop in specific heat below 1 K. In Lu2Fe3Si5, we can reproduce C(T) below Tc, assuming two distinct energy gaps 2? 1/kBTc = 4.4 and 2? 2/kBTc = 1.1, with nearly equal weights, indicating that Lu2Fe3Si5 is a two-gap superconductor similar to MgB2. Hall coefficient measurements and band structure calculation also support the multiband contributions to the normal-state properties. The specific heat in the Sc2Fe3Si5 single crystals also shows the two-gap feature. R5Ir4Si10 (R = Sc, rare earth) is also a superconductor where competition between superconductivity and the charge-density wave is known for rare earths but not for Sc. We have performed detailed specific heat measurements on Sc5Ir4Si10 single crystals and found that C(T) deviates slightly from the behavior expected for weak-coupling superconductors. C(T) for these superconductors can also be reproduced well by assuming two superconducting gaps.

Tamegai, Tsuyoshi; Nakajima, Yasuyuki; Nakagawa, Tsuyoshi; Li, Guoji; Harima, Hisatomo

2008-12-01

52

Superconducting magnetic energy storage for asynchronous electrical systems  

DOEpatents

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.

Boenig, H.J.

1984-05-16

53

Doping dependence of the superconducting gap in Bi2Sr2CaCu2O8+delta  

Microsoft Academic Search

Bi2Sr2CaCu2O8+delta crystals with varying hole concentrations (0.12superconducting gap [Delta(k)]. Electronic Raman scattering experiments that sample regions of the Fermi surface near the diagonal (B2g) and principal axes (B1g) of the Brillouin zone have been utilized. The frequency dependence of the Raman response function chi''

K. C. Hewitt; J. C. Irwin

2002-01-01

54

Total energy intake, adolescent discretionary behaviors and the energy gap  

Microsoft Academic Search

Objective:To estimate total energy intake and the energy gap—the daily imbalance between energy intake and expenditure—associated with discretionary behaviors of adolescents, namely their leisure active behaviors (playing or participating in sports and heavy chores), leisure sedentary behaviors (television (TV) viewing and playing video and computer games), productive sedentary behaviors (reading or doing homework).Design:Prospective observational study.Participants:A total of 538 students (mean

K R Sonneville; S L Gortmaker

2008-01-01

55

Method for making mirrored surfaces comprising superconducting material  

DOEpatents

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.

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

1989-12-12

56

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

57

Flywheel energy storage using superconducting magnetic bearings  

SciTech Connect

Storage of electrical energy on a utility scale is currently not practicable for most utilities, preventing the full utilization of existing base-load capacity. A potential solution to this problem is Flywheel Energy Storage (FES), made possible by technological developments in high-temperature superconducting materials. Commonwealth Research Corporation (CRC), the research arm of Commonwealth Edison Company, and Argonne National Laboratory are implementing a demonstration project to advance the state of the art in high temperature superconductor (HTS) bearing performance and the overall demonstration of efficient Flywheel Energy Storage. Currently, electricity must be used simultaneously with its generation as electrical energy storage is not available for most utilities. Existing storage methods either are dependent on special geography, are too expensive, or are too inefficient. Without energy storage, electric utilities, such as Commonwealth Edison Company, are forced to cycle base load power plants to meet load swings in hourly customer demand. Demand can change by as much as 30% over a 12-hour period and result in significant costs to utilities as power plant output is adjusted to meet these changes. HTS FES systems can reduce demand-based power plant cycling by storing unused nighttime capacity until it is needed to meet daytime demand.

Abboud, R.G. [Commonwealth Research Corp., Chicago, IL (United States); Uherka, K.; Hull, J.; Mulcahy, T. [Argonne National Lab., IL (United States)

1994-04-01

58

Superconductivity  

SciTech Connect

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.

Langone, J.

1989-01-01

59

Superconducting phase coherence and pairing gap in the three-dimensional attractive Hubbard model  

Microsoft Academic Search

We consider a lattice version of the ``negative-U'' Hubbard model in three dimensions, to study the crossover from a superconducting phase transition (dominated by phase fluctuation) to a regime where the amplitude of the superconducting order parameter controls the critical temperature. Starting from a fermionic Hamiltonian, we give a microscopic derivation of the effective action in terms of the relevant

T. K. Kopec

2002-01-01

60

A rotating superconducting solenoid for 100 kWh energy storage  

SciTech Connect

Two concentric superconducting solenoids, one rotating, the other stationary are analyzed for energy storage in space. Energy is transferred from the rotating mass through a shaft coupled to a motorgenerator. The inner windings interact with the magnetic field of the outer solenoid to cancel the centrifugal and self-field forces of the flywheel rim. Current is induced in the inner solenoid thus requiring no separate power supply, while the current in the outer solenoid must vary with the angular velocity of the flywheel. The effect of the gap and scaling laws are developed. The efficiency in energy per unit mass is marginally attractive.

Waynert, J.; Eyssa, Y.M.; Feng, Z.; McIntosh, G.E.

1985-03-01

61

System modeling for Superconducting Magnetic Energy Storage (SMES)  

E-print Network

SYSTEM MODELING FOR SUPERCONDUCTING MAGNETIC ENERGY STORAGE (SMES) A Thesis by NAYANA PHADKE Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... August 1992 Major Subject: Electrical Engineering SYSTEM MODELING FOR SUPERCONDUCTING MAGNETIC ENERGY STORAGE (SMES) A Thesis by NAYANA PHADKE Approved as to style and content by Alton D. Patton (Chair of Committee) Chanan Singh (Member) Karan...

Phadke, Nayana

2012-06-07

62

Homolumo Gap from Dynamical Energy Levels  

E-print Network

We introduce a dynamical matrix model where the matrix $X$ is interpreted as a Hamiltonian representing interaction of a bosonic system with a single fermion. We show how a system of second-quantized fermions influences the ground state of the whole system by producing a gap between the highest occupied eigenvalue and the lowest unoccupied eigenvalue. We describe the development of the gap in both, strong and weak coupling regime, while for the intermediate coupling strength we expect formation of homolumo "kinks".

I. Andric; L. Jonke; D. Jurman; H. B. Nielsen

2009-09-12

63

Fermi surface and superconducting gap of FeTe1-xSex superconductor studied by high-resolution ARPES  

NASA Astrophysics Data System (ADS)

The origin of superconductivity in FeTe1-xSex superconductor is a subject of intensive debate, since the parent compound FeTe shows considerably different electronic and magnetic properties compared to FeAs-based families. To clarify the superconducting mechanism, an experimental investigation of the low-energy electronic structure is of particular importance. Here, we report our recent high-resolution ARPES results on FeTe1-xSex superconductor, and demonstrate several universalities in the electronic states between FeTe1-xSex and FeAs-based superconductors.

Nakayama, Kosuke; Sato, Takafumi; Kawahara, Takuma; Sekiba, Yoichi; Richard, Pierre; Chen, Gen-Fu; Qian, Tian; Luo, Jian-Lin; Wang, Nan-Lin; Ding, Hong; Takahashi, Takashi

2010-03-01

64

Progress of superconducting bearing technologies for flywheel energy storage systems  

Microsoft Academic Search

We report present status of NEDO project on “Superconducting bearing technologies for flywheel energy storage systems”. We fabricated a superconducting magnetic bearing module consisting of a stator of resin impregnated YBaCuO bulks and a rotor of NdFeB permanent magnet circuits. We obtained levitation force density of 8 N\\/cm2 at 81 K and rotation loss per levitation force of 3 mW\\/N

N. Koshizuka; F. Ishikawa; H. Nasu; M. Murakami; K. Matsunaga; S. Saito; O. Saito; Y. Nakamura; H. Yamamoto; R. Takahata; Y. Itoh; H. Ikezawa; M. Tomita

2003-01-01

65

Toroidal constant-tension superconducting magnetic energy storage units  

DOEpatents

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.

Herring, J. Stephen (Idaho Falls, ID)

1992-01-01

66

Superconducting gap induced barrier enhancement in a BiFeO3-based heterostructure  

NASA Astrophysics Data System (ADS)

We report the synthesis and characterization of an epitaxial heterostructure composed of multiferroic BiFeO3 and superconducting YBa2Cu3O7-? thin films grown on (001) SrTiO3. Both the superconductivity of YBa2Cu3O7-? and the ferroelectricity of BiFeO3 are retained in the heterostructure. Current density-electric field characteristics measured from 30 to 170 K suggest a Schottky-emission-like transport at the BiFeO3/YBa2Cu3O7-? interface. Furthermore, the temperature dependence of the barrier height shows an anomalous enhancement at TC, indicating an intimate coupling between the multiferroic and the superconducting layers.

Lu, C. L.; Wang, Y.; You, L.; Zhou, X.; Peng, H. Y.; Xing, G. Z.; Chia, E. E. M.; Panagopoulos, C.; Chen, L.; Liu, J.-M.; Wang, J.; Wu, T.

2010-12-01

67

Tunneling spectra of submicron Bi2Sr2CaCu2O8+ ? intrinsic Josephson junctions: evolution from superconducting gap to pseudogap  

NASA Astrophysics Data System (ADS)

Tunneling spectra of near optimally doped, submicron Bi2Sr2CaCu2O8+ ? intrinsic Josephson junctions are presented, and examined in the region where the superconducting gap evolves into pseudogap. The spectra are analyzed using a self-energy model, proposed by Norman et al., in which both quasiparticle scattering rate ? and pair decay rate ?? are considered. The density of states derived from the model has the familiar Dynes’ form with a simple replacement of ? by ?+ = (?+??)/2. The ?+ parameter obtained from fitting the experimental spectra shows a roughly linear temperature dependence, which puts a strong constraint on the relation between ? and ??. We discuss and compare the Fermi arc behavior in the pseudogap phase from the tunneling and angle-resolved photoemission spectroscopy experiments. Our results indicate an excellent agreement between the two experiments, which is in favor of the precursor pairing view of the pseudogap.

Zhao, S. P.; Zhu, X. B.; Tang, H.

2009-09-01

68

Energy gap of Kronig-Penney-type hydrogenated graphene superlattices  

E-print Network

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 ...

Lee, Joo-Hyoung

69

Controlling the band gap energy of cluster-assembled materials.  

PubMed

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

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

2013-11-19

70

Is There an Energy Efficiency Gap?  

E-print Network

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 ...

Allcott, Hunt Volney

71

Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap  

NASA Astrophysics Data System (ADS)

Using two experimental techniques, we studied single crystals of the 122-FeAs family with almost the same critical temperature, Tc. We investigated the temperature dependence of the lower critical field Hc1(T ) of a Ca0.32Na0.68Fe2As2 (Tc?34K) single crystal under static magnetic fields H parallel to the c axis. The temperature dependence of the London penetration depth can be described equally well either by a single anisotropic s-wave-like gap or by a two-gap model, while a d-wave approach cannot be used to fit the London penetration depth data. Intrinsic multiple Andreev reflection effect spectroscopy was used to detect bulk gap values in single crystals of the intimate compound Ba0.65K0.35Fe2As2, with the same Tc. We estimated the range of the large gap value ?L=6-8 meV (depending on small variation of Tc) and its a k space anisotropy of about 30%, and the small gap ?S?1.7±0.3 meV. This clearly indicates that the gap structure of our investigated systems more likely corresponds to a nodeless s-wave two gaps.

Abdel-Hafiez, M.; Pereira, P. J.; Kuzmichev, S. A.; Kuzmicheva, T. E.; Pudalov, V. M.; Harnagea, L.; Kordyuk, A. A.; Silhanek, A. V.; Moshchalkov, V. V.; Shen, B.; Wen, Hai-Hu; Vasiliev, A. N.; Chen, Xiao-Jia

2014-08-01

72

Staying adiabatic with unknown energy gap  

E-print Network

We introduce an algorithm to perform an optimal adiabatic evolution that operates without an apriori knowledge of the system spectrum. By probing the system gap locally, the algorithm maximizes the evolution speed, thus minimizing the total evolution time. We test the algorithm on the Landau-Zener transition and then apply it on the quantum adiabatic computation of 3-SAT: The result is compatible with an exponential speed-up for up to twenty qubits with respect to classical algorithms. We finally study a possible algorithm improvement by combining it with the quantum Zeno effect.

J. Nehrkorn; S. Montangero; A. Ekert; A. Smerzi; R. Fazio; T. Calarco

2011-05-09

73

Doping dependence of low-energy quasiparticle excitations in superconducting Bi2212  

PubMed Central

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

2013-01-01

74

Superconductivity.  

PubMed

Electrons in metals can self-organise. The complex interplay between lattice dynamics, electrostatic interaction and band structure brings forth numerous types of electronic order. Because of its spectacular phenomenology, superconductivity has enjoyed a central place among these, since its discovery nearly 100 years ago. This short introduction into one of the largest fields of condensed matter research focuses on the most fundamental experimental signatures of superconductivity--perfect conductivity and perfect diamagnetism--and their explanation. A conventional broken symmetry argument is presented, which introduces a superconducting order parameter in analogy to the case of superfluid 4He, and discusses its microscopic origin in the framework of the BCS model of superconductivity. New materials have brought to light novel forms of superconductivity. Many cases are now known which fall outside the orthodox BCS model, ranging from the high temperature superconductors, to various organic and d- and f- metal compounds. The article presents key concepts from this intense area of research and touches on the equally puzzling behaviour of many of these materials above their superconducting transition temperature. PMID:15651639

Grosche, F M

2004-01-01

75

Spin gap and superconductivity in the three-dimensional attractive Hubbard model  

Microsoft Academic Search

We study the phase diagram for the attractive (i.e., negative-U) Hubbard model on a simple-cubic lattice, through Monte Carlo simulations. We obtain the critical temperature Tc for superconductivity from a finite-size scaling analysis of the data for the pairing correlations. For fixed on-site attraction U, Tc displays a maximum near the filling factor 0.9, roughly independent of U. For fixed

Raimundo R dos Santos

1994-01-01

76

Spin gap and superconductivity in the three-dimensional attractive Hubbard model  

Microsoft Academic Search

We study the phase diagram for the attractive ({\\\\it i.e.,} negative-$U$) Hubbard model on a simple cubic lattice, through Monte Carlo simulations. We obtain the critical temperature, $T_c$, for superconductivity from a finite-size scaling analysis of the data for the pairing correlations. For fixed on-site attraction, $U$, $T_c$ displays a maximum near the filling factor 0.9, roughly independent of $U$.

Raimundo R dos Santos

1994-01-01

77

Langmuir vacuum and superconductivity  

SciTech Connect

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.

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

2012-06-15

78

Nuclear energy in Malaysia - closing the gaps  

NASA Astrophysics Data System (ADS)

This article is prepared by the Malaysian Nuclear Society (MNS) to present the views of the Malaysian scientific community on the need for Malaysia to urgently upgrade its technical know-how and expertise to support the nuclear energy industry for future sustainable economic development of the country. It also present scientific views that nuclear energy will bring economic growth as well as technically sound industry, capable of supporting nuclear energy industry needs in the country, and recommend action items for timely technical upgrading of Malaysian expertise related to nuclear energy industry.

>Malaysian Nuclear Society (Mns,

2013-06-01

79

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

SciTech Connect

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 the economically irrigatable areas in the region make up 20% of those for the entire country. On the other hand, the GAP region is the richest region of the country in terms of its hydroelectric potential as well as its oil and asphalt reserves. The GAP region has a 22% share of the country's total hydroelectric potential, with plans for 22 dams and 19 hydropower plants. Once completed, 27 billion kWh of electricity will be generated. In addition to this hydropower and oil potential, the GAP region is also the richest region of Turkey as far as solar energy production is concerned. In meeting the energy requirements of the developing regions worldwide and in Turkey, solar energy is being taken into account as an important renewable source of energy.

Kaygusuz, K.

1999-12-01

80

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

SciTech Connect

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.

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

81

Is There an Energy Efficiency Gap?  

E-print Network

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 ...

Alcott, Hunt

2012-01-17

82

Is There An Energy Efficiency Gap?  

E-print Network

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 ...

Allcott, Hunt

2012-01-17

83

Color-Superconducting Gap in the Presence of a Magnetic Field  

E-print Network

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.

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

2006-03-29

84

Superconducting energy storage flywheel—An attractive technology for energy storage  

Microsoft Academic Search

Flywheel energy storage (FES) can have energy fed in the rotational mass of a flywheel, store it as kinetic energy, and release\\u000a out upon demand. The superconducting energy storage flywheel comprising of magnetic and superconducting bearings is fit for\\u000a energy storage on account of its high efficiency, long cycle life, wide operating temperature range and so on. According to\\u000a the

Ji-qiang Tang; Gang Liu; Jian-cheng Fang

2010-01-01

85

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

SciTech Connect

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.

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

1993-11-01

86

Impact of superconductive magnetic energy storage on electric power transmission  

Microsoft Academic Search

The authors demonstrate that a superconductive magnetic energy storage (SMES) system can provide a significant positive impact on electric power transmission. By using SMES, transmission-line loadings during heavy load hours can be reduced if the SMES system is located near the major load. Transmission losses as well as the fuel cost for the losses over a 24 hr period can

K.-S. Tam; P. Kumar

1990-01-01

87

Toroidal constant-tension superconducting magnetic energy storage units  

DOEpatents

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.

Herring, J.S.

1992-11-03

88

Axionic superconductivity in three-dimensional doped narrow-gap semiconductors  

NASA Astrophysics Data System (ADS)

We consider the competition between the conventional s-wave and the triplet Balian-Werthamer or the B-phase pairings in doped three-dimensional narrow-gap semiconductors, such as CuxBi2Se3 and Sn1-xInxTe. When the coupling constants of the two contending channels are comparable, we find a simultaneously time-reversal and parity violating p +is state at low temperatures, which provides an example of a dynamic axionic state of matter. In contradistinction to the time-reversal invariant, topological B phase, the p +is state possesses gapped Majorana fermions as surface Andreev bound states, which give rise to an anomalous surface thermal Hall effect. The anomalous gravitational and electrodynamic responses of the p +is state can be described by the ? vacuum structure, where ? ?0 or ?.

Goswami, Pallab; Roy, Bitan

2014-07-01

89

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

PubMed Central

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

Potocnik, Anton; Krajnc, Andraz; Jeglic, Peter; Takabayashi, Yasuhiro; Ganin, Alexey Y.; Prassides, Kosmas; Rosseinsky, Matthew J.; Arcon, Denis

2014-01-01

90

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

SciTech Connect

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.

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

2009-10-10

91

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3.1 The Liquid Argon Calorimeter . . . . . . . . . . . . . . . . . . 14 2.3.2 The Spa Evolution Mechanism . . . . . . . . . . . . . . . 37 3.3.2 The BFKL Evolution Mechanism

92

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

SciTech Connect

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.

He, R.

2010-05-04

93

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

SciTech Connect

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.

Not Available

2011-08-11

94

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

SciTech Connect

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.

Tanaka, K.

2011-08-19

95

Numerical analysis of magnetic field in superconducting magnetic energy storage  

SciTech Connect

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.

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

1991-09-01

96

Energy gaps in Bi2Sr2CaCu2O8+? cuprate superconductors  

PubMed Central

The relationship between the cuprate pseudogap (?p) and superconducting gap (?s) remains an unsolved mystery. Here, we present a temperature- and doping-dependent tunneling study of submicron Bi2Sr2CaCu2O8+? intrinsic Josephson junctions, which provides a clear evidence that ?s closes at a temperature Tc0 well above the superconducting transition temperature Tc but far below the pseudogap opening temperature T*. We show that the superconducting pairing first occurs predominantly on a limited Fermi surface near the node below Tc0, accompanied by a Fermi arc due to the lifetime effects of quasiparticles and Cooper pairs. The arc length has a linear temperature dependence, and as temperature decreases below Tc it reduces to zero while pairing spreads to the antinodal region of the pseudogap leading to a d-wave superconducting gap on the entire Fermi surface at lower temperatures. PMID:22355760

Ren, J. K.; Zhu, X. B.; Yu, H. F.; Tian, Ye; Yang, H. F.; Gu, C. Z.; Wang, N. L.; Ren, Y. F.; Zhao, S. P.

2012-01-01

97

Superconducting magnetic energy storage apparatus structural support system  

DOEpatents

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.

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

98

Progress of superconducting bearing technologies for flywheel energy storage systems  

NASA Astrophysics Data System (ADS)

We report present status of NEDO project on “Superconducting bearing technologies for flywheel energy storage systems”. We fabricated a superconducting magnetic bearing module consisting of a stator of resin impregnated YBaCuO bulks and a rotor of NdFeB permanent magnet circuits. We obtained levitation force density of 8 N/cm 2 at 81 K and rotation loss per levitation force of 3 mW/N at 77 K. We confirmed that both pre-loading and excess cooling methods are effective for suppressing gradual fall of rotor due to flux creep. We designed a 10 kW h class flywheel energy storage test system and investigated feasibility of active magnetic bearings for controlling rotation axis vibration under high speed rotation of the flywheel.

Koshizuka, N.; Ishikawa, F.; Nasu, H.; Murakami, M.; Matsunaga, K.; Saito, S.; Saito, O.; Nakamura, Y.; Yamamoto, H.; Takahata, R.; Itoh, Y.; Ikezawa, H.; Tomita, M.

2003-04-01

99

Superconducting magnetic energy storage for BPA transmission line stabilization  

Microsoft Academic Search

The Bonneville Power Administration (BPA) operates the electrical transmission system that joins the Pacific Northwest with southern California. A 30 MJ (8.4 kWh) Superconducting Magnetic Energy Storage (SMES) unit with a 10 MW converter is being installed at the Tacoma Substation to provide system damping for low frequency oscillations of 0.35 Hz. The integrated system status is described and reviewed.

J. Rogers; M. Barron; H. Boenig; A. Criscuolo; J. Dean; R. Schermer

1983-01-01

100

Optical and electrical properties of thin superconducting films  

NASA Technical Reports Server (NTRS)

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.

Covington, Billy C.; Jing, Feng Chen

1990-01-01

101

Spectral Gap Energy Transfer in Atmospheric Boundary Layer  

NASA Astrophysics Data System (ADS)

Experimental measurements of atmospheric turbulence energy spectra show E(k) ~ k-3 slopes at synoptic scales (~ 600 km - 2000 km) and k-5/3 slopes at the mesoscales (< 400 km). The -5/3 spectra is presumably related to 3D turbulence which is dominated by the classical Kolmogrov energy cascade. The -3 spectra is related to 2D turbulence, which is dominated by strong forward scatter of enstrophy and weak forward scatter of energy. In classical 2D turbulence theory, it is expected that a strong backward energy cascade would develop at the synoptic scale, and that circulation would grow infinitely. To limit this backward transfer, energy arrest at macroscales must be introduced. The most commonly used turbulence models developed to mimic the above energy transfer include the energy backscatter model for 2D turbulence in the horizontal plane via Large Eddy Simulation (LES) models, dissipative URANS models in the vertical plane, and Ekman friction for the energy arrest. One of the controversial issues surrounding the atmospheric turbulence spectra is the explanation of the generation of the 2D and 3D spectra and transition between them, for energy injection at the synoptic scales. Lilly (1989) proposed that the existence of 2D and 3D spectra can only be explained by the presence of an additional energy injection in the meso-scale region. A second issue is related to the observations of dual peak spectra with small variance in meso-scale, suggesting that the energy transfer occurs across a spectral gap (Van Der Hoven, 1957). Several studies have confirmed the spectral gap for the meso-scale circulations, and have suggested that they are enhanced by smaller scale vertical convection rather than by the synoptic scales. Further, the widely accepted energy arrest mechanism by boundary layer friction is closely related to the spectral gap transfer. This study proposes an energy transfer mechanism for atmospheric turbulence with synoptic scale injection, wherein the generation of 2D and 3D spectra is explained using spectral gap energy transfer. The existence of the spectral gap energy transfer is validated by performing LES for the interaction of large scale circulation with a wall, and studying the evolution of the energy spectra both near to and far from the wall. Simulations are also performed using the Advanced Weather and Research Forecasting (WRF-ARW) for moist zonal flow over Gaussian ridge, and the energy spectra close and away from the ground are studied. The energy spectra predicted by WRF-ARW are qualitatively compared with LES results to emphasize the limitations of the currently used turbulence parameterizations. Ongoing validation efforts include: (1) extending the interaction of large scale circulation with wall simulations to finer grids to capture a wider range of wavenumbers; and (2) a coupled 2D-3D simulation is planned to predict the entire atmospheric turbulence spectra at a very low computational expense. The overarching objective of this study to develop turbulence modeling capability based on the energy transfer mechanisms proposed in this study. Such a model will be implemented in WRF-ARW, and applied to atmospheric simulations, for example the prediction of moisture convergence patterns at the meso-scale in the southeast United States (Tao & Barros, 2008).

Bhushan, S.; Walters, K.; Barros, A. P.; Nogueira, M.

2012-12-01

102

Photonic Band Gap resonators for high energy accelerators  

SciTech Connect

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.

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

103

One gap, two gaps, and universality in high temperature superconductors  

NASA Astrophysics Data System (ADS)

A dramatic change in energy gap anisotropy upon reducing carrier concentration has often been observed in the cuprate high temperature superconductors (HTSC). A simple d-wave gap in materials with the optimal Tc evolves with underdoping into a ?two-gap? structure, with different dependences in different regions of momentum space. It is tempting to associate the large antinodal gap with a second order parameter distinct from d-wave superconductivity. We use angle-resolved photoemission spectroscopy (ARPES) to show that this two-gap behavior, and the concomitant destruction of well defined electronic excitations, are not universal features of HTSC, and depend sensitively on how the underdoped materials are prepared. Depending on cation substitution, underdoped crystals either show two-gap behavior or not. In contrast, many characteristics of HTSC like the superconducting dome (Tc versus doping), nodal quasiparticles, antinodal gap that decreases monotonically with doping, and the pseudogap, are present in all samples, irrespective of whether they exhibit two-gap behavior or not. Our results imply that universal aspects of high Tc superconductivity are insensitive to differences in the electronic states in the antinodal region of the Brillouin zone.

Zhao, Junjing; Chatterjee, Utpal; Norman, Mike; Randeria, Mohit; Campuzano, Juan Carlos

2012-02-01

104

Modeling of laser energy concentration in narrow gap joints  

SciTech Connect

A three-dimensional, computer based, optical ray tracing model is used to simulate the combined effect of key geometric parameters for laser welding. This allows one to characterize a range of joint designs for their ability to concentrate or dissipate laser energy. The effects of angle dependent absorption and diffuse reflections on beam transport are evaluated through simulation to determine the contributions of these effects on the system. The effects of energy loss through weld joint gaps are modeled for common weld joint preparations. Practical applications of extending the optical design of the system to include the weld joint are proposed.

Milewski, J.O. [Los Alamos National Lab., NM (United States); Mustaleski, T.M. [Lockheed Martin Energy Systems, Inc., TN (United States)

1998-12-01

105

Topological phase transitions with and without energy gap closing  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

106

Energy Band-Gap Engineering of Graphene Nanoribbons Melinda Y. Han,1  

E-print Network

Energy Band-Gap Engineering of Graphene Nanoribbons Melinda Y. Han,1 Barbaros O¨ zyilmaz,2 Yuanbo an energy gap near the charge neutrality point. Individual graphene layers are contacted with metal. The temperature dependent conductance measurements show larger energy gaps opening for narrower ribbons. The sizes

Kim, Philip

107

Superconductivity and the quantization of energy  

NASA Astrophysics Data System (ADS)

Attention is presently drawn to the established fact that the innumerable interactions among the trillion or so particles of such macroscopic devices as Josephson junctions, in producing sharply defined energy levels, can be regarded as a dynamical state which is effectively divorced from environmental complexities. This degree of isolation from intrinsic perturbations has only recently been shown to be extraordinary, in light of new measurements with precision improvements of about ten orders of magnitude; these are presently evaluated in view of highly accurate results from QED and atomic spectroscopy investigations, as well as the standards of metrology.

McDonald, D. G.

1990-01-01

108

ORNL superconducting technology program for electric energy systems  

NASA Astrophysics Data System (ADS)

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-92 Peer Review of Projects, which was 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.

Hawsey, R. A.

1993-02-01

109

ORNL Superconducting Technology Program for Electric Energy Systems  

SciTech Connect

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.

Hawsey, R.A. (comp.)

1993-02-01

110

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

111

Nanoscale Superconductivity:. Physics and Applications  

NASA Astrophysics Data System (ADS)

Conventional superconductivity in bulk objects is characterized by three phenomenological features: zero resistivity, perfect diamagnetism (Meissner effect) and energy gap in the excitation spectrum. In this paper we demonstrate that these attributes of superconductivity do not apply to ultra-small objects governed by the essentially nanoscale phenomenon which is quantum fluctuations. The observation results in fundamental limitations of utilization of superconducting elements in nanoelectronic circuits. However, together with this rather pessimistic conclusion, the indicated size phenomena lead to a new class of nanoscale devices and applications.

Arutyunov, K.

2013-05-01

112

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

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.

Hashimoto, M.

2011-01-04

113

Magnetic Resonant Mode in the Low-Energy Spin-Excitation Spectrum of Superconducting Rb2Fe4Se5 Single Crystals  

NASA Astrophysics Data System (ADS)

We have studied the low-energy spin-excitation spectrum of the single-crystalline Rb2Fe4Se5 superconductor (Tc=32K) by means of inelastic neutron scattering. In the superconducting state, we observe a magnetic resonant mode centered at an energy of ??res=14meV and at the (0.5 0.25 0.5) wave vector (unfolded Fe-sublattice notation), which differs from the ones characterizing magnetic resonant modes in other iron-based superconductors. Our finding suggests that the 245-iron selenides are unconventional superconductors with a sign-changing order parameter, in which bulk superconductivity coexists with the 5×5 magnetic superstructure. The estimated ratios of ??res/kBTc?5.1±0.4 and ??res/2??0.7±0.1, where ? is the superconducting gap, indicate moderate pairing strength in this compound, similar to that in optimally doped 1111 and 122 pnictides.

Park, J. T.; Friemel, G.; Li, Yuan; Kim, J.-H.; Tsurkan, V.; Deisenhofer, J.; Krug von Nidda, H.-A.; Loidl, A.; Ivanov, A.; Keimer, B.; Inosov, D. S.

2011-10-01

114

Interplay between superconductivity and pseudogap state in bilayer cuprate superconductors  

NASA Astrophysics Data System (ADS)

The interplay between the superconducting gap and normal-state pseudogap in the bilayer cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. It is shown that the charge carrier interaction directly from the interlayer coherent hopping in the kinetic energy by exchanging spin excitations does not provide the contribution to the normal-state pseudogap in the particle-hole channel and superconducting gap in the particle-particle channel, while only the charge carrier interaction directly from the intralayer hopping in the kinetic energy by exchanging spin excitations induces the normal-state pseudogap in the particle-hole channel and superconducting gap in the particle-particle channel, and then the two-gap behavior is a universal feature for the single layer and bilayer cuprate superconductors.

Lan, Yu; Qin, Jihong; Feng, Shiping

2013-11-01

115

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

PubMed Central

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

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

116

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

SciTech Connect

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.

Rogers, J.D. (comp.)

1982-02-01

117

Superconducting cascade electron refrigerator  

NASA Astrophysics Data System (ADS)

The design and operation of an electronic cooler based on a combination of superconducting tunnel junctions is described. The cascade extraction of hot-quasiparticles, which stems from the energy gaps of two different superconductors, allows for a normal metal to be cooled down to about 100 mK starting from a bath temperature of 0.5 K. We discuss the practical implementation, potential performance, and limitations of such a device.

Camarasa-Gómez, M.; Di Marco, A.; Hekking, F. W. J.; Winkelmann, C. B.; Courtois, H.; Giazotto, F.

2014-05-01

118

Low cost composite structures for superconducting magnetic energy storage systems  

NASA Astrophysics Data System (ADS)

As part of the Superconducting Magnetic Energy Storage/Engineering Test Model (SMES-ETM) program, design, analysis, fabrication and test programs were conducted to evaluate the low cost manufacturing of Fiberglass Reinforced Plastic (FRP) beams for usage as major components of the structural and electrical insulation systems. These studies utilized pultrusion process technologies and vinylester resins to produce large net sections at costs significantly below that of conventional materials. Demonstration articles incorporating laminate architectures and design details representative of SMES-ETM components were fabricated using the pultrusion process and epoxy, vinylester, and polyester resin systems. The mechanical and thermal properties of these articles were measured over the temperature range from 4 K to 300 K. The results of these tests showed that the pultruded, vinylester components have properties comparable to those of currently used materials, such as G-10, and are capable of meeting the design requirements for the SMES-ETM system.

Rix, Craig; McColskey, David; Acree, Robert

1994-07-01

119

High Energy Emission from Rotation-Powered Pulsars: Outer-gap vs. Slot-gap Models  

E-print Network

We explore particle accelerator electrodynamics in the magnetosphere of a rapidly rotating neutron star (NS). We address the importance of a self-consistent treatment of pair production, solving the Poisson equation describing the acceleration electric field, the Boltzmann equations for produced electrons and positrons, and the radiative transfer equation simultaneously. It is demonstrated that the accelerator solution is obtained if we only specify the NS spin period, magnetic dipole moment, magnetic inclination angle with respect to the rotation axis, and the NS surface temperature, and that the solution corresponds to a quantitative extension of previous outer-gap models. We apply the scheme to the Crab pulsar and show that the predicted pulse profiles and phase-resolved spectrum are roughly consistent with observations. Applying the same scheme to the slot-gap model, we show that this alternative model predicts too small photon flux to reproduce observations, because the gap trans-field thickness is significantly restricted by its pair-free condition.

Kouichi Hirotani

2008-09-08

120

Superconducting RF cavities and magnets for a 4-TeV energy muon collider  

SciTech Connect

The accelerators must take the muon beams from {approximately} 100 MeV to 2 TeV energies within the muon lifetime for a 4 TeV energy muon collider. These constraints plus the muon decay heating seriously challenge the designs of the superconducting RF (SRF) cavities and magnets in the accelerators and collider ring. The multiple superconducting recirculation linac and the very rap8id-cycling superconducting synchrotron approach are both studied. The authors briefly introduce the technical considerations and preliminary designs of the SRF systems and magnets.

Shu, Q.S. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)]|[Northrop-Grumman Co., Bethpage, NY (United States); Green, M. [Lawrence Berkeley National Lab., CA (United States); Neuffer, D. [Fermi National Accelerator Lab., Batavia, IL (United States); Summers, D. [Univ. of Mississippi, Oxford, MI (United States); Simrock, S. [DESY, Hamburg (Germany); Willen, E. [Brookhaven National Lab., Upton, NY (United States)

1997-11-01

121

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

E-print Network

losses. Thus, the superconducting transmission and distribu- tion system would allow more electricity to reach consumers with no increase in fossil fuel-related CO2 emissions, using smaller sized equipment. It is estimated that 40 percent of US’s total... of superconducting devices is the significant amount of saved energy. Moreover, they can reduce device dimensions and are more green and safe. For instance, su- perconducting cables act as ’energy superhighways’ with a higher capacity while eliminating resistive...

Yuan, Weijia

2010-11-16

122

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)

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.

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

2014-08-01

123

Basis set effects on relative energies and HOMO–LUMO energy gaps of fullerene C 36  

Microsoft Academic Search

Fifteen C36 isomers were examined to determine the influence that the quality of basis sets has on the geometry parameters, the relative stability and HOMO–LUMO energy gaps of fullerene isomers calculated with density functional theory. It is worthwhile to note that the geometry parameters of all C36 isomers are insensitive to basis sets. On the other hand, one set of

Kyoung Hoon Kim; Young-Kyu Han; Jaehoon Jung

2005-01-01

124

Superconducting gamma and fast-neutron spectrometers with high energy resolution  

DOEpatents

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.

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

2008-11-04

125

Localization of Metal-Induced Gap States at the Metal-Insulator Interface: Origin of Flux Noise in SQUIDs and Superconducting Qubits  

NASA Astrophysics Data System (ADS)

The origin of magnetic flux noise in dc Superconducting Quantum Interference Devices (SQUIDs) with a power spectrum scaling as 1/f (f is frequency) has been a puzzle for over 25 years. This noise limits both the low frequency performance of SQUIDs and the decoherence time of flux-sensitive superconducting qubits, making scaling-up for quantum computing problematic. Recent calculations and experiments indicate that the noise is generated by electrons that randomly reverse their spin directions. Their areal density of ˜ 5 x 10^17 m-2 is relatively insensitive to the nature of the superconductor and substrate. Here, we propose that the local magnetic moments originate in metal-induced gap states (MIGSs) localized by potential disorder at the metal-insulator interface. MIGSs are particularly sensitive to such disorder, so that the localized states have a Coulomb repulsion sufficiently large to make them singly occupied. Our calculations demonstrate that a modest level of disorder generates the required areal density of localized moments. This result suggests that magnetic flux noise could be reduced by fabricating superconductor-insulator interfaces with less disorder. Support: NSF DMR07-05941, US DOE De-AC02-05CH11231, Samsung Foundation, Teragrid, NERSC.

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

2010-03-01

126

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

ERIC Educational Resources Information Center

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…

Precker, Jurgen W.

2007-01-01

127

Fully gapped s-wave-like superconducting state and electronic structure in Ir0.95Pd0.05Te2 single crystals with strong spin-orbital coupling  

NASA Astrophysics Data System (ADS)

Due to the large spin-orbital coupling in the layered 5d-transition metal chalcogenides compound, the occurrence of superconductivity in doped Ir2-xPdxTe2 offers a good chance to search for possible topological superconducting states in this system. We did comprehensive studies on the superconducting properties and electronic structures of single crystalline Ir0.95Pd0.05Te2 samples. The superconducting gap size, critical fields, and coherence length along different directions were experimentally determined. Macroscopic bulk measurements and microscopic low temperature scanning tunneling spectroscopy results suggest that Ir0.95Pd0.05Te2 possesses a BCS-like s-wave state. No sign of zero bias conductance peak was found in the vortex core at 0.4 K.

Yu, D. J.; Yang, F.; Miao, Lin; Han, C. Q.; Yao, Meng-Yu; Zhu, Fengfeng; Song, Y. R.; Zhang, K. F.; Ge, J. F.; Yao, X.; Zou, Z. Q.; Li, Z. J.; Gao, B. F.; Liu, Canhua; Guan, D. D.; Gao, C. L.; Qian, Dong; Jia, Jin-feng

2014-03-01

128

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

E-print Network

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.

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

2014-10-14

129

Double Moral Hazard and the Energy Efficiency Gap Louis-Gatan Giraudet1  

E-print Network

Double Moral Hazard and the Energy Efficiency Gap Louis-Gaëtan Giraudet1 , Sébastien Houde2 Submission for the Winter issue of the IAEE `Energy Forum' newsletter, which will focus on energy efficiency. Abstract (23 words) Moral hazard issues can deter profitable investments in energy efficiency. Energy

Boyer, Edmond

130

Concepts of flywheels for energy storage using autostable highT(sub c) superconducting magnetic bearings  

Microsoft Academic Search

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

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

1994-01-01

131

Hybrid fuel cell and energy storage systems using superconducting coil or batteries for clean electricity generation  

Microsoft Academic Search

This paper described a novel design of a hybrid fuel cell and energy storage system using high temperature superconducting energy storage system (HT-SMES) or batteries to meet fast changing load. The power electronic switches in the converter of the energy storage system are controlled in such a way that the amplitude and waveform of the inverter output current from the

Darmawan Sutanto; Kai Ding

2009-01-01

132

Design and cost of a utility scale superconducting magnetic energy storage plant  

SciTech Connect

Superconducting Magnetic Energy Storage (SMES) has potential as a viable technology for use in electric utility load leveling. The advantage of SMES over other energy storage technologies is its high net roundtrip energy efficiency. This paper reports the major features and costs of a jointly developed 5000 MWh SMES plant design.

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

1985-01-01

133

SUBHARMONIC ENERGY GAP STRUCTURE AND GAP-ENHANCEMENT BY THE JOSEPHSON RADIATION IN SMALL DAYEM BRIDGES  

E-print Network

BRIDGES P. E. GREGERS-HANSEN and G. R. PICKETT (*) Physics Laboratory I, H C Ã?rsted Institute University012703C9)/Ne. We explain the observed behaviour in terms of pair-breaking in the region of the bridge of the subharmonic peaks we deduce that the energy near the bridge is enhanced above the BCS bulk value, apparently

Paris-Sud XI, Université de

134

Relationship of the second order nonlinear optical coefficient to energy gap in inorganic non-centrosymmetric crystals  

Microsoft Academic Search

Second order nonlinear optical coefficient and energy gap data collected from the literature have been classified and are organized by plotting their respective values. The two-dimensional plots indicate that both large energy gap and small chi(2) and small energy gap and large chi(2) are highly correlated. It was found that a single power law expression cannot represent the data well

A. G. Jackson; M. C. Ohmer; S. R. Leclair

1997-01-01

135

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

SciTech Connect

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.

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

136

Gap length effect on electron energy distribution in capacitive radio frequency discharges  

SciTech Connect

A study on the dependence of electron energy distribution function (EEDF) on discharge gap size in capacitive rf discharges was conducted. The evolution of the EEDF over a gap size range from 2.5 to 7 cm in 65 mTorr Ar discharges was investigated both experimentally and theoretically. The measured EEDFs exhibited typical bi-Maxwellian forms with low energy electron groups. A significant depletion in the low energy portion of the bi-Maxwellian was found with decreasing gap size. The results show that electron heating by bulk electric fields, which is the main heating process of the low-energy electrons, is greatly enhanced as the gap size decreases, resulting in the abrupt change of the EEDF. The calculated EEDFs based on nonlocal kinetic theory are in good agreement with the experiments.

You, S. J.; Kim, S. S.; Kim, Jung-Hyung; Seong, Dae-Jin; Shin, Yong-Hyeon; Chang, H. Y. [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2007-11-26

137

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

SciTech Connect

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.

Duca, V.D.

1993-08-01

138

Parton-parton elastic scattering and rapidity gaps at Tevatron energies  

SciTech Connect

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.

Del Duca, V.; Tang, Wai-Keung

1993-08-01

139

Nonequilibrium superconductivity for particle detectors  

SciTech Connect

A considerable amount of attention has been devoted to nonequilibrium superconductivity over the last 10 to 15 years. A fairly complete and quantatitive understanding of the experimental and theoretical aspects of the subject has emerged. In this paper aspects of nonequilibrium superconductivity which are relevant to a majority of particle detector applications will be reviewed, and new calculations, more specific to actual detector applications, will be presented. The primary focus is on ionizing particles for which the characteristic energy is greater than typical superconducting energy gap values, ..delta.., of about 1 MeV. Thus microwave and far-infrared detection is excluded, although many of the results and consequences may also apply in those cases. 36 refs., 1 fig.

Gray, K.E.

1987-10-01

140

Graphene field effect transistor without an energy gap.  

PubMed

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

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

2013-05-28

141

Development of 50kWh-class superconducting flywheel energy storage system  

Microsoft Academic Search

We report a development of 50 kWh-class flywheel energy storage system using a new type of axial bearing which is based on powerful magnetic force generated by a superconducting coil. This axial bearing can support a large mass. So, even at low rotational speeds, the flywheel system can have larger energy storage capacity by enlarging the mass of flywheel. Thus,

Yusuke YAMAUCHI; Nobuhito UCHIYAMA; Eiji SUZUKI; Michiaki KUBOTA; Madoka FUJII; Hiroyuki OHSAKI

2006-01-01

142

Calculation of free-energy differences and potentials of mean force by a multi-energy gap method  

E-print Network

Calculation of free-energy differences and potentials of mean force by a multi-energy gap method the convergence of free-energy calculations. It introduces a bias factor in Monte Carlo simulations or.e., the difference in energy function between two states, and is therefore specifically designed for calculating free-energy

Weston, Ken

143

Capacitor energy needed to induce transitions from the superconducting to the normal state  

SciTech Connect

The purpose of this paper is to describe a technique to turn a long length of superconducting wire normal by dumping a charged capacitor into it and justify some formulae needed in the design. The physical phenomenon is described. A formula for the energy to be stored in the capacitor is given. There are circumstances where the dc in an electrical circuit containing superconducting elements has to be turned off quickly and where the most convenient way to switch the current off is to turn a large portion or all of the superconducting wire normal. Such was the case of the Time Projection Chamber (TPC) superconducting magnet as soon as a quench was detected. The technique used was the discharge of a capacitor into the coil center tap. It turned the magnet winding normal in ten milliseconds or so and provided an adequate quench protection. The technique of discharging a capacitor into a superconducting wire should have many other applications whenever a substantial resistance in a superconducting circuit has to be generated in that kind of time scale. The process involves generating a pulse of large currents in some part of the circuit and heating the wire up by ac losses until the value of the wire critical current is smaller than the dc current. Use of low inductance connections to the circuit is necessary. Then the dc gets turned off due to the resistance of the wire as in a magnet quench.

Eberhard, P.H.; Ross, R.R.

1985-08-01

144

Design of an energy storage flywheel system using permanent magnet bearing (PMB) and superconducting magnetic bearing (SMB)  

Microsoft Academic Search

We propose a new energy storage flywheel system using a superconducting magnetic bearing (SMB) and a permanent magnet bearing (PMB). The superconducting magnetic bearing (SMB) suppresses the vibrations of the flywheel rotor. And the permanent magnet bearing (PMB) passively controls the rotor position. The energy storage flywheel system is characterized by using the two different type magnetic bearings of permanent

K. Murakami; M. Komori; H. Mitsuda; A. Inoue

2007-01-01

145

Hybrid superconducting magnetic bearing for kinetic energy storage applications and its frictional energy loss  

SciTech Connect

A hybrid superconducting magnetic bearing (HSMB) has been designed, constructed and implemented in a flywheel energy storage (FES) prototype. The HSMB design uses magnetic forces from permanent magnets for levitation and high temperature superconductor YBCO in between the magnets for stabilization. A 19 kg (42 lb.) flywheel currently can rotate up to 6,000 RPM with kinetic energy of 8 Wh stored. To identify the factors of frictional energy loss in the bearings, the authors have conducted a series of spin-down experiments in different operational conditions. The result from the recent test under the air pressure of 10{sup {minus}5} torr indicates an average frictional energy loss <2% per hour, with the imperfect system alignment and an unbalanced rotor.

Xia, Zule; Ma, Ki; Chen, Quark [Univ. of Houston, TX (United States)] [and others

1996-12-31

146

Scaling up energy efficiency: bridging the action gap  

E-print Network

related to both energy security and the global climate. In the Reference Scenario of the International concentrations, accelerating global warming and climate change. The importance of energy efficiency The Alternative Policy Scenario of the International Energy Agency sets out what could happen were energy security

147

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

NASA Astrophysics Data System (ADS)

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.

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

2004-11-01

148

Possible nodal superconducting gap in Fe1+y(Te1-xSex) single crystals from ultralow temperature penetration depth measurements  

NASA Astrophysics Data System (ADS)

Using a radio-frequency tunnel diode oscillator technique, we measured the temperature dependence of the in-plane London penetration depth ??ab(T) in Fe1+y(Te1-xSex) single crystals, down to temperatures as low as 50 mK. A significant number of samples, with nominal Se concentrations x=0.36, 0.40, 0.43, and 0.45, respectively, were studied and in many cases we found that ??ab(T) shows an upturn below 0.7 K, indicative of a paramagnetic-type contribution. After subtracting the magnetic background, the low-temperature behavior of penetration depth is best described by a power law with exponent n?2 and with no systematic dependence on the Se concentration. Most importantly, in the limit of T?0, in some samples we observed a narrow region of linear temperature dependence of penetration depth, suggestive of nodes in the superconducting gap of Fe1+y(Te1-xSex).

Diaconu, Andrei; Martin, Catalin; Hu, Jin; Liu, Tijiang; Qian, Bin; Mao, Zhiqiang; Spinu, Leonard

2013-09-01

149

Tuning Band Gap Energies in Pb3(C6X6) Extended Solid-State Structures  

SciTech Connect

A detailed plane-wave density functional theory investigation of the solid-state properties of the extended organometallic system Pb{sub 3}C{sub 6}X{sub 6} for X = O, S, Se, and Te has been performed. Initial geometry parameters for the Pb-X and C-X bond distances were obtained from optimized calculations on molecular fragment models. The Pb{sub 3}C{sub 6}X{sub 6} extended solid molecular structures were constructed in the space group P6/mmm on the basis of the known structure for X = S. Ground-state geometries, band gap energies, densities of states, and charge densities were calculated with the PBE-generalized gradient exchange-correlation functional and the HSE06 hybrid exchange-correlation functional. The PBE band gap energies were found to be lower than the HSE06 values by >0.7 eV. The band energies at points of high symmetry along the first Brillouin zone in the crystal were larger than the overall band gap of the system. Pb{sub 3}C{sub 6}O{sub 6} was predicted to be a direct semiconductor ({Lambda} point) with a PBE band gap of 0.28 eV and an HSE06 band gap of 1.06 eV. Pb{sub 3}C{sub 6}S{sub 6} and Pb{sub 3}C{sub 6}Se{sub 6} were predicted to have indirect band gaps. The PBE band gap for Pb{sub 3}C{sub 6}S{sub 6} was 0.98 eV, and the HSE06 band gap was 1.91 eV. The HSE06 value is in good agreement with the experimentally observed band gap of 1.7 eV. Pb{sub 3}C{sub 6}Se{sub 6} has a PBE band gap of 0.56 eV and a HSE06 band gap of 1.41 eV. Pb{sub 3}C{sub 6}Te{sub 6} was predicted to be metallic with both of the PBE and HSE06 functionals. A detailed analysis of the PBE band structure and partial density of states at two points before and after the metallic behavior reveals a change in orbital character indicative of band crossing in Pb{sub 3}C{sub 6}Te{sub 6}. These results show that the band gap energies can be fine-tuned by changing the substituent X atom.

Stott, Amanda C.; Vaid, Thomas P.; Bylaska, Eric J.; Dixon, David A.

2012-04-19

150

Erbium energy levels relative to the band gap of gadolinium oxide  

Microsoft Academic Search

Undoped and Er3+ doped Gd2O3 single crystal fibers were prepared by the laser heated pedestal growth (LHPG) method. The absorption and emission spectra of the samples were studied. The band gap of Gd2O3 crystal is found at 5.2 eV. A two-step photoconductivity measurement was designed to determine the Er3+ energy level position relative to the host band gap. The lowest

D. Jia; L. Lu; W. M Yen

2002-01-01

151

Energy resolution improvement of superconducting tunnel junction particle detectors with infrared-blocking filters  

Microsoft Academic Search

The energy resolution of a superconducting tunnel junction particle detector was significantly improved by the addition of a metal mesh infrared-blocking filter. The energy resolution was 138–215eV full width at half maximum for 1.5–3.0keV Ar ions. The infrared-blocking filter reduces the loss of energy resolution due to infrared radiation at room temperature.

Shigetomo Shiki; Masahiro Ukibe; Ryutaro Maeda; Masataka Ohkubo; Yuki Sato; Shigeo Tomita

2008-01-01

152

Superconducting Tunnel Junction Array Development for High-Resolution Energy-Dispersive X-ray Spectroscopy  

Microsoft Academic Search

: Cryogenic energy-dispersive X-ray detectors are being developed because of their superior energy resolution (10 eV FWHM for keV X-rays) compared to that achieved in semiconductor energy-dispersive spectrometry (EDS) systems. So far, their range of application is limited because of their comparably small size and low count rate. We present data on the development of superconducting tunnel junction (STJ) detector

S. Friedrich; C. A. Mears; B. Nideröst; L. J. Hiller; M. Frank; S. E. Labov; A. T. Barfknecht; S. P. Cramer

1998-01-01

153

Improving the dynamics of a flywheel energy storage system with superconducting magnetic bearings  

Microsoft Academic Search

This paper describes a new method for improving the dynamics of a flywheel energy storage system using superconducting magnetic bearings (SMBs). The SMBs are composed of a ring-shaped superconductor and some permanent magnets (PM). Changes in stiffness and damping coefficient of the SMBs were investigated. Forced displacements are given to the SMBs to improve the stiffness and the damping coefficient.

Mochimitsu Komori; Toru Kawashima

2004-01-01

154

30 MJ superconducting magnetic energy storage for BPA transmission line stabilizer  

Microsoft Academic Search

The development of a 30 MJ (8.4 kWh) superconducting magnetic energy storage (SMES) unit with a 10 MW converter which can provide system damping for low frequency oscillations is described. The coil is complete and all major components of the electrical and cryogenic systems were received and are tested. Computer control hardware is in place and software development is proceeding.

R. I. Schermer; H. J. Boenig; J. Dean

1981-01-01

155

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

NASA Astrophysics Data System (ADS)

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.

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

1994-05-01

156

Progress of Theoretical Physics, Vol. 110, No. 5, November 2003 Directionally Independent Energy Gap Formation  

E-print Network

for the origin of the transition or, in other words, to determine how an energy gap is formed at the level-spaced levels. When considering the crossing of such a set of energy levels, we cannot simply estimate the probability of the adiabatic change of a state using the Landau-Zener-St¨uckelberg (LZS) formula, 1), 9) P = 1

157

A Novel Approach for the Evaluation of Band Gap Energy in Semiconductors  

Microsoft Academic Search

On the basis of absorption nature of semiconductors, we present a novel and simple method to determine the band gap energies of semiconductors directly from their absorption spectra at any temperatures, without any fitting processes and restrictions of sample thickness. The key point of the approach is the different dependence of the absorption coefficient derivative on the photon energy at

W. Z. Shen

2002-01-01

158

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

SciTech Connect

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 Fernandez 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.

Gonzalez-Jimenez, Nicolas; Petrovich, Cristobal; Reisenegger, Andreas [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)

2010-08-04

159

Pressure-Induced Structural Transition and Enhancement of Energy Gap of CuAlO2  

NASA Astrophysics Data System (ADS)

By using first-principles calculations, we studied the stable crystal structures and energy gaps of CuAlO2 under high pressure. Our simulation shows that CuAlO2 transforms from a delafossite structure to a leaning delafossite structure. The critical pressure of the transition was determined to be 60 GPa. The energy gap of CuAlO2 increases through the structural transition due to the enhanced covalency of Cu 3d and O 2p states. We found that a chalcopyrite structure does not appear as a stable structure under high pressure.

Nakanishi, Akitaka

2011-02-01

160

Modeling US Adult Obesity Trends: A System Dynamics Model for Estimating Energy Imbalance Gap  

PubMed Central

Objectives. We present a system dynamics model that quantifies the energy imbalance gap responsible for the US adult obesity epidemic among gender and racial subpopulations. Methods. We divided the adult population into gender–race/ethnicity subpopulations and body mass index (BMI) classes. We defined transition rates between classes as a function of metabolic dynamics of individuals within each class. We estimated energy intake in each BMI class within the past 4 decades as a multiplication of the equilibrium energy intake of individuals in that class. Through calibration, we estimated the energy gap multiplier for each gender–race–BMI group by matching simulated BMI distributions for each subpopulation against national data with maximum likelihood estimation. Results. No subpopulation showed a negative or zero energy gap, suggesting that the obesity epidemic continues to worsen, albeit at a slower rate. In the past decade the epidemic has slowed for non-Hispanic Whites, is starting to slow for non-Hispanic Blacks, but continues to accelerate among Mexican Americans. Conclusions. The differential energy balance gap across subpopulations and over time suggests that interventions should be tailored to subpopulations’ needs. PMID:24832405

Rahmandad, Hazhir; Huang, Terry T.-K.; Bures, Regina M.; Glass, Thomas A.

2014-01-01

161

Dynamic characteristics of a flywheel energy storage system using superconducting magnetic bearings  

Microsoft Academic Search

The high-temperature superconducting magnetic bearing flywheel energy storage system (SMB-FESS) is proposed as an efficient energy storage system. It is important to identify the dynamic behaviour and the characteristics of the SMB-FESS. First, a new method for identifying SMB characteristics has been suggested. The suggested modelling method is verified by comparing the experimental and analytical frequency response functions. In this

Jong-Soo Kim; Soo-Hun Lee

2003-01-01

162

Energy Transmission in the Forbidden Band Gap of a Nonlinear Chain  

NASA Astrophysics Data System (ADS)

A nonlinear chain driven by one end may propagate energy in the forbidden band gap by means of nonlinear modes. For harmonic driving at a given frequency, the process occurs at a threshold amplitude by sudden large energy flow that we call nonlinear supratransmission. The bifurcation of energy transmission is demonstrated numerically and experimentally on the chain of coupled pendula (sine-Gordon and nonlinear Klein-Gordon equations) and sustained by an extremely simple theory.

Geniet, F.; Leon, J.

2002-09-01

163

Unoccupied orbital energies of 1,4-benzenedithiol and the HOMO–LUMO gap  

Microsoft Academic Search

The energies of the temporary anion states of 1,4-benzenedithiol (BDT) are determined by electron scattering and compared with those computed by density functional theory (DFT) and Hartree–Fock (HF) methods. Using semi-empirical scalings derived from the ionization energies and electron affinities of a series of phenyl–ethynyl compounds, we compute the HOMO–LUMO energy gap of BDT. We show that without such scalings

A. M. Scheer; G. A. Gallup; P. D. Burrow

2008-01-01

164

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

165

Introduction to progress and promise of superconductivity for energy storage in the electric power sector  

SciTech Connect

Around the world, many groups conduct research, development and demonstration (RD and D) to make storage an economic option for the electric power sector. The progress and prospects for the application of superconductivity, with emphasis on high-temperature superconductivity, to the electric power sector has been the topic of an IEA Implementing Agreement, begun in 1990. The present Task members are Canada, Denmark, Finland, Germany, Israel, Italy, Japan, Korea, the Netherlands, Norway, Sweden, Switzerland, Turkey, the United Kingdom and the US. As a result of the Implementing Agreement, work has been done by the Operating Agent with the full participation of all the member countries. This work has facilitated the exchange of informtion among experts in all countries and has documented relevant assessments. Further, this work has reviewed the status of SMES and is now updating same, as well as investigating the progress on and prospects for flywheels with superconducting bearings. The Operating Agent and Task members find a substantially different set of opportunities for and alternatives to storage than was the case before the 1987 discovery of high-temperature superconductivity. Beside the need to level generation, there is also the need to level the load on transmission lines, increase transmission stability, and increase power quality. These needs could be addressed by high power storage that could be brought in and out of the grid in fractions of a second. Superconducting Magnetic Energy Storage and flywheels with superconducting bearings are devices that deserve continued RD and D because they promise to be the needed storage devices.

Wolsky, A.M.

1998-05-01

166

Band-gap energy and electron effective mass of polycrystalline Zn3N2  

NASA Astrophysics Data System (ADS)

Zn3N2 polycrystalline films with n+-type conductivity have been grown by metalorganic chemical vapor deposition and rf-molecular beam epitaxy with carrier concentration in the range between 1019 and ~1020 cm-3. Oxygen contamination without an intentional doping was found to be a cause of high electron concentration, leading to a larger band-gap energy due to Burstein-Moss shift. The significant blue shift of the optical band gap Eopt with increasing carrier concentration ne obeys the relation Eopt=1.06+1.30×10-14ne2/3. This evaluation enables the conclusion that the actual band-gap energy of Zn3N2 is 1.06 eV. Electron effective mass m* for Zn3N2 has been deduced from Fourier transform infrared reflectivity measurements to be (0.29+/-0.05)mo.

Suda, Toshikazu; Kakishita, Kazuhiko

2006-04-01

167

Erbium energy levels relative to the band gap of gadolinium oxide  

NASA Astrophysics Data System (ADS)

Undoped and Er 3+ doped Gd 2O 3 single crystal fibers were prepared by the laser heated pedestal growth (LHPG) method. The absorption and emission spectra of the samples were studied. The band gap of Gd 2O 3 crystal is found at 5.2 eV. A two-step photoconductivity measurement was designed to determine the Er 3+ energy level position relative to the host band gap. The lowest Er 3+ 4f-5d transition energy (5.93 eV) exceeds the host band gap. By measuring the photoconductivity induced from an excited state to the 5d bands, the Er 3+ ground state is found to be 0.7±0.2 eV below the valence band.

Jia, D.; Lu, L.; Yen, W. M.

2002-10-01

168

DETECTION MECHANISMS IN SUPERCONDUCTING POINT CONTACTS AT FREQUENCIES OF 44 TIMES THE ENERGY GAP  

E-print Network

Standards, National Bureau of Standards Boulder, Colorado, USA Résumé. 2014 Nous avons réalisé à l'aide de considérons pas cette expérience comme un test définitif du mécanisme de mélange entre deux sources externes à lorsqu'elle correspond à un rayonnement infrarouge. Un modèle théorique permettant de calculer la

Paris-Sud XI, Université de

169

Momentum-dependent multiple gaps in magnesium diboride probed by electron tunnelling spectroscopy  

Microsoft Academic Search

The energy gap is the most fundamental property of a superconductor. MgB2, a superconductor discovered in 2001, exhibits two different superconducting gaps caused by the different electron–phonon interactions in two weakly interacting bands. Theoretical calculations predict that the gap values should also vary across the Fermi surface sheets of MgB2. However, until now, no such variation has been observed. It

Wenqing Dai; C. G. Zhuang; Qi Li; Steve Carabello; Joseph G. Lambert; Jerome T. Mlack; Roberto C. Ramos; X. X. Xi; Ke Chen

2012-01-01

170

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

NASA Technical Reports Server (NTRS)

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 the spectra from these pulsars (e.g., Cheng et al. 1986b; Ho 1989) by following the variation in particle production and radiation properties with position in the outer gap. Curvature, synchotron, and inverse-Compton scattering fluxes vary significantly over the gap, and their interactions via photon-photon pair production build up the radiating charge populations at varying rates. We have also incorporated an approximate treatment of the transport particle and photon fluxes between gap emission zones. These effects, along with improved computations of the particle and photon distribution, provide very important modifications of the model gamma-ray flux. In paticular, we attempt to make specific predictions of pulse profile shapes and spectral variations as a function of pulse phase and suggest further extensions to the model which may provide accurate computations of the observed high-energy emissions.

Chiang, James; Romani, Roger W.

1994-01-01

171

PHYSICAL REVIEW B 85, 115431 (2012) Energy gaps in graphene nanomeshes  

E-print Network

, 71.15.Mb I. INTRODUCTION Graphene, a two-dimensional (2D) single-layer honeycomb structure of carbonPHYSICAL REVIEW B 85, 115431 (2012) Energy gaps in graphene nanomeshes William Oswald and Zhigang opening and electronic structures of graphene nanomeshes (GNMs), the defected graphene containing a high

Wu, Zhigang

172

The binding energy and the charged gaps in the negative- U Hubbard model: some rigorous results  

Microsoft Academic Search

By applying Lieb's spin-reflection-positivity method and exploiting a commutation relation satisfied by the negative-U Hubbard Hamiltonian, we prove two rigorous theorems on the binding energy of fermions, the one-particle and the two-particle gaps for the model on an arbitrary finite lattice.

Guang-Shan Tian

1997-01-01

173

The binding energy and the charged gaps in the negative- U Hubbard model: some rigorous results  

NASA Astrophysics Data System (ADS)

By applying Lieb's spin-reflection-positivity method and exploiting a commutation relation satisfied by the negative-U Hubbard Hamiltonian, we prove two rigorous theorems on the binding energy of fermions, the one-particle and the two-particle gaps for the model on an arbitrary finite lattice.

Tian, Guang-Shan

1997-08-01

174

DFT study of conjugated biheterocyclic oligomers exhibiting a very low HOMO–LUMO energy gap  

Microsoft Academic Search

Density functional theory (DFT) is applied to study the structure and electronic properties of oligomers based on bithiophene bridged by a sp2 carbon substituted by a chalcogen atom (O, S, Se and Te), and their polybifurane and polybipyrrole analogues. The important reduction of the energy gap which is observed for the whole series of biheterocyclic compounds, when going down the

Hafida Ammar Aouchiche; Sema Djennane; Abdou Boucekkine

2004-01-01

175

Accurate Zero Parameter Correlation Energy Functional Obtained from the Homogeneous Electron Gas with an Energy Gap  

NASA Astrophysics Data System (ADS)

We have obtained an analytic approximation to E_c(r_g, ?,G) where G is an energy gap separating the occupied and unoccupied states of a homogeneous electron gas for ?=3D0 and ?=3D1. When G=3D0, E_c(r_g, ?) reduces to the usual LSD result. This functional is employed in calculating correlation energies for unpolarized atoms and ions for Z <= 18 by taking G[n]=3D1/8|nabla ln n|^2, which reduces to the ionization energy in the large r limit in an exact Kohn-Sham (KS) theory. The resulting functional is self-interaction-corrected employing a method which is invariant under a unitary transformation. We find that the application of this approach to the calculation of the Ec functional reduces the error in the LSD result by more than 95%. When the value of G is approximately corrected to include the effect of higher lying unoccupied localized states, the resulting values of Ec are within a few percent of the exact results.

Krieger, J. B.; Chen, Jiqiang; Iafrate, G. J.; Savin, A.

1998-03-01

176

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

NASA Astrophysics Data System (ADS)

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.

Abdul-Kader, A. M.

2013-04-01

177

CW Superconducting RF Photoinjector Development for Energy Recovery Linacs  

SciTech Connect

ERLs have the powerful potential to provide very high current beams with exceptional and tailored parameters for many applications, from next-generation light sources to electron coolers. However, the demands placed on the electron source are severe. It must operate CW, generating a current of 100 mA or more with a normalized emittance of order 1 {micro}m rad. Beyond these requirements, issues such as dark current and long-term reliability are critical to the success of ERL facilities. As part of the BERLinPro project, Helmholtz Zentrum Berlin (HZB) is developing a CWSRF photoinjector in three stages, the first of which is currently being installed at HZB's HoBiCaT facility. It consists of an SRF-cavity with a Pb cathode and a superconducting solenoid. Subsequent development stages include the integration of a high-quantum-efficiency cathode and RF components for high-current operation. This paper discusses the first stage towards an ERL-suitable SRF photoinjector, the present status of the facility and first cavity tests.

Neumann A.; Rao T.; Anders, W.; Dirsat, M.; Frahm, A. Jankowiak, A.; Kamps, T.; Knobloch, J.; Kugeler, O.; Quast, T.; Rudolph, J.; Schenk, M.; Schuster, M.; Smedley, J.; Sekutowicz, J.; Kneisel, P.; Nietubyc, R.; Will, I.

2010-10-31

178

Intrinsic superconductivity in ABA-stacked trilayer graphene  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

179

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

SciTech Connect

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.

Rogers, J.D. (comp.)

1981-03-01

180

Photoreflectance Investigations of Temperature Dependence of the ``Different'' Energy Gaps in GaInNAs Compounds  

NASA Astrophysics Data System (ADS)

In this paper, we report photoreflectance investigations of GaInNAs layers almost lattice-matched to GaAs substrate and annealed at different temperatures. Our investigations done from 10 K to room temperature give evidence that these layers exhibit several distinct band gaps. These distinct band gaps, which were found to co-exist, are associated with different nitrogen bonding configurations (N-Ga4-mInm (0? m ?4) short-range-order clusters). The annealing-induced blueshift of GaInNAs band gap energy, which is usually observed in this system, is due to the change in the intensity of PR resonances related to different N-Ga4-mInm configurations.

Kudrawiec, R.; Misiewicz, J.; Pavelescu, E.-M.; Konttinen, J.; Pessa, M.

2005-06-01

181

Effect of superconducting magnetic energy storage on automatic generation control considering governor deadband and boiler dynamics  

Microsoft Academic Search

A comprehensive digital computer model of a two-area interconnected power system including the governor deadband nonlinearity, steam reheat constraints, and the boiler dynamics is developed. The improvement in automatic generation control (AGC) with the addition of a small-capacity superconducting magnetic energy storage (SMES) unit is studied. Time-domain simulations were used to study the performance of the power system and control

S. C. Tripathy; R. Balasubramanian; P. S. C. Nair

1992-01-01

182

Distribution of Time-Energy Entanglement over 100 km fiber using superconducting single-photon detectors  

E-print Network

In this letter, we report an experimental realization of distributing entangled photon pairs over 100 km of dispersion-shifted fiber. In the experiment, we used a periodically poled lithium niobate waveguide to generate the time-energy entanglement and superconducting single-photon detectors to detect the photon pairs after 100 km. We also demonstrate that the distributed photon pairs can still be useful for quantum key distribution and other quantum communication tasks.

Qiang Zhang; Hiroki Takesue; Sae Woo Nam; Carsten Langrock; Xiuping Xie; M. M. Fejer; Yoshihisa Yamamoto

2007-12-25

183

Application of superconducting magnetic bearings to a 10 kWh-class flywheel energy storage system  

Microsoft Academic Search

Radial type superconducting magnetic bearings have been developed for a 10 kWh-class flywheel energy storage system. The bearings consist of an inner-cylindrical stator of YBCO bulk superconductors and an outer-rotor of permanent magnets. The rotor is suspended without contact via the pinning forces of the bulk superconductors that are arranged such that the c-axis of each superconductor is aligned parallel

Takumi Ichihara; Koji Matsunaga; Makoto Kita; Izumi Hirabayashi; Masayuki Isono; Makoto Hirose; Keiji Yoshii; Kazuaki Kurihara; Osamu Saito; Shinobu Saito; Masato Murakami; Hirohumi Takabayashi; Mitsutoshi Natsumeda; Naoki Koshizuka

2005-01-01

184

Present status of R&D on superconducting magnetic bearing technologies for flywheel energy storage system  

Microsoft Academic Search

We report on the NEDO project of superconducting magnetic bearing (SMB) technologies for flywheel energy storage system. We fabricated SMB modules which consist of a stator of roof-tile shape YBaCuO bulks and a NdFeB permanent magnet circuit. The levitation force density of the bearings was 9 N\\/cm2. It was confirmed that pre-loading and excess cooling methods are both effective for

N. Koshizuka; F. Ishikawa; H. Nasu; M. Murakami; K. Matsunaga; S. Saito; O. Saito; Y. Nakamura; H. Yamamoto; R. Takahata; T. Oka; H. Ikezawa; M. Tomita

2002-01-01

185

Superconductivity-induced optical anomaly in an iron arsenide  

PubMed Central

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

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

2011-01-01

186

Vortex system dynamics and energy losses in a current-carrying 2D superconducting wafer  

SciTech Connect

The dynamic processes occurring in the vortex system of a 2D superconducting wafer carrying transport current are investigated using the model of the vortex system of high-temperature superconductors. Calculations are performed by the Monte Carlo method. For the first time, the dynamics of magnetic field penetration in a current-carrying HTSC wafer is demonstrated and the energy losses associated with a change in transport current are calculated. It is shown that changes in the transport current amplitude and in the number of defects lead to a change in the energy liberation mechanism: hysteresis energy losses are replaced by the losses in the saturated layer.

Odintsov, D. S., E-mail: dodintsov@hotmail.com; Rudnev, I. A.; Kashurnikov, V. A. [Moscow Institute of Engineering Physics (Russian Federation)

2006-07-15

187

Momentum-dependent multiple gaps in magnesium diboride probed by electron tunnelling spectroscopy  

NASA Astrophysics Data System (ADS)

The energy gap is the most fundamental property of a superconductor. MgB2, a superconductor discovered in 2001, exhibits two different superconducting gaps caused by the different electron-phonon interactions in two weakly interacting bands. Theoretical calculations predict that the gap values should also vary across the Fermi surface sheets of MgB2. However, until now, no such variation has been observed. It has been suggested that two gap values were sufficient to describe real MgB2 samples. Here we present an electron tunnelling spectroscopy study on MgB2/native oxide/Pb tunnel junctions that clearly shows a distribution of gap values, confirming the importance of the anisotropic electron-phonon interaction. The gap values, and their spreads found from the tunnel junction measurements, provide valuable experimental tests for various theoretical approaches to the multi-band superconductivity in MgB2.

Chen, Ke; Dai, Wenqing; Zhuang, C. G.; Li, Qi; Carabello, Steve; Lambert, Joseph G.; Mlack, Jerome T.; Ramos, Roberto C.; Xi, X. X.

2012-01-01

188

Momentum-dependent multiple gaps in magnesium diboride probed by electron tunnelling spectroscopy.  

PubMed

The energy gap is the most fundamental property of a superconductor. MgB(2), a superconductor discovered in 2001, exhibits two different superconducting gaps caused by the different electron-phonon interactions in two weakly interacting bands. Theoretical calculations predict that the gap values should also vary across the Fermi surface sheets of MgB(2). However, until now, no such variation has been observed. It has been suggested that two gap values were sufficient to describe real MgB(2) samples. Here we present an electron tunnelling spectroscopy study on MgB(2)/native oxide/Pb tunnel junctions that clearly shows a distribution of gap values, confirming the importance of the anisotropic electron-phonon interaction. The gap values, and their spreads found from the tunnel junction measurements, provide valuable experimental tests for various theoretical approaches to the multi-band superconductivity in MgB(2). PMID:22233629

Chen, Ke; Dai, Wenqing; Zhuang, C G; Li, Qi; Carabello, Steve; Lambert, Joseph G; Mlack, Jerome T; Ramos, Roberto C; Xi, X X

2012-01-01

189

Band gap energy and optical transitions in polyenes formed by thermal decomposition of polyvinyl alcohol  

NASA Astrophysics Data System (ADS)

The band gap of the ensemble of oligoene clusters formed by thermocatalytic decomposition of polyvinyl alcohol is parametrized using optical absorption spectra. A band gap energy of E gm =1.53 ± 0.02 eV at the end of an infinite polyene chain is found by extrapolating the energies of ? ? ?* transitions in clusters with a number of double bonds varying from 4 to 12. This value is close to the band gap of trans-polyacetylene and the lower bound for the Tauc energy E gT =1.50 eV, which characterizes the minimum interband transition energy. E gT is essentially independent of the concentration of oligoene clusters, which is determined by the concentration of the AlCl3 thermal decomposition catalyst. The Urbach energy determined from the long wavelength edge of the spectrum falls from 2.21 to 0.66 eV as the AlCl3 concentration is raised from 11.1 to 41.7 mmol per mol of polyvinyl alcohol structural units.

Kulak, A. I.; Bondarava, G. V.; Shchurevich, O. A.

2013-07-01

190

Outer-gap vs. Slot-gap Models for Pulsar High Energy Emissions: The Case of the Crab Pulsar  

E-print Network

We analytically examine the capabilities of rotation-powered pulsars as the sources of gamma-rays and show that their phase-averaged gamma-ray flux is proportional to the product of the spin-down flux and the gap trans-field thickness cubed irrespective of the emission models. Applying the scheme to the Crab pulsar, we demonstrate that the outer-gap model reproduces the observed GeV fluxes and that the slot-gap model reproduces at most twenty per cent of the observed fluxes because of the small trans-field thickness. An implication on the relationship between the gamma-ray and the spin-down fluxes is discussed.

Kouichi Hirotani

2008-10-06

191

Hermetically sealed superconducting magnet motor  

DOEpatents

A hermetically sealed superconducting magnet motor includes a rotor separated from a stator by either a radial gap, an axial gap, or a combined axial and radial gap. Dual conically shaped stators are used in one embodiment to levitate a disc-shaped rotor made of superconducting material within a conduit for moving cryogenic fluid. As the rotor is caused to rotate when the field stator is energized, the fluid is pumped through the conduit.

DeVault, Robert C. (Knoxville, TN); McConnell, Benjamin W. (Knoxville, TN); Phillips, Benjamin A. (Benton Harbor, MI)

1996-01-01

192

Evidence for phonon-mediated coupling in superconducting Ba1-xKxBiO3  

Microsoft Academic Search

Superconducting Ba1-xKxBiO3, with a Tc of 30K, shows a large 18O isotope effect which indicates that phonons are involved in the pairing mechanism. Superconducting energy gap measurements from IR reflectivity and tunneling are consistent with moderate coupling (2Delta\\/kTc = 3.5 +\\/- 0.5). A characteristic phonon energy of about 40 meV would be required to obtain the high Tc. Neuron scattering

D. G. Hinks; B. Dabrowski; D. R. Richards; J. D. Jorgensen; Shiyou Pei; J. F. Zasadzinski

1989-01-01

193

Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

194

Magnetic energy change available to superconducting condensation in optimally  

E-print Network

from specific heat measurements for YBa2Cu3O6.95 (YBCO) to be 3 K per formula unit15,16 (f.u.). Within of the magnetic excitations, it is possible to calculate the change in the exchange energy available the t­J model, the change in magnetic exchange energy can be calculated from the nearest-neighbour spin

Loss, Daniel

195

Free energy surfaces in the superconducting mixed state  

NASA Technical Reports Server (NTRS)

The free energy surface for Tl2Ba2Ca2Cu3O1O has been measured as a function of temperature and magnetic field to determine the fundamental thermodynamic properties of the mixed state. The change in free energy, G(H)-G(O), is found to be linear in temperature over a wide range indicating that the specific heat is independent of field.

Finnemore, D. K.; Fang, M. M.; Bansal, N. P.; Farrell, D. E.

1989-01-01

196

Preparation of Nb3Al by high-energy ball milling and superconductivity  

NASA Astrophysics Data System (ADS)

The A15 phase superconductor Nb3Al has been considered as an alternative to Nb3Sn for high field and large scale applications. However, to prepare a stoichiometric Nb3Al with fine grain structures is very difficult. High-energy ball milling is a solid state powder processing technique and is a very useful for preparing Nb-Al alloys (Nb3Al). The effects of ball milling time and annealing temperature on the formation of Nb3Al superconducting phase have been studied. Pure Nb and Al powders with stoichiometric ratio of Nb3Al were mixed and milled, and the charging and milling were performed in an inert atmosphere. Phase formation and structural evolution during high-energy ball milling have been examined by X-ray diffraction. Al disappeared and Nb peaks broadened after about one hour of milling. With increasing milling time, the peaks of Nb became considerably broader and intensities decreased, the Nb-Al solid solution phase was extensive when milled about 3 hours. In order to obtain Nb3Al superconducting phase, a subsequent anneal was required. We have annealed the as-milled powders at 800-900°C for different times to prepared Nb3Al superconducting alloy. The results indicated that Nb3Al with small amount of impurity phase can be obtained on annealing the Nb-Al solid solution phase and the superconducting transition temperature was about 15K, but it is difficult to obtain a homogeneous Nb3Al phase by annealing the amorphous powder.

Chen, Yongliang; Liu, Zhao; Li, Pingyuan; Zhang, Xiaolan; Yang, Suhua; Yang, Dawei; Du, Lupeng; Cui, Yajing; Pan, Xifeng; Yan, Guo; Zhao, Yong

2014-05-01

197

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

E-print Network

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.

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

198

Energy-gap opening in a Bi110 nanoribbon induced by edge reconstruction.  

PubMed

Scanning tunnelling microscopy and spectroscopy experiments complemented by first-principles calculations have been conducted to study the electronic structure of 4 monolayer Bi(110) nanoribbons on epitaxial graphene on silicon carbide [4H-SiC(0001)]. In contrast with the semimetal property of elemental bismuth, an energy gap of 0.4 eV is measured at the centre of the Bi(110) nanoribbons. Edge reconstructions, which can facilitate the edge strain energy release, are found to be responsible for the band gap opening. The calculated density of states around the Fermi level are decreased quickly to zero from the terrace edge to the middle of a Bi(110) nanoribbon potentially signifying a spatial metal-to-semiconductor transition. This study opens new avenues for room-temperature bismuth nanoribbon-based electronic devices. PMID:23368363

Sun, Jia-Tao; Huang, Han; Wong, Swee Liang; Gao, H-J; Feng, Yuan Ping; Wee, Andrew Thye Shen

2012-12-14

199

Coil protection for a utility scale superconducting magnetic energy storage plant  

SciTech Connect

Superconducting Magnetic Energy Storage (SMES) is proposed for electric utility load leveling. Attractive costs, high diurnal energy efficiency (greater than or equal to 92%), and rapid response are advantages relative to other energy storage technologies. Recent industry-led efforts have produced a conceptual design for a 5000 MWh/1000 MW energy storage plant which is technically feasible at commercially attractive estimated costs. The SMES plant design includes a protection system which prevents damage to the magnetic coil if events require a rapid discharge of stored energy. This paper describes the design and operation of the coil protection system, which is primarily passive and uses the thermal capacity of the coil itself to absorb the stored electromagnetic energy.

Loyd, R.J.; Schoenung, S.M.; Hassenzahl, W.V.; Rogers, J.D.; Purcell, J.R.

1986-01-01

200

High Energy Emission from the Polar Cap: The Slot Gap Revisited  

E-print Network

The characteristics of the high-energy emission from polar cap accelerators will be discussed. Particles accelerated in the "slot gap" near the polar cap rim will reach altitudes of several stellar radii before initiating pair cascades, producing a wide hollow cone of emission in young pulsars and some millisecond pulsars. Model X-ray and gamma-ray spectra and pulse profiles, based on Monte-Carlo simulations of polar cap pair cascades, will be presented.

Alice K. Harding; Alexander G. Muslimov

2003-04-07

201

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

202

Theoretical and experimental investigation of variable band gap cells in thermophotovoltaic energy conversion  

Microsoft Academic Search

Using a theoretical model for the performance of a thermophotovoltaic (TPV) energy conversion cell, and values of saturation-current density and diode ideality factor obtained experimentally for two types of InCaAs cells, one GaAs, and two Si cells, the TPV efficiency at various temperatures was calculated for these cells. The results disclosed an apparent advantage of InGaAs cells (with band gaps

L. D. Woolf; J. C. Bass; N. B. Elsner

1986-01-01

203

Predicted energy band gaps of (AIIIBV)1-xXIV2x metastable, substitutional, crystalline alloys  

Microsoft Academic Search

Predictions of the energy band gaps as functions of alloy composition are given for the Greene alloys, which are metastable, crystalline, substitutional alloys of III-V compounds and group-IV elemental materials. All possible combinations of these alloys involving Al, Ga, In, P, As, Sb, Si, Ge, and Sn are considered. The Gamma and L conduction-band minima, relative to the valence-band maxima,

David W. Jenkins; Kathie E. Newman; John D. Dow

1985-01-01

204

Increasing the ? = 5/2 gap energy: an analysis of MBE growth parameters  

NASA Astrophysics Data System (ADS)

The fractional quantized Hall state at the filling factor ? = 5/2 is of special interest due to its possible application for quantum computing. Here we report on the optimization of growth parameters that allowed us to produce two-dimensional electron gases (2DEGs) with a 5/2 gap energy up to 135 mK. We concentrated on optimizing the molecular beam epitaxy (MBE) growth to provide high 5/2 gap energies in ‘as-grown’ samples, without the need to enhance the 2DEGs properties by illumination or gating techniques. Our findings allow us to analyse the impact of doping in narrow quantum wells with respect to conventional DX-doping in AlxGa1-xAs. The impact of the setback distance between doping layer and 2DEG was investigated as well. Additionally, we found a considerable increase in gap energy by reducing the amount of background impurities. To this end growth techniques like temperature reductions for substrate and effusion cells and the reduction of the Al mole fraction in the 2DEG region were applied.

Reichl, C.; Chen, J.; Baer, S.; Rössler, C.; Ihn, T.; Ensslin, K.; Dietsche, W.; Wegscheider, W.

2014-02-01

205

Large gap magnetic suspension system  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

206

Superconducting transmission line particle detector  

Microsoft Academic Search

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

Gray

1988-01-01

207

Superconducting transmission line particle detector  

Microsoft Academic Search

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

Gray; Kenneth E

1989-01-01

208

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

SciTech Connect

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.

Cook, J.M.

1990-09-24

209

0.54MJ superconducting magnetic energy transfer and storage  

Microsoft Academic Search

A previous design optimization study (Rogers et al., 1974) has been made for the magnetic energy transfer and storage system (METS), leading to the adoption of an efficient resonant L-C-L capacitive transfer circuit with an HVDC vacuum interrupter to initiate the transfer. The characteristics of the SFTR (Scyllac Fusion Test Reactor)-METS system are discussed, where the system can provide the

J. D. Rogers; D. J. Blevins; J. D. G. Lindsay; G. A. Miranda; C. E. Swannack; D. M. Weldon; J. J. Wollan; C. J. Mole; E. Mullan; P. W. Eckels

1978-01-01

210

Energy-band gap of monolayer superlattices calculated by a modified tight-binding method with electronegativity  

Microsoft Academic Search

The tight-binding method is modified successfully to calculate the energy-band gap at the Gamma point for monolayer superlattices in which each monolayer comprises a binary and ternary compound semiconductor. In the case of (InAs)1\\/(GaAs)1 monolayer superlattices, the energy-band gap is 5% smaller than that of In0.5Ga0.5As ternary compound semiconductors. The energy-band gap of (InAs)1\\/(GaAs)1 monolayer superlattices increases nonlinearly to that

Y. Matsui; Y. Kusumi; A. Nakaue

1993-01-01

211

Higgsless superconductivity from topological defects in compact BF terms  

E-print Network

We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalizable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D-1)-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact low-energy effective BF theories. In the average field approximation, the corresponding uniform emergent charge creates a gap for the (D-2)-dimensional branes via the Magnus force, the dual of the Lorentz force. One particular combination of intrinsic and emergent charge fluctuations that leaves the total charge distribution invariant constitutes an isolated gapless mode leading to superfluidity. The remaining massive modes organise themselves into a D-dimensional charged, massive vector. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2) and the topological order (4) are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D this type of superconductivity is explicitly realized as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.

M. Cristina Diamantini; Carlo A. Trugenberger

2014-08-21

212

Optimization of a Superconducting Magnetic Energy Storage Device via a CPU-Efficient Semi-Analytical Simulation  

E-print Network

Recent advances in second generation (YBCO) high temperature superconducting wire could potentially enable the design of super high performance energy storage devices that combine the high energy density of chemical storage with the high power of superconducting magnetic storage. However, the high aspect ratio and considerable filament size of these wires requires the concomitant development of dedicated optimization methods that account for both the critical current density and ac losses in type II superconductors. Here, we report on the novel application and results of a CPU-efficient semi-analytical computer code based on the Radia 3D magnetostatics software package. Our algorithm is used to simulate and optimize the energy density of a superconducting magnetic energy storage device model, based on design constraints, such as overall size and number of coils. The rapid performance of the code is pivoted on analytical calculations of the magnetic field based on an efficient implementation of the Biot-Savart...

Dimitrov, I K; Solovyov, V F; Chubar, O; Li, Qiang

2014-01-01

213

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

SciTech Connect

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.

Hawsey, R.A. [comp.

1993-02-01

214

Manifestation of a gap due to the exchange energy in a spinor condensate  

NASA Astrophysics Data System (ADS)

We investigate the dynamic response of population transfer between two components of a finite temperature spinor Bose condensed gas to a time-dependent coupling potential. Comparison between the results obtained in the Bogoliubov-Popov approximation (BPA) and in the generalized random phase approximation (GRPA) shows noticeable discrepancies. In particular, the inter-component current response function calculated in the GRPA displays a gapped spectrum due to the exchange interaction energy whereas the corresponding density response function is gapless. We verify that, contrary to the BPA, the GRPA preserves the SU(2) symmetry and the f-sum rule associated to the spinor gas. In order to validate the approximation, we propose an experimental setup that allows the observation of the predicted gap.

Navez, Patrick

2008-07-01

215

Hybrid superconducting magnetic bearing and its frictional energy loss and dynamics  

SciTech Connect

A hybrid superconducting magnetic bearing (SMB) has been designed and tested. A flywheel energy storage (FES) prototype has been constructed for testing bearing friction loss and characterizing the dynamics of the rotor. The hybrid SMB design uses magnetic forces from permanent magnets for levitation and high temperature superconductor YBCO in between the magnets for stabilization. A 42 lb. flywheel currently can rotate up to 6,000 RPM with kinetic energy of 8 Wh stored. The result from the recent rotor spin-down experiment indicates an average frictional energy loss <2% per hour in a vacuum of 10 {sup {minus}5} torr, with imperfect system alignment and balance of rotor. The system dynamics has been conducted to improve upon the energy loss and rotor-bearing modeling.

Xia, Z.; Ma, K.B.; Chen, Q.Y.; Cooley, R.R. [Univ. of Houston, TX (United States)] [and others

1995-12-31

216

Low-energy response of superconducting tunnel junction x-ray spectrometers  

SciTech Connect

Thin film structures incorporating metallic superconducting layers and tunnel junctions can be configured as low-energy X-ray spectrometers. We present results obtained when low-energy X-rays are absorbed in niobium films coupled to aluminum layers that serve as quasiparticle traps in an Nb/Al/Al{sub 2}O{sub 3}/Al/Nb tunnel junction X-ray detector. The linearity of the pulse height as a function of energy is discussed along with the energy dependence of the observed resolution and its relation to the broadening mechanisms. A resolution of 14 eV at 1 keV has been measured with our detector cooled to 0.3 K.

Labov, S.E.; Hiller, L.H.; Measrs, C.A.; Frank, M.; Netel, H.; Azgui, F. [Lawrence Livermore National Lab., CA (United States); Barfknecht, A.T. [Conductus, Inc., Sunnyvale, CA (United States)

1994-12-31

217

Superconducting Memristors  

NASA Astrophysics Data System (ADS)

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.

Peotta, Sebastiano; Di Ventra, Massimiliano

2014-09-01

218

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

SciTech Connect

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.

NONE

1983-03-01

219

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

E-print Network

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.

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

2014-09-21

220

Large intrinsic energy band gaps in annealed nanotube-derived graphene nanoribbons  

NASA Astrophysics Data System (ADS)

The usefulness of graphene for electronics is diminished by an absent energy bandgap. While graphene nanoribbons have non-zero bandgaps, lithographic fabrication methods introduce defects which decouple the bandgap from electronic properties and compromise performance [1]. Here, we present direct measurements of a large intrinsic energy bandgap of approximately 50 meV in 100 nm-width level nanoribbons fabricated by high-temperature annealing of unzipped carbon nanotubes [2]. The activation energy is seven times greater than those in [1], and is close to the width of the transport gap in the differential conductance. This similarity suggests that the activation energy is in fact the intrinsic bandgap. High-resolution TEM and Raman spectroscopy, along with an absence of hopping conductance and stochastic charging effects, suggest a low defect density. [1] M.Y. Han, P. Kim et al., PRL 104, 056801 (2010) [2] J.Haruyama, J.M.Tour, et al., Nature Nanotech. (December 2010)

Haruyama, J.; Shimizu, T.; Marcano, D. C.; Kosinkin, D. V.; Tour, J. M.; Hirose, K.; Suenaga, K.

2011-03-01

221

Optimized use of superconducting magnetic energy storage for electromagnetic rail launcher powering  

NASA Astrophysics Data System (ADS)

Electromagnetic rail launchers (EMRLs) require very high currents, from hundreds of kA to several MA. They are usually powered by capacitors. The use of superconducting magnetic energy storage (SMES) in the supply chain of an EMRL is investigated, as an energy buffer and as direct powering source. Simulations of direct powering are conducted to quantify the benefits of this method in terms of required primary energy. In order to enhance further the benefits of SMES powering, a novel integration concept is proposed, the superconducting self-supplied electromagnetic launcher (S3EL). In the S3EL, the SMES is used as a power supply for the EMRL but its coil serves also as an additional source of magnetic flux density, in order to increase the thrust (or reduce the required current for a given thrust). Optimization principles for this new concept are presented. Simulations based on the characteristics of an existing launcher demonstrate that the required current could be reduced by a factor of seven. Realizing such devices with HTS cables should be possible in the near future, especially if the S3EL concept is used in combination with the XRAM principle, allowing current multiplication.

Badel, Arnaud; Tixador, Pascal; Arniet, Michel

2012-01-01

222

Modelling of Superconducting Pancake Coil  

Microsoft Academic Search

\\u000a Superconducting pancake coils can be used in a range of large scale applications—for example, superconducting Magnetic Energy\\u000a Storage, Superconducting Fault Current limiter, MRI, and so on. Predicting AC losses are also very important for the applications\\u000a of superconducting coils in machines. Therefore an understanding of the electromagnetic behaviour of the superconducting pancake\\u000a coils are important before using them in real

Weijia Yuan

223

Graded-gap Al x Ga 1? x As high-energy X-ray radiation dosimeter  

Microsoft Academic Search

The detectors for high-energy X-ray dosimetry based on graded-gap AlxGa1?xAs structures were developed. Two types of graded-gap AlxGa1?xAs structures characterized by different operating mechanisms (the first type, an internal optical response, and the second one, a charge collection by an internal graded-gap field) were investigated as high-energy X-ray radiation detectors. The linear response on absorbed dose and dose rate for

Aldis Silenas; Albert Miller; Juras Pozela; Karolis Pozela; Leonas Dapkus; Vida Juciene

2009-01-01

224

High Temperature Superconductivity in Cuprates: a model  

E-print Network

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.

P. R. Silva

2010-07-16

225

Modeling the energy thermalization of x-ray photons in a microcalorimeter with superconducting absorber  

NASA Astrophysics Data System (ADS)

We present a modeling of the response of a microcalorimeter to the absorption of X-ray photons, based on the main microscopical processes responsible for the energy thermalization. In particular, we have modeled a microcalorimeter with superconducting tin absorber (350 micron x 350 micron x 7 micron) and neutron transmutation doped (NTD) germanium thermistor (75 micron x 50 micron x 150 micron). Such a detector, operated at 60 mK, is expected to achieve a spectral resolution as good as 1 eV FWHM in the soft X-ray energy range, based on the known sources of thermal and electronic noise. Nevertheless, the best spectral resolution measured in laboratory experimental tests is of about 5 eV FWHM (at 5.89 keV). We have investigated how the microscopic processes of energy thermalization, involving both quasiparticles and phonons, and the position of absorption of the photons may affect the spectral resolution of the detector.

Perinati, Emanuele; Barbera, Marco; Collura, Alfonso; Serio, Salvatore; Silver, Eric H.; Beeman, Jeffrey W.; Haller, Eugene E.; Landis, Don A.; Madden, Norman W.

2003-03-01

226

Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission  

E-print Network

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. 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. The estimated theoretical high-energy luminosities of the SG cascade radiation 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.

Alex G. Muslimov; Alice K. Harding

2003-01-02

227

Wave equations for determining energy-level gaps of quantum systems  

E-print Network

An differential equation for wave functions is proposed, which is equivalent to Schr\\"{o}dinger's wave equation and can be used to determine energy-level gaps of quantum systems. Contrary to Schr\\"{o}dinger's wave equation, this equation is on `bipartite' wave functions. It is shown that those `bipartite' wave functions satisfy all the basic properties of Schr\\"{o}dinger's wave functions. Further, it is argued that `bipartite' wave functions can present a mathematical expression of wave-particle duality. This provides an alternative approach to the mathematical formalism of quantum mechanics.

Zeqian Chen

2006-04-12

228

Field-Induced-Gap Infrared Detectors  

NASA Technical Reports Server (NTRS)

Semimetals become semiconductors under applied magnetic fields. New detectors require less cooling equipment because they operate at temperatures higher than liquid-helium temperatures required by extrinsic-semiconductor detectors. Magnetic fields for detectors provided by electromagnets based on recently-discovered high-transition-temperature superconducting materials. Detector material has to be semiconductor, in which photon absorbed by exciting electron/hole pair across gap Eg of forbidden energies between valence and conduction energy bands. Magnetic- and compositional-tuning effects combined to obtain two-absorber detector having narrow passband. By variation of applied magnetic field, passband swept through spectrum of interest.

Elliott, C. Thomas

1990-01-01

229

Magnetic Properties of Iron Chalcogenide Superconducting Materials for Energy Storage Applications  

NASA Astrophysics Data System (ADS)

A superconductor is characterized by its ability to conduct electricity without loss and expel magnetic flux when exposed to an external magnetic field. Additionally, the smaller the relaxation rate (S=dM/dt), the better the material for energy storage. This research focuses on the recently discovered high-quality, single-crystalline Iron-based superconductors of FeTe1-xSex (x =0.5), with a transition temperature at Tc=14.5K. Standard creep models are used to analyze the data and determine the effective pinning potential. The magnetization relaxation were measured the Superconducting Quantum Interference Device (SQUID). The relaxation rate appears to be independent of field and temperature for fields below 3T and temperatures below 7K. This result shows that the thermally activated flux motion is not as significant as in other high temperature superconductors, hence FeTe1-xSex, can be a candidate for wire development to be used in Superconducting Magnetic Energy Storage systems.

Knock, Destenie; Pough, Korey; Kebede, Abebe; Seifu, Dereje

2013-03-01

230

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

231

Superconductivity in an electron band just above the Fermi level: possible route to BCS-BEC superconductivity  

PubMed Central

Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals and ultra-cold gases, respectively, are connected by the BCS-BEC crossover. Here we investigate the band dispersions in FeTe0.6Se0.4(Tc = 14.5?K ~ 1.2?meV) in an accessible range below and above the Fermi level(EF) using ultra-high resolution laser angle-resolved photoemission spectroscopy. We uncover an electron band lying just 0.7?meV (~8?K) above EF at the ?-point, which shows a sharp superconducting coherence peak with gap formation below Tc. The estimated superconducting gap ? and Fermi energy indicate composite superconductivity in an iron-based superconductor, consisting of strong-coupling BEC in the electron band and weak-coupling BCS-like superconductivity in the hole band. The study identifies the possible route to BCS-BEC superconductivity. PMID:24576851

Okazaki, K.; Ito, Y.; Ota, Y.; Kotani, Y.; Shimojima, T.; Kiss, T.; Watanabe, S.; Chen, C.-T.; Niitaka, S.; Hanaguri, T.; Takagi, H.; Chainani, A.; Shin, S.

2014-01-01

232

Superconductivity in an electron band just above the Fermi level: possible route to BCS-BEC superconductivity.  

PubMed

Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals and ultra-cold gases, respectively, are connected by the BCS-BEC crossover. Here we investigate the band dispersions in FeTe(0.6)Se(0.4)(Tc = 14.5 K ~ 1.2 meV) in an accessible range below and above the Fermi level(EF) using ultra-high resolution laser angle-resolved photoemission spectroscopy. We uncover an electron band lying just 0.7 meV (~8 K) above EF at the ?-point, which shows a sharp superconducting coherence peak with gap formation below Tc. The estimated superconducting gap ? and Fermi energy [Symbol: see text]F indicate composite superconductivity in an iron-based superconductor, consisting of strong-coupling BEC in the electron band and weak-coupling BCS-like superconductivity in the hole band. The study identifies the possible route to BCS-BEC superconductivity. PMID:24576851

Okazaki, K; Ito, Y; Ota, Y; Kotani, Y; Shimojima, T; Kiss, T; Watanabe, S; Chen, C-T; Niitaka, S; Hanaguri, T; Takagi, H; Chainani, A; Shin, S

2014-01-01

233

energy gap determination by scanning tunnelling spectroscopy This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

MgB 2 energy gap determination by scanning tunnelling spectroscopy This article has been downloaded. 17 (2004) 237­242 PII: S0953-2048(04)68995-0 MgB2 energy gap determination by scanning tunnelling tunnelling spectroscopy (STS) measurements of the gap properties of both ceramic MgB2 and c-axis oriented

Eom, Chang Beom

234

A study of the fractional quantum Hall energy gap at half filling  

NASA Astrophysics Data System (ADS)

A complete understanding of the nu = 52 fractional quantum hall effect (FQHE) continues to be among the most exciting problems in semiconductor physics. It is widely believed that this unique electron state is described by the Moore-Read Pfaffian wavefunction, resulting from a BCS-like pairing of composite fermions. In recent years this wavefunction has received special interest owing to its non-abelian quantum statistics which underlies a new paradigm for fault tolerant quantum computation. However, in spite of several theoretical advancements, an unequivocal experimental verification of the Moore-Read description is still missing. We studied the 52 state in a very high quality 2DEG sample with the lowest electron density reported to date, by nearly a factor of two. We demonstrate that large discrepancies between experimentally measured values of the 52 energy gap, and theoretical calculations based on the Moore-Read theory, can not be trivially attributed to disorder as has conventionally been assumed. Using a tilted field geometry, we investigated the effect of applying an in-plane magnetic field on the 52 state. We observe the 52 energy gap to collapse linearly with the in-plane field, whereas the neighbouring 73 shows a strong enhancement. The opposite behaviour between the two states is in startling contrast to theory which predicts both gaps should be similarly suppressed. Since the early theoretical foundation in support of the Moore-Read interpretation presumed the two states should behave the same, our experimental finding of opposite behaviour may necessitate a fundamental rethinking of the nature of the 52 FQHE. A crucial step towards verifying the Moore-Read description of the nu = 52 FQHE will be an unambiguous measurement of its spin state. In an effort to measure the 52 spin directly, we implemented a resistively detected nuclear magnetic resonance (RDNMR) technique. I report on our detailed study of the anomalous RDNMR lineshape around nu = 1, and discuss progress made towards measuring the 52 spin with this technique.

Dean, Cory R.

235

Present status of R&D on superconducting magnetic bearing technologies for flywheel energy storage system  

NASA Astrophysics Data System (ADS)

We report on the NEDO project of superconducting magnetic bearing (SMB) technologies for flywheel energy storage system. We fabricated SMB modules which consist of a stator of roof-tile shape YBaCuO bulks and a NdFeB permanent magnet circuit. The levitation force density of the bearings was 9 N/cm 2. It was confirmed that pre-loading and excess cooling methods are both effective for suppressing the gradual fall of rotor due to flux creep. We designed a basic concept of 10 kW h class flywheel energy storage system and investigated the feasibility of active magnetic bearings for the 10 kW h system. We also examined the fabrication condition of CFRP flywheels for the system.

Koshizuka, N.; Ishikawa, F.; Nasu, H.; Murakami, M.; Matsunaga, K.; Saito, S.; Saito, O.; Nakamura, Y.; Yamamoto, H.; Takahata, R.; Oka, T.; Ikezawa, H.; Tomita, M.

2002-10-01

236

Closing data gaps for LCA of food products: estimating the energy demand of food processing.  

PubMed

Food is one of the most energy and CO2-intensive consumer goods. While environmental data on primary agricultural products are increasingly becoming available, there are large data gaps concerning food processing. Bridging these gaps is important; for example, the food industry can use such data to optimize processes from an environmental perspective, and retailers may use this information for purchasing decisions. Producers and retailers can then market sustainable products and deliver the information demanded by governments and consumers. Finally, consumers are increasingly interested in the environmental information of foods in order to lower their consumption impacts. This study provides estimation tools for the energy demand of a representative set of food process unit operations such as dehydration, evaporation, or pasteurization. These operations are used to manufacture a variety of foods and can be combined, according to the product recipe, to quantify the heat and electricity demand during processing. In combination with inventory data on the production of the primary ingredients, this toolbox will be a basis to perform life cycle assessment studies of a large number of processed food products and to provide decision support to the stakeholders. Furthermore, a case study is performed to illustrate the application of the tools. PMID:24344613

Sanjuán, Neus; Stoessel, Franziska; Hellweg, Stefanie

2014-01-21

237

Superconducting magnetic energy storage: Technical considerations and relative capital cost using high-temperature superconductors  

SciTech Connect

Superconducting magnetic energy storage plants could significantly benefit form using high-temperature superconductors. Benefits would include greatly lowered operation and maintenance expenses and modestly reduced capital costs. The project team compared present HTSC capabilities to the minimum requirements for SMES superconductors. Next, they projected potential cost reductions, assuming one-for-one replacement of conventional low-temperature superconductors with HTSC at equal installed cost. The estimated captial-cost savings from substituting HTSC for conventional superconductors in large-scale SMES plants ranged from 7% for 5000 MWh to 10% for 20 MWh. In addition, HTSC used in SMES plants would provide six design benefits -- better stability, lower refrigeration needs, lower thermal shielding needs, easier cooldown, no helium use, and possibly no vacuum system. Partially offsetting these is the need for more support structure, caused by the lower strength of materials at 77 K versus 4 K, and loss of the cryopumping ability of 4 K surfaces. To realize these benefits, the HTSC primary SMES coil conductor must be robust enough to be formed into a coal, and it must superconduct in a magnetic field of at least 3 tesla at a current density of at least 12,000 A/cm{sup 2}.

Loyd, R.J.; Bulc, A.M.; Majumdar, D. (Bechtel National, Inc., San Francisco, CA (United States))

1992-04-01

238

Compositional and temperature dependence of the energy band gap of CuxInySe2 epitaxial layers  

NASA Astrophysics Data System (ADS)

The compositional and temperature dependence of the energy band gap of CuxInySe2 epitaxial layers grown by metal-organic chemical vapour deposition on GaAs(1 0 0) substrates was studied by photoreflectance (PR) spectroscopy. Investigation of the compositional dependence at 20 K showed a slight increase in the energy gap with the increase in the [Cu]/[In] fraction. Line-shape analysis of PR spectra indicated that near stoichiometric and slightly Cu-rich CuInSe2 layers have a better crystallinity than In-rich ones. Investigation of the temperature dependence for both Cu-rich and In-rich modifications, in the range 300-20 K, demonstrated a red-shift of band-gap energies with the decrease in temperature below 70 K and provided experimental evidence of the anomalous temperature dependence of the energy gap in this material. Moreover, a combination of modulation power-dependent PR and photoluminescence studies at 20 K revealed that the optical emission interfering in the PR spectra at energies below the band-gap energy originates from donor-acceptor pair recombination and diminishes at low modulation powers.

Xu, H. Y.; Papadimitriou, D.; Zoumpoulakis, L.; Simitzis, J.; Lux-Steiner, M.-Ch

2008-08-01

239

A study of energy band gap versus temperature for Cu2ZnSnS4 thin films  

Microsoft Academic Search

The temperature dependent band gap energy of Cu2ZnSnS4 thin film was studied in the temperature range of 77-410 K. Various relevant parameters, which explain the temperature variation of the fundamental band gap, have been calculated using empirical and semi-empirical models. Amongst the models evaluated, the Varshni and Pässler models show the best agreement with experimental data in the middle temperature

Prashant K. Sarswat; Michael L. Free

2012-01-01

240

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

PubMed

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 Bi(2)Sr(2)CaCu(2)O(8+?) crystals the pairing gap amplitude monotonically extends well beyond Tc, while the phase coherence shows a pronounced power-law divergence as T ? T(c), thus showing that phase coherence and gap formation are distinct processes which occur on different timescales. PMID:25014162

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

2014-01-01

241

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

PubMed Central

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

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

2014-01-01

242

SUPERCONDUCTING PHOTOINJECTOR  

SciTech Connect

One of the frontiers in FEL science is that of high power. In order to reach power in the megawatt range, one requires a current of the order of one ampere with a reasonably good emittance. The superconducting laser-photocathode RF gun with a high quantum efficiency photocathode is the most natural candidate to provide this performance. The development of a 1/2 cell superconducting photoinjector designed to operate at up to a current of 0.5 amperes and beam energy of 2 MeV and its photocathode system are the subjects covered in this paper. The main issues are the photocathode and its insertion mechanism, the power coupling and High Order Mode damping. This technology is being developed at BNL for DOE nuclear physics applications such as electron cooling at high energy and electron ion colliders..

BEN-ZVI,I.; BURRILL, A.; CALAGA, R.; CHANG, X.; GROVER, R.; GUPTA, R.; HAHN, H.; HAMMONS, L.; KAYRAN, D.; KEWISCH, J.; LAMBIASE, R.; LITVINENKO, V.; MCINTYRE, G.; NAIK, D.; PATE, D.; PHILLIPS, D.; POZDEYEV, E.; RAO, T.; SMEDLEY, J.; THAN, R.; TODD, R.; WEISS, D.; WU, Q.; ZALTSMAN, A.; ET AL.

2007-08-26

243

Joint operation of the superconducting fault current limiter and magnetic energy storage system in an electric power network  

NASA Astrophysics Data System (ADS)

An opportunity of using superconductors as active elements of electric power systems designed to control the electric power distribution, to enhance the systems operating modes and to limit fault currents, was very attractive for investigators for a long time. In this paper, is considered an opportunity to enhance the electric power systems with the aid of superconducting magnetic energy storage systems (SMES) and superconducting fault current limiters (SFCL) operating together. It has been shown that the joint operation of both these superconducting devices allows additional varying of their parameters, what in turn gives a further opportunity to reduce their mass and dimensions and consequently the costs. There had been also shown an additional advantage of the SMES and SFCL joint operation consisting in that they ensure a more effective protection for a power system, preventing its uncontrolled load-off and subsequent acceleration up to the inaccessible rotation speed.

Kopylov, S. I.; Balashov, N. N.; Ivanov, S. S.; Veselovsky, A. S.; Zhemerikin, V. D.

2010-06-01

244

SUPERCONDUCTING PHOTOCATHODES.  

SciTech Connect

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.

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

2005-10-09

245

Self Consistent Calculations of Electronic Properties of Systems with an Energy or a Band Gap  

NASA Astrophysics Data System (ADS)

We re-examine the process of performing self consistent calculations of electronic and related properties of finite systems (with an energy gap) and of crystals with a band gap. This work applies to calculations utilizing density functional and X? potentials and to other approaches that entail solving a system of inherently coupled equations. In particular, the local density approximation (LDA) is defined by a system of equations that reduces to two equations upon the selection of Vxc. We show how the Bagayoko, Zhao, and Williams (BZW) method solves the relevant system of equations and leads to results in excellent agreement with experimental ones. We discuss such results for w-ZnO, rutile TiO2, w-CdS, zb-CdS, zb-InP, Ge, Ca B6, and other materials. Work funded by the National Science Foundation, through LASiGMA [NSF AwardEPS-1003897 and No. NSF (2010-15)-RII-SUBR], LONI [Award No. 2-10915], and Ebonyi State, Federal Republic of Nigeria.

Bagayoko, Diola; Franklin, Lashounda; Ekuma, Chinedu; Malozovsky, Yuriy

2012-02-01

246

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)

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.

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

2014-10-01

247

Singularity analysis of Ginzburg-Landau energy related to p-wave superconductivity  

NASA Astrophysics Data System (ADS)

The following Ginzburg-Landau energy in the absence of a magnetic field E_\\varepsilon(?) = intlimits_G[1/2|nabla?|^2 + 1/4\\varepsilon^2(1-|?|^2)^2]dx was well studied during recent twenty years. Here, {G subset {R}^2} is a bounded smooth domain, {?} is an order parameter, {\\varepsilon >0 } . In particular, several global properties including the weighted energy estimation, the concentration compactness properties and the quantization effect of the energy had been established. This paper is concerned with another Ginzburg-Landau type free energy associated with p-wave superconductivity E_\\varepsilon (?, u; G) = 1/2 intlimits_G(|nabla ?|^2 + |nabla u|^2 - |nabla|?||^2)dx + 1/4\\varepsilon^2 intlimits_G(1-|?|^2)^2dx. Here, u is also an order parameter. We will prove that those global properties still hold for this more complicated energy functional. Such global properties describe the locations of the regular and the singular domains, and also show the convergence relation between the Ginzburg-Landau minimizers and the harmonic maps.

Lei, Yutian

2013-08-01

248

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

NASA Astrophysics Data System (ADS)

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.

Farahani, Mohsen; Ganjefar, Soheil

2013-04-01

249

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

SciTech Connect

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.

Lee, S.J.

1988-01-01

250

Superconducting transmission line particle detector  

DOEpatents

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.

Gray, Kenneth E. (Naperville, IL)

1989-01-01

251

Superconducting transmission line particle detector  

DOEpatents

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.

Gray, K.E.

1988-07-28

252

Pulsar High-Energy Emission From the Polar Cap and Slot Gap  

E-print Network

Forty years after the discovery of rotation-powered pulsars, we still do not understand many aspects of their pulsed emission. In the last few years there have been some fundamental developments in acceleration and emission models. I will review both the basic physics of the models as well as 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 current and future X-ray and gamma-ray detectors can test the predictions of these models.

Alice K. Harding

2007-10-18

253

High-Energy Emission From the Polar Cap and Slot Gap  

NASA Technical Reports Server (NTRS)

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.

Harding, Alice K.

2006-01-01

254

Analysis of superconducting magnetic energy storage applications at a proposed wind farm site near Browning, Montana  

NASA Astrophysics Data System (ADS)

A computer program was developed to analyze the viability of integrating superconducting magnetic energy storage (SMES) with proposed wind farm scenarios at a site near Browning, Montana. The program simulated an hour-by-hour account of the charge/discharge history of a SMES unit for a representative wind-speed year. Effects of power output, storage capacity, and power conditioning capability on SMES performance characteristics were analyzed on a seasonal, diurnal, and hourly basis. The SMES unit was assumed to be charged during periods when power output of the wind resource exceeded its average value. Energy was discharged from the SMES unit into the grid during periods of low wind speed to compensate for below-average output of the wind resource. The option of using SMES to provide power continuity for a wind farm supplemented by combustion turbines was also investigated. Levelizing the annual output of large wind energy systems operating in the Blackfeet area of Montana was found to require a storage capacity too large to be economically viable. However, it appears that intermediate-sized SMES economically levelize the wind energy output on a seasonal basis.

Gaustad, K. L.; Desteese, J. G.

1993-07-01

255

Energy losses in superconductive DC-electromagnets due to ferromagnetic movement  

SciTech Connect

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.

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

1996-05-01

256

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

and renewable energy to climate change impacts on water and agriculture sectors. Dr. Debele has published, 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

Johnson, Eric E.

257

Superconducting transmission line particle detector  

Microsoft Academic Search

This paper describes 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

Gray

1989-01-01

258

Anchoring energy and cell gap effects on liquid crystal response time Xiangyi Nie, Ruibo Lu, Haiqing Xianyu, Thomas X. Wu, and Shin-Tson Wua  

E-print Network

Anchoring energy and cell gap effects on liquid crystal response time Xiangyi Nie, Ruibo Lu 2007 The anchoring energy and cell gap effects on liquid crystal response time 0 is analyzed relatively weak anchoring energy, such as LC cells with multidomain vertical alignment MVA

Wu, Shin-Tson

259

Defect Formation Energies without the Band-Gap Problem: Combining Density-Functional Theory and the GW Approach for the Silicon Self-Interstitial  

E-print Network

Defect Formation Energies without the Band-Gap Problem: Combining Density-Functional Theory energies that overcomes the band-gap problem of Kohn-Sham density-functional theory (DFT) and reduces self-interstitial that combining LDA with quasiparticle energy calculations in the G0W0 approach

260

Band gap energies of solar micro/meso-porous composites of zinc (hydr)oxide with graphite oxides  

NASA Astrophysics Data System (ADS)

The band gap energies of micro/meso-porous zinc (hydr)oxide and its composites with 2 wt. % and 5 wt. % graphite oxides are reported using three optical characterization techniques. The obtained energy gaps (from 2.84 eV to 2.95 eV) of the composites are smaller than that for zinc oxide (˜3.2 eV) and zinc (hydr)oxide (˜3.06 eV). The band gap narrowing of the composite materials is due to the presence of defects, larger particle size, and weaker confinement. The bonds between zinc (hydr)oxide lattice and the carbon of graphene phase also contribute to this phenomenon. The structural properties of these materials are presented using Transmission Electron Microscopy, Scanning Tunneling Electron Microscopy, X-Ray analysis, and Two-Photon Fluorescence imaging Microscopy.

Islam, SM Z.; Gayen, Taposh; Seredych, Mykola; Mabayoje, Oluwaniyi; Shi, Lingyan; Bandosz, Teresa J.; Alfano, Robert R.

2013-07-01

261

Direct observation of half-metallic energy gap in Co{sub 2}MnSi by tunneling conductance spectroscopy  

SciTech Connect

Magnetic tunnel junctions with a Co{sub 2}MnSi/Al-O/CoFe structure are prepared by magnetron sputtering and investigated with respect to the energy gap near the Fermi energy level. The plasma oxidation time for the Al-O barrier is found to affect the condition of the Co{sub 2}MnSi/Al-O interface. The optimized sample (50 s oxidation time) exhibits a magnetoresistance ratio of 159% and tunneling spin polarization of 0.89 at 2 K. The bias voltage dependence of tunneling conductance (dI/dV-V) reveals a clear half-metallic energy gap at 350-400 meV for Co{sub 2}MnSi, with an energy separation of just 10 meV between the Fermi energy and the bottom edge of conduction band.

Sakuraba, Y.; Miyakoshi, T.; Oogane, M.; Ando, Y.; Sakuma, A.; Miyazaki, T.; Kubota, H. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-05, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba 305-8568 (Japan)

2006-07-31

262

Size dependence in hexagonal mesoporous germanium : pore wall thickness versus energy gap and photoluinescence.  

SciTech Connect

A series of hexagonal mesoporous germanium semiconductors with tunable wall thickness is reported. These nanostructures possess uniform pores of 3.1-3.2 nm, wall thicknesses from 1.3 to 2.2 nm, and large internal BET surface area in the range of 404-451 m{sup 2}/g. The porous Ge framework of these materials is assembled from the templated oxidative self-polymerization of (Ge{sub 9}){sup 4-} Zintl clusters. Total X-ray scattering analysis supports a model of interconnected deltahedral (Ge{sub 9})-cluster forming the framework and X-ray photoelectron spectroscopy indicates nearly zero-valence Ge atoms. We show the controllable tuning of the pore wall thickness and its impact on the energy band gap which increases systematically with diminishing wall thickness. Furthermore, there is room temperature photoluminescence emission which shifts correspondingly from 672 to 640 nm. The emission signal can be quenched via energy transfer with organic molecules such as pyridine diffusing into the pores.

Armatas, G. S.; Kanatzidis, M. G.; Materials Science Division; Northwestern Univ.; Univ. of Crete

2010-08-10

263

Magnesium diboride superconducting RF resonant cavities for high energy particle acceleration  

Microsoft Academic Search

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

E W Collings; M D Sumption; T Tajima

2004-01-01

264

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

E-print Network

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 ...

Vodhanel, Mark E

2005-01-01

265

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

PubMed Central

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

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

2014-01-01

266

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

PubMed

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

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

2014-01-01

267

Evidence of a Nonequilibrium Distribution of Quasiparticles in the Microwave Response of a Superconducting Aluminum Resonator  

NASA Astrophysics Data System (ADS)

In a superconductor, absorption of photons with an energy below the superconducting gap leads to redistribution of quasiparticles over energy and thus induces a strong nonequilibrium quasiparticle energy distribution. We have measured the electrodynamic response, quality factor, and resonant frequency of a superconducting aluminium microwave resonator as a function of microwave power and temperature. Below 200 mK, both the quality factor and resonant frequency decrease with increasing microwave power, consistent with the creation of excess quasiparticles due to microwave absorption. Counterintuitively, above 200 mK, the quality factor and resonant frequency increase with increasing power. We demonstrate that the effect can only be understood by a nonthermal quasiparticle distribution.

de Visser, P. J.; Goldie, D. J.; Diener, P.; Withington, S.; Baselmans, J. J. A.; Klapwijk, T. M.

2014-01-01

268

Conformal GaP layers on Si wire arrays for solar energy applications Adele C. Tamboli,a  

E-print Network

Conformal GaP layers on Si wire arrays for solar energy applications Adele C. Tamboli,a Manav silicon wire arrays using Cu- catalyzed vapor-liquid-solid growth.3 Multijunction wire ar- ray solar cells represent a new avenue for attaining higher efficiencies in wire array solar cells than are achievable

Kimball, Gregory

269

An overview of Boeing flywheel energy storage systems with high-temperature superconducting bearings  

NASA Astrophysics Data System (ADS)

An overview summary of recent Boeing work on high-temperature superconducting (HTS) bearings is presented. A design is presented for a small flywheel energy storage system that is deployable in a field installation. The flywheel is suspended by a HTS bearing whose stator is conduction cooled by connection to a cryocooler. At full speed, the flywheel has 5 kW h of kinetic energy, and it can deliver 3 kW of three-phase 208 V power to an electrical load. The entire system, which includes a containment structure, is compatible with transportation by forklift or crane. Laboratory measurements of the bearing loss are combined with the parasitic loads to estimate the efficiency of the system. Improvements in structural composites are expected to enable the operation of flywheels with very high rim velocities. Small versions of such flywheels will be capable of very high rotational rates and will likely require the low loss inherent in HTS bearings to achieve these speeds. We present results of experiments with small-diameter rotors that use HTS bearings for levitation and rotate in vacuum at kHz rates. Bearing losses are presented as a function of rotor speed.

Strasik, M.; Hull, J. R.; Mittleider, J. A.; Gonder, J. F.; Johnson, P. E.; McCrary, K. E.; McIver, C. R.

2010-03-01

270

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

SciTech Connect

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.

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

1984-01-01

271

Topological superconductivity at the edge of transition-metal dichalcogenides  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

272

Development and Test of a Superconducting Fault Current Limiter-Magnetic Energy Storage (SFCL-MES) System  

Microsoft Academic Search

A superconducting fault current limiter-magnetic energy storage (SFCL-MES) system for substation applications is proposed. SFCL-MES system can limit not only the peak fault current, but also the steady fault current. Moreover, it can provide high-quality power for the critical customers of the substation at the same time. A 100 kJ\\/1000 A\\/20 kVA SFCL-MES prototype system is developed, and it mainly

Caihong Zhao; Zikai Wang; Dong Zhang; Jingye Zhang; Xiaoji Du; Wengyong Guo; Liye Xiao; Liangzhen Lin

2007-01-01

273

Fabrication and evaluation of superconducting magnetic bearing for 10 kW h-class flywheel energy storage system  

Microsoft Academic Search

Radial-type superconducting magnetic bearings (SMB) have been developed for a 10kWh-class flywheel energy storage system. The bearings consist of an inner-cylindrical stator composed of YBCO bulk superconductors and an outer-rotor composed of permanent magnets. The rotor is suspended without contact using the pinning forces of the bulk superconductors. After construction of the whole system, various tests on both static and

T. Ichihara; K. Matsunaga; M. Kita; I. Hirabayashi; M. Isono; M. Hirose; K. Yoshii; K. Kurihara; O. Saito; S. Saito; M. Murakami; H. Takabayashi; M. Natsumeda; N. Koshizuka

2005-01-01

274

Tunneling investigation of the electron scattering effect on the momentum-dependent energy gap distribution in MgB2  

NASA Astrophysics Data System (ADS)

We have studied the effect of electron scattering on the momentum-dependent energy gap distributions in MgB2 by measuring planar tunnel junctions made from epitaxial MgB2 thin films on different substrates, of different thicknesses, with different junction interface properties, and different counter-electrode materials. The phonon features in the tunneling spectra indicated that the native oxide barrier is mainly MgO with estimated barrier thickness ranging from 1.1 to 1.5 nm and the average barrier height from 1.7 to 2.6 eV. When tunneling into the ab-plane occurred in very clean films, both the ? (˜1.8 meV) and ? (˜7.2 meV) gaps were observed with fine structures in the conductance peaks, indicating a distribution of gap values due to anisotropic electron-phonon interaction. The ? gap was enhanced (˜7.9 meV) in MgB2 thin films on SiC substrates which had Tc values over 40 K due to epitaxial tensile strain. As the MgB2 film thickness decreased from 100 nm to 33 nm, the ? gap distribution range was narrowed from ˜1.7 meV to ˜1.4 meV, and the fine peak structures disappeared due to the reduced electron mean free path limited by the film thickness. The fine peak structures were also gradually smeared out when the junction resistance increased. The results show that the electron scattering, either from the MgB2 film or the junction interface or barrier, can smear out the gap distribution structures in the tunneling spectra. Deterioration of the MgB2 film surface was also found to cause an increase in the ? gap value, likely due to an enhancement of interband scattering.

Dai, Wenqing; Chen, Ke; Xi, X. X.; Li, Qi

2013-02-01

275

Measurements of the energy band gap and valence band structure of AgSbTe2  

NASA Astrophysics Data System (ADS)

The de Haas-van Alphen effect, galvanomagnetic and thermomagnetic properties of high-quality crystals of AgSbTe2 are measured and analyzed. The transport properties reveal the material studied here to be a very narrow-gap semiconductor (Eg?7.6±3meV) with ˜5×1019cm-3 holes in a valence band with a high density of states and thermally excited ˜1017cm-3 high-mobility (2200cm2/Vs) electrons at 300 K. The quantum oscillations are measured with the magnetic field oriented along the ?111? axis. Taken together with the Fermi energy derived from the transport properties, the oscillations confirm the calculated valence band structure composed of 12 half-pockets located at the X -points of the Brillouin zone, six with a density-of-states effective mass mda??0.21me and six with mdb??0.55me , giving a total density-of-states effective mass, including Fermi pocket degeneracy, of md??1.7±0.2me ( me is the free electron mass). The lattice term dominates the thermal conductivity, and the electronic contribution in samples with both electrons and holes present is in turn dominated by the ambipolar term. The low thermal conductivity and very large hole mass of AgSbTe2 make it a most promising p -type thermoelectric material.

Jovovic, V.; Heremans, J. P.

2008-06-01

276

Dust filtration at gap edges: Implications for the spectral energy distributions of discs with embedded planets  

E-print Network

The spectral energy distributions (SEDs) of some T Tauri stars display a deficit of near-IR flux that could be a consequence of an embedded Jupiter-mass planet partially clearing an inner hole in the circumstellar disc. Here, we use two-dimensional numerical simulations of the planet-disc interaction, in concert with simple models for the dust dynamics, to quantify how a planet influences the dust at different radii within the disc. We show that pressure gradients at the outer edge of the gap cleared by the planet act as a filter - letting particles smaller than a critical size through to the inner disc while holding back larger particles in the outer disc. The critical particle size depends upon the disc properties, but is typically of the order of 10 microns. This filtration process will lead to discontinuous grain populations across the planet's orbital radius, with small grains in the inner disc and an outer population of larger grains. We show that this type of dust population is qualitatively consistent with SED modelling of systems that have optically thin inner holes in their circumstellar discs. This process can also produce a very large gas-to-dust ratio in the inner disc, potentially explaining those systems with optically thin inner cavities that still have relatively high accretion rates.

W. K. M. Rice; Philip J. Armitage; Kenneth Wood; Giuseppe Lodato

2006-09-29

277

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

SciTech Connect

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.

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

278

30-MJ superconducting magnetic-energy-storage stabilizing system: an overview  

SciTech Connect

The 30-MJ superconducting magnetic-energy-storage (SMES) system was devised as an alternate means to modulate the Bonneville Power Administration (BPA) Pacific AC Intertie, a part of the Western US Power System, to prevent undamped power oscillations at 0.35 Hz that were observed to be associated with high power transmission. The SMES system was installed at the BPA Tacoma Substation and successfully operated as an experimental device to initiate tests to determine power system dynamics, to investigate their variability, to assess system response to SMES modulation with a major variable load, and to use SMES to develop stability-control techniques. The system has been operated at frequencies of 0.1 to 1.0 Hz at power levels of +- 8.3 MW with a parallel modulation of the converter bridges and up to 9.5 MW reactive power together with +- 4.5 MW real power in constant VAR mode with buck-boost modulation of the bridges. The coil has been charged at a maximum rate of 11.8 MW. Operation of the SMES system is now under BPA jurisdiction, and all hardware has been transferred to BPA.

Roger, J.D.; Boenig, H.J.; Dean, J.W.; Schermer, R.I.; Annestrand, S.A.; Hauer, J.F.; Miller, B.L.

1983-01-01

279

Biological effects of magnetic fields from superconducting magnetic energy storage systems  

SciTech Connect

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.

Tenforde, T.S.

1989-12-01

280

Design and testing of a 13. 75-MW converter for a superconducting magnetic-energy-storage system  

SciTech Connect

A 30 MJ superconducting magnetic energy storage system will be installed in 1982 in Tacoma, WA, to act as a transmission line stabilizer. Two 6 MVA transformers and a 5.5 kA, + 2.5 kV converter will connect the superconducting coil to the 13.8 kV bus and regulate the power flow between the coil and the three phase system. The design philosophy for the converter including its control and protection system is given in the paper. The converter has been tested with 10% overvoltage at no load, with 10% overcurrent at zero output voltage and with a watercooled resistive load of about 1 MW. These test results show that the converter will meet the expected full load operating conditions.

Boenig, H.J.; Turner, R.D.; Neft, C.L.; Sueker, K.H.

1981-01-01

281

Superconductivity-Induced Self-Energy Evolution of the Nodal Electron in Optimally-Doped Bi2212  

SciTech Connect

The temperature dependent evolution of the renormalization effect in optimally-doped Bi2212 along the nodal direction has been studied via angle-resolved photoemission spectroscopy. Fine structure is observed in the real part of the self-energy (Re{Sigma}), including a subkink and maximum, suggesting that electrons couple to a spectrum of bosonic modes, instead of just one mode. Upon cooling through the superconducting phase transition, the fine structures of the extracted Re{Sigma} exhibit a two-processes evolution demonstrating an interplay between kink renormalization and superconductivity. We show that this two-process evolution can be qualitatively explained by a simple Holstein model in which a spectrum of bosonic modes is considered.

Lee, W.S.

2010-05-03

282

Design and testing of a 13.75 MW converter for a superconducting magnetic-energy-storage system  

NASA Astrophysics Data System (ADS)

A 30 MJ superconducting magnetic energy storage system to act as a transmission line stabilizer is described. Two 6 MVA transformers and a 5.5 kA, + 2.5 kV converter connects the superconducting coil to the 13.8 kV bus and regulates the power flow between the coil and the three phase system. The design philosophy for the converter including its control and protection system is given. The converter was tested with 10% overvoltage at no load, with 10% overcurrent at zero output voltage and with a watercooled resistive load of about 1 MW. These test results show that the converter meets the expected full load operating conditions.

Boenig, H. J.; Turner, R. D.; Neft, C. L.; Sueker, K. H.

283

Evidence for phonon-mediated coupling in superconducting Ba sub 0.6 K sub 0.4 BiO3  

Microsoft Academic Search

Superconducting Ba sub 0.6 K sub 0.4 BiO3, with a T sub c of 30K, shows a large O-18 isotope effect which indicates that phonons are involved in the pairing mechanism. Infrared reflectivity measurements indicate a value for the superconducting gap consistent with moderate coupling (2 delta kT sub c = 3.5 + or - 0.5). A mediating energy for

D. G. Hinks; B. Dabrowski; D. R. Richards; J. D. Jorgensen; Shiyou Pei; J. F. Zasadzinski

1989-01-01

284

Potential for Precision Measurement of Low-Energy Antiprotons with GAPS for Dark Matter and Primordial Black Hole Physics  

E-print Network

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.

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

2014-01-31

285

The dipole model of narrowing of the energy gap between the Hubbard bands in slightly compensated semiconductors  

Microsoft Academic Search

A model of the narrowing of the energy gap between the Hubbard bands (the A\\u000a 0 and A\\u000a + bands for acceptors and the D\\u000a 0 and D\\u000a ? bands for donors) with increasing concentration of hydrogen-like dopants at low concentrations of the compensating impurity\\u000a is suggested. The width of the impurity bands is assumed to be small compared to

N. A. Poklonski; S. A. Vyrko; A. G. Zabrodski?

2006-01-01

286

PUBLISHED ONLINE: 22 SEPTEMBER 2013 | DOI: 10.1038/NPHYS2762 A large-energy-gap oxide topological insulator  

E-print Network

that a known superconductor BaBiO3 (BBO) with a Tc of nearly 30 K (refs 4,5) emerges as a topological insulator in the electron-doped region. BBO exhibits a large topological energy gap of 0.7 eV, inside which a Dirac type of TSSs exists. As the first oxide topological insulator, BBO is naturally sta- ble against surface

Loss, Daniel

287

Self-Interaction Corrected Electronic Structure and Energy Gap of CuAlO2 beyond Local Density Approximation  

NASA Astrophysics Data System (ADS)

We implemented a self-interaction correction (SIC) into first-principles calculation code to go beyond local density approximation and applied it to CuAlO2. Our simulation shows that the valence band width calculated within the SIC is narrower than that calculated without the SIC because the SIC makes the d-band potential deeper. The energy gap calculated within the SIC expands and is close to experimental data.

Nakanishi, Akitaka

2011-05-01

288

Principal energy band gaps of the quaternary alloy Al x Ga 1? x Sb y As 1? y  

Microsoft Academic Search

The correlated function expansion (CFE) interpolation procedure was presented to efficiently estimate principal energy band gaps and lattice constants of the quaternary alloy AlxGa1?xSbyAs1?y over the entire composition variable space. The lattice matching conditions between x and y for the alloy AlxGa1?xSbyAs1?y substrated to InAs and GaSb were obtained by optimizing the alloy lattice constant to that of the substrates.

Kyurhee Shim

2005-01-01

289

Ambipolar Charge Transport in Organic Field-Effect Transistors Based on Lead Phthalocyanine with Low Band Gap Energy  

Microsoft Academic Search

The organic semiconductor, lead phthalocyanine (PbPc) with a low band gap energy of 1.2 eV is demonstrated as an active material for high-performance ambipolar organic field-effect transistors (OFETs). For the ambipolar OFETs with Au source-drain electrodes, the field-effect electron mobility was calculated to be 8.3×10-4 cm2 V-1 s-1, when the threshold voltage was 31 V. On the other hand, the

Takeshi Yasuda; Tetsuo Tsutsui

2006-01-01

290

Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates.  

PubMed

In strongly correlated systems the electronic properties at the Fermi energy (E(F)) 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-E(F)|>1 eV) is involved in the condensate formation. Here, we report the interplay between the many-body high-energy CuO(2) 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 Bi(2)Sr(2)Ca(0.92)Y(0.08)Cu(2)O(8+?) 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 (T(c)). PMID:21673674

Giannetti, Claudio; Cilento, Federico; Dal Conte, Stefano; 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

291

Enhancement of magnetic flux distribution in a DC superconducting electric motor  

NASA Astrophysics Data System (ADS)

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.

Hamid, N. A.; Ewe, L. S.; Chin, K. M.

2013-06-01

292

Evidence for conventional superconducting behavior in noncentrosymmetric Mo3Al2C  

NASA Astrophysics Data System (ADS)

We report on measurements of the magnetic penetration depth of polycrystalline samples of nonmagnetic Mo3Al2C (Tc=9 K) without inversion symmetry. Two previous specific-heat measurements in this compound found different anomalous peaks in the low-temperature limit. One of these peaks was attributed to the superconducting transition at 3 K of the impurity phase Mo2C. We argue here that the second anomalous peak may be caused by the superconducting transition of SiC:Al at 1.45 K, another impurity phase possibly present in Mo3Al2C samples. The temperature-independent behavior of the penetration depth observed below 0.5 K is taken as firm evidence for the presence of a nodeless superconducting gap in Mo3Al2C. Numerical calculations using the BCS expression for the penetration depth give qualitative support for an isotropic energy gap in Mo3Al2C. The present results suggest that Mo3Al2C is a conventional s-wave superconductor, although two-gap or anisotropic-gap superconductivity cannot be ruled out.

Bonalde, I.; Kim, H.; Prozorov, R.; Rojas, C.; Rogl, P.; Bauer, E.

2011-10-01

293

Superconductivity of Magnesium Diboride: Theoretical Aspects  

Microsoft Academic Search

In this work we review our present understanding of superconductivity in Magnesium Diboride from the theoretical perspective as it evolves from band structure calculations. Particular emphasis is placed on two gap superconductivity. Some of its peculiar consequences are discussed, in particular upper critical field anisotropy and microwave conductivity.

Thomas Dahm

2004-01-01

294

Superconductive wire  

SciTech Connect

This invention is comprised of a superconductive article including a first metallic tube having an interior surface and an exterior surface, said interior surface defining an interior hollow cavity, a layer of superconductive material surrounding said exterior surface of said first metallic tube, and, a second metallic tube having an interior surface and an exterior surface, said interior surface adjacent to said layer of superconductive material is provided together with processes of making such a superconductive article including, e.g., 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 and/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.

Korzekwa, D.A.; Bingert, J.F.; Peterson, D.E.; Sheinberg, H.

1992-12-31

295

Experimental study of high energy electron interactions in a superconducting aluminum alloy resonant bar  

E-print Network

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.

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

296

Progress in Superconducting Metamaterials  

E-print Network

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.

Philipp Jung; Alexey V. Ustinov; Steven M. Anlage

2014-03-25

297

Progress in Superconducting Metamaterials  

E-print Network

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.

Jung, Philipp; Anlage, Steven M

2014-01-01

298

Progress in superconducting metamaterials  

NASA Astrophysics Data System (ADS)

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.

Jung, Philipp; Ustinov, Alexey V.; Anlage, Steven M.

2014-07-01

299

Large energy band-gap tuning of 980 nm InGaAs/InGaAsP quantum well structure via quantum well intermixing  

NASA Astrophysics Data System (ADS)

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.

Zhongliang, Qiao; Xiaohong, Tang; Kenneth, Lee Eng Kian; Huei, Lim Peng; BaoXue, Bo

2013-01-01

300

MgB{sub 2}: directional tunneling two-band superconductivity.  

SciTech Connect

We have studied the anisotropic superconductor MgB{sub 2} using a combination of scanning electron microscopy and scanning tunneling spectroscopy. Tunneling spectroscopy performed on thin films and pellets reveals two distinct energy gaps at {Delta}{sub 1} = 2.3 meV and {Delta}{sub 2} = 7.1 meV. On different crystallites within the polycrystalline sample different spectral weights of the partial densities of states (PDOS) were observed. They reflect different tunneling directions with respect to the crystallographic orientation of the grain in a multiband system. Indeed when tunneling in the c-axis films only one superconducting gap is observed, which is associated with the 3D band in this system. Temperature evolution of the tunneling spectra reveals that both gaps close simultaneously near the bulk critical temperature. Our experimental findings are consistent with the two-band superconductivity scenario in the presence of strong pair interaction between the two bands [1].

Iavarone, M.; Karapetrov, G.; Koshelev, A.; Kwok, W. K.; Hinks, D.; Crabtree, G. W.; Kang, W. N.; Choi, E.-M.; Kim, H. J.; Lee, S.-I.; Pohang Univ.

2003-02-01

301

Dependence of Mobility on Density of Gap States in Organics by GAMEaS - Gate Modulated Activation Energy Spectroscopy  

E-print Network

We develop a broadly applicable transport-based technique, GAte Modulated activation Energy Spectroscopy (GAMEaS), for determining the density of states (DOS) in the energy gap. GAMEaS is applied to field effect transistors made from different single crystal oligomer semiconductors to extract the free-carrier mobility, u_0, from the field effect mobility, u_eff. Samples with a lower DOS exhibit higher u_eff. Values of u_0 up to 100 +/- 40 cm2/Vs at 300K are observed, showing that performance can be greatly enhanced by improving sample purity and crystal quality.

W. So; D. V. Lang; V. Y. Butko; X. Chi; J. C. Lashley; A. P. Ramirez

2006-08-30

302

Effect of Li-Al co-doping on the energy gaps of MgB2  

NASA Astrophysics Data System (ADS)

We studied the effects of co-doping with Li and Al on the energy gaps of MgB2 by performing point-contact Andreev-reflection spectroscopy (PCAR) in polycrystalline Mg1-x(Al?Li1-?)xB2 samples with x<=0.4. Even though the lattice parameters and the critical temperature of the compound simply scale with the effective Al content ?x, irrespective of the Li concentration, the energy gaps do not. In particular, for a given effective Al content, the comparison with Mg1-y(Al)yB2 with y = ?x shows that the ? bandgap is practically the same while the ? bandgap is higher. A clear gap merging is observed in the most doped sample (x = 0.4) when Tc<20 K. The results are discussed within the two-band Eliashberg theory and compared to the outcomes of first-principles calculations of the effects of Li and Al co-doping on the electronic structure of magnesium diboride.

Daghero, D.; Ummarino, G. A.; Tortello, M.; Delaude, D.; Gonnelli, R. S.; Stepanov, V. A.; Monni, M.; Palenzona, A.

2009-02-01

303

ARPES Studies of Cuprate Fermiology: Superconductivity, Pseudogap and Quasiparticle Dynamics  

SciTech Connect

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.

Vishik, Inna

2011-06-23

304

Executive summary of NIH workshop on the Use and Biology of Energy Drinks: Current Knowledge and Critical Gaps.  

PubMed

Sales of energy drinks in the United States reached $12.5 billion in 2012. Emergency department visits related to consumption of these products have increased sharply, and while these numbers remain small relative to product sales, they raise important questions regarding biological and behavioral effects. Although some common ingredients of energy drinks have been extensively studied (e.g., caffeine, B vitamins, sugars, inositol), data on other ingredients (e.g., taurine) are limited. Summarized here are data presented elsewhere in this issue on the prevalence and patterns of caffeine-containing energy drink use, the effects of these products on alertness, fatigue, cognitive functions, sleep, mood, homeostasis, as well as on exercise physiology and metabolism, and the biological mechanisms mediating the observed effects. There are substantial data on the effects of some energy drink ingredients, such as caffeine and sugars, on many of these outcomes; however, even for these ingredients many controversies and gaps remain, and data on other ingredients in caffeine-containing energy drinks, and on ingredient interactions, are sparse. This summary concludes with a discussion of critical gaps in the data and potential next steps. PMID:25293538

Sorkin, Barbara C; Camp, Kathryn M; Haggans, Carol J; Deuster, Patricia A; Haverkos, Lynne; Maruvada, Padma; Witt, Ellen; Coates, Paul M

2014-10-01

305

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)

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.

Patterson, James D.

1996-01-01

306

Energy and critical current considerations of Bi(2223)\\/Ag coils for micro-superconducting magnetic energy storage: influence of operating temperature and winding geometry within the same overall tape length  

Microsoft Academic Search

A detailed theoretical qualitative, as well as quantitative, analysis of the influence of the dimensions of Bi(2223)\\/Ag based cylindrical magnets on the energy stored in the magnet's winding was performed for various operating temperatures. The results achieved can be used to consider the potential suitability of the high-temperature superconductivity magnets for the purposes of micro-superconducting magnetic energy storage applications. A

Jozef Pitel; Pavol Kovác; Jorma Lehtonen; Jaakko Paasi

2001-01-01

307

NLO Vertex for a Forward Jet plus a Rapidity Gap at High Energies  

E-print Network

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).

Hentschinski, Martin; Murdaca, Beatrice; Vera, Agustín Sabio

2014-01-01

308

Superconducting thermoelectric generator  

DOEpatents

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.

Metzger, J.D.; El-Genk, M.S.

1996-01-01

309

Microscopic Inhomogeneity and Superconducting Properties of a Two-dimensional Hubbard Model for High-$T_c$ Cuprates  

SciTech Connect

Recent scanning tunneling microscopy measurements on cuprate superconductors have revealed remarkable spatial inhomogeneities in the single-particle energy gap. Using cellular dynamical mean-field theory, we study the zero temperature superconducting properties of a single-band Hubbard model with a spatial modulation of the electron density. We find that the inhomogeneity in the electronic structure results in a substantial spatial variation of the superconducting order parameter and single-particle energy gap, reminiscent of the experimental results. In particular, we find that the order parameter and gap amplitudes in the hole-rich regions are significantly enhanced over the corresponding quantities in a uniform system, if the hole-rich regions are embedded in regions with smaller hole density.

Okamoto, Satoshi [ORNL; Maier, Thomas A [ORNL

2010-01-01

310

Low-energy excitations of the correlation-gap insulator SmB{sub 6}: A light-scattering study  

SciTech Connect

We present the results of Raman scattering studies of single-crystal SmB{sub 6} for temperatures down to 4 K and in magnetic fields up to 8 T. At temperatures below T{sup {asterisk}}{approximately}50K the electronic Raman continuum exhibits an abrupt redistribution of scattering intensity around a temperature-independent ({open_quotes}isobestic{close_quotes}) energy, {Delta}{sub c}{approximately}290cm{sup {minus}1}, reflecting the opening of a pseudogap which is larger than previously suggested by transport measurements. Additionally, the Raman response exhibits at least four well-defined excitations within the gap below T{sup {asterisk}}. The field dependencies of some of these in-gap states are consistent with the expected g factor (g{sub eff}=2/7) for the Sm{sup 3+} {Gamma}{sub 8} level, suggesting that these gap edge states are crystal-electric-field excitations of the Sm{sup 3+} ion split by magnetoelastic coupling. {copyright} {ital 1997} {ital The American Physical Society}

Nyhus, P.; Cooper, S.L. [Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801 (United States)] [Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801 (United States); Fisk, Z.; Sarrao, J. [Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306 (United States)] [Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306 (United States)

1997-05-01

311

Energy Transmission in the Forbidden Band Gap of a Nonlinear Chain F. Geniet and J. Leon  

E-print Network

, as an effect of nonintegrability, nonlinear modes do ex- change energy and the spatial localization acquires) at one end. The related brutal energy flow through the medium is illus- trated in Fig. 1 where the energy

Levelut, Claire

312

Electron excitations in solid C[sub 60]: Energy gap, band dispersions, and effects of orientational disorder  

SciTech Connect

Electron excitation energies and photoemission spectra in undoped, solid C[sub 60] are calculated using a quasiparticle approach. The effects of orientational disorder and electron correlations are studied. We find a band gap of 2.15 eV, in good agreement with experiment, and [similar to]1 eV widths for the highest-occupied-molecular-orbital (HOMO) and lowest-unoccupied-molecular-orbital (LUMO) bands. Calculated angle-resolved, inverse photoemission spectra for the LUMO bands show very little angular dependence, explaining recent experimental work on epitaxial thin films. The present results suggest that undoped, solid C[sub 60] is a standard band insulator.

Shirley, E.L.; Louie, S.G. (Department of Physics, University of California, Berkeley, California 94720 (United States) Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States))

1993-07-05

313

Korea's developmental program for superconductivity  

NASA Technical Reports Server (NTRS)

Superconductivity research in Korea was firstly carried out in the late 70's by a research group in Seoul National University (SNU), who fabricated a small scale superconducting magnetic energy storage system under the financial support from Korea Electric Power Company (KEPCO). But a few researchers were involved in superconductivity research until the oxide high Tc superconductor was discovered by Bednorz and Mueller. After the discovery of YBaCuO superconductor operating above the boiling point of liquid nitrogen (77 K)(exp 2), Korean Ministry of Science and Technology (MOST) sponsored a special fund for the high Tc superconductivity research to universities and national research institutes by recognizing its importance. Scientists engaged in this project organized 'High Temperature Superconductivity Research Association (HITSRA)' for effective conducting of research. Its major functions are to coordinate research activities on high Tc superconductivity and organize the workshop for active exchange of information. During last seven years the major superconductivity research has been carried out through the coordination of HITSRA. The major parts of the Korea's superconductivity research program were related to high temperature superconductor and only a few groups were carrying out research on conventional superconductor technology, and Korea Atomic Energy Research Institute (KAERI) and Korea Electrotechnology Research Institute (KERI) have led this research. In this talk, the current status and future plans of superconductivity research in Korea will be reviewed based on the results presented in interim meeting of HITSRA, April 1-2, 1994. Taejeon, as well as the research activity of KAERI.

Hong, Gye-Won; Won, Dong-Yeon; Kuk, Il-Hyun; Park, Jong-Chul

1995-01-01

314

The Cost of Superconducting Magnets as a Function of Stored Energy and Design Magnetic Induction Times the Field Volume  

SciTech Connect

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.

Green, Mike; Green, M.A.; Strauss, B.P.

2007-08-27

315

Mechanical Design of a High Energy Beam Absorber for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab  

SciTech Connect

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.

Baffes, C.; Church, M.; Leibfritz, J.; Oplt, S.; Rakhno, I.; /Fermilab

2012-05-10

316

Probing the superconducting order parameter of high-Tc superconductor bismuth strontium calcium copper oxide by scanning Josephson tunneling microscopy  

NASA Astrophysics Data System (ADS)

The technique of scanning tunneling microscopy (STM) with a normal metal tip has recently been used to study the high transition temperature ( TC) superconducting cuprates and has revealed many fascinating and complex features of quasiparticle excited states of these materials. For conventional superconductors, the Bardeen-Cooper-Schrieffer theory connects the pair amplitude and the superconducting gap as measured from the quasiparticle excitation spectra, while for the high-TC materials there is still no theory to connect these quantities. We are unable to make any quantitative analysis of the superconducting ground state from the quasiparticle data. Josephson tunneling is the tunneling of the Cooper pairs between two superconductors and the Josephson current directly relates to the superconducting pair wave function amplitude. In this thesis, we have developed the superconducting STM as a local Josephson probe and carried out direct measurements of the superconducting pair amplitude of Bi2Sr2CaCu2O 8+delta single crystals via the c-axis Josephson tunneling between Bi2Sr2CaCu2O8+delta and a conventional superconducting STM tip. Josephson measurements at different surface locations of overdoped Bi2Sr2CaCu 2O8+delta yield local values for the Josephson ICRN product, indicating an inhomogeneous structure of the ICRN product in overdoped Bi 2Sr2CaCu2O8+delta on a nanometer length scale. The corresponding energy gap, Delta, was also measured at the same locations and an unexpected inverse correlation is observed between the local ICRN product and the local energy gap Delta. Our interpretation of the ICR N vs. Delta relation with the phase fluctuation model for the phase diagram of high-TC superconducting cuprates will be presented. A preliminary study of the high current density effect on the density of states of Bi2Sr2CaCu2O8+delta will also be reported. The effect of cleaving the Bi2Sr2CaCu2O 8+delta surface on its electronic structure is also discussed. This is motivated by the question that the gap inhomogeneity observed by STM is intrinsic property of this material or induced by the cleaving. Since the superconducting tunneling probes the depth of a coherence length into the sample surface and Bi2Sr2CaCu2O 8+delta has a very short c-axis coherence length, it's important to address this question. I will present some preliminary results of the superconducting STM studies on chemically etched Bi2Sr 2CaCu2O8+delta surfaces.

Kimura, Hikari

317

Superconducting structure  

DOEpatents

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.

Kwon, Chuhee (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM); Foltyn, Stephen R. (Los Alamos, NM)

2003-04-01

318

Superconducting Structure  

DOEpatents

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.

Kwon, Chuhee (Los Alamos, NM); Jia, Quanxi (Los Alamos, NM); Foltyn, Stephen R. (Los Alamos, NM)

2005-09-13

319

Hard-gapped Holographic Superconductors  

E-print Network

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.

Pallab Basu; Jianyang He; Anindya Mukherjee; Hsien-Hang Shieh

2009-11-26

320

Superconducting terahertz metamaterials  

SciTech Connect

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.

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

321

HOM damping properties of fundamental power couplers in the superconducting electron gun of the energy recovery LINAC at Brookhaven National Laboratory  

SciTech Connect

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.

Hammons, L.; Hahn, H.

2011-03-28

322

Direct Evidence for Cage Conduction Band in Superconducting Cement 12CaO\\cdot7Al2O3 by Low-Energy High-Resolution Photoemission Spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Souma, Seigo; Arakane, Toshiyuki; Sato, Takafumi; Takahashi, Takashi; Kim, Sung Wng; Matsuishi, Satoru; Hosono, Hideo

2010-10-01

323

Determination of the fundamental and spin-orbit-splitting band gap energies of InAsSb-based ternary and pentenary alloys using mid-infrared photoreflectance  

Microsoft Academic Search

In narrow-gap semiconductors, non-radiative Auger recombination losses (via conduction, heavy-hole, spin split-off hole, heavy-hole processes) are sensitive to how the band gap energy, E0, compares to the spin-orbit splitting, ?0. However, narrow-gap band structures have often not been very well characterised. We report on the mid-infrared photo-modulated reflectance of E0 and E0+?0 transitions in high-quality, InAs-rich InAsSb and GaInAsPSb samples

S. A. Cripps; T. J. C. Hosea; A. Krier; V. Smirnov; P. J. Batty; Q. D. Zhuang; H. H. Lin; Po-Wei Liu; G. Tsai

2008-01-01

324

Gap Winds  

NSDL National Science Digital Library

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.

Comet

2003-03-20

325

Large-gap magnetic suspension systems  

NASA Technical Reports Server (NTRS)

The classification of magnetic suspension devices into small-gap and large-gap categories is addressed. The relative problems of position sensing, control systems, power supplies, electromagnets, and magnetic field or force analysis are discussed. The similarity of all systems from a controls standpoint is qualified. Some applications where large-gap technology is being applied to systems with a physically small air-gap are mentioned. Finally, the applicability of some other suspension approaches, such as electrodynamic or superconducting are briefly addressed.

Britcher, Colin P.

1992-01-01

326

Abnormal temperature dependence of band-gap energies observed in (InAs)\\/(GaAs) and (InP)\\/(GaP) superlattices with strong lateral composition modulation  

Microsoft Academic Search

An abnormal variation of the band-gap energy with temperature was observed in both the (InAs)2.2\\/(GaAs)2 and (InP)2\\/(GaP)2 short-period-superlattice (SPS) structures. Strong lateral composition modulation induced two horizontally adjacent regions with different In content in the SPS regions. Due to the difference of thermal expansion coefficients among the substrate and the two adjacent regions in the SPS structures, it is proposed

Shu-Tsun Chou

2000-01-01

327

Superconducting magnet development in Japan  

SciTech Connect

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.

Yasukochi, K.

1983-05-01

328

Superconductivity from repulsion in LiFeAs: Novel s-wave symmetry and potential time-reversal symmetry breaking  

NASA Astrophysics Data System (ADS)

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.

Ahn, F.; Eremin, I.; Knolle, J.; Zabolotnyy, V. B.; Borisenko, S. V.; Büchner, B.; Chubukov, A. V.

2014-04-01

329

The effects of potting on training and quench propagation in a large stored energy superconducting dipole coil  

NASA Astrophysics Data System (ADS)

The training and quench behavior of a superconducting racetrack dipole coil were compared in potted and non-potted coils. The coil stored energy was 175 KJoules at the conductor's short sample limit of 238 amp with a peak field of 7.6 Tesla. Steel and aluminum rods were tested with helium flow provided by fiberglass cable tape channels permitting direct access to the He supply to 1/4 of the conductor surface. The coil was trained to 90% of the short sample limit, the tie rods were relaxed, and the whole coil was impregnated with a standard clear magnet epoxy. The tests showed that fully impregnated coils of this design are not suitable for thermally cycled magnets operating above 80% of the short sample limit.

Cox, B.; Garbincius, P. H.; Guerra, J.; Mazur, P. O.; Satti, J. A.; Tilles, E. B.

1981-01-01

330

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)

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.

Patterson, James D.; Li, Wei-Gang

1995-01-01

331

A large-energy-gap oxide topological insulator based on the superconductor BaBiO3  

NASA Astrophysics Data System (ADS)

Topological insulators are a new class of quantum materials that are characterized by robust topological surface states (TSSs) inside the bulk insulating gap, which hold great potential for applications in quantum information and spintronics as well as thermoelectrics. One major obstacle is the relatively small size of the bulk bandgap, which is typically around 0.3eV for the known topological insulator materials (ref. and references therein). Here we demonstrate through ab initio calculations that a known superconductor BaBiO3 (BBO) with a Tc of nearly 30K (refs , ) emerges as a topological insulator in the electron-doped region. BBO exhibits a large topological energy gap of 0.7eV, inside which a Dirac type of TSSs exists. As the first oxide topological insulator, BBO is naturally stable against surface oxidization and degradation, distinct from chalcogenide topological insulators. An extra advantage of BBO lies in its ability to serve as an interface between TSSs and superconductors to realize Majorana fermions for future applications in quantum computation.

Yan, Binghai; Jansen, Martin; Felser, Claudia

2013-11-01

332

Attempting to bridge the gap between laboratory and seismic estimates of fracture energy  

USGS Publications Warehouse

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.

McGarr, A.; Fletcher, J. B.; Beeler, N. M.

2004-01-01

333

Nuclear Energy Advanced Modeling and Simulation (NEAMS) waste Integrated Performance and Safety Codes (IPSC) : gap analysis for high fidelity and performance assessment code development  

Microsoft Academic Search

This report describes a gap analysis performed in the process of developing the Waste Integrated Performance and Safety Codes (IPSC) in support of the U.S. Department of Energy (DOE) Office of Nuclear Energy Advanced Modeling and Simulation (NEAMS) Campaign. The goal of the Waste IPSC is to develop an integrated suite of computational modeling and simulation capabilities to quantitatively assess

Joon H. Lee; Malcolm Dean Siegel; Arguello Jose Guadalupe Jr; Stephen Walter Webb; Thomas A. Dewers; Paul E. Mariner; Harold Carter Edwards; Timothy J. Fuller; Geoffrey A. Freeze; Carlos F. Jove-Colon; Yifeng Wang

2011-01-01

334

Superconductivity in the Einstein solid VAl(10.1).  

PubMed

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

Klimczuk, T; Szlawska, M; Kaczorowski, D; O'Brien, J R; Safarik, D J

2012-09-12

335

Ultrasonic attenuation in superconducting molybdenum-rhenium alloys.  

NASA Technical Reports Server (NTRS)

Investigation of longitudinal sound attenuation in superconducting Mo-Re alloys as a function of temperature, magnetic field, and frequency. Evaporated thin film CdS transducers were used for the measurements at frequencies up to 3 GHz. The normal state attenuation coefficient was found to be proportional to the square of frequency over this frequency range. Measurements in zero magnetic field yielded a value of the energy gap parameter close to the threshold value of 3.56 kTc, appropriate to a weakly coupled dirty limit superconductor.

Ashkin, M.; Deis, D. W.; Gottlieb, M.; Jones, C. K.

1971-01-01

336

? pairing and superconductivity in the negative-U Hubbard model  

NASA Astrophysics Data System (ADS)

It is proved explicitly that the strong on-site attractive interaction acts to form ? pairings which make full use of the phase coherence of Bloch electrons. The U(1) gauge symmetry breaks spontaneously in the formation, which is accompanied by the creation of ?-paired boson, ``? pairon.'' The condensation of ? pairons takes place at a finite temperature to make up the ground-state condensate which has off-diagonal long-range order. The resulting ground state is a singlet and the energy spectrum has a gap. This type of superconductivity based on ? pairing exhibits the same peculiar properties as observed in high-Tc oxide superconductors.

Betsuyaku, Hiroshi

1991-07-01

337

The origin of the anomalous superconducting properties of MgB(2).  

PubMed

Magnesium diboride differs from ordinary metallic superconductors in several important ways, including the failure of conventional models to predict accurately its unusually high transition temperature, the effects of isotope substitution on the critical transition temperature, and its anomalous specific heat. A detailed examination of the energy associated with the formation of charge-carrying pairs, referred to as the 'superconducting energy gap', should clarify why MgB(2) is different. Some early experimental studies have indicated that MgB(2) has multiple gaps, but past theoretical studies have not explained from first principles the origin of these gaps and their effects. Here we report an ab initio calculation of the superconducting gaps in MgB(2) and their effects on measurable quantities. An important feature is that the electronic states dominated by orbitals in the boron plane couple strongly to specific phonon modes, making pair formation favourable. This explains the high transition temperature, the anomalous structure in the specific heat, and the existence of multiple gaps in this material. Our analysis suggests comparable or higher transition temperatures may result in layered materials based on B, C and N with partially filled planar orbitals. PMID:12181561

Choi, Hyoung Joon; Roundy, David; Sun, Hong; Cohen, Marvin L; Louie, Steven G

2002-08-15

338

The origin of the anomalous superconducting properties of MgB2  

SciTech Connect

Magnesium diboride differs from ordinary metallic superconductors in several important ways, including the failure of conventional models to predict accurately its unusually high transition temperature, the effects of isotope substitution on the critical transition temperature, and its anomalous specific heat. A detailed examination of the energy associated with the formation of charge-carrying pairs, referred to as the 'superconducting energy gap', should clarify why MgB2 is different. Some early experimental studies have indicated that MgB2 has multiple gaps, but past theoretical studies have not explained from first principles the origin of these gaps and their effects. Here we report an ab initio calculation of the superconducting gaps in MgB2 and their effects on measurable quantities. An important feature is that the electronic states dominated by orbitals in the boron plane couple strongly to specific phonon modes, making pair formation favourable. This explains the high transit ion temperature, the anomalous structure in the specific heat, and the existence of multiple gaps in this material. Our analysis suggests comparable or higher transition temperatures may result in layered materials based on B, C, and N with partially filled planar orbitals.

Choi, Hyoung Joon; Roundy, David; Sun, Hong; Cohen, Marvin L.; Louie, Steven G.

2002-01-31

339

Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit.  

PubMed

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

Löptien, P; Zhou, L; Khajetoorians, A A; Wiebe, J; Wiesendanger, R

2014-10-22

340

Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit  

NASA Astrophysics Data System (ADS)

The thickness dependence of the superconducting energy gap ΔLa 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, ΔLa 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.

Löptien, P.; Zhou, L.; Khajetoorians, A. A.; Wiebe, J.; Wiesendanger, R.

2014-10-01

341

Study of the superconducting phase in silicene under biaxial tensile strain  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

342

Electron energy level calculations for cylindrical narrow gap semiconductor quantum dot  

Microsoft Academic Search

Three computational techniques are presented for approximation of the ground state energy and wave function of an electron confined by a disk-shaped InAs quantum dot (QD) embedded in GaAs matrix. The problem is treated with the effective one electronic band Hamiltonian, the energy and position dependent electron effective mass approximation, and the Ben-Daniel Duke boundary conditions. To solve the three

Yiming Li; Jinn-Liang Liu; O. Voskoboynikov; C. P. Lee; S. M. Sze

2001-01-01

343

Measurements of Multiple Gap Substructure in MgB2 Below 1 Kelvin  

NASA Astrophysics Data System (ADS)

The two superconducting energy gaps of magnesium diboride (MgB2) are well established. First-principles calculations have also predicted substructure within the sigma- and pi-band gaps. However, due to anticipated intraband impurity scattering, there is controversy as to whether these finer structures can be observed in real samples. Prior experimental evidence above 1 Kelvin has provided evidence supportive of these features. We have performed tunneling spectroscopy experiments on MgB2/insulator/Pb Josephson junctions on SiC substrates, at temperatures as low as 20 mK. By measuring differential conductance at low temperatures, and by using extremely clean MgB2 thin films, we have resolved features within the energy gaps to under 1 meV. We report results of these experiments, which are in remarkable agreement with theoretical predictions for this substructure.

Carabello, Steven; Lambert, Joseph; Ramos, Roberto

2011-03-01

344

Band gap tuning of InAs/InP quantum sticks using low-energy ion-implantation-induced intermixing  

SciTech Connect

Low-energy (18 keV) phosphorus ion implantation and rapid thermal annealing at 650 deg. C for 120 s were used to create point defects and promote intermixing in InAs/InP quantum stick structures grown by molecular beam epitaxy. With these soft conditions for ion-implantation-induced intermixing, photoluminescence measurements at low temperature show a very large blueshift up to 350 nm and a narrow emission linewidth (down to 30 nm for ion dose equal to 5x10{sup 13} cm{sup -2}). The band gap tuning limit in this system was evaluated using implantation of phosphorus ions at various doses (1x10{sup 11}-5x10{sup 14} cm{sup -2}), at a temperature of 200 deg. C followed by rapid thermal annealing.

Salem, B.; Aimez, V.; Morris, D.; Turala, A.; Regreny, P.; Gendry, M. [Centre de Recherche en Nanofabrication et Nanocaracterisation (CRN2), Universite de Sherbrooke (Quebec) J1K 2R1 (Canada); Laboratoire d'Electronique, Optoelectronique et Microsystemes - LEOM, UMR CNRS 5512, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully Cedex (France)

2005-12-12

345

Flux sensitivity of a piecewise normal and superconducting metal loop  

SciTech Connect

We consider a loop composed of a superconducting segment and a normal segment with an Aharonov-Bohm flux through the hole of the loop. The normal segment is assumed to be long compared to the superconducting coherence length xi but short compared to a mean inelastic diffusion length. The elementary excitation spectrum of the ground state of this loop is periodic with period hc/2e as long as the superconducting segment is larger than xi. If the superconducting segment length becomes of the order of xi, quasiparticles can tunnel through the superconducting gap and give rise to an excitation spectrum which is periodic with period hc/e. .AE

Buettiker, M.; Klapwijk, T.M.

1986-04-01

346

Building and Testing a Superconductivity Measurement Platform for a Helium Cryostat  

NASA Astrophysics Data System (ADS)

Superconductivity experiments using Josephson junctions are an excellent environment to study quantum mechanics and materials science. A standard electrical transport technique uses filtered four wire measurement of these superconducting devices. We report our experience as undergraduates in a liberal arts college in building and testing an experimental platform anchored on the cold-finger of a helium cryostat and designed for performing differential conductance measurements in Josephson junctions. To filter out RF, we design, build and test cryogenic filters using ceramic capacitors and inductors and thermocoax cables. We also use fixed attenuators for thermal anchoring and use miniature connectors to connect wires and coax to a sample box. We report on progress in our diagnostic measurements as well as low-temperature tunneling experiments to probe the structure of the energy gap in both single- and multi-gapped superconductors.

Rose, Heath; Ostrander, Joshua; Wu, Jim; Ramos, Roberto

2013-03-01

347

Topological superconductivity and Majorana fermions in hybrid structures involving cuprate high-Tc superconductors  

NASA Astrophysics Data System (ADS)

The possibility of inducing topological superconductivity with cuprate high-temperature superconductors (HTSC) is studied for various heterostructures. We first consider a ballistic planar junction between a HTSC and a metallic ferromagnet. We assume that inversion symmetry breaking at the tunnel barrier gives rise to Rashba spin-orbit coupling in the barrier and allows equal-spin triplet superconductivity to exist in the ferromagnet. Bogoliubov-de Gennes equations are obtained by explicitly modeling the barrier and taking account of the transport anisotropy in the HTSC. By making use of the self-consistent boundary conditions and solutions for the barrier and HTSC regions, an effective equation of motion for the ferromagnet is obtained where Andreev scattering at the barrier is incorporated as a boundary condition for the ferromagnetic region. For a ferromagnet layer deposited on a (100) facet of the HTSC, triplet p-wave superconductivity is induced. For the layer deposited on a (110) facet, the induced gap does not have the p-wave orbital character, but has an even orbital symmetry and an odd dependence on energy. For the layer on the (001) facet, an exotic f-wave superconductivity is induced. We also consider the induced triplet gap in a one-dimensional half-metallic nanowire deposited on a (001) facet of a HTSC. Due to the breaking of translational symmetry in the direction perpendicular to the wire axis, the expression for the gap receives contributions from different perpendicular momentum eigenstates in the superconductor. We find that for a wire axis along the a axis, these different contributions constructively interfere and give rise to a robust triplet p-wave gap. For a wire oriented 45? away from the a axis, the different contributions destructively interfere and the induced triplet p-wave gap vanishes. For the appropriately oriented wire, the induced p-wave gap may give rise to Majorana fermions at the ends of the half-metallic wire. In light of the recent experimental progress in the quest for realizing Majorana fermions, we also discuss inducing superconductivity in the spin-orbit-coupled nanowire using a HTSC. Based on our result, topological superconductivity in a semiconductor nanowire may be possible given that it is oriented along the a axis of the HTSC.

Takei, So; Fregoso, Benjamin M.; Galitski, Victor; Das Sarma, S.

2013-01-01

348

Temperature-dependent energy band gap variation in self-organized InAs quantum dots  

Microsoft Academic Search

We investigated the temperature-dependent variation of the photoluminescence emission energy of self-organized InAs\\/GaAs quantum dots (QDs) grown by conventional Stranski-Krastanov (SK) molecular beam epitaxy and migration-enhanced molecular beam epitaxy (MEMBE) and that of MEMBE InAs QDs in a symmetric and an asymmetric In0.2Ga0.8As\\/GaAs well. The temperature-dependent energy variation of each QD is analyzed in low and high temperature regions, including

Inah Yeo; Jin Dong Song; Jungil Lee

2011-01-01

349

Non-empirical nuclear energy functionals, pairing gaps and odd-even mass differences  

E-print Network

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.

T. Duguet; T. Lesinski

2009-07-06

350

Evaluation of Band-Gap Energies and Characterization of Nonradiative Recombination Centers of Film and Bulk GaN Crystals  

NASA Astrophysics Data System (ADS)

We have measured photothermal spectra of bulk and film GaN crystals by the photothermal divergence (PTD) method in the temperature range from 110 K to 320 K. The band-gap energy of the GaN film grown by metalorganic chemical vapor deposition (MOCVD) method on a sapphire substrate shifts toward a higher energy because of the stress, compared with that of the bulk GaN grown by hydride vapor-phase epitaxy (HVPE) method. Moreover, the dependence of the PTD signal intensity, IPTD, on the doping has been observed. From IPTD spectra, we have found that a doping procedure may induce the degradation of the crystalline quality of GaN. For the bulk, two peaks in the energy region below the band edge have been observed in the IPTD spectra, and it has been found that such peaks may originate in nonradiative recombination centers. The two peaks have been characterized to be related to deep levels observed previously by means of the so-called deep-level transient-scan method.

Kamano, Masaru; Haraguchi, Masanobu; Fukui, Masuo; Kuwahara, Minoru; Okamoto, Toshihiro; Mukai, Takashi; Shinomiya, Genichi

2003-08-01

351

Electron Energy Distribution in Hotspots of Cygnus A:Filling the Gap with Spitzer Space Telescope  

SciTech Connect

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.

Stawarz, L.; Cheung, C.C.; Harris, D.E.; Ostrowski, M.

2007-03-06

352

FOREWORD: Focus on Superconductivity in Semiconductors Focus on Superconductivity in Semiconductors  

NASA Astrophysics Data System (ADS)

Since the discovery of superconductivity in diamond, much attention has been given to the issue of superconductivity in semiconductors. Because diamond has a large band gap of 5.5 eV, it is called a wide-gap semiconductor. Upon heavy boron doping over 3×1020 cm-3, diamond becomes metallic and demonstrates superconductivity at temperatures below 11.4 K. This discovery implies that a semiconductor can become a superconductor upon carrier doping. Recently, superconductivity was also discovered in boron-doped silicon and SiC semiconductors. The number of superconducting semiconductors has increased. In 2008 an Fe-based superconductor was discovered in a research project on carrier doping in a LaCuSeO wide-gap semiconductor. This discovery enhanced research activities in the field of superconductivity, where many scientists place particular importance on superconductivity in semiconductors. This focus issue features a variety of topics on superconductivity in semiconductors selected from the 2nd International Workshop on Superconductivity in Diamond and Related Materials (IWSDRM2008), which was held at the National Institute for Materials Science (NIMS), Tsukuba, Japan in July 2008. The 1st workshop was held in 2005 and was published as a special issue in Science and Technology of Advanced Materials (STAM) in 2006 (Takano 2006 Sci. Technol. Adv. Mater. 7 S1). The selection of papers describe many important experimental and theoretical studies on superconductivity in semiconductors. Topics on boron-doped diamond include isotope effects (Ekimov et al) and the detailed structure of boron sites, and the relation between superconductivity and disorder induced by boron doping. Regarding other semiconductors, the superconducting properties of silicon and SiC (Kriener et al, Muranaka et al and Yanase et al) are discussed, and In2O3 (Makise et al) is presented as a new superconducting semiconductor. Iron-based superconductors are presented as a new series of high-TC superconductors (Tamegai et al), and the mechanism of superconductivity is discussed. Last but not least, a novel highest-density phase of boron is produced and characterized (Zarechnaya et al). We hope that this focus issue will help readers to understand the frontiers of superconductivity in semiconductors and assist in the application of new devices using a combination of superconductivity and semiconductivity.

Takano, Yoshihiko

2008-12-01

353

Surface Sensitivity of Fast Superconducting Ion Detectors for Time-of-Flight Mass Spectrometry  

SciTech Connect

We are developing the spatial uniformity of superconducting tunnel junction detectors with a size of 200 {micro}m is improved by increasing the Al thickness of the Nb/Al proximitized electrodes in an energy range of 5-10 keV, which is in the same order as an acceleration energy in time-of-flight mass spectroscopy (TOF-MS). It has been confirmed in TOF experiments with Ta ions and Ta clusters that the proximitized junction detectors clearly separate different ionic states and multi-hit events in impact energy spectra, and moreover can reveal a difference in ion species or ion-surface collision dynamics. However, a better spatial uniformity is not always good for TOF-MS, because a detector with the thicker Al layers has a lower superconducting energy gap, which results in improper detector operation because of a temperature rise due to heat radiation.

Ohkubo, M; Ukibe, M; Saito, N; Kushino, A; Ichimura, S; Friedrich, S

2004-11-05

354

Making Superconducting Welds between Superconducting Wires  

NASA Technical Reports Server (NTRS)

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.

Penanen, Konstantin I.; Eom, Byeong Ho

2008-01-01

355

Band Edge Energies and Band Gaps of Quaternary GaInAsSb Alloys  

Microsoft Academic Search

Quaternary alloys without a common atom such as (Ga,In)-(As,Sb) pose a difficult combinatorially design problem in that there are many different atomic configurations even when the system is constrained to be lattice-matched on a substrate. Using an atomistic pseudopotential approach we have calculated the band edge energies of this quaternary random alloys as a function of Ga\\/In (x) and As\\/Sb

Rita Magri; Alex Zunger; Herbert Kroemer

2007-01-01

356

Solvent effect on bell-shaped energy gap dependence for charge transfer triplet exciplexes  

NASA Astrophysics Data System (ADS)

The decay kinetics of charge transfer triplet exciplexes—radical ion pairs formed by electron transfer from aromatic amines to the quinones in the triplet excited states in benzene, ethyl acetate and tert-amyl alcohol was studied by laser photolysis. The bell-shaped dependence for the intersystem electron transfer becomes more pronounced and narrow with the increasing polarity of the medium, which may be explained in terms of the single quantum mode approximation within the non-adiabatic multiphonon electron transfer theory by means of the decrease in the vibrational frequency of the quantum mode and in the quantum reorganization energy.

Levin, P. P.; Raghavan, P. K. N.

1991-08-01

357

Superconducting frustration bit  

NASA Astrophysics Data System (ADS)

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.

Tanaka, Y.

2014-10-01

358

Anomalous superconductivity of Pb/La0.7Sr0.3MnO3 point contacts  

NASA Astrophysics Data System (ADS)

Recent experimental results indicate the possible realization of an even frequency p -wave triplet superconducting state in proximity affected La0.65Ca0.35MnO3-X(X=Pb,MgB2) point contacts (PCs). Motivated by this we present a study of the current-voltage characteristics and of the dynamic conductance of PCs between Pb and another member of a ferromagnetic manganite family La0.7Sr0.3MnO3 (LSMO). For proximity affected contacts we have observed a spectacular drop of the contact’s resistance with the onset of the Pb superconductivity and, for small voltage, an excess current and doubling of the normal-state conductance. We also detected the subharmonic gap resonances and found that proximity induced superconducting state of LSMO corresponds to that with the energy of the quasiparticle gap much larger than that of Pb. The results most reasonably can be explained by assuming a conversion of spin singlet pairs into triplet pairs at the Pb/LSMO interface and intrinsic superconductivity of LSMO with the actual gap independent on Pb. The mechanism of a conversion has been discussed. Systematic character and repeatability of a number of principal experimental facts suggest that some general physical phenomena have been documented in transport properties of proximity affected singlet superconductor/half-metallic manganite heterostructures.

Krivoruchko, V. N.; Tarenkov, V. Yu.

2008-08-01

359

Bridging the energy gap: Anadromous blueback herring feeding in the Hudson and Mohawk rivers, New York  

USGS Publications Warehouse

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.

Simonin, P. W.; Limburg, K. E.; Machut, L. S.

2007-01-01

360

Fabrication and evaluation of superconducting magnetic bearing for 10 kW h-class flywheel energy storage system  

NASA Astrophysics Data System (ADS)

Radial-type superconducting magnetic bearings (SMB) have been developed for a 10 kW h-class flywheel energy storage system. The bearings consist of an inner-cylindrical stator composed of YBCO bulk superconductors and an outer-rotor composed of permanent magnets. The rotor is suspended without contact using the pinning forces of the bulk superconductors. After construction of the whole system, various tests on both static and dynamic characteristics of the SMB were carried out to confirm that the SMB has sufficient performance for 10 kW h-class flywheel systems. Besides, the bearing rotation loss was measured. In this paper, we describe the implementation of the stator part and report the SMB test results, namely that the rotor was successfully suspended up to 7500 rpm. Thus we succeeded in the energy storage of 2.24 kW h. The rotation loss of the SMB was estimated as 40 W at 7500 rpm, which was mainly caused by the inhomogeneous magnetic field of the bulk superconductors.

Ichihara, T.; Matsunaga, K.; Kita, M.; Hirabayashi, I.; Isono, M.; Hirose, M.; Yoshii, K.; Kurihara, K.; Saito, O.; Saito, S.; Murakami, M.; Takabayashi, H.; Natsumeda, M.; Koshizuka, N.

2005-10-01

361

Superconducting thermoelectric generator  

DOEpatents

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.

Metzger, J.D.; El-Genk, M.S.

1994-01-01

362

Superconducting magnets  

SciTech Connect

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.

Willen, E.; Dahl, P.; Herrera, J.

1985-01-01

363

Non-BCS superconductivity for underdoped cuprates by spin-vortex attraction  

E-print Network

Within a gauge approach to the t-J model, we propose a new, non-BCS mechanism of superconductivity for underdoped cuprates. The gluing force of the superconducting mechanism is an attraction between spin vortices on two different N\\'eel sublattices, centered around the empty sites described in terms of fermionic holons. The spin fluctuations are described by bosonic spinons with a gap generated by the spin vortices. Due to the no-double occupation constraint, there is a gauge attraction between holon and spinon binding them into a physical hole. Through gauge interaction the spin vortex attraction induces the formation of spin-singlet (RVB) spin pairs with a owering of the spinon gap. Lowering the temperature the approach exhibits two crossover temperatures: at the higher crossover a finite density of incoherent holon pairs are formed leading to a reduction of the hole spectral weight, at the lower crossover also a finite density of incoherent spinon RVB pairs are formed, giving rise to a gas of incoherent preformed hole pairs, and magnetic vortices appear in the plasma phase. Finally, at a even lower temperature the hole pairs become coherent, the magnetic vortices become dilute and superconductivity appears. The superconducting mechanism is not of BCS-type since it involves a gain in kinetic energy (for spinons) coming from the spin interactions.

P. A. Marchetti; F. Ye; Z. B. Su; L. Yu

2011-02-21

364

Spectral broadening by incomplete thermalization of the energy in X-ray microcalorimeters with superconducting absorber and NTD-Ge thermal sensor  

NASA Astrophysics Data System (ADS)

We present a model of the response of a cryogenic microcalorimeter with superconducting absorber and phonon sensitive thermal sensor to the absorption of X-ray photons. The model is based on the main microscopic processes responsible for the thermalization of the deposited energy. We use a system of rate equations to describe the energy downconversion in the superconductor and transport to the thermal sensor. The model is a tool to investigate the thermalization efficiency with respect to the device characteristics (i.e. absorber material, geometry), in order to optimize the performances of these detectors. As a first case study, we report results of simulations for a microcalorimeter with superconducting Sn absorber and neutron transmutation doped (NTD) Ge thermistor, where the experimentally measured spectral resolution is still a factor ˜3 worse than the limit predicted by the macroscopic formula.

Perinati, E.; Barbera, M.; Collura, A.; Serio, S.; Silver, E.

2004-10-01

365

Athermal Energy Loss from X-Rays Deposited in Thin Superconducting Bilayers on Solid Substrates  

NASA Technical Reports Server (NTRS)

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.

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

366

PREFACE: Superconducting materials Superconducting materials  

NASA Astrophysics Data System (ADS)

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

Charfi Kaddour, Samia; Singleton, John; Haddad, Sonia

2011-11-01

367

Band gap and band parameters of InN and GaN from quasiparticle energy calculations based on exact-exchange density-functional theory  

E-print Network

Band gap and band parameters of InN and GaN from quasiparticle energy calculations based on exact-exchange density-functional theory P. Rinkea and M. Scheffler Fritz-Haber-Institut der Max G0W0 calculations based on exact-exchange density-functional theory. For InN their approach predicts

368

J. Am. Chem. SOC.1982, 104, 2719-2724 2719 reaction is afraction of the energy gap at the reactant end, and  

E-print Network

J. Am. Chem. SOC.1982, 104, 2719-2724 2719 reaction is afraction of the energy gap at the reactant to thermoneutral as well as to exothermic (and endothermic) reactions, and thus it compliments both the Marcus the ensemble of sN2 reaction will exhibit (a) electron-transfer-controlledreactivity patterns which obey

Goddard III, William A.

369

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

E-print Network

- energy neutrons. Results will be compared with simula- tions using the FLUKA code [7]. STUDY II TARGET, and the total power deposited in the 13 SC coils would be 37 kW. Energy-deposition results from a FLUKA deposited in all 13 SC coils would be 58 kW and there is better agreement with FLUKA. The peak energy

McDonald, Kirk

370

Fields and forces in flywheel energy storage with high-temperature superconducting bearings  

SciTech Connect

The development of low-loss bearings employing high-temperature superconductors has brought closer the advent of practical flywheel energy storage systems. These systems require magnetic fields and forces for levitation, stabilization, and energy transfer. This paper describes the status of experiments on flywheel energy storage at Argonne National Laboratory and computations in support of that project, in particular computations for the permanent-magnet rotor of the motor-generator that transfers energy to and from the flywheel, for other energy-transfer systems under consideration, and for the levitation and stability subsystems.

Turner, L.R. [Argonne National Lab., IL (United States). Energy Technology Div.] [Argonne National Lab., IL (United States). Energy Technology Div.

1997-03-01

371

Fields and forces in flywheel energy storage with high-temperature superconducting bearings  

SciTech Connect

The development of low-loss bearings employing high-temperature superconductors has brought closer the advent of practical flywheel energy storage systems. These systems require magnetic fields and forces for levitation, stabilization, and energy transfer. This paper describes the status of experiments on flywheel energy storage at Argonne National Laboratory and computations in support of that project, in particular computations for the permanent-magnet rotor of the motor-generator that transfers energy to and from the flywheel, for other energy-transfer systems under consideration, and for the levitation and stabilization subsystem.

Turner, L.R. [Argonne National Lab., IL (United States). Energy Technology Div.

1996-05-01

372

A Study of Higher-Order Mode Damping in the Superconducting Energy Recovery LINAC at Brookhaven National Laboratory  

NASA Astrophysics Data System (ADS)

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.

Hammons, Lee Reginald, III

373

Mesoscopic superconductivity in ultrasmall metallic grains  

NASA Astrophysics Data System (ADS)

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.

Alhassid, Y.; Nesterov, K. N.

2014-10-01

374

Mesoscopic superconductivity in ultrasmall metallic grains  

E-print Network

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.

Y. Alhassid; K. N. Nesterov

2014-07-31

375

Operational Merits of Maritime Superconductivity  

NASA Astrophysics Data System (ADS)

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.

Ross, R.; Bosklopper, J. J.; van der Meij, K. H.

376

Evidence of a nonequilibrium distribution of quasiparticles in the microwave response of a superconducting aluminum resonator.  

PubMed

In a superconductor, absorption of photons with an energy below the superconducting gap leads to redistribution of quasiparticles over energy and thus induces a strong nonequilibrium quasiparticle energy distribution. We have measured the electrodynamic response, quality factor, and resonant frequency of a superconducting aluminium microwave resonator as a function of microwave power and temperature. Below 200 mK, both the quality factor and resonant frequency decrease with increasing microwave power, consistent with the creation of excess quasiparticles due to microwave absorption. Counterintuitively, above 200 mK, the quality factor and resonant frequency increase with increasing power. We demonstrate that the effect can only be understood by a nonthermal quasiparticle distribution. PMID:24580483

de Visser, P J; Goldie, D J; Diener, P; Withington, S; Baselmans, J J A; Klapwijk, T M

2014-01-31

377

Magnetic Levitators With Superconductive Components  

NASA Technical Reports Server (NTRS)

Magnetic noncontact levitators that include superconductive components provide vibration-damping suspension for cryogenic instruments, according to proposal. Because superconductive components attached to levitated cryogenic instruments, no additional coolant liquid or refrigeration power needed. Also because vibration-damping components of levitators located outside cold chambers, in ambient environment, not necessary to waste coolant liquid or refrigeration power on dissipation of vibrational energy. At least three levitating magnets and three superconductors necessary for stable levitation.

Dolgin, Benjamin P.

1995-01-01

378

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

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.

Padamsee, Hasan S.

2014-10-01

379

Superconducting magnets  

SciTech Connect

This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-{Tc} superconductor at low temperature.

Not Available

1994-08-01

380

The collective emission of electromagnetic waves from astrophysical jets - Luminosity gaps, BL Lacertae objects, and efficient energy transport  

NASA Technical Reports Server (NTRS)

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.

Baker, D. N.; Borovsky, Joseph E.; Benford, Gregory; Eilek, Jean A.

1988-01-01

381

Tuning the band structure and superconductivity in single-layer FeSe by interface engineering.  

PubMed

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

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

382

Vacuum low-temperature superconductivity is the essence of superconductivity - Atomic New Theory  

NASA Astrophysics Data System (ADS)

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

Yongquan, Han

2010-10-01

383

Fast-cycling superconducting synchrotrons and possible path to the future of US experimental high-energy particle physics  

SciTech Connect

The authors outline primary physics motivation, present proposed new arrangement for Fermilab accelerator complex, and then discuss possible long-range application of fast-cycling superconducting synchrotrons at Fermilab.

Piekarz, Henryk; /Fermilab

2008-02-01

384

Athermal Energy Loss from X-rays Deposited in Thin Superconducting Films on Solid Substrates  

NASA Technical Reports Server (NTRS)

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.

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

385

Aromaticity of simple hydrocarbons evaluated through computing isodesmic energies, rings bond order uniformity, and HOMO–LUMO energy gaps  

Microsoft Academic Search

The AM1 computational study of open-chain conjugated and cyclic chemical systems was performed with the aim of evaluating their aromatic character through frontier molecular orbital (FMO) change during the course of the ring formation. The change of the FMO energy difference was also used to determine the relative stability of fused unsaturated cyclic compounds. The relative change of the FMO

Branko S Jursic

1999-01-01

386

Measurement of two low-temperature energy gaps in the electronic structure of antiferromagnetic USb2 using ultrafast optical spectroscopy.  

PubMed

Ultrafast optical spectroscopy is used to study the antiferromagnetic f-electron system USb(2). We observe the opening of two charge gaps at low temperatures (gap is due to hybridization between localized f-electron and conduction electron bands, while band renormalization involving magnons leads to the emergence of the second gap. These experiments thus enable us to shed light on the complex electronic structure emerging at the Fermi surface in f-electron systems. PMID:23952443

Qi, J; Durakiewicz, T; Trugman, S A; Zhu, J-X; Riseborough, P S; Baumbach, R; Bauer, E D; Gofryk, K; Meng, J-Q; Joyce, J J; Taylor, A J; Prasankumar, R P

2013-08-01

387

Uncertainties in Gapped Graphene  

E-print Network

Motivated by graphene-based quantum computer we examine the time-dependence of the position-momentum and position-velocity uncertainties in the monolayer gapped graphene. The effect of the energy gap to the uncertainties is shown to appear via the Compton-like wavelength $\\lambda_c$. The uncertainties in the graphene are mainly contributed by two phenomena, spreading and zitterbewegung. While the former determines the uncertainties in the long-range of time, the latter gives the highly oscillation to the uncertainties in the short-range of time. The uncertainties in the graphene are compared with the corresponding values for the usual free Hamiltonian $\\hat{H}_{free} = (p_1^2 + p_2^2) / 2 M$. It is shown that the uncertainties can be under control within the quantum mechanical law if one can choose the gap parameter $\\lambda_c$ freely.

Eylee Jung; Kwang S. Kim; DaeKil Park

2011-07-27

388

Nanoscale phase separation of antiferromagnetic order and superconductivity in K0.75Fe1.75Se2  

PubMed Central

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

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

389

Static forces in a superconducting magnet bearing  

SciTech Connect

Static levitation forces and stiffnesses in a superconducting bearing consisting of concentric ring magnets and a superconducting YBaCuO ring are investigated. In the field-cooled mode a levitation force of 20 N has been achieved. The axial and radial stiffnesses have values of 15 N/mm and 10 N/mm, respectively. An arrangement with two bearings supporting a high speed shaft is now under development. A possible application of superconducting magnetic bearings is flywheels for energy storage.

Stoye, P.; Fuchs, G. [Institut fuer Festkoerper- und Werkstofforschung, Dresden (Germany)] [Institut fuer Festkoerper- und Werkstofforschung, Dresden (Germany); Gawalek, W.; Goernert, P. [Institut fuer Physikalische Hochtechnologie, Jena (Germany)] [Institut fuer Physikalische Hochtechnologie, Jena (Germany); Gladun, A. [Technische Univ., Dresden (Germany)] [Technische Univ., Dresden (Germany)

1995-11-01

390

Evidence for phonon-mediated coupling in superconducting Ba\\/sub 0. 6\\/K\\/sub 0. 4\\/BiOâ  

Microsoft Academic Search

Superconducting Ba\\/sub 0.6\\/K\\/sub 0.4\\/BiOâ, with a T\\/sub c\\/ of 30K, shows a large ¹⁸O isotope effect which indicates that phonons are involved in the pairing mechanism. Infrared reflectivity measurements indicate a value for the superconducting gap consistent with moderate coupling (2..delta..\\/kT\\/sub c\\/ = 3.5 +- 0.5). A mediating energy for pairing of about 40 MeV would be required to obtain

D. G. Hinks; B. Dabrowski; D. R. Richards; J. D. Jorgensen; Shiyou Pei; J. F. Zasadzinski

1989-01-01

391

Superconductivity from orbital nematic fluctuations  

NASA Astrophysics Data System (ADS)

Recent experiments suggest that, besides antiferromagnetic fluctuations, nematic fluctuations may contribute to the occurrence of superconductivity in iron pnictides. Motivated by this observation, we study superconductivity from nematic fluctuations in a minimal two-band model. The employed band parameters are appropriate for iron pnictides and lead to four pockets for the Fermi line. It is shown that low-energy, long-wavelength nematic fluctuations within the pockets give rise to strong-coupling superconductivity whereas the large momenta density fluctuations between pockets are rather irrelevant. The obtained transition temperatures are similar to those typically found in the pnictides and are rather robust against repulsive Coulomb interactions. The superconducting and nematic states coexist in a large region of the phase diagram.

Yamase, Hiroyuki; Zeyher, Roland

2013-11-01

392

Coexistence of periodic modulation of quasiparticle states and superconductivity in Bi2Sr2CaCu2O8+?  

PubMed Central

In this article we show, using scanning tunneling spectroscopy, the existence of static striped density of electronic states in nearly optimally doped Bi2Sr2CaCu2O8+? in zero field. This modulation is aligned with the Cu—O bonds, with a periodicity of four lattice constants, and exhibits features characteristic of a two-dimensional system of line objects. We further show that the density of states modulation manifests itself as a shift of states from above to below the superconducting gap. The fact that a single energy scale (i.e., the gap) appears for both superconductivity and stripes suggests that these two effects have the same origin. PMID:12913127

Howald, C.; Eisaki, H.; Kaneko, N.; Kapitulnik, A.

2003-01-01

393

Selective Intermixing of InAs\\/InGaAs\\/InP Quantum Dot Structure With Large Energy Band Gap Tuning  

Microsoft Academic Search

Selective postgrowth band gap tuning of self-assembled InAs\\/InGaAs\\/InP quantum dot (QD) structures has been investigated. Very large band gap blueshift of over 158 meV of the InAs QD structure has been received through the intermixing by exposing the sample under argon plasma and followed by thermal annealing at 780 degC. Selective intermixing of the InAs QD structure has been studied

Tang Xiaohong; Yin Zongyou; Teng Jinghua; Du Anyan; Chin Mee Koy

2008-01-01

394

Superconducting magnet  

NASA Technical Reports Server (NTRS)

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.

1985-01-01

395

ASC 84: applied superconductivity conference. Final program and abstracts  

SciTech Connect

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)

Not Available

1984-01-01

396

Superconducting and magnetic properties of Sr3Ir4Sn13  

NASA Astrophysics Data System (ADS)

Magnetization and muon spin rotation and relaxation (?SR) measurements have been performed to study the superconducting and magnetic properties of Sr3Ir4Sn13. From magnetization measurements the lower and upper critical fields T =0K are found to be 8.5(1) mT and 1.44(2) T, respectively. Zero-field ?SR data show no sign of any magnetic ordering or weak magnetism. Transverse-field ?SR measurements in the vortex state provide the temperature dependence of the magnetic penetration depth ?. The temperature dependence of ?-2 is consistent with the existence of a single s-wave energy gap in the superconducting state of Sr3Ir4Sn13 with a gap value of 0.82(2) meV at absolute zero temperature. However, a two-gap s +s-wave model fit with gap values of 0.91(4) and 0.14(7) meV cannot be ruled out completely. The magnetic penetration depth at zero temperature ? (0) is 291(3) nm. The ratio ?(0)/kBTc=2.1(1) indicates that Sr3Ir4Sn13 should be considered a strong-coupling superconductor.

Biswas, P. K.; Amato, A.; Khasanov, R.; Luetkens, H.; Wang, Kefeng; Petrovic, C.; Cook, R. M.; Lees, M. R.; Morenzoni, E.

2014-10-01

397

Understanding Superconducting Magnetic Energy Storage (SMES) technology, applications, and economics, for end-use workshop  

Microsoft Academic Search

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

R. J. Ferraro; B. W. McConnell

1993-01-01

398

Superconductive Magnetic Energy Storage (SMES) System Studies for Electrical Utility at Wisconsin  

E-print Network

in superfluid helium provides extended time cryogenic stability. Axial structure also functions as a protective heat absorbing secondary during emergency discharge. The cost of the conductor, trench, dewar, ,truts, radial structure, plus others are ~ EZ 3... 35% heat rate energy at night with acceptable storage losses may be more efficient than instantaneous generation at a 25% heat rate regardless of fuel used. System operation can be improved by rapid load following with storage units. For example...

Boom, R. W.; Eyssa, Y. M.; Abdelsalem, M. K.; Huang, X.

399

Coupled even-parity superconducting states  

SciTech Connect

In situations involving two successive superconducting transitions or in situations in which one superconducting transition induces a secondary superconducting state, the nature of the coupling between the states is of interest. Examples of such coupling include heavy-fermion systems and possibly the recently discovered high-T/sub c/ superconductors. We use symmetry principles to enumerate the Ginzburg-Landau free energies associated with the coupling between s- and d-wave superconducting states in the square planar, cubic, tetragonal, orthorhombic, and hexagonal crystal classes.

Sahu, D.; Langner, A.; George, T.F.

1988-08-01

400

Measured performance of hybrid small-gap in-vacuum undulator 08ID-1 at the CLS intermediate energy storage ring  

NASA Astrophysics Data System (ADS)

The recent development of undulator in-vacuum technology has allowed intermediate energy storage rings, such the Canadian Light Source (CLS), to build high brilliance protein crystallography beamlines. The Canadian Macromolecular Crystallography Facility (CMCF) beamline 08ID-1 is the first small period (20 mm) hybrid small-gap in-vacuum undulator (SGU) to be employed at the CLS as a source of high harmonic, high brightness radiation (6.5 - 18 keV). The SGU was assembled and shimmed at the CLS Magnetic Mapping Facility. It is installed in the upstream part of straight section 8 of the CLS ring and chicaned inboard by 0.75 mrad. The downstream half of this section is reserved for future development. To achieve a maximum undulator field (B0) in conjunction with low sensitivity to radiation damage, a hybrid layout for the undulator is used with Sm2Co17 permanent magnets sandwiched between Vanadium Permendur ferromagnetic poles. To date, operations in the 6.5 - 18 keV energy range have been achieved using the 3rd to 9th harmonics, with gap sizes of 5.9 - 8.6 mm. Gaps smaller than 5.9 mm are not being used since in the 5.0 - 5.9 mm range the rms phase errors are larger than 2.5° and lower harmonics at larger gaps are being used instead. The goal of the present study is to measure the output spectrum for various gap sizes and compare these with theoretical expectations calculated from the magnetic characteristics of the undulator measured at the CLS Magnetic Mapping Facility. The 08ID-1 beamline now has several years of successful operation as a highly competitive, high brilliance beamline.

Gorin, James; Blomqvist, Ingvar; Sigrist, Michael; Summers, Tasha; Fodje, Michel; Grochulski, Pawel

2013-03-01

401

Z .Physica C 317318 1999 592595 The meaning of strange momentum structures in the gap  

E-print Network

Z .Physica C 317­318 1999 592­595 The meaning of strange momentum structures in the gap E of the superconducting gap is usually associated with the anisotropy of the pairing scattering, and in the exception of the gap symmetry structure, like the nodes, it is expected to be smooth and predictable. There is, however

Cappelluti, Emmanuele

402

Superconducting augmented rail gun (SARG)  

NASA Astrophysics Data System (ADS)

Design details and theoretical modeling of the performance of a SARG for which compensation has been made for energy dissipation effects are described. SARG features a superconducting coil closely coupled magnetically to the rail gun and operating in the persistent mode. The efficiency and the launching force of the rail gun is enhanced by the flux trapping property of a closed superconducting coil causing a significant increase in the magnetic field strength. Dissipative forces were accounted for in terms of the total exit kinetic energy of the projectile. The test railgun nearing operational status has a 1 m long, 0.91 cm square bore with Cu rails and fiberglass insulation. Energy to the railgun is supplied by a 5 KV, 1440 microfarad capacitor, sufficient to accelerate a 4 gr armature/projectile to 0.8 km/sec when coupled with a 4 Tesla dipole magnet for superconducting augmentation.

Homan, C. G.; Cummings, C. E.; Fowler, C. M.

1986-11-01

403

Single fermion manipulation via superconducting phase differences in multiterminal Josephson junctions  

NASA Astrophysics Data System (ADS)

We show how the superconducting phase difference in a Josephson junction may be used to split the Kramers degeneracy of its energy levels and to remove all the properties associated with time-reversal symmetry. The superconducting phase difference is known to be ineffective in two-terminal short Josephson junctions, where irrespective of the junction structure the induced Kramers degeneracy splitting is suppressed and the ground state fermion parity must stay even, so that a protected zero-energy Andreev level crossing may never appear. Our main result is that these limitations can be completely avoided by using multiterminal Josephson junctions. There the Kramers degeneracy breaking becomes comparable to the superconducting gap, and applying phase differences may cause the change of the ground state fermion parity from even to odd. We prove that the necessary condition for the appearance of a fermion parity switch is the presence of a "discrete vortex" in the junction: the situation when the phases of the superconducting leads wind by 2 ? . Our approach offers strategies for creation of Majorana bound states as well as spin manipulation. Our proposal can be implemented using any low density, high spin-orbit material such as InAs quantum wells, and can be detected using standard tools.

van Heck, B.; Mi, S.; Akhmerov, A. R.

2014-10-01

404

Band-gap energy of heteropoly compounds containing Keggin polyanion-[PVxMo12-xO40]-(3+x) relates to counter-cations and temperature studied by UV-VIS diffuse reflectance spectroscopy  

NASA Astrophysics Data System (ADS)

The band gap energy (absorption edge energies) of the pure H3[PMo12O40].13H2O and H4[PVMo11O40].13H2O, respectively, supported on SiO2 and SiC and some of its NH4+ and Cs+ salts were determined by different methods. The influence of the counter-cations and the temperature on band gap energy was studied. In this purpose, the diffuse reflectance spectra of above mentioned compounds were registered at different temperatures, and it were transposed in the curves of the Kubelka-Munk function vs. wavelength. The band gap energies were determined by processing of low field energy of the ligand-metal charge transfer band (O2- ? Mo6+ and O2- ? V5+) usually observed between 200 and 400 nm on these curves. In this aim, the Tauc's relation was adapted for Kubelka-Munk function use and it was plotted for n = 1/2 (direct transition) and 2 (indirect transition) vs. wave energy (photon energy). The intersection of the curves' tangent drawn to their point of inflection with horizontal axis gives the band gap energy. The other method for calculation of band gap energy was the differential calculus on the Kubelka-Munk function vs. wave energy curve where the x value corresponding to curves' maximum is the found value. The comparison between experimental band gap values and literature data showed their partial fit. The higher temperature produces the band gap energy diminution as a result of a stronger interaction between Keggin Units, which occurs especially by the crystallization water loss. The Keggin Units isolation one from another by voluminous counter-ion or their spreading on a support leads to a weaker interaction between them and as a consequence, the increasing of absorption edge energy. A linear correlation of the crystallites size with band gap energy was observed.

Sasca, Viorel; Popa, Alexandru

2013-10-01

405

Cryogenic structural materials for superconducting magnets  

SciTech Connect

This paper reviews research in the United States and Japan on structural materials for high-field superconducting magnets. Superconducting magnets are used for magnetic fusion energy devices and for accelerators that are used in particle-physics research. The cryogenic structural materials that we review are used for magnet cases and support structures. We expect increased materials requirements in the future.

Dalder, E.N.C.; Morris, J.W. Jr.

1985-02-22

406

Quantum manipulation of low-frequency fluctuators by superconducting resonator  

Microsoft Academic Search

Two-level system fluctuators in superconducting devices have demonstrated coherent coupling with superconducting qubits. Here, we show that universal quantum logic gates can be realized in these two-level systems solely by tuning a superconducting resonator in which they are imbedded. Because of the large energy separation between the fluctuators, conventional gate schemes in the cavity QED approach that are widely used

L. Tian; K. Jacobs

2009-01-01

407

Modulating Sub-THz Radiation with Current in Superconducting Metamaterial V. Savinov,1,* V. A. Fedotov,1  

E-print Network

Modulating Sub-THz Radiation with Current in Superconducting Metamaterial V. Savinov,1,* V. A at frequencies below the superconducting gap in the THz and subterahertz bands. DOI: 10.1103/PhysRevLett.109 show how superconducting metamaterials can be used to create agile radiation modu- lators in the THz

Gruner, Daniel S.

408

Development of Energy-Efficient Cryogenic Leads with High Temperature Superconducting Films on Ceramic Substrates  

NASA Astrophysics Data System (ADS)

High temperature superconductor (HTS) material can be used for the implementation of high-speed low-heat conduction data links to transport digital data from 4 K superconductor integrated circuits to higher-temperature parts of computing systems. In this work, we present a conceptual design of energy efficient interface and results in fabricating such HTS leads. Initial calculations have shown that the microstrip line cable geometry for typical materials employed in production of HTS thin films can be a two-layered film for which the two layers of about 10 cm long are separated by an insulation layer with as low permittivity as possible. With this architecture in mind, the pulsed laser deposition process has been designed in a 45 cm diameter vacuum chamber to incorporate an oscillating sample holder with homogeneous substrate heating up to 900°C, while the laser plume is fixed. This design has allowed us to produce 200 nm to 500 nm thick, 7 cm to 10 cm long YBa2Cu3O7 thin films with the homogeneous critical temperature (Tc) of about 90 K. The critical current density (Jc) of the short samples obtained from the long sample is of (2 ± 1) × 1010 A/m2. Lines of 3-100 ?m wide have been successfully patterned along the length of the samples in order to directly measure the Tc and Jc values over the entire length of the samples, as well as to attempt the structuring of multichannel data lead prototype.

Pan, A. V.; Fedoseev, S. A.; Shcherbakova, O. V.; Golovchanskiy, I. A.; Zhou, S.; Dou, S. X.; Webber, R. J.; Mukhanov, O. A.; Yamashita, T.; Taylor, R.

409

A 0.5 kWh flywheel energy storage system using a high-Tc superconducting magnetic bearing  

Microsoft Academic Search

A flywheel rotor having a main shaft, two flywheel disks and one permanent magnet for a SMB (superconducting magnetic bearing) was designed and manufactured. The flywheel was made of CFRP material which is light weight and has high tensile strength. The permanent magnet was hooped by CPRP in order to prevent centrifugal bursting. The rotor was levitated by a SMB

Y. Miyagawa; H. Kameno; R. Takahata; H. Ueyama

1999-01-01

410

Superconducting Materials, Magnets and Electric Power Applications  

NASA Astrophysics Data System (ADS)

The surprising discovery of superconductivity a century ago launched a chain of convention-shattering innovations and discoveries in superconducting materials and applications that continues to this day. The range of large-scale applications grows with new materials discoveries - low temperature NbTi and Nb3Sn for liquid helium cooled superconducting magnets, intermediate temperature MgB2 for inexpensive cryocooled applications including MRI magnets, and high temperature YBCO and BSSCO for high current applications cooled with inexpensive liquid nitrogen. Applications based on YBCO address critical emerging challenges for the electricity grid, including high capacity superconducting cables to distribute power in urban areas; transmission of renewable electricity over long distances from source to load; high capacity DC interconnections among the three US grids; fast, self-healing fault current limiters to increase reliability; low-weight, high capacity generators enabling off-shore wind turbines; and superconducting magnetic energy storage for smoothing the variability of renewable sources. In addition to these grid applications, coated conductors based on YBCO deposited on strong Hastelloy substrates enable a new generation of all superconducting high field magnets capable of producing fields above 30 T, approximately 50% higher than the existing all superconducting limit based on Nb3Sn. The high fields, low power cost and the quiet electromagnetic and mechanical operation of such magnets could change the character of high field basic research on materials, enable a new generation of high-energy colliding beam experiments and extend the reach of high density superconducting magnetic energy storage.

Crabtree, George

2011-03-01

411

Recent progress on photonic band gap accelerator cavities  

SciTech Connect

We report on the current status of our program to apply Photonic Band Gap (PBG) concepts to produce novel high-energy, high-intensity accelerator cavities. The PBG design on which we have concentrated our initial efforts consists of a square array of metal cylinders, terminated by conducting or superconducting sheets, and surrounded by microwave absorber on the periphery of the structure. A removed cylinder from the center of the array constitutes a site defect where a localized electromagnetic mode can occur. In previous work, we have proposed that this structure could be utilized as an accelerator cavity, with advantageous properties over conventional cavity designs. In the present work, we present further studies, including MAFIA-based numerical calculations and experimental measurements, demonstrating the feasibility of using the proposed structure in a real accelerator application.

Smith, D.R.; Li, D.; Vier, D.C. [and others

1997-02-01

412

Direct Probe of Interplay between Local Structure and Superconductivity in FeTe0.55Se0.45  

NASA Astrophysics Data System (ADS)

We explore the interplay between local crystallographic structure, composition and local electronic and superconductive properties. Direct structural analysis of scanning tunneling microscopy (STM) data allows local lattice distortions and structural defects across a FeTe0.55Se0.45 surface to be explored on a single unit-cell level. Concurrent superconducting gap (SG) mapping reveals suppression of the SG at well-defined structural defects, identified as a local structural distortion (Guinier-Preston zone). The strong structural distortion is related to the vanishing of the superconducting state. This study provides insight into the origins of superconductivity in iron chalcogenides by providing an example of atomic-level studies of the structure-property relationship. Research was supported (WL, BCS, AS, SVK) by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division. This research was conducted (MP, QL) at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. (Wenzhi Lin and Qing Li, these authors contributed equally to this work)

Lin, Wenzhi; Li, Qing; Sales, Brian; Jesse, Stephen; Safa-Sefat, Athena; Kalinin, Sergei; Pan, Minghu

2013-03-01

413

Gap states in HTSC by infrared spectroscopy  

SciTech Connect

Recent infrared reflectance spectroscopy on high quality crystals of a number of HTSC systems shows that all have finite conductivity in the frequency region of the superconducting gap. Results on untwinned YBCO from a number of laboratories show that this absorption is not due to experimental problems or sample-to-sample variations. Other materials also show absorption features in the gap region in the form of peaks. The authors discuss these results in terms of recent ideas of the effect of impurities in d-wave superconductors.

Timusk, T.; Basov, D.N.; Puchkov, A.V. [McMaster Univ., Ontario (Canada)] [and others

1995-08-01

414

Vortex pinning in two-gap superconductors  

NASA Astrophysics Data System (ADS)

We discuss vortices and their pinning in two-gap superconductors, in which two superconducting gaps are opened around two different Fermi surfaces. We found that there are two kinds of vortices with continuously valuable fractions of the unit flux quanta hc/2e. These two kinds of vortices are tightly bound and cannot be separated in the ground state, but can be when deconfinement occurs by the finite temperature effect as is pointed out (See, Jun Goryo, Shingo Soma, and Hiroshi Matsukawa, Europhys. Lett. 80 (2007) 17002). In this paper, we show that two kinds of vortices can be split by the pinning effect.

Goryo, Jun; Saito, Tatsuro; Matsukawa, Hiroshi

2007-11-01

415

Numerical analysis of a new hybrid superconducting magnetic bearing flywheel system  

Microsoft Academic Search

High temperature superconducting magnetic bearings have several significant advantages over conventional magnetic bearings. However, the low stiffness, low damping, flux creep and flux flow make it difficult to realize a flywheel energy storage system using superconducting magnetic bearings. In order to deal with these problems, a hybrid superconducting magnetic bearing system which consists of superconducting magnetic bearings, permanent magnetic bearings,

J. R. Fang; L. Z. Lin; L. G. Yan

2002-01-01

416

A superconducting transistor with improved isolation between the input and output terminals  

NASA Astrophysics Data System (ADS)

A new design for a multi-terminal superconducting transistor-like device exploiting tunnelling injection of quasiparticles is proposed, in which parasitic back-action of the acceptor junction (S1IS2) bias current on the injector junction (S2FIS3) current-voltage characteristic (CVC) is dramatically reduced as compared with that for the formerly reported quiteron (here S, I, and F denote a superconductor, an insulator and a ferromagnetic material). Improvement of the isolation is achieved owing to the short electron mean free path and short coherence length in a thin F layer that screens the superconducting energy gap in the perturbed S2 layer preventing its manifestation in the CVC of the injector.

Nevirkovets, I. P.

2009-10-01

417

Observational Properties of Protoplanetary Disk Gaps  

NASA Astrophysics Data System (ADS)

We study the effects of an annular gap induced by an embedded protoplanet on disk scattered light images and the infrared spectral energy distribution (SED). We find that the outer edge of a gap is brighter in the scattered light images than a similar location in a gap-free disk. The stellar radiation that would have been scattered by material within the gap is instead scattered by the disk wall at the outer edge of the gap, producing a bright ring surrounding the dark gap in the images. Given sufficient resolution, such gaps can be detected by the presence of this bright ring in scattered light images. A gap in a disk also changes the shape of the SED. Radiation that would have been absorbed by material in the gap is instead reprocessed by the outer gap wall. This leads to a decrease in the SED at wavelengths corresponding to the temperature at the radius of the missing gap material, and to a corresponding flux increase at longer wavelengths corresponding to the temperature of the outer wall. We note, however, that the presence of an annular gap does not change the bolometric IR flux; it simply redistributes the radiation previously produced by material within the gap to longer wavelengths. Although it will be difficult on the basis of the SED alone to distinguish between the presence of a gap and other physical effects, the level of changes can be sufficiently large to be measurable with current instruments (e.g., Spitzer).

Varnière, Peggy; Bjorkman, J. E.; Frank, Adam; Quillen, Alice C.; Carciofi, A. C.; Whitney, Barbara A.; Wood, Kenneth

2006-02-01

418

GAP FILLING CERAMIC INSULATING PUTTY FOR HIGH FIELD MAGNETS  

SciTech Connect

Gaps between the A15 superconducting cable and its supports can sometimes occur requiring expensive rework of the support or filling with a non-optimal material. Recently, a new ceramic putty has been developed that can fill these gaps to fully support the superconducting cable. This ceramic material can withstand the extreme temperature differences between the high temperature heat treatment and the cryogenic operation. Significant performance improvements have been made that will enable the insulating putty to be used in some accelerator magnet systems. Processing methods will be discussed as well as strength and thermal data.

Rice, J. A.; Rice, H. M. [MultiPhase Composites, LLC Longmont, CO, 80501 (United States)

2008-03-03

419

Diagrammatic approach to crystalline color superconductivity  

NASA Astrophysics Data System (ADS)

We present a derivation of the gap equation for the crystalline color superconducting phase of QCD which begins from a one-loop Schwinger-Dyson equation written using a Nambu-Gorkov propagator modified to describe the spatially varying condensate. Some aspects of previous variational calculations become more straightforward when rephrased beginning from a diagrammatic starting point. This derivation also provides a natural base from which to generalize the analysis to include quark masses, nontrivial crystal structures, gluon propagation at asymptotic densities, and nonzero temperature. In this paper, we analyze the effects of nonzero temperature on the crystalline color superconducting phase.

Bowers, Jeffrey A.; Kundu, Joydip; Rajagopal, Krishna; Shuster, Eugene

2001-07-01

420

Ab-Initio Calculations of Electronic Properties of InP and GaP  

NASA Astrophysics Data System (ADS)

We present results from ab-initio, self-consistent local density approximation (LDA) calculations of electronic and related properties of zinc blende indium phosphide (InP) and gallium phosphide (GaP). We employed a LDA potential and implemented the linear combination of atomic orbitals (LCAO) formalism. This implementation followed the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). This method searches for the optimal basis set that yields the minima of the occupied energies. This search entails increases of the size of the basis set and the related modifications of angular symmetry and of radial orbitals. Our calculated, direct band gap of 1.398 eV (1.40 eV), at the ? point, is in excellent agreement with experimental values, for InP, and our preliminary result for the indirect gap of GaP is 2.135 eV, from the ? to X high symmetry points. We have also calculated electron and hole effective masses for both InP and GaP. These calculated properties also agree with experimental findings. We conclude that the BZW-EF method could be employed in calculations of electronic properties of high-Tc superconducting materials to explain their complex properties.

Malozovsky, Y.; Franklin, L.; Ekuma, E. C.; Zhao, G. L.; Bagayoko, D.

2013-06-01

421

Superconductivity in oxygen doped iron telluride by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Iron base superconductor have gained much attention in the research community. They offer great potentials to improve our understanding of the subject of superconductivity by having another family of high temperature superconductors to compare and contrast to the cuprates. Practically, the iron based superconductors seems to be even better candidates for applications in power generation and power transmission. Iron telluride is regarded as the parent compound of the "11" family, the family of iron chalcogenide that has the simplest structure. Iron telluride itself is not a superconductor, by can become one when doped with oxygen. In this investigation, we developed the growth recipe of thin film iron telluride by Molecular Beam Epitaxy (MBE). We found the growth to be self-regulated, similar to that of GaAs. The initial layers of growth seem to experience a spontaneous crystallization, as the film quickly go from the initial polycrystalline phase to highly crystalline in just a few unit cells. We studied oxygen doping to the iron telluride thin films and the resultant superconductivity. We characterized the sample with AFM, XRD, transport, and STEM-EELS, and we found that interfacial strain is not an essential ingredient of superconductivity in this particular case. We investigated the doping conditions for two candidate oxygen doping modes: substitution and interstitial. We found that substitution occurs when the film grown in oxygen, while interstitial oxygen is primarily incorporated during annealing after growth. The substitutional oxygen are concentrated in small local regions where substitution is around 100%, but does not contribute to superconductivity. We estimated substitutional oxygen to be about 5%, and is the proximate cause of superconductivity. Hall experiment on our sample showed a shift of dominant carrier type from holes to electrons around 35 K, but the transition was set in motion as early as the structural phase transition around 70 K. We believe the shift is a result of enhanced mobility of electrons at low temperatures. Using the capability of MBE to make pristine and abrupt interfaces, we grow two film structures: FeTe:Ox/AlO x/Au and FeTe:Ox/Al/AlO x/Au. We explored processing recipes to fabricate these films into tunel junctions devices. FeTe:Ox/AlO x/Au type of devices turned out to be suffering from nanoshorts and exhibit point contact spectroscopy junction behaviors. We observed evolution of enhanced conduction peaks around 20mV, consistent with published literature. FeTe:Ox/Al/AlOx/Au junctions behave differently, showing a evolving energy gap around 3mV. The fact that the energy gap evolved together with the superconducting transition, and the close match of gap size to these of the other iron chalcogenide superconductors, gives evidence of proximity coupling between the iron telluride layer and the aluminum layer.

Zheng, Mao

422

Comparison of the Strain-modified Band Gap Energies of Truncated and Untruncated InAs Quantum Dots in GaAs Matrix at Varying Inter-dot Spacings  

Microsoft Academic Search

The change in strain-modified band gap energies in truncated and untruncated InAs quantum dots (QDs) in the GaAs matrix has been comparatively investigated as a function of vertical inter-dot spacing, based on the strain-modified band lineups. The direct band gap energy is larger for truncated QDs at a given inter-dot spacing and shows more uniform band lineups in the truncated

Hyunho Shin; Euijoon Yoon; Yo-Han Yoo; Woong Lee

2004-01-01

423

Energy Band Gap, Intrinsic Carrier Concentration and Fermi Level of CdTe Bulk Crystal between 304 K and 1067 K  

NASA Technical Reports Server (NTRS)

Optical transmission measurements were performed on CdTe bulk single crystal. It was found that when a sliced and polished CdTe wafer was used, a white film started to develop when the sample was heated above 530 K and the sample became opaque. Therefore, a bulk crystal of CdTe was first grown in the window area by physical vapor transport; the optical transmission was then measured and from which the energy band gap was derived between 304 and 1067 K. The band gaps of CdTe can be fit well as a function of temperature using the Varshini expression: Eg (e V) = 1.5860 - 5.9117xl0(exp -4) T(sup 2)/(T + 160). Using the band gap data, the high temperature electron-hole equilibrium was calculated numerically by assuming the Kane's conduction band structure and a heavy-hole parabolic valance band. The calculated intrinsic carrier concentrations agree well with the experimental data reported previously. The calculated intrinsic Fermi levels between 270 and 1200 K were also presented.

Su, Ching-Hua

2007-01-01

424

Design and operating experience of an ac-dc power converter for a superconducting magnetic energy storage unit  

SciTech Connect

The design philosophy and the operating behavior of a 5.5 kA, +-2.5 kV converter, being the electrical interface between a high voltage transmission system and a 30 MJ superconducting coil, are documented in this paper. Converter short circuit tests, load tests under various control conditions, dc breaker tests for magnet current interruption, and converter failure modes are described.

Boenig, H.J.; Nielsen, R.G.; Sueker, K.H.

1984-01-01

425

Magnetic fluctuations and heavy electron superconductivity  

NASA Astrophysics Data System (ADS)

A magnetic fluctuation self-energy based on neutron scattering data is used to calculate mass renormalizations, and superconducting critical temperatures and order parameters, for various heavy electron metals.

Norman, M. R.

426

Near-zero modes in superconducting graphene  

E-print Network

Vortices in the simplest superconducting state of graphene contain very-low-energy excitations whose existence is connected to an index theorem that applies strictly to an approximate form of the relevant Bogoliubov–de ...

Ghaemi, Pouyan

427

Stripes and superconductivity in cuprates  

NASA Astrophysics Data System (ADS)

Holes doped into the CuO2 planes of cuprate parent compounds frustrate the antiferromagnetic order. The development of spin and charge stripes provides a compromise between the competing magnetic and kinetic energies. Static stripe order has been observed only in certain particular compounds, but there are signatures which suggest that dynamic stripe correlations are common in the cuprates. Though stripe order is bad for superconducting phase coherence, stripes are compatible with strong pairing. Ironically, magnetic-field-induced stripe order appears to enhance the stability of superconducting order within the planes.

Tranquada, John M.

2012-06-01

428

High field superconducting magnets  

NASA Technical Reports Server (NTRS)

A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

2011-01-01

429

Multigap superconductivity in doped p-type cuprates  

NASA Astrophysics Data System (ADS)

Andreev and tunneling spectroscopy studies of Bi2Sr2Ca n - 1Cu n O2 n + 4 + ?, HgBa2Ca n - 1Cu n O2 n + 2 + ? and Tl2Ba2Ca n - 1Cu2 n + 4 + ? have shown that superconductivity in single-layer ( n = 1) and two-layer ( n = 2) phases has a single-gap character. Qualitatively different results were obtained for three-layer phases. In doped p-type Hg-1223, Bi-2223, and Tl-2223 samples two (or three) superconducting gaps were observed. The existence of multigap superconductivity in superconducting cuprates with n ? 3 is explained by a difference in doping levels of outer (OP) and internal (IP) CuO2 planes.

Ponomarev, Ya. G.; Alyoshin, V. A.; Antipov, E. V.; Oskina, T. E.; Krapf, A.; Kulbachinskii, S. V.; Mikheev, M. G.; Sudakova, M. V.; Tchesnokov, S. N.; Fisher, L. M.

2014-09-01

430

Energy band-gap calculations of short-period (ZnTe)m(ZnSe)n and (ZnS)m(ZnSe)n strained-layer superlattices  

Microsoft Academic Search

We report on the calculations of energy band gaps based on the semiempirical tight-binding model for short-period (ZnTe)m(ZnSe)n and (ZnS)m(ZnSe)n strained-layer superlattices (SLSs). During the calculation, much attention has been paid to the modeling of strain effect. It is found that (ZnTe)m(ZnSe)n superlattices grown on InAs, InP, and GaAs substrates show very different electronic properties from each other, which is

Yi-Hong Wu; Shizuo Fujita; Shigeo Fujita

1990-01-01

431

Forward energy flow, central charged-particle multiplicities, and pseudorapidity gaps in W and Z boson events from pp collisions at $\\sqrt{s}= 7$ TeV  

SciTech Connect

A study of forward energy flow and central charged-particle multiplicity in events with W and Z bosons decaying into leptons is presented. The analysis uses a sample of 7 TeV pp collisions, corresponding to an integrated luminosity of 36 inverse picobarns, recorded by the CMS experiment at the LHC. The observed forward energy depositions, their correlations, and the central charged-particle multiplicities are not well described by the available non-diffractive soft-hadron production models. A study of about 300 events with no significant energy deposited in one of the forward calorimeters, corresponding to a pseudorapidity gap of at least 1.9 units, is also presented. An indication for a diffractive component in these events comes from the observation that the majority of the charged leptons from the (W/Z) decays are found in the hemisphere opposite to the gap. When fitting the signed lepton pseudorapidity distribution of these events with predicted distributions from an admixture of diffractive (POMPYT) and non-diffractive (PYTHIA) Monte Carlo simulations, the diffractive component is determined to be (50.0 +/- 9.3 (stat.) +/- 5.2 (syst.))%.

Chatrchyan, Serguei; et al.

2012-01-01

432

Low-energy effective Hamiltonian for giant-gap quantum spin Hall insulators in honeycomb X-hydride/halide (X=N-Bi) monolayers  

NASA Astrophysics Data System (ADS)

Using the tight-binding method in combination with first-principles calculations, we systematically derive a low-energy effective Hilbert subspace and Hamiltonian with spin-orbit coupling for two-dimensional hydrogenated and halogenated group-V monolayers. These materials are proposed to be giant-gap quantum spin Hall insulators with record huge bulk band gaps opened by the spin-orbit coupling at the Dirac points, e.g., from 0.74 to 1.08 eV in BiX (X =H, F, Cl, and Br) monolayers. We find that the low-energy Hilbert subspace mainly consists of px and py orbitals from the group-V elements, and the giant first-order effective intrinsic spin-orbit coupling is from the on-site spin-orbit interaction. These features are quite distinct from those of group-IV monolayers such as graphene and silicene. There, the relevant orbital is pz and the effective intrinsic spin-orbit coupling is from the next-nearest-neighbor spin-orbit interaction processes. These systems represent the first real 2D honeycomb lattice materials in which the low-energy physics is associated with px and py orbitals. A spinful lattice Hamiltonian with an on-site spin-orbit coupling term is also derived, which could facilitate further investigations of these intriguing topological materials.

Liu, Cheng-Cheng; Guan, Shan; Song, Zhigang; Yang, Shengyuan A.; Yang, Jinbo; Yao, Yugui

2014-08-01

433

Forward Energy Flow, Central Charged-Particle Multiplicities, and Pseudorapidity Gaps in W and Z Boson Events from pp Collisions at $\\sqrt{s}$ = 7 TeV  

E-print Network

A study of forward energy flow and central charged-particle multiplicity in events with W and Z bosons decaying into leptons is presented. The analysis uses a sample of 7 TeV pp collisions, corresponding to an integrated luminosity of 36 inverse picobarns, recorded by the CMS experiment at the LHC. The observed forward energy depositions, their correlations, and the central charged-particle multiplicities are not well described by the available non-diffractive soft-hadron production models. A study of about 300 events with no significant energy deposited in one of the forward calorimeters, corresponding to a pseudorapidity gap of at least 1.9 units, is also presented. An indication for a diffractive component in these events comes from the observation that the majority of the charged leptons from the (W/Z) decays are found in the hemisphere opposite to the gap. When fitting the signed lepton pseudorapidity distribution of these events with predicted distributions from an admixture of diffractive (POMPYT) and ...

Chatrchyan, Serguei; Sirunyan, Albert M; Tumasyan, Armen; Adam, Wolfgang; Bergauer, Thomas; Dragicevic, Marko; Erö, Janos; Fabjan, Christian; Friedl, Markus; Fruehwirth, Rudolf; Ghete, Vasile Mihai; Hammer, Josef; Haensel, Stephan; Hoch, Michael; Hörmann, Natascha; Hrubec, Josef; Jeitler, Manfred; Kiesenhofer, Wolfgang; Krammer, Manfred; Liko, Dietrich; Mikulec, Ivan; Pernicka, Manfred; Rahbaran, Babak; Rohringer, Herbert; Schöfbeck, Robert; Strauss, Josef; Taurok, Anton; Teischinger, Florian; Trauner, Christine; Wagner, Philipp; Waltenberger, Wolfgang; Walzel, Gerhard; Widl, Edmund; Wulz, Claudia-Elisabeth; Mossolov, Vladimir; Shumeiko, Nikolai; Suarez Gonzalez, Juan; Bansal, Sunil; Benucci, Leonardo; De Wolf, Eddi A; Janssen, Xavier; Maes, Thomas; Mucibello, Luca; Ochesanu, Silvia; Roland, Benoit; Rougny, Romain; Selvaggi, Michele; Van Haevermaet, Hans; Van Mechelen, Pierre; Van Remortel, Nick; Blekman, Freya; Blyweert, Stijn; D'Hondt, Jorgen; Devroede, Olivier; Gonzalez Suarez, Rebeca; Kalogeropoulos, Alexis; Maes, Michael; Van Doninck, Walter; Van Mulders, Petra; Van Onsem, Gerrit Patrick; Villella, Ilaria; Charaf, Otman; Clerbaux, Barbara; De Lentdecker, Gilles; Dero, Vincent; Gay, Arnaud; Hammad, Gregory Habib; Hreus, Tomas; Marage, Pierre Edouard; Raval, Amita; Thomas, Laurent; Vander Marcken, Gil; Vander Velde, Catherine; Vanlaer, Pascal; Adler, Volker; Cimmino, Anna; Costantini, Silvia; Grunewald, Martin; Klein, Benjamin; Lellouch, Jérémie; Marinov, Andrey; Mccartin, Joseph; Ryckbosch, Dirk; Thyssen, Filip; Tytgat, Michael; Vanelderen, Lukas; Verwilligen, Piet; Walsh, Sinead; Zaganidis, Nicolas; Basegmez, Suzan; Bruno, Giacomo; Caudron, Julien; Ceard, Ludivine; Cortina Gil, Eduardo; De Favereau De Jeneret, Jerome; Delaere, Christophe; Favart, Denis; Giammanco, Andrea; Grégoire, Ghislain; Hollar, Jonathan; Lemaitre, Vincent; Liao, Junhui; Militaru, Otilia; Nuttens, Claude; Ovyn, Severine; Pagano, Davide; Pin, Arnaud; Piotrzkowski, Krzysztof; Schul, Nicolas; Beliy, Nikita; Caebergs, Thierry; Daubie, Evelyne; Alves, Gilvan; Brito, Lucas; De Jesus Damiao, Dilson; Pol, Maria Elena; Henrique Gomes E Souza, Moacyr; Aldá Júnior, Walter Luiz; Carvalho, Wagner; Da Costa, Eliza Melo; De Oliveira Martins, Carley; Fonseca De Souza, Sandro; Matos Figueiredo, Diego; Mundim, Luiz; Nogima, Helio; Oguri, Vitor; Prado Da Silva, Wanda Lucia; Santoro, Alberto; Silva Do Amaral, Sheila Mara; Sznajder, Andre; Souza Dos Anjos, Tiago; Bernardes, Cesar Augusto; De Almeida Dias, Flavia; Tomei, Thiago; De Moraes Gregores, Eduardo; Lagana, Caio; Da Cunha Marinho, Franciole; Mercadante, Pedro G; Novaes, Sergio F; Padula, Sandra; Darmenov, Nikolay; Genchev, Vladimir; Iaydjiev, Plamen; Piperov, Stefan; Rodozov, Mircho; Stoykova, Stefka; Sultanov, Georgi; Tcholakov, Vanio; Trayanov, Rumen; Dimitrov, Anton; Hadjiiska, Roumyana; Karadzhinova, Aneliya; Kozhuharov, Venelin; Litov, Leander; Mateev, Matey; Pavlov, Borislav; Petkov, Peicho; Bian, Jian-Guo; Chen, Guo-Ming; Chen, He-Sheng; Jiang, Chun-Hua; Liang, Dong; Liang, Song; Meng, Xiangwei; Tao, Junquan; Wang, Jian; Wang, Jian; Wang, Xianyou; Wang, Zheng; Xiao, Hong; Xu, Ming; Zang, Jingjing; Zhang, Zhen; Ban, Yong; Guo, Shuang; Guo, Yifei; Li, Wenbo; Mao, Yajun; Qian, Si-Jin; Teng, Haiyun; Zhu, Bo; Zou, Wei; Cabrera, Andrés; Gomez Moreno, Bernardo; Ocampo Rios, Alberto Andres; Osorio Oliveros, Andres Felipe; Sanabria, Juan Carlos; Godinovic, Nikola; Lelas, Damir; Lelas, Karlo; Plestina, Roko; Polic, Dunja; Puljak, Ivica; Antunovic, Zeljko; Dzelalija, Mile; Brigljevic, Vuko; Duric, Senka; Kadija, Kreso; Luetic, Jelena; Morovic, Srecko; Attikis, Alexandros; Galanti, Mario; Mousa, Jehad; Nicolaou, Charalambos; Ptochos, Fotios; Razis, Panos A; Finger, Miroslav; Finger Jr, Michael; Assran, Yasser; Ellithi Kamel, Ali; Khalil, Shaaban; Mahmoud, Mohammed; Radi, Amr; Hektor, Andi; Kadastik, Mario; Müntel, Mait; Raidal, Martti; Rebane, Liis; Tiko, Andres; Azzolini, Virginia; Eerola, Paula; Fedi, Giacomo; Czellar, Sandor; Härkönen, Jaakko; Heikkinen, Mika Aatos; Karimäki, Veikko; Kinnunen, Ritva; Kortelainen, Matti J; Lampén, Tapio; Lassila-Perini, Kati; Lehti, Sami; Lindén, Tomas; Luukka, Panja-Riina; Mäenpää, Teppo; Tuominen, Eija; Tuominiemi, Jorma; Tuovinen, Esa; Ungaro, Donatella; Wendland, Lauri; Banzuzi, Kukka; Karjalainen, Ahti; Korpela, Arja; Tuuva, Tuure; Sillou, Daniel; Besancon, Marc; Choudhury, Somnath; Dejardin, Marc; Denegri, Daniel; Fabbro, Bernard; Faure, Jean-Louis; Ferri, Federico; Ganjour, Serguei; Gentit, François-Xavier; Givernaud, Alain; Gras, Philippe

2012-01-01

434

Free-standing oxide superconducting articles  

DOEpatents

A substrate-free, free-standing epitaxially oriented superconductive film including a layer of a template material and a layer of a ceramic superconducting material is provided together with a method of making such a substrate-free ceramic superconductive film by coating an etchable material with a template layer, coating the template layer with a layer of a ceramic superconductive material, coating the layer of ceramic superconductive material with a protective material, removing the etchable material by an appropriate means so that the etchable material is separated from a composite structure including the template lay This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

Wu, Xin D. (Greenbelt, MD); Muenchausen, Ross E. (Espanola, NM)

1993-01-01

435

Superconducting Radio Frequency Technology: An Overview  

SciTech Connect

Superconducting RF cavities are becoming more often the choice for larger scale particle accelerator projects such as linear colliders, energy recovery linacs, free electron lasers or storage rings. Among the many advantages compared to normal conducting copper structures, the superconducting devices dissipate less rf power, permit higher accelerating gradients in CW operation and provide better quality particle beams. In most cases these accelerating cavities are fabricated from high purity bulk niobium, which has superior superconducting properties such as critical temperature and critical magnetic field when compared to other superconducting materials. Research during the last decade has shown, that the metallurgical properties--purity, grain structure, mechanical properties and oxidation behavior--have significant influence on the performance of these accelerating devices. This contribution attempts to give a short overview of the superconducting RF technology with emphasis on the importance of the material properties of the high purity niobium.

Peter Kneisel

2003-06-01

436

Energy scale directly related to superconductivity in high-Tc cuprates: Universality from the temperature-dependent angle-resolved photoemission of Bi2Sr2Ca2Cu3O10+?  

NASA Astrophysics Data System (ADS)

We have performed a temperature-dependent angle-resolved photoemission spectroscopy (ARPES) study of the trilayer high-Tc cuprate superconductor (HTSC) Bi2Sr2Ca2Cu3O10+? (Bi2223), and have shown that the Tc (=110 K) and “effective” superconducting gap ?sc defined at the end point of the Fermi arc follow the relationship 2?sc?4kBTc. Combining this result with previous ARPES results on single- and double-layer cuprates, we show that the relationship 2?sc?4kBTc holds for various HTSCs.

Ideta, Shin-Ichiro; Yoshida, Teppei; Fujimori, Atsushi; Anzai, Hiroaki; Fujita, Taisuke; Ino, Akihiro; Arita, Masashi; Namatame, Hirohumi; Taniguchi, Masaki; Shen, Zhi-Xun; Takashima, Kenichi; Kojima, Kenji; Uchida, Shin-Ichi

2012-03-01

437

Reply to ``Comment on `Muon-spin-rotation study of the superconducting properties of Mo3Sb7 ' ''  

NASA Astrophysics Data System (ADS)

Khasanov [preceding Comment, Phys. Rev. B82, 016501 (2010)]10.1103/PhysRevB.82.016501 have published a Comment aiming to show that our analysis with the assumption of two superconducting energy gaps in Mo3Sb7 [Tran , Phys. Rev. B 78, 172505 (2008)10.1103/PhysRevB.78.172505; Acta Mater. 56, 5694 (2008)10.1016/j.actamat.2008.07.048] cannot be justified. Further, they have shown that our heat-capacity data can be accounted for using a single isotropic gap with a small amount of impurity but failed to mention the quantitative amount of the impurity. In this Reply, we address the key issues raised by Khasanov in their Comment and show again with our analysis that our ?SR data fit better with two energy gaps. Furthermore, our reanalysis of the heat-capacity data based on a single gap with the impurity term reveals that one needs 7.3% of the impurity to account for the low-temperature heat capacity, which is very high and has not been seen in our x-ray diffraction or electron probe micro-analyzer studies. We also discuss the point on the London model raised by Khasanov Further, we present some experimental evidence that supports the two-gap model over the one-gap model.

Tran, V. H.; Hillier, A. D.; Adroja, D. T.

2010-07-01

438

One Gap. Two Gaps. Universality in High Temperature Superconductors  

NASA Astrophysics Data System (ADS)

One of the goals in contemporary condensed matter physics, is to understand various emergent properties of matter due to many body interactions --- e.g. superfluidity, superconductivity, colossal magnetoresistance and so on. Superconductors, discovered more than a century ago, have the remarkable property of zero resistance to electrical current below certain temperatures, commonly known as critical temperatures (Tc). The Tc value for conventional superconductor is relatively low, less than 30K, while it could be as high as 150K for a new class of materials, known as high temperature superconductors (HTSCs). The mechanism behind superconductivity in conventional superconductors can be well understood under the framework of the famous BCS (Bardeen, Cooper, Schrieffer) theory, while for HTSCs, it is still a mystery. Angle Resolved Photoemission Spectroscopy (ARPES), which directly probes the momentum space structure of a physical system, has been instrumental to provide new insights in understanding various strongly correlated systems --- particularly the HTSC materials. In this thesis, I will present and discuss our recent research on various Bi2212 HTSCs using ARPES. For the first time, we provided the spectroscopic evidence for the three distinct phases in the normal state of Bi2212 HTSC. By comparing the systematic ARPES data of pure Bi2212 and cation-doped Bi2212 HTSCs, we found that introducing different elements would not only change the carrier concentration, but also create additional disorders inside the system, which is responsible for the different spectroscopic properties. In additon, we found that the deviation from d-wave gap anisotropy in cation-doped Bi2212 is correlated to the lack of coherent spectral peaks. I will also give an overview of the synthesis of La-doped Bi2212 single crystals by using floating zone technique. Even though the La content varies along the crystal growth direction, our crystals are of the pure Bi2212 crystal structure, and their carrier concentrations are in the underdoped side of the superconducting dome.

Zhao, Junjing

439

?-pairing superconductivity in the negative-U Hubbard model  

NASA Astrophysics Data System (ADS)

In this Letter we study the ?-pairing superconductivity in the negative- U Hubbard model using a mean-field approach, find a relationship between the zero temperature gap and the doping concentration, and derive an integral equation for the transition temperature which is numerically solved. Our results are in good agreement, within a considerably wide range of the doping concentration, with the familiar experiments on high- Tc superconductivity.

Qiu, X. M.; Wang, Z. J.; Li, H. X.; Xiao, Y. G.

1993-11-01

440

Optimized configurations of autostable superconducting magnetic bearings for practical applications  

SciTech Connect

In order to establish an optimized bearing design for a flywheel for energy storage, the authors have studied model bearing configurations involving bulk YBCO pellets and double-dipole magnet configurations. They were interested to see what is the correlation between the maximum attainable levitation force, measured for a typical bearing gap of 3 mm, and the separation between the magnetic poles. Equal polarity (north-north) and alternate polarity (north-south) configurations were investigated. The maximum levitation force was obtained with the alternate polarity arrangement for a separation between the magnetic poles of 6 mm. It represents an increase of 19% compared to a non-optimized configuration. The experiments demonstrate that configurations of superconducting magnetic bearings can