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1

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

SciTech Connect

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

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

2007-05-26

2

Effect of Magnetic Field on Thermal Conductivity and Energy Gap of Superconducting Films  

Microsoft Academic Search

We have measured the change in the thermal conductivity of superconducting tin, indium, and lead films upon application of a magnetic field in the plane of the film. These experiments were undertaken to explore the dependence of the energy gap upon magnetic field and to determine the thermodynamic order of the field-induced transition in films. Within the range of temperatures

D. E. Morris; M. Tinkham

1964-01-01

3

Electronic structure and superconducting energy gap in Rb3C60 single crystals studied by photoemission spectroscopy  

NASA Astrophysics Data System (ADS)

We report an ultrahigh-resolution photoemission study of Rb3C60 single crystals (Tc=30.5 K) and the measurement of the superconducting energy gap. The crystals were cleaved at 13 K to expose the (111) plane. They show a sharp Fermi cutoff above Tc and a superconducting gap opening below Tc (2?/kBTc~4.1 at 13 K). The valence band shows a ~0.15-eV-wide band near EF that is consistent with calculations, and a broad band at 0.15-1.3 eV, possibly contributed by the surface C60 layer.

Gu, Chun; Veal, B. W.; Liu, R.; Paulikas, A. P.; Kostic, P.; Ding, H.; Gofron, K.; Campuzano, J. C.; Schlueter, J. A.; Wang, H. H.; Geiser, U.; Williams, J. M.

1994-12-01

4

Direct observation of a nodeless superconducting energy gap in the optical conductivity of iron-pnictides  

Microsoft Academic Search

The temperature-dependent optical reflectivity and complex transmissivity of an epitaxially grown Ba(Fe$_{0.9}$Co$_{0.1}$)$_2$As$_2$ thin film were measured and the optical conductivity and permittivity evaluated over a wide frequency range. The opening of the superconducting gap $2\\\\Delta_0 = 3.7$ meV below $T_c\\\\approx 20$ K is {\\\\em directly} observed by a completely vanishing optical conductivity. The temperature and frequency dependent electrodynamic properties of

B. Gorshunov; D. Wu; A. A. Voronkov; P. Kallina; K. Iida; S. Haindl; F. Kurth; L. Schultz; B. Holzapfel; M. Dressel

2009-01-01

5

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

Microsoft Academic Search

The detailed angular dependence of the Fermi radius k\\/sub F\\/, the Fermi velocity v\\/sub F\\/(k), the many-body enhancement factor lambda(k), and the superconducting energy gap ..delta..(k), for electrons on the Fermi surface of Nb are derived with use of the de Haas--van Alphen (dHvA) data of Karim, Ketterson, and Crabtree (J. Low Temp. Phys. 30, 389 (1978)), a Korringa-Kohn-Rostoker parametrization

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

1987-01-01

6

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

Microsoft Academic Search

The detailed angular dependence of the Fermi radius kF, the Fermi velocity vF(k), the many-body enhancement factor lambda(k), and the superconducting energy gap Delta(k), for electrons on the Fermi surface of Nb are derived with use of the de Haas-van Alphen (dHvA) data of Karim, Ketterson, and Crabtree [J. Low Temp. Phys. 30, 389 (1978)], a Korringa-Kohn-Rostoker parametrization scheme, and

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

1987-01-01

7

Anisotropic energy gaps of iron-based superconductivity from intraband quasiparticle interference in LiFeAs.  

PubMed

If strong electron-electron interactions between neighboring Fe atoms mediate the Cooper pairing in iron-pnictide superconductors, then specific and distinct anisotropic superconducting energy gaps ?(i)(k) should appear on the different electronic bands i. Here, we introduce intraband Bogoliubov quasiparticle scattering interference (QPI) techniques for determination of ?(i)(k) in such materials, focusing on lithium iron arsenide (LiFeAs). We identify the three hole-like bands assigned previously as ?, ?(2), and ?(1), and we determine the anisotropy, magnitude, and relative orientations of their ?(i)(k). These measurements will advance quantitative theoretical analysis of the mechanism of Cooper pairing in iron-based superconductivity. PMID:22556247

Allan, M P; Rost, A W; Mackenzie, A P; Xie, Yang; Davis, J C; Kihou, K; Lee, C H; Iyo, A; Eisaki, H; Chuang, T-M

2012-05-01

8

Anisotropic Energy Gaps of Iron-Based Superconductivity from Intraband Quasiparticle Interference in LiFeAs  

SciTech Connect

If strong electron-electron interactions between neighboring Fe atoms mediate the Cooper pairing in iron-pnictide superconductors, then specific and distinct anisotropic superconducting energy gaps {Delta}{sub i}(k) should appear on the different electronic bands i. Here, we introduce intraband Bogoliubov quasiparticle scattering interference (QPI) techniques for determination of {Delta}{sub i}(k) in such materials, focusing on lithium iron arsenide (LiFeAs). We identify the three hole-like bands assigned previously as {gamma}, {alpha}{sub 2}, and {alpha}{sub 1}, and we determine the anisotropy, magnitude, and relative orientations of their {Delta}{sub i}(k). These measurements will advance quantitative theoretical analysis of the mechanism of Cooper pairing in iron-based superconductivity.

Davis J. C.; Allan, M.P.; Rost, A.W.; Mackenzie, A.P.; Xie, Y.; Kihou, K.; Lee, C.H.; Iyo, A.; Eisaki, H.; Chuang, T.-M.

2012-05-04

9

Normal state electronic structure and the superconducting energy gap in HTSC's as determined from photoemission spectroscopy  

SciTech Connect

Photoemission spectroscopy has been utilized to determine the electronic structure of high-T{sub c} materials. The observation of dispersive bands at E{sub F} suggests a Fermi surface similar to that obtained from a band calculation. The results apparently are not inconsistent with the notion of a correlated Fermi liquid consisting of hybridized p-d bands. However, it is becoming more and more difficult to distinguish between Fermi liquid behavior in the new high-T{sub c} superconductors and behavior expected on the basis of the novel new non-Fermi liquid theories. The differences are now predicted to be on an energy scale smaller than our experimental resolution. We point out that, while deviations from simple band theory certainly do exist in the form of core and valence band satellites, band narrowing, and rapid photoemission peak broadening away from E{sub F}, there are sufficient agreements with the overall DOS that it should be considered a good starting point for the electronic structure. For example, the calculated Fermi surface for both the 123 and 2212 structures is reasonably well reproduced experimentally and the bands at E{sub F} consist of p-d hybridized orbitals just as predicted by local density functional theory. Our spectra clearly show that a BCS-like DOS is obtained at the Fermi energy as a gap opens up below T{sub c}. This is just one more indication that the old conventional models should be considered more seriously. 18 refs., 6 figs.

Arko, A.J.; List, R.S.; Bartlett, R.J.; Cheong, S.W.; Fisk, Z.; Thompson, J.D. (Los Alamos National Lab., NM (USA)); Olson, C.G.; Yang, A.B.; Liu, R.; Gu, C. (Ames Lab., IA (USA)); Veal, B.W.; Liu, J.Z.; Paulikas, A.P.; Vandervoort, K.; Claus, H.; Campuzano, J.C. (Argonne National Lab., IL (USA))

1989-01-01

10

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

11

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

Microsoft Academic Search

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 pm in a quasioptical mixer configuration employing

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

1999-01-01

12

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

13

The soft superconducting gap in semiconductor Majorana nanowires  

NASA Astrophysics Data System (ADS)

We theoretically consider the mysterious topic of the soft gap in the tunneling conductance of the proximity-induced superconductivity in a semiconductor-superconductor hybrid structure, where the observation of a zero-bias conductance peak has created considerable excitement because of its possible connection with the elusive zero-energy Majorana mode. The observed experimental superconducting tunneling gap in the semiconductor nanowire looks v-shaped with considerable subgap conductance even at very low temperatures in sharp contrast to the theoretically expected hard BCS gap with exponentially suppressed subgap conductance. We systematically study, by solving the appropriate BdG equations both numerically and analytically, a number of physical mechanisms (e.g. magnetic and non-magnetic disorder, finite temperature, dissipative Cooper pair breaking, interface fluctuations), which could, in principle, lead to a soft gap, finding that only the interface fluctuation effect is a quantitatively and qualitatively viable mechanism that is consistent with the experimental observations. Our work indicates that improving the quality of the superconductor-semiconductor interface would go a long way in enhancing the gap in the hybrid structures being used for studying the Majorana mode.

Takei, So; Fregoso, Benjamin M.; Hui, Hoi-Yin; Lobos, Alejandro M.; Das Sarma, Sankar

2013-03-01

14

Superconducting gaps and pseudogaps in a composite model of two-component cuprate  

NASA Astrophysics Data System (ADS)

A descriptive interband model of cuprate superconductivity with two-subbands of the defect-component is developed. These are related to ``hot'' and ``cold'' regions of the momentum space. Two pseudogaps appear as the minimal quasiparticle excitations energies. The smaller one transforms with extended doping to the superconducting gap of the itinerant component. At a critical overdoping concentration the larger pseudogap transforms into the defect component superconducting gap. The presence of two pseudogaps in the underdoped state and the extension of the larger pseudogap to overdoping agree with the recent experimental data. The relations between various observed cuprate gaps and other properties are discussed.

Kristoffel, N.; Rubin, P.

2004-02-01

15

Direct observation of superconducting gaps in iron-based superconductors by laser ARPES  

NASA Astrophysics Data System (ADS)

We have developed a new apparatus for carrying out ultra-high energy resolution laser-excited angle-resolved photoemission spectroscopy (laser ARPES). The achieved energy resolution is ~ 70 ?eV at a sample temperature ~ 1.5 K. As a test case, we have measured the superconducting gap of elemental metal Sn (Tc = 3.7 K). We have used this laser-ARPES apparatus, to directly observe the superconducting gap of various iron-based superconductors. The spectra of FeTe0.6Se0.4 below Tc show a very clear temperature dependent superconducting coherence peak. Preliminary momentum-dependent results indicate an anisotropic superconducting gap in FeTe0.6Se0.4.

Okazaki, Kozo

2013-07-01

16

Triple-gap superconductivity of MgB2-(La,Sr)MnO3 composite  

NASA Astrophysics Data System (ADS)

The interplay of superconductivity and magnetism was studied in a composite prepared from ferromagnetic half-metallic La0.67Sr0.33MnO3 (LSMO) nanoparticles and the s-wave superconductor MgB2. A few principal effects have been found. With the onset of MgB2 superconductivity, a spectacular drop of the sample resistance was detected and complete superconductivity was observed at temperatures up to 20 K. The basic nanocomposite characteristics (critical temperature, current-voltage dependence, percolation threshold, etc.) are strongly affected by the half-metallic LSMO and, most probably, cannot be quantitatively explained within the framework of a conventional percolation scenario. Point contact (PC) spectroscopy was used to measure directly the superconducting energy coupling. For small voltage, an excess current and doubling of the PC normal-state conductance were detected. Conductance peaks corresponding to three energy gaps are clearly observed. Two of these gaps we identified as enhanced ?? and ?? gaps originating from the MgB2; the third gap ?tr is more than three times larger than the largest MgB2 gap. The temperature behavior of ?tr does not follow the BCS dependence. The experimental results have a natural and qualitative explanation within the phase-coherency scenario of proximity-induced superconductivity. Specifically, at low temperature, a p-wave spin-triplet condensate with pairing energy ?tr is essentially sustained in LSMO but is incapable of displaying a long-range superconducting response because of a phase-disordered state. The proximity coupling to MgB2 restores the long-range phase coherency of the superconducting state, which, in turn, enhances the superconducting state of the MgB2.

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

2012-09-01

17

Soft superconducting gap in semiconductor Majorana nanowires.  

PubMed

We theoretically consider the ubiquitous soft gap measured in the tunneling conductance of semiconductor-superconductor hybrid structures, in which recently observed signatures of elusive Majorana bound states have created much excitement. We systematically study the effects of magnetic and nonmagnetic disorder, temperature, dissipative Cooper pair breaking, and interface inhomogeneity, which could lead to a soft gap. We find that interface inhomogeneity with moderate dissipation is the only viable mechanism that is consistent with the experimental observations. Our work indicates that improving the quality of the superconductor-semiconductor interface should result in a harder induced gap. PMID:23683232

Takei, So; Fregoso, Benjamin M; Hui, Hoi-Yin; Lobos, Alejandro M; Das Sarma, S

2013-04-30

18

Optical investigations of the superconducting energy gap in b00-(BEDT-TTF)2SF5CH2CF2SO3  

SciTech Connect

The organic salt {beta}''-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} is a two-dimensional metal with a quarter-filled conduction band. In the metallic state the optical conductivity evidences interaction of the charge carriers with charge-order fluctuations that become stronger as temperature decreases. In the superconducting phase below T{sub c} {approx} 5K, indications of the superconducting gap with 2{Delta} {approx} 12 cm{sup -1} are observed in the optical spectrum, corresponding to 2{Delta}/k{sub B}T{sub c} {approx} 3.3. Its temperature and magnetic field dependences are also consistent with predictions by the BCS theory of a weakly coupled superconductor. The conductivity ratio {sigma}{sub 1}(T = 1.75 K)/{sigma}{sub 1}(10 K) indicates the opening of the superconducting gap in {beta}''-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}.

Kaiser, S.; Yasin, S.; Drichko, N.; Dressel, M.; Room, T.; Huvonen, D.; Nagel, U.; Gard, G. L.; Schlueter, J. A. (Materials Science Division); (Universitat Stuttgart); (Nat. Inst. Chem. Phys. Biophys.); (Portland State Univ.)

2012-01-01

19

On Pokrovskii's anisotropic gap equations in superconductivity theory  

NASA Astrophysics Data System (ADS)

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

Yang, Yisong

2003-11-01

20

Perfect switching of the spin polarization in a ferromagnetic gapless graphene/superconducting gapped graphene junction  

NASA Astrophysics Data System (ADS)

With the fabrication of gapped graphene, interest in the tunneling spectroscopy in graphene-based FG/SG junctions in which one side consists of a gapless ferro-magnetic graphene (FG) and the other side, of a gapped superconducting graphene (SG) has arisen. The carriers in the gapless (gapped) graphene are 2D relativistic particles having an energy spectrum given by E=?2vF2k2+(mvF2)2 (where mvF2 is the gap and vF is the Fermi velocity). The spin currents in this FG/SG junction are obtained within the framework of the extended Blonder-Tinkham-Klapwijk (BTK) formalism. The effects of the superconducting energy gap in SG, of the gap mvF2 which opened in the superconducting graphene, of the exchange field in FG, of the spin-dependent specular Andreev reflection, of the effective Fermi energy (EFF) of FG and of the bias voltage across the junction (V) are simulated. It is seen that by adjusting EFF or V, the spin polarization (defined as SP(%) = 100% × (G? - G?)/(G? + G?)) can be switched from a pure spin up (SP = +100%) state to pure spin down (SP = -100%) state.

Soodchomshom, Bumned; Tang, I.-Ming; Hoonsawat, Rassmidara

2010-01-01

21

Direct observation of superconducting gaps in iron-based superconductors by laser ARPES  

NASA Astrophysics Data System (ADS)

We have developed a new apparatus for carrying out ultra-high energy resolution laser-based angle-resolved photoemission spectroscopy (laser ARPES). From the spectra of the evaporated gold and superconducting (SC) gap of Sn (Tc = 3.7 K) sample, we conclude that the best energy resolution is ˜70 ?eV and the lowest sample temperature is ˜1.0 K. We have used this laser-ARPES apparatus, to directly observe the SC gap of various iron-based superconductors. The spectra of FeTe0.6Se0.4 below Tc show a very clear temperature-dependent superconducting coherence peak, and the SC-gap nodes of KFe2As2 are found in the middle Fermi surface (FS) around the FS angle ? = ±5.0°.

Okazaki, Kozo

2013-11-01

22

Multiple Superconducting Gaps, Anisotropic Spin Fluctuations and Spin-Orbit Coupling in Iron-Pnictides  

NASA Astrophysics Data System (ADS)

This article reviews the NMR and NQR studies on iron-based high-temperature superconductors by the IOP/Okayama group. It was found that the electron pairs in the superconducting state are in the spin-singlet state with multiple fully-opened energy gaps. The antiferromagnetic spin fluctuations in the normal state are found to be closely correlated with the superconductivity. Also, the antiferromagnetic spin fluctuations are anisotropic in the spin space, which is different from the case in copper oxide superconductors. This anisotropy originates from the spin-orbit coupling and is an important reflection of the multiple-bands nature of this new class of superconductors.

Yang, Jie; Zheng, Guo-Qing

2012-06-01

23

Mathematical analysis of the multiband BCS gap equations in superconductivity  

NASA Astrophysics Data System (ADS)

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

Yang, Yisong

2005-01-01

24

Superconducting gap structure of the 115s revisited  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

25

Evidence for fully gapped strong coupling s-wave superconductivity in Bi4O4S3  

NASA Astrophysics Data System (ADS)

We report on the superconducting gap and pairing symmetry in the layered superconductor Bi4O4S3. The measurement of temperature dependence of magnetic penetration depth was carried out using the tunnel diode oscillator technique. It is observed that Bi4O4S3 is a conventional s-wave type superconductor with a fully developed gap. The zero-temperature value of the superconducting energy gap ?0 was found to be 1.54 meV, corresponding to the ratio 2?0/kBTc = 7.2 which is much higher than the BCS value of 3.53. In the superconducting range, superfluid density is very well described by the single gap s-wave model.

Shruti; Srivastava, P.; Patnaik, S.

2013-08-01

26

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

PubMed

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

Bara?ski, J; Doma?ski, T

2013-10-09

27

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

NASA Astrophysics Data System (ADS)

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

Bara?ski, J.; Doma?ski, T.

2013-10-01

28

Superconducting magnetic energy storage  

SciTech Connect

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

Hassenzahl, W.

1988-08-01

29

Superconducting Gap and Strong In-Plane Anisotropy in Untwinned YBa2Cu3O7-delta  

Microsoft Academic Search

With significantly improved sample quality and instrumental resolution, we clearly identify in the ( pi,0) photoemission spectra from YBa2Cu3O6.993, in the superconducting state, the long-sought ``peak-dip-hump'' structure. This advance allows us to investigate the large a-b anisotropy of the in-plane electronic structure including, in particular, a 50% difference in the magnitude of the superconducting gap that scales with the energy

D. H. Lu; D. L. Feng; N. P. Armitage; K. M. Shen; A. Damascelli; C. Kim; F. Ronning; Z.-X. Shen; D. A. Bonn; R. Liang; W. N. Hardy; A. I. Rykov; S. Tajima

2001-01-01

30

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

31

Gluon self-energy effect on color-flavor-locked gap equation  

SciTech Connect

I investigate the effects of the gluon self-energy in the color-flavor-locked phase of color superconductivity on the value of the gap. The light plasmon modes, which appear for energies smaller than twice the gap energy, provide the largest contribution. They modify the subsubleading term in the solution of the gap equation.

Malekzadeh, H. [Institut fuer Theoretische Physik, Westfaelische Wilhelms-Universitaet Muenster, Wilhelm-Klemm-Strasse 9, 48149 Muenster (Germany)

2009-02-01

32

First High Power Test Results for 2.1 GHz Superconducting Photonic Band Gap Accelerator Cavities  

NASA Astrophysics Data System (ADS)

We report the results of the recent high power testing of superconducting radio frequency photonic band gap (PBG) accelerator cells. Tests of the two single-cell 2.1 GHz cavities were performed at both 4 and 2 K. An accelerating gradient of 15MV/m and an unloaded quality factor Q0 of 4×109 were achieved. It has been long realized that PBG structures have great potential in reducing long-range wakefields in accelerators. A PBG structure confines the fundamental TM01-like accelerating mode, but does not support higher order modes. Employing PBG cavities to filter out higher order modes in superconducting particle accelerators will allow suppression of dangerous beam instabilities caused by wakefields and thus operation at higher frequencies and significantly higher beam luminosities. This may lead towards a completely new generation of colliders for high energy physics and energy recovery linacs for the free-electron lasers.

Simakov, Evgenya I.; Haynes, W. Brian; Madrid, Michael A.; Romero, Frank P.; Tajima, Tsuyoshi; Tuzel, Walter M.; Boulware, Chase H.; Grimm, Terry L.

2012-10-01

33

Properties of High Temperature Superconducting Magnet With Optimized Air Gap Between Pancake Windings  

Microsoft Academic Search

In a magnet with pancake windings, inserting a gap between the pancake windings can increase the central magnetic field. This paper shows the optimized length of each gap is able to maximize the central magnetic field. Inserting a gap also im- proves field uniformity because the pancake windings are spread across a wider area. A high temperature superconducting (HTS) magnet

Youngmin Kim; Myunghwan Ku; Gueesoo Cha

2011-01-01

34

Andreev spectroscopy of FeSe: Evidence for two-gap superconductivity  

SciTech Connect

Current-voltage characteristics (CVCs) of Andreev superconductor-constriction-superconductor (ScS) contacts in polycrystalline samples of FeSe with the critical temperature T{sub C} = (12 {+-} 1) K have been measured using the break-junction technique. In Sharvin-type nanocontacts, two sets of subharmonic gap structures were detected due to multiple Andreev reflections, indicating the existence of two nodeless superconducting gaps {Delta}{sub L} = (2.75 {+-} 0.3) meV and {Delta}{sub S} = (0.8 {+-} 0.2) meV. Well-shaped CVCs for stacks of Andreev contacts with up to five contacts were observed due to the layered structure of FeSe (the intrinsic multiple Andreev reflections effect). An additional fine structure in the CVCs of Andreev ScS nanocontacts is attributed to the existence of a Leggett mode. A linear relation between the superconducting gap {Delta}{sub L} and the magnetic resonance energy E{sub magres} Almost-Equal-To 2{Delta}{sub L} is found to be valid for layered iron pnictides.

Ponomarev, Ya. G.; Kuzmichev, S. A.; Mikheev, M. G.; Sudakova, M. V.; Tchesnokov, S. N.; Shanygina, T. E.; Volkova, O. S.; Vasiliev, A. N., E-mail: vasil@mig.phys.msu.ru [Moscow State University, Low Temperature Physics and Superconductivity Department (Russian Federation); Wolf, Th. [Institut fur Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany)

2011-09-15

35

Generation and detection of high-energy phonons by superconducting junctions  

Microsoft Academic Search

It is demonstrated that phonons with energy greater than the superconducting gap escape Sn junction generators in sufficient number to be detected by Pb superconducting junctions. The phonon transconductance signal, observed with high generator bias, can be largely understood in terms of the relaxation of injected quasiparticles which emit high-energy phonons. The high-energy phonons are in turn reabsorbed to form

I. L. Singer; W. E. Bron

1976-01-01

36

Generation and detection of high-energy phonons by superconducting junctions  

Microsoft Academic Search

It is demonstrated that phonons, with energy greater than the superconducting gap, escape Sn junction generators in sufficient number to be detected by Pb superconducting junctions. The phonon transconductance signal, observed with high generator bias, can be largely understood in terms of the relaxation of injected quasiparticles which emit high-energy phonons. The high-energy phonons are in turn reabsorbed to form

I. L. Singer; W. E. Bron

1976-01-01

37

Superconducting energy storage magnet  

SciTech Connect

A superconducting magnet is described comprising: (a) a coil of turns of conductor including at least a superconducting composite material, the turns of conductor lying substantially on a surface which defines a frustum of a cone having a wide end and a narrow end, such that the outward pressure as a result of current flowing through the conductor in the magnetic field produced by the magnet at the wide end of the coil is less than the outward pressure at the narrow end of the coil; and (b) means for supporting the coil of conductors in the magnet to carry the outward pressure imposed on the coil by the interaction of the current flowing in the conductor with the magnetic field, wherein the turns of the conductor in the coil have outwardly bowed ripples therein and inner portions between the ripples with the ripple pattern extending around the circumferential periphery of the magnet structure, and wherein the means for supporting includes support struts extending from a surrounding support mass to engage the conductor at the inwardly bowed portions of the rippled conductor forming the coil.

Boom, R.W.; Eyssa, Y.M.; Abdelsalam, M.K.; Xianrui Huang.

1993-08-17

38

NUCLEAR AND HEAVY ION PHYSICS: An Abelian Ward identity and the vertex corrections to the color superconducting gap  

NASA Astrophysics Data System (ADS)

We derive an Abelian-like Ward identity in the 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.

Xu, Hao-Jie; Wang, Qun

2009-09-01

39

An Attempt at a Resonating Mean-Field Theoretical Description of Thermal Behavior of Two-Gap Superconductivity  

NASA Astrophysics Data System (ADS)

The resonating mean-field theory (Res-MFT) has been applied and shown to effectively describe two-gap superconductivity (SC). Particularly at T = 0 using a suitable chemical potential, the two-gap SC in MgB2 has been well described by the Res-Hartree-Bogoliubov theory (Res-HBT). The Res-HB ground state generated with HB wavefunctions almost exhausts the ground-state correlation energy in all the correlation regimes. In this paper we make an attempt at a Res-MF theoretical description of thermal behavior of the two-gap SC. In an equal energy-gap case we find a new formula leading to a higher critical temperature Tc than the Tc of the usual HB formula.

Nishiyama, Seiya; da Providência, João; Providência, Constança; Ohnishi, Hiromasa

2013-07-01

40

Superconducting energy gap and c-axis plasma frequency of (Nd,Sm)FeAsO0.82F0.18 superconductors from infrared ellipsometry.  

PubMed

We present far-infrared ellipsometric measurements of polycrystalline samples of the pnictide superconductor RFeAsO0.82F0.18 (R=Nd and Sm). We find evidence that the electronic properties are strongly anisotropic such that the optical spectra are dominated by the weakly conducting c-axis response similar to the cuprate high-temperature superconductors. We deduce an upper limit of the c-axis superconducting plasma frequency of omega pl,c(SC)< or =260 cm(-1) corresponding to a lower limit of the c-axis magnetic penetration depth of lambda c > or =6 microm and lambda c/lambda ab > or =30 as compared to lambda ab=185 nm from muon spin rotation [A. Drew, arXiv:0805.1042 [Phys. Rev. Lett. (to be published)

Dubroka, A; Kim, K W; Rössle, M; Malik, V K; Drew, A J; Liu, R H; Wu, G; Chen, X H; Bernhard, C

2008-08-29

41

Doping - dependent anisotropy of the superconducting gap in underdoped pnictide superconductors  

NASA Astrophysics Data System (ADS)

The in-plane London penetration depth, ??(T), was studied in single crystals of Ba1-xKxFe2As2 (``Ba122") and Ca10(Pt3As8)[(Fe1-xPtx)2As2]5 (``10-3-8"). Whereas in Ba122 magnetism and superconductivity coexist in the underdoped regime, the 10-3-8 compound exhibits a clear separation of two order parameters. By comparing the results obtained in these two systems, we could study general features of the superconducting gap structure as function of doping in the underdoped regime. Similar to all other pnictides, the low-temperature variation of London penetration depth exhibits a power-law behavior, ??(T)= AT^n, in both systems. Moving towards the underdoped edge of the superconducting dome, the exponent n decreases well below scattering - limited value of n=2 and, at the same time, the pre-factor A increases. Both trends indicate an increasing anisotropy of the superconducting gap in more underdoped compounds. These and previous results suggest that the development of the superconducting gap anisotropy towards the underdoped edge of the superconducting dome is an intrinsic property of iron pnictides, similar to the known tendency on the overdoped side where magnetism and superconductivity do not interfere.[4pt] In collboration with M.A. Tanatar, H. Kim, The Ames Laboratory; Bing Shen, Hai-Hu Wen, Nanjing University; and N. Ni, R.J. Cava, Princeton University.

Prozorov, Ruslan

2012-02-01

42

The energy band gap of cadmium sulphide  

Microsoft Academic Search

The energy band gap of cadmium sulphide has been determined for the bulk specimen and films prepared by thermal evaporation on glass substrates in vacuum. The energy band gap of the specimens were deduced from their temperature variation of their resistance in the intrinsic range. The results reveal higher energy gaps in the films than in the bulk specimen. The

F. Boakye; D. Nusenu

1997-01-01

43

Direct observation of the superconducting energy gap in the optical conductivity of the iron pnictide superconductor Ba(Fe0.9Co0.1)2As2  

Microsoft Academic Search

The temperature-dependent optical reflectivity and complex transmissivity of an epitaxially grown Ba(Fe0.9Co0.1)2As2 thin film were measured over a wide frequency range (4-35000cm-1) . The opening of the superconducting gap 2Delta0=(3.7±0.3)meV is directly observed by vanishing optical conductivity at 30cm-1 for T

B. Gorshunov; D. Wu; A. A. Voronkov; P. Kallina; K. Iida; S. Haindl; F. Kurth; L. Schultz; B. Holzapfel; M. Dressel

2010-01-01

44

Doping-induced evolution of superconducting gap in iron-based superconductors: a point-contact Andreev reflection study of BaNi-122 single crystals  

NASA Astrophysics Data System (ADS)

We report a systematic investigation on c-axis point-contact Andreev reflection (PCAR) in superconducting BaFe2-xNixAs2 single crystals from underdoped to overdoped regions (0.075 < x < 0.15). At optimal doping (x = 0.1) the PCAR spectrum feature a dip-hump structure at the edge of the conductance gap, which corresponds to electron-boson coupling mode in energy scale. Two-superconducting-gap structure is resolved in the PCAR spectroscopy. In the s± scenario, quantitative analysis using a generalized Blonder-Tinkham-Klapwijk (BTK) formalism with two gaps: one isotropic and another angle dependent, suggest a nodeless state in strong-coupling limit with gap minima on the Fermi surfaces. Upon crossing above the optimal doping (x > 0.1), the PCAR spectrum show an in-gap sharp narrow peak at low bias, in contrast to the case of underdoped samples (x < 0.1), signaling the onset of deepened gap minima or nodes in the superconducting gap. This result provides evidence of the modulation of the gap amplitude with doping concentration, consistent with the calculations for the orbital dependent pair interaction mediated by the antiferromagne

Ren, Cong; Wang, Zhaosheng; Shen, Bing; Luo, Huiqian; Lu, Xingye; Wang, Zhenyu; Zhu, Jun; Gong, Jun; Hou, Xingyuan; Li, Chunhong; Shan, Lei; Yang, Huan; Wen, Haihu

2012-02-01

45

A Superconductive, Low-Beta Single-Gap Cavity for a High Intensity Proton Linac  

Microsoft Academic Search

A single gap, 352 MHz superconducting reentrant cavity for 5-100 MeV beams has been designed and it is presently under construction. This development is being done in the framework of a 30 mA proton linac project for nuclear waste transmutation. Mechanical, cryogenic and rf design characteristics of such cavities will be described.

Alberto Facco; V. Zviagintsev

2000-01-01

46

Observation of multiple superconducting gaps in Fe1+yTe1-xSex via a nanoscale approach to point-contact spectroscopy  

NASA Astrophysics Data System (ADS)

We report a novel experimental approach to point-contact Andreev reflection spectroscopy with diagnostic capability via a unique design for nanoscale normal metal/superconductor devices with excellent thermomechanical stability, and have employed this method to unveil the existence of two superconducting energy gaps in iron chalcogenide Fe1+yTe1-xSex, which is crucial for understanding its pairing mechanism. This work opens up new opportunities to study gap structures in superconductors and elemental excitations in solids.

Peng, Haibing; De, Debtanu; Wu, Zheng; Diaz-Pinto, Carlos

2012-11-01

47

Direct band-gap energy of semiconductors  

Microsoft Academic Search

Empirical formulae are obtained relating the direct band-gap energy of semiconductors and the mean atomic number of the constituent atoms. The formulae are used to indicate doubtful values and to obtain the values of bowing parameters of energy band-gaps of ternaries and quaternaries. Derived values of the bowing parameter give band-gap energies of ternaries and quaternaries agreeing with experiments to

B. R. Nag

1995-01-01

48

Superconducting magnets in high energy physics  

SciTech Connect

The applications of superconducting magnets in high energy physics in the last ten years have made feasible developments which are vital to high energy research. These developments include high magnetic field, large volume detectors, such as bubble chambers, required for effective resolution of high energy particle trajectories, particle beam transport magnets, and superconducting focusing and bending magnets for the very high energy accelerators and storage rings needed to pursue the study of interactions between elementary particles. The acceptance of superconductivity as a proven technology in high energy physics was reinforced by the recognition that the existing large accelerators using copper-iron magnets had reached practical limits in terms of magnetic field intensity, cost, space, and energy usage, and that large-volume, high-field, copper-iron magnets were not economically feasible. Some of the superconducting magnets and associated systems being used in and being developed for high energy physics are described.

Prodell, A G

1978-01-01

49

On kinetic energy stabilized superconductivity in cuprates  

SciTech Connect

The possibility of kinetic energy driven superconductivity in cuprates as was recently found in the tJ model is discussed. We argue that the violation of the virial theorem implied by this result is serious and means that the description of superconductivity within the tJ model is pathological.

Singh, David J [ORNL

2007-01-01

50

Neutron Diffraction Study on Stoner Gap in the Superconducting Ferromagnet UGe2  

NASA Astrophysics Data System (ADS)

We report the neutron diffraction study on the temperature dependence of Bragg peak intensities (IB) in the superconducting ferromagnet UGe2. When the temperature is lowered, IB(T) steeply increases below a characteristic temperature (TX) in the ferromagnetic phase. We have found that it can be explained in terms of a simple Stoner model, and that the so-called Stoner gap ? decreases with increasing pressure and collapses to zero around a critical pressure (PX˜ 1.2 GPa) where the superconducting transtion temperature displays a maximum. We speculate that a transition from the paramagnetic to perfect polarized state takes place at TX and PX in heavy electron bands.

Aso, Naofumi; Motoyama, Gaku; Ban, Seiko; Homma, Yoshiya

2005-03-01

51

Observation of the Crossover from Two-Gap to Single-Gap Superconductivity through Specific Heat Measurements in Neutron-Irradiated MgB{sub 2}  

SciTech Connect

We report specific heat measurements on neutron-irradiated MgB{sub 2} samples, for which the critical temperature is lowered to 8.7 K, but the superconducting transition remains extremely sharp, indicative of a defect structure extremely homogeneous. Our results evidence the presence of two superconducting gaps in the temperature range above 21 K, while single-gap superconductivity is well established as a bulk property, not associated with local disorder fluctuations, when T{sub c} decreases to 11 K.

Putti, M.; Ferdeghini, C.; Manfrinetti, P.; Tarantini, C. [CNR-INFM-LAMIA and Dipartimento di Fisica, Universita di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Affronte, M. [CNR-INFM-S3 and Dipartimento di Fisica, Universita di Modena e Reggio Emilia, Via G. Campi 213/A, I-41100 Modena (Italy); Lehmann, E. [Paul Scherrer Institut, CH-5232 Villigen (Switzerland)

2006-02-24

52

Complementary Theories of Energy Gaps in HTSC  

Microsoft Academic Search

We examine experiments on energy gaps in high temperature superconductors (HTSC) in terms of experimental probes that utilize momentum, position, or neither. Experiments on very high quality mechanical tunnel junctions show a sharp energy gap with a maximum anisotropy of ~ 10%, while ultrahigh precision ARPES experiments show 100% anisotropy (d-wave pairing). We resolve this conbflict by showing that the

J. C. Phillips; J. Jung; D. Shimada; N. Tsuda

2001-01-01

53

Interrelation of superconducting and antiferromagnetic gaps in high- T(c) compounds: A test case for the SO(5) theory  

PubMed

Recent angle resolved photoemission data, which found evidence for a d-wave-like modulation of the antiferromagnetic gap, suggest an intimate interrelation between the antiferromagnetic insulator and the superconductor with its d-wave gap. It is shown here that a projected SO(5) theory, which explicitly takes the Mott-Hubbard gap into account, correctly describes the observed gap characteristics. Specifically, it accounts for the order of magnitude difference between the antiferromagnetic gap modulation and the superconducting gap and is also consistent with the gap dispersion. PMID:10991408

Zacher; Hanke; Arrigoni; Zhang

2000-07-24

54

High speed superconducting flywheel system for energy storage  

NASA Astrophysics Data System (ADS)

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

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

1994-12-01

55

Superconductivity in the Narrow-Gap Semiconductor CsBi4Te6.  

PubMed

Superconductivity was discovered in the narrow-gap semiconductor CsBi4Te6. A superconducting transition around 4.4 K was observed for p-type samples in temperature-dependent resistivity and magnetic susceptibility data. Stoichiometric CsBi4Te6 is not a superconductor. A remarkably high critical field of ?10 T was estimated from the field-dependent resistivity data. The strongly anisotropic CsBi4Te6 system is monoclinic and the first member of a larger homologous series Cs4[Bi2n+4Te3n+6] that exhibits unconventional superconductivity, suggesting that proper doping of the homologous series may create a novel class of superconductors from semiconductors. PMID:24028315

Malliakas, Christos D; Chung, Duck Young; Claus, Helmut; Kanatzidis, Mercouri G

2013-09-23

56

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

Microsoft Academic Search

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

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

2008-01-01

57

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

58

Parity Effect in Ground State Energies of Ultrasmall Superconducting Grains  

SciTech Connect

We study the superconductivity in small grains in the regime when the quantum level spacing {delta}{var_epsilon} is comparable to the gap {Delta}. As {delta}{var_epsilon} is increased, the system crosses over from superconducting to normal state. This crossover is studied by calculating the dependence of the ground state energy of a grain on the parity of the number of electrons. The states with odd numbers of particles carry an additional energy {Delta}{sub P}, which shows nonmonotonic dependence on {delta}{var_epsilon}. Our predictions can be tested experimentally by studying the parity-induced alternation of Coulomb blockade peak spacings in grains of different sizes. {copyright} {ital 1997} {ital The American Physical Society}

Matveev, K. [Department of Physics, Duke University, Durham, North Carolina 27708-0305 (United States); Matveev, K. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Larkin, A. [Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Larkin, A. [L.D. Landau Institute for Theoretical Physics, 117940 Moscow (Russia)

1997-05-01

59

Superconductivity  

NASA Astrophysics Data System (ADS)

Many potential high-temperature superconductivity (HTS) military applications have been demonstrated by low-temperature superconductivity systems; they encompass high efficiency electric drives for naval vessels, airborne electric generators, energy storage systems for directed-energy weapons, electromechanical launchers, magnetic and electromagnetic shields, and cavity resonators for microwave and mm-wave generation. Further HST applications in militarily relevant fields include EM sensors, IR focal plane arrays, SQUIDs, magnetic gradiometers, high-power sonar sources, and superconducting antennas and inertial navigation systems. The development of SQUID sensors will furnish novel magnetic anomaly detection methods for ASW.

Yeo, Yung K.

60

Energy Gaps in Graphene Nanoribbons  

Microsoft Academic Search

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

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

2006-01-01

61

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

62

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

63

Surface-plasmon energy gaps and photoluminescence  

NASA Astrophysics Data System (ADS)

Excited dye molecules on a metallic grating can relax by generating surface plasmon polaritons (SPP's). These SPP's can scatter from the grating reradiating their energy as photons. For dye molecules in contact with the metal, light radiated by SPP's dominates the optical emission from the system. If the wavelength of the SPP is equal to half the pitch of the grating then the mode can Bragg reflect from the surface and an energy gap opens up in the SPP dispersion. This paper examines the effect that such an energy gap has on the emission properties of the dye. Experimentally it is found that the SPP energy gap significantly inhibits emission from the system. Numerical modeling is used to show that the modified emission spectrum is determined by the wavelength dependence of the density of available SPP states.

Kitson, S. C.; Barnes, W. L.; Sambles, J. R.

1995-10-01

64

Indication of Both d- and s-Wave like Superconducting Gaps in YBa2Cu3O7  

NASA Astrophysics Data System (ADS)

Both of the d- and s- wave interpretations of the superconducting gaps in high Tc superconductors are separately supported by experiments, leading sometimes to conflicting views. In an effort to resolve this conflict, we performed first-principle quantum calculations as follows. We utilized self-consistent, electronic wave functions and electron-phonon interaction matrix elements, and we solved four-dimensional Eliashberg gap equations. Our results showed that on three sheets of the Fermi surfaces, the calculated superconducting gap exhibits a strong anisotropy and can lend itself to a d-wave interpretation. In contrast, the calculated superconducting gap on the small sheet of the Fermi surface around the S-Point only shows a relatively small variation from about 18 meV to 25 meV and there is no node on this sheet, leading to s-wave interpretation. Our findings point to the need for measurements of the superconducting gap on this sheet of the Fermi surface around the S-point. Such measurements are expected to shed light on the gap symmetry properties of high Tc superconductors. Work funded in part by the Department of the Navy, Office of Naval Research (ONR, Grant No. N00014-4-1-0587) and by the National Science Foundation (Award No. HRD 0503362)

Zhao, G. L.; Bagayoko, D.

2008-03-01

65

Nodeless superconducting gap in A(x)Fe2Se2 (A=K,Cs) revealed by angle-resolved photoemission spectroscopy.  

PubMed

Pairing symmetry is a fundamental property that characterizes a superconductor. For the iron-based high-temperature superconductors, an s(±)-wave pairing symmetry has received increasing experimental and theoretical support. More specifically, the superconducting order parameter is an isotropic s-wave type around a particular Fermi surface, but it has opposite signs between the hole Fermi surfaces at the zone centre and the electron Fermi surfaces at the zone corners. Here we report the low-energy electronic structure of the newly discovered superconductors, A(x)Fe(2)Se(2) (A=K,Cs) with a superconducting transition temperature (Tc) of about 30 K. We found A(x)Fe(2)Se(2) (A=K,Cs) is the most heavily electron-doped among all iron-based superconductors. Large electron Fermi surfaces are observed around the zone corners, with an almost isotropic superconducting gap of ~10.3 meV, whereas there is no hole Fermi surface near the zone centre, which demonstrates that interband scattering or Fermi surface nesting is not a necessary ingredient for the unconventional superconductivity in iron-based superconductors. Thus, the sign change in the s(±) pairing symmetry driven by the interband scattering as suggested in many weak coupling theories becomes conceptually irrelevant in describing the superconducting state here. A more conventional s-wave pairing is probably a better description. PMID:21358648

Zhang, Y; Yang, L X; Xu, M; Ye, Z R; Chen, F; He, C; Xu, H C; Jiang, J; Xie, B P; Ying, J J; Wang, X F; Chen, X H; Hu, J P; Matsunami, M; Kimura, S; Feng, D L

2011-02-27

66

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

67

Evidence for an excited nonequilibrium quasiparticle distribution in superconducting tunnel junctions resulting from energy accumulation via sequential tunneling  

Microsoft Academic Search

We have observed experimentally and modeled theoretically a previously unidentified nonequilibrium state in superconducting tunnel junctions. The state occurs in small gap, multiple tunneling junctions, and is caused by the raising in energy of the quasiparticle distribution through multiple cycles of sequential forward- and back-tunneling events. Because of the low-energy gap, quasiparticles may survive in the higher-energy states until they

A. G. Kozorezov; J. K. Wigmore; A. Peacock; R. den Hartog; D. Martin; G. Brammertz; P. Verhoeve; N. Rando

2004-01-01

68

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

SciTech Connect

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

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

1993-08-01

69

Isotropic Superconducting Gaps with Enhanced Pairing on Electron Fermi Surfaces in FeTe0.55Se0.45  

SciTech Connect

We used angle-resolved photoemission spectroscopy to reveal directly the momentum distribution of the superconducting gap in FeTe{sub 1-x}Se{sub x}, 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.

Yang H.; 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.

2012-03-06

70

Energy Gap Evolution in the Tunneling Spectra of Bi2Sr2CaCu2O8+?  

NASA Astrophysics Data System (ADS)

On the basis of the tunneling spectra in Bi2212/vaccum/Bi2212 junctions fabricated using STM, we report that, in the electronic excitations, there exist two kinds of pseudogaps; one with a characteristic energy comparable to the superconducting (SC) gap and another one that is 3 to 4 times larger. The smaller energy-scale pseudogap (SPG) develops progressively below temperature T*, which nearly scales with the SC gap amplitude ?0 at T ? Tc, in addition to the larger energy-scale pseudogap (LPG), which already exists above T*. The SPG smoothly develops into the SC-state gap with no tendency to close at Tc.

Dipasupil, R. M.; Oda, M.; Momono, N.; Ido, M.

2002-06-01

71

On the organic energy gap problem  

NASA Astrophysics Data System (ADS)

In conjugated organic molecules, the difference between the HOMO and LUMO Kohn-Sham eigenvalues is significantly smaller than the transport gap measured experimentally. We discuss here, within a local-orbital formulation of DFT, how this problem can be corrected using appropriate hybrid potentials, that add a fraction of Hartree-Fock exchange interaction in the DFT calculation. We illustrate this approach presenting calculations for two simple systems: H2 and C6H6; then, we discuss how to implement this hybrid approach in a general local-orbital calculation, adjusting the hybrid contribution to yield the correct experimental HOMO/LUMO energy gap for the molecule. We also consider the case of an organic molecule on a metal and analyze the effect of the molecule-metal interaction on the organic energy gap. In particular, we discuss how to introduce in this hybrid-potential scheme the effect of the image potential, and present results for the organic molecules PTCDA, TTF, benzene and pentacene on the metal surfaces Au(111), Ag(111) and Cu(111).

Flores, F.; Abad, E.; Martínez, J. I.; Pieczyrak, B.; Ortega, J.

2013-03-01

72

A superconducting linac for the energy amplifier  

SciTech Connect

Because of the safer and more reliable mode of operation, a Superconducting Linac has been proposed as the proton beam accelerator which drives a nuclear plant based on the concept of the Energy Amplifier. An example based on the net generation of 400 MW (electric) is described. This requires a proton beam energy of 1 GeV with a continuous beam current of 10 mA, corresponding to a beam power of 10 MW. Two frequency cases, 360 and 805 MHz, have been considered for the Linac design. Performance and cost comparison for the two cases are given.

Ruggiero, A.G.

1997-07-01

73

Point-Contact Study of the Superconducting Gap in the Magnetic Rare-Earth Nickel-Borocarbide RNi2B2C (R = Dy, Ho, Er, Tm) Compounds  

NASA Astrophysics Data System (ADS)

We present an overview of the efforts in point-contact (PC) study of the superconducting (SC) gap in the antiferromagnetic (AF) nickel-borocarbide compounds RNi2B2C (R = Dy, Ho, Er, Tm), for which the energy scales of AF and SC order, measured by the Neel temperature T N and the critical temperature T c, respectively, can be varied over a wide range. The SC gap was determined from the experimental dV / dI curves of PCs employing the well-known BTK theory of conductivity for normal metal-superconductor PCs accounting Andreev reflection. Additionally, the mentioned theory including pair-breaking effect due to magnetic impurities was employed and a multiband structure of the title compounds was taken into consideration. Recent directional PC study of the SC gaps gives evidence for the anisotropic two-band (two-gap) nature of SC-ty in R = Er (T N ? 6 K < T c ? 11 K). Additionally, a distinct decrease of both gaps in this compound in the AF state is observed. The SC gap in R = Ho (T N ? 5. 2 K < T c ? 8. 5 K) exhibits below T ? ? 5. 6 K a standard single-band BCS-like dependence vanishing above T ?, where a specific magnetic ordering starts to play a role. For R = Tm (T N ? 1. 5 K < T c ? 10. 5 K) a decrease of the SC gap is observed below ˜ 5 K, while for R = Dy (T N ? 10. 5 K > T c ? 6. 5 K) the SC gap has BCS-like dependence in the AF state. Distinct features of the SC gap behavior in the mentioned magnetic superconductors are discussed.

Naidyuk, Yu. G.; Bobrov, N. L.; Chernobay, V. N.; Drechsler, S.-L.; Fuchs, G.; Kvitnitskaya, O. E.; Naugle, D. G.; Rathnayaka, K. D. D.; Tyutrina, L. V.; Yanson, I. K.

74

Inelastic neutron and x-ray scattering as probes of the sign structure of the superconducting gap in iron pnictides  

NASA Astrophysics Data System (ADS)

Neutron spin-flip scattering observations of a resonance in the superconducting state is often taken as evidence of an unconventional superconducting state in which the gap changes sign ?(k+Q)=-?(k) for momentum transfers Q which play an important role in the pairing. Recently questions regarding this identification for the Fe-pnictide superconductors have been raised and it has been suggested that ?(k+Q)=?(k). Here we propose that inelastic neutron or x-ray scattering measurements of the spectral weight of a phonon of momentum Q can distinguish between these two pairing scenarios.

Maier, Thomas A.; Graser, Siegfried; Hirschfeld, Peter J.; Scalapino, Douglas J.

2011-06-01

75

The role of engineered materials in superconducting tunnel junction X-ray detectors - Suppression of quasiparticle recombination losses via a phononic band gap  

NASA Astrophysics Data System (ADS)

An engineered structure is proposed that can alleviate quasi-particle recombination losses via the existence of a phononic band gap that overlaps the 2-Delta energy of phonons produced during recombination of quasi-particles. Attention is given to a 1D Kronig-Penny model for phonons normally incident to the layers of a multilayered superconducting tunnel junction as an idealized example. A device with a high density of Bragg resonances is identified as desirable; both Nb/Si and NbN/SiN superlattices have been produced, with the latter having generally superior performance.

Rippert, Edward D.; Ketterson, John B.; Chen, Jun; Song, Shenian; Lomatch, Susanne; Maglic, Stevan R.; Thomas, Christopher; Cheida, M. A.; Ulmer, Melville P.

1992-10-01

76

Observation of below-gap plasmon excitations in superconducting YBa{sub 2}Cu{sub 3}O{sub 7} films  

SciTech Connect

Finite-wave-vector collective plasmon resonances have been observed in far-infrared transmission measurements on superconducting YBa{sub 2}Cu{sub 3}O{sub 7} films. An Al grating is used to couple IR radiation to collective two-dimensional plasma modes. The plasmon dispersion, measured by using different grating periods, spans the frequency range of the energy gap. The strengths of the plasma resonances weaken as the temperature approaches {ital T}{sub {ital c}} from below. The results are analyzed using a grating coupler theory that includes the hybridization of the plasmons with the diffraction modes.

Dunmore, F.J.; Liu, D.Z.; Drew, H.D.; Das Sarma, S. [Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)]|[Laboratory for Physical Sciences, College Park, Maryland 20740 (United States); Li, Q.; Fenner, D.B. [Advanced Fuel Research Inc., East Hartford, Connecticut 06138 (United States)

1995-07-01

77

Ion-size effects in HTS cuprates - superfluid density and energy gaps  

NASA Astrophysics Data System (ADS)

The demonstrated central role that ion size plays in determining Tc in the HTS cuprates needs to be further explored in order to determine whether the demonstrated systematic behaviour plays out in other superconducting properties. After all, Tc can be diminished simply by disorder effects. What is the effect of systematic ion-size variation on the superfluid density and superconducting energy gap? And can these effects be used to infer details concerning the pairing mechanism? To address these issues we report the effect of changing ion size on muon spin relaxation measurements of the superfluid density and Raman measurements of the superconducting gap in the model system RA2Cu3Oy (where R = La,..., Lu and A=Ba2-xSrx). The electronic density of states is determined from the effect of Zn substitution in this system and we are able to discount disorder scattering as the source of the systematic changes in superconducting properties. Our results confirm a picture where the polarizability of the charge-reservoir layer plays a key role in setting the energy scale for pairing in this system.

Mallett, Benjamin; Bernhard, Christian; Wolf, Thomas; Gilioli, Edi; Tallon, Jeff

2013-03-01

78

A superconducting high-speed flywheel energy storage system  

Microsoft Academic Search

High-speed flywheel systems have been studied as compensators of voltage sags and momentary interruptions of energy. Besides the complexity of these systems, the main concerns are bearing losses. This work is part of the development of a superconducting high-speed flywheel energy storage prototype. In order to minimize the bearing losses, this system uses a superconducting axial thrust magnetic bearing in

R. de Andrade; A. C. Ferreira; G. G. Sotelo; W. I. Suemitsu; L. G. B. Rolim; J. L. Silva Neto; M. A. Neves; V. A. dos Santos; G. C. da Costa; M. Rosario; R. Stephan; R. Nicolsky

2004-01-01

79

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

80

Research for superconducting energy storage patterns and its practical countermeasures  

NASA Astrophysics Data System (ADS)

In this paper, we attempt to introduce briefly the significance, the present status, as well as the working principle of the primary patterns of the superconducting energy storage system, first of all. According to the defect on the lower energy storage density of existed superconducting energy storage device, we proposed some new ideas and strategies about how to improve the energy storage density, in which, a brand-new but a tentative proposal regarding the concept of energy compression was emphasized. This investigation has a certain reference value towards the practical application of the superconducting energy storage.

Lin, D. H.; Cui, D. J.; Li, B.; Teng, Y.; Zheng, G. L.; Wang, X. Q.

2013-10-01

81

Thermal conductivity of the pyrochlore superconductor KOs2O6: strong electron correlations and fully gapped superconductivity.  

PubMed

To elucidate the nature of the superconducting ground state of the geometrically frustrated pyrochlore KOs2O6 (Tc=9.6 K), the thermal conductivity was measured down to low temperatures (approximately Tc/100). We found that the quasiparticle mean free path is strikingly enhanced below a transition at Tp=7.8 K, indicating enormous electron inelastic scattering in the normal state. In magnetic fields, the conduction at T-->0 K is nearly constant up to approximately 0.4Hc2, in contrast with the rapid growth expected for superconductors with an anisotropic gap. This unambiguously indicates a fully gapped superconductivity, in contrast with previous studies. These results highlight that KOs2O6 is unique among superconductors with strong electron correlations. PMID:16907273

Kasahara, Y; Shimono, Y; Shibauchi, T; Matsuda, Y; Yonezawa, S; Muraoka, Y; Hiroi, Z

2006-06-23

82

Superconducting Gap and Pseudogap in Iron-Based Layered Superconductor La(O1-xFx)FeAs  

Microsoft Academic Search

We report high-resolution photoemission spectroscopy of newly-discovered iron-based layered superconductor La(O0.93F0.07)FeAs (Tc = 24 K). We found that the superconducting gap shows a marked deviation from the isotropic s-wave symmetry. The estimated gap size at 5 K is 3.6 meV in the s- or axial p-wave case, while it is 4.1 meV in the polar p- or d-wave case. We

Takafumi Sato; Seigo Souma; Kosuke Nakayama; Kensei Terashima; Katsuaki Sugawara; Takashi Takahashi; Yoichi Kamihara; Masahiro Hirano; Hideo Hosono

2008-01-01

83

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.degree. 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, James T. (Livermore, CA); Hargrove, R. Steven (Danville, CA)

1989-01-01

84

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

85

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

Microsoft Academic Search

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

H. Chehime; D. Zeppenfeld

1993-01-01

86

To close or not to close: the fate of the superconducting gap across the topological quantum phase transition in Majorana-carrying semiconductor nanowires.  

PubMed

We investigate theoretically the low-energy physics of semiconductor Majorana wires in the vicinity of a magnetic field-driven topological quantum phase transition (TQPT). The local density of states at the end of the wire, which is directly related to the differential conductance in the limit of point-contact tunneling, is calculated numerically. We find that the dependence of the end-of-wire local density of states on the magnetic field is nonuniversal and that the signatures associated with the closing of the superconducting gap at the Majorana TQPT are essentially invisible within a significant range of experimentally relevant parameters. Our results provide a possible explanation for the recent observation of the apparent nonclosure of the gap at the Majorana TQPT in semiconductor nanowires. PMID:23368589

Stanescu, Tudor D; Tewari, Sumanta; Sau, Jay D; Sarma, S Das

2012-12-26

87

Anomalous capacitance response induced by the superconducting gap in an Au/BiFeO3/La1.84Sr0.16CuO4/LaSrAlO4 heterostructure  

NASA Astrophysics Data System (ADS)

Film capacitor characteristics of Au/BiFeO3/La1.84Sr0.16CuO4 on LaSrAlO4 (001) substrate were studied in the temperature range 10-300 K under magnetic fields up to 7 T. Apparent capacitance anomalies were observed at the superconducting transition temperature Tc of La1.84Sr0.16CuO4. Furthermore, the magnetic field dependences of the dielectric relaxation related activation energy can be well fitted from 10 K to Tc by the superconducting gap versus magnetic field. These results suggest an alternative technique for detecting the superconductivity related features in superconducting film, and also may be useful for future tunable multifunctional devices.

Liu, F. G.; Xie, L.; Liu, W.

2013-10-01

88

Superconducting Magnetic Energy Storage for Electric Utilities and Fusion Systems.  

National Technical Information Service (NTIS)

Superconducting inductors provide a compact and efficient means of storing electrical energy without an intermediate conversion process. Energy storage inductors are under development for load leveling and transmission line stabilization in electric utili...

J. D. Rogers H. J. Boenig W. V. Hassenzahl

1978-01-01

89

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

90

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

91

Voltage sags compensation using a superconducting flywheel energy storage system  

Microsoft Academic Search

This paper presents a voltage sag compensator, which uses a flywheel energy storage system with superconducting magnetic axial thrust bearing (SMB) and a permanent magnet radial bearing (PMB). The SMB was built with Nd-Fe-B magnet and YBCO superconducting blocks, refrigerated with liquid Nitrogen. The magnets are assembled with magnetic flux shapers in order to increase the levitation force and the

Antonio C. Ferreira; Guilherme G. Sotelo; José L. Silva Neto; Luiz G. B. Rolim; Walter I. Suemitsu; Márcio F. Bessa; Richard M. Stephan; Roberto Nicolsky

2005-01-01

92

High-Energy Neutron Irradiation of Superconducting Compounds.  

National Technical Information Service (NTIS)

The effect of high-energy neutron irradiation (E greater than 1 MeV) at ambient reactor temperatures on the superconducting properties of a variety of superconducting compounds is reported. The materials studied include the A-15 compounds Nb sub 3 Sn, Nb ...

A. R. Sweedler C. L. Snead L. Newkirk F. Valencia T. H. Geballe

1975-01-01

93

Composite laminate applications in magnetic fusion energy superconducting magnet systems  

Microsoft Academic Search

The application of advanced composite laminates in the cryogenic portion of magnetic fusion energy systems is considered. It is suggested that laminates, characterized by high modulus, low thermal conductivity, and high electrical conductivity, can substitute for stainless steel in some components of superconducting magnets. Thermal insulation, nonmetallic dewars, and superconducting composites are discussed. Problems associated with the use of current

M. B. Kasen

1978-01-01

94

Superconducting magnetic energy storage for asynchronous electrical systems  

DOEpatents

A superconducting magnetic energy storage coil connected in parallel between converters of two or more ac power systems provides load leveling and stability improvement to any or all of the ac systems. Control is provided to direct the charging and independently the discharging of the superconducting coil to at least a selected one of the ac power systems.

Boenig, Heinrich J. (Los Alamos, NM)

1986-01-01

95

Energy Band Gap in Quasi-Particle Local Density Theory.  

National Technical Information Service (NTIS)

We present a general approach for calculating the quasiparticle excitation energies of semiconductors which includes the energy dependence of the self-energy within the density functional formalism. In silicon the zone boundary optical gaps and the valenc...

C. S. Wang W. E. Pickett

1983-01-01

96

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

97

Energy band gaps of silicon-carbon alloys  

Microsoft Academic Search

The energy band gaps of silicon-carbon alloys are calculated using a GW approach with local density approximation (LDA) eigenfunctions. These band gaps are compared with those calculated with nonlocal corrections for the exchange-correlation energy functional. For small concentrations of carbon, it is found that carbon-silicon alloys are semiconducting with a very small band gap. These results are consistent with former

Jan Gryko; Otto F. Sankey

1995-01-01

98

Electron tunneling in single layer graphene with an energy gap  

NASA Astrophysics Data System (ADS)

When a single layer graphene is epitaxially grown on silicon carbide, it will exhibit a finite energy gap like a conventional semiconductor, and its energy dispersion is no longer linear in momentum in the low energy regime. In this paper, we have investigated the tunneling characteristics through a two-dimensional barrier in a single layer graphene with an energy gap. It is found that when the electron is at a zero angle of incidence, the transmission probability as a function of incidence energy has a gap. Away from the gap the transmission coefficient oscillates with incidence energy which is analogous to that of a conventional semiconductor. The conductance under zero temperature has a gap. The properties of electron transmission may be useful for developing graphene-based nano-electronics.

Xu, Xu-Guang; Zhang, Chao; Xu, Gong-Jie; Cao, Jun-Cheng

2011-02-01

99

Energy Gap Evolution over Wide Temperature and Doping Ranges in Bi2Sr2CaCu2O8+?  

NASA Astrophysics Data System (ADS)

In this article we report the energy gap evolution in Bi2Sr2CaCu2O8+?(Bi2212) on the basis of recent tunneling and Raman scattering experiments over wide temperature and hole-doping (p) ranges. It has been demonstrated that in the normal-state electronic excitations, there exist two kinds of pseudogaps (LPG and SPG) with different characteristic energies. The LPG, which is 3 to 4 times larger than the superconducting (SC) gap at T ? Tc, develops below ~ Tmax, where the magnetic susceptibility starts to decrease because of the gradual development of antiferromagnetic spin fluctuations. On the other hand, the SPG, whose magnitude is comparable to the SC gap, develops progressively, in addition to the LPG, below the mean-field characteristic temperature Tco for d-wave superconductors, and then evolves into the SC gap below Tc, suggesting that it will be some kind of precursor of superconductivity. It has also been demonstrated that the maximal gap ?0 or the gap at the positions near (±?, 0) and (0,±?), determined at T ? Tc by tunneling technique, does not scale with Tc, while the gap around (±?/2,±?/2), determined at T ? Tc from the coherence peak energy in B2g Raman spectra, scales with Tc, suggesting that the latter gap will function as an effective SC gap ?eff in determining Tc. Furthermore, we will report that ?eff is given by the product of p and ?0 ?eff ~ 5.3p?0 in Bi2212, and discuss some scenarios for the SC transition which is consistent with the present result on the effective SC gap.

Momono, Naoki; Oda, Migaku; Ido, Masayuki; Sakai, A.

100

Ultrahigh energy neutrinos from superconducting cosmic strings  

NASA Astrophysics Data System (ADS)

Superconducting cosmic strings naturally emit highly boosted charge carriers from cusps. This occurs when a cosmic string or a loop moves through a magnetic field and develops an electric current. The charge carriers and the products of their decay, including protons, photons, and neutrinos, are emitted as narrow jets with opening angle ?˜1/?c, where ?c is the Lorentz factor of the cusp. The excitation of electric currents in strings occurs mostly in clusters of galaxies, which are characterized by magnetic fields B˜10-6G and a filling factor fB˜10-3. Two string parameters determine the emission of the particles: the symmetry breaking scale ?, which for successful applications should be of order 109-1012GeV, and the dimensionless parameter ic, which determines the maximum induced current as Jmax?=ice? and the energy of emitted charge carriers as ?X˜ic?c?, where e is the electric charge of a particle. For the parameters ? and B mentioned above, the Lorentz factor reaches ?c˜1012 and the maximum particle energy can be as high as ?c?˜1022GeV. The diffuse fluxes of ultrahigh energy neutrinos are close to the cascade upper limit, and can be detected by future neutrino observatories. The signatures of this model are: very high energies of neutrinos, in excess of 1020eV; correlation of neutrinos with clusters of galaxies; simultaneous appearance of several neutrino-produced showers in the field of view of very large detectors, such as JEM-EUSO; and 10 TeV gamma radiation from the Virgo cluster. The flux of ultrahigh energy protons from cusps may account for a large fraction of the observed events at the highest energies.

Berezinsky, Veniamin; Olum, Ken D.; Sabancilar, Eray; Vilenkin, Alexander

2009-07-01

101

Globally optimal, minimum stored energy, double-doughnut superconducting magnets.  

PubMed

The use of the minimum stored energy current density map-based methodology of designing closed-bore symmetric superconducting magnets was described recently. The technique is further developed to cater for the design of interventional-type MRI systems, and in particular open symmetric magnets of the double-doughnut configuration. This extends the work to multiple magnet domain configurations. The use of double-doughnut magnets in MRI scanners has previously been hindered by the ability to deliver strong magnetic fields over a sufficiently large volume appropriate for imaging, essentially limiting spatial resolution, signal-to-noise ratio, and field of view. The requirement of dedicated interventional space restricts the manner in which the coils can be arranged and placed. The minimum stored energy optimal coil arrangement ensures that the field strength is maximized over a specific region of imaging. The design method yields open, dual-domain magnets capable of delivering greater field strengths than those used prior to this work, and at the same time it provides an increase in the field-of-view volume. Simulation results are provided for 1-T double-doughnut magnets with at least a 50-cm 1-ppm (parts per million) field of view and 0.7-m gap between the two doughnuts. PMID:19950210

Tieng, Quang M; Vegh, Viktor; Brereton, Ian M

2010-01-01

102

Towards Measuring Variations of Casimir Energy by a Superconducting Cavity  

SciTech Connect

We consider a Casimir cavity, one plate of which is a thin superconducting film. We show that when the cavity is cooled below the critical temperature for the onset of superconductivity, the sharp variation (in the far infrared) of the reflection coefficient of the film engenders a variation in the value of the Casimir energy. Even though the relative variation in the Casimir energy is very small, its magnitude can be comparable to the condensation energy of the superconducting film, and this gives rise to a number of testable effects, including a significant increase in the value of the critical magnetic field, required to destroy the superconductivity of the film. The theoretical ground is therefore prepared for the first experiment ever aimed at measuring variations of the Casimir energy itself.

Bimonte, Giuseppe; Calloni, Enrico; Esposito, Giampiero; Milano, Leopoldo; Rosa, Luigi [Dipartimento di Scienze Fisiche, Universita di Napoli Federico II, Via Cintia I-80126 Naples (Italy); INFN, Sezione di Napoli, Naples (Italy)

2005-05-13

103

Evaluation of superconducting magnetic energy storage systems  

NASA Astrophysics Data System (ADS)

The breakeven capital cost of Superconducting Magnetic Energy Storage (SMES) and its highest possible value were studied. The results are compared by EPRI to the capital cost of SMES being estimated by Bechtel in a related study. The best and most reasonable estimate of the SMES breakeven capital cost is 1080 $/kW in 1981 dollars. The highest possible value for an ideal SMES with perfect availability, zero refrigeration load and 100% incremental cycle efficiency is 1510 $/kW when installed in a utility approximately one third of the US in size. Two methods of analysis are used. A single year analysis that assigns an energy credit and a capacity credit to SMES provides the method for parametric and sensitivity analyses. A thirty year life cycle analysis comparing SMES to a coal fired generation alternative recognizes fuel cost escalation effects. The value of SMES to each of the six EPRI Regional Systems is computed. In comparison with pumped storage, SMES is worth 14% more to a utility.

Lee, S. T.; Albert, R. S.; Imamura, D. T.

1983-02-01

104

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

105

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 in the magnet.

Herring, J.S.

1990-10-26

106

Superconducting magnetis in spectrometers of high-energy particles  

Microsoft Academic Search

This is a retrospective review of superconducting magnets for spectrometers of high-energy particles. The magnets are grouped\\u000a according to the purpose of the spectrometers and the shape of coils. Data on the thermostatting and electrical protection\\u000a of the coils are presented. Design features of various-type magnets are described. The first large superconducting solenoids\\u000a were constructed for hydrogen bubble chambers. Further

Yu. A. Shishov

2006-01-01

107

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

108

Angular Position of Nodes in the Superconducting Gap of Quasi-2D Heavy-Fermion Superconductor CeCoIn{sub 5}  

SciTech Connect

The thermal conductivity of the heavy-fermion superconductor CeCoIn{sub 5} has been studied in a magnetic field rotating within the 2D planes. A clear fourfold symmetry of the thermal conductivity which is characteristic of a superconducting gap with nodes along the ({+-}{pi},{+-}{pi}) directions is resolved. The thermal conductivity measurement also reveals a first-order transition at H{sub c2} , indicating a Pauli limited superconducting state. These results indicate that the symmetry most likely belongs to d{sub x{sup 2}-y{sup 2}} , implying that the anisotropic antiferromagnetic fluctuation is relevant to the superconductivity.

Izawa, K.; Yamaguchi, H.; Matsuda, Yuji; Shishido, H.; Settai, R.; Onuki, Y.

2001-07-30

109

Angular position of nodes in the superconducting gap of quasi-2D heavy-fermion superconductor CeCoIn5.  

PubMed

The thermal conductivity of the heavy-fermion superconductor CeCoIn5 has been studied in a magnetic field rotating within the 2D planes. A clear fourfold symmetry of the thermal conductivity which is characteristic of a superconducting gap with nodes along the ( +/- pi,+/- pi) directions is resolved. The thermal conductivity measurement also reveals a first-order transition at H(c2), indicating a Pauli limited superconducting state. These results indicate that the symmetry most likely belongs to d(x(2)-y(2)), implying that the anisotropic antiferromagnetic fluctuation is relevant to the superconductivity. PMID:11497799

Izawa, K; Yamaguchi, H; Matsuda, Y; Shishido, H; Settai, R; Onuki, Y

2001-07-12

110

Four-Josephson-junction flux qubit with controllable energy gap  

Microsoft Academic Search

We report the measurements of a double-loop four-Josephson-junction flux qubit. By varying the magnetic flux in one of the two loops, the energy gap at the classical degeneracy point can be controlled in situ. The basic operation of the system is illustrated by the appearance of a qubit step on a two-dimensional flux map. The energy gap can be indirectly

Y. Shimazu; Y. Saito; Z. Wada

2009-01-01

111

Photoacoustic determination of energy band gap of semiconductors  

Microsoft Academic Search

Semiconducting materials are employed in the fabrication of a number of semiconductor devices and opto-electronic detectors\\u000a etc depending on their properties, state of purity and perfection and energy band gap values. In the present study, a latest\\u000a and novel photoacoustic spectroscopic technique has been employed for the determination of energy band gap of some semiconductors\\u000a namely CdS, CdSe, CdTe, ZnS,

R S Ram; O M Prakash; A N Pandey

1987-01-01

112

Langmuir vacuum and superconductivity  

NASA Astrophysics Data System (ADS)

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.

2012-06-01

113

Superconductivity  

SciTech Connect

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

Mayo, J.L.

1988-01-01

114

A superconducting high-speed flywheel energy storage system  

NASA Astrophysics Data System (ADS)

High-speed flywheel systems have been studied as compensators of voltage sags and momentary interruptions of energy. Besides the complexity of these systems, the main concerns are bearing losses. This work is part of the development of a superconducting high-speed flywheel energy storage prototype. In order to minimize the bearing losses, this system uses a superconducting axial thrust magnetic bearing in a vacuum chamber, which guarantees low friction losses, and a switched reluctance motor-generator to drive the flywheel system. Dynamic simulations made for this prototype, connected to the electric power network, show the viability of use it as a compensator.

de Andrade, R.; Ferreira, A. C.; Sotelo, G. G.; Suemitsu, W. I.; Rolim, L. G. B.; Silva Neto, J. L.; Neves, M. A.; Dos Santos, V. A.; da Costa, G. C.; Rosario, M.; Stephan, R.; Nicolsky, R.

2004-08-01

115

Unusual nature of fully gapped superconductivity in In-doped SnTe  

NASA Astrophysics Data System (ADS)

The superconductor Sn1-xInxTe is a doped topological crystalline insulator and has become important as a candidate topological superconductor, but its superconducting phase diagram is poorly understood. By measuring about 50 samples of high-quality, vapor-grown single crystals, we found that the dependence of the superconducting transition temperature Tc on the In content x presents a qualitative change across the critical doping xc?3.8%, at which a structural phase transition takes place. Intriguingly, in the ferroelectric rhombohedral phase below the critical doping, Tc is found to be strongly enhanced with impurity scattering. It appears that the nature of electron pairing changes across xc in Sn1-xInxTe.

Novak, Mario; Sasaki, Satoshi; Kriener, Markus; Segawa, Kouji; Ando, Yoichi

2013-10-01

116

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

117

Observation of orbital governed surface selection of superconducting gap in iron Pnictides with low temperature STM/S  

NASA Astrophysics Data System (ADS)

The strong anisotropy of orbitals plays important roles in strongly correlated electron systems. For iron pnictides, due to their layered structure, overlaping of iron 3d with arsenic 4p orbitals is essential in the pairing mechanism. To reveal such physics, Ba(K)Fe2As2 and LiFeAs are the ideal candidates owing to their integrity in the Fe-As layer. We have used low temperature scanning tunneling microscopy/spectroscopy (STM/STS) to investigate the orbital physics in Ba0.6K0.4Fe2As2 and LiFeAs at atomic level. By comparing the STM/S results on these two materials and referring to the results of angle resolved photoemission spectroscopy (ARPES), we found the phenomenon of surface dependent selection of superconducting gaps. We discuss the implications of these observations with the orbital physics in these materials.

Yin, Jiaxin; Li, Ang; Wu, Zhen; Wang, Jihui; Li, Jian; Ting, Chin-Sen; Zhang, Chenglin; Dai, Pengcheng; Jin, Changqing; Ding, Hong; Pan, Shuheng H.

2013-03-01

118

Energy gap refractive index relations in semiconductors An overview  

NASA Astrophysics Data System (ADS)

An overview of the understanding of correlations between energy gap and refractive index of semiconductors is presented here. The atomic approach of Moss, the nearly free electron model of Penn, the oscillator concept of Wemple and the optical polarizability approach of Finkenrath are considered in this study. The Ravindra relation is discussed in the context of alternate approaches that have been presented in the literature. Case studies of applications of these relations to infrared materials and wide band gap semiconductors are presented.

Ravindra, N. M.; Ganapathy, Preethi; Choi, Jinsoo

2007-03-01

119

Energy BandGap Engineering of Graphene Nanoribbons  

Microsoft Academic Search

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

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

2007-01-01

120

Energy levels of exciton in a gapped graphene sheet  

NASA Astrophysics Data System (ADS)

A theory is presented for exciton formation in a graphene sheet using the center-of-mass approximation. The energy levels and wavefunctions of exciton are calculated analytically which show that the exciton can form if the band gap of graphene is not zero. We show that the energy gap of graphene plays the role of the mass which if not zero, leads to formation of the excitons. It is shown that the main quantum number of the exciton ground state changes with the graphene dielectric constant. Also, all of the states are found to be four-fold degenerate. The binding energy of exciton can reach as high as 1/4 of the energy gap of graphene which is notable among the conventional quasi-2D systems. This result can play an important rule in the photonics of graphene.

Fallah, Farhang; Esmaeilzadeh, Mahdi

2013-08-01

121

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

122

MgB2 Energy Gap Determination by Scanning Tunneling Spectroscopy  

Microsoft Academic Search

We report scanning tunneling spectroscopy (STS) measurements of the gap properties of both ceramic MgB2 and c-axis oriented epitaxial MgB2 thin films. Both show a temperature dependent zero bias conductance peak and evidence for two superconducting gaps. We report tunneling spectroscopy of superconductor-insulator-superconductor (S-I-S) junctions formed in two ways in addition to normal metal-insulator-superconductor (N-I-S) junctions. We find a gap

T. W. Heitmann; S. D. Bu; D. M. Kim; J. H. Choi; J. Giencke; C. B. Eom; K. A. Regan; N. Rogado; M. A. Hayward; T. He; J. S. Slusky; P. Khalifah; M. Haas; R. J. Cava; D. C Larbalestier; M. S. Rzchowski

2002-01-01

123

Design of the BPA superconducting 30 MJ energy storage coil  

NASA Astrophysics Data System (ADS)

The design of a superconducting magnetic energy storage coil is presented. The purpose of this coil is to stabilize low frequency power oscillations in long high voltage ac power lines. The practical application for this specific coil will be the installation in the Pacific intertie between Washington State and Los Angeles, California. The guiding principles of the design are performance, fabrication economy and reliability.

Hoffmann, E.; Alcorn, J.; Chen, W.; Hsu, Y.-H.; Purcell, J.; Schermer, R.

1981-01-01

124

Control Aspects of the Tacoma Superconducting Magnetic Energy Storage Project  

Microsoft Academic Search

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

J. F. Hauer; H. J. Boenig

1987-01-01

125

Power conditioning systems for superconductive magnetic energy storage  

Microsoft Academic Search

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

R. H. Lasseter; S. G. Jalali

1991-01-01

126

The Energy and Environmental Benefits of Superconducting Power Products  

Microsoft Academic Search

Superconductivity has the potential to bring a more fundamental change to electric power technologies than has occurred since electricity use became widespread nearly a century ago. The potential is for an energy revolution as profound as the impact fiber optics has had on communications. The fiber optic ‘information superhighway’ was constructed by replacing copper wires with a higher capacity alternative.

Robert A. Hawsey; Satoshi Morozumi

2005-01-01

127

Feasible utility scale superconducting magnetic energy storage system  

NASA Astrophysics Data System (ADS)

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

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

128

Optimal state control for CSI superconducting magnetic energy storage system  

Microsoft Academic Search

This paper discusses the design and analysis of the multivariable optimal state current source inverter control (feedback and feed-forward) for a superconducting magnetic energy storage system (SMES) for use in a wind farm. In optimal control, the control strategy is sought that gives the best control performance. High stability and robustness against parameter changes are two important advantages of optimal

Fengquan Zhou; G. Joos; C. Abbey; Lianwei Jiao

2004-01-01

129

Scaling of the Energy Gap in Pattern-Hydrogenated Graphene  

NASA Astrophysics Data System (ADS)

Recent experiments show that a substantial energy gap in graphene can be induced via patterned hydrogenation on an iridium substrate. Here, we show that the energy gap is roughly proportional to $\\sqrt{N_{H}}/N_{C}$ when disorder is accounted for, where $N_H$ and $N_C$ denote concentration of hydrogen and carbon atoms, respectively. The dispersion relation, obtained through calculation of the momentum-energy resolved density of states, is shown to agree with previous angle-resolved photoemission spectroscopy results. Simulations of electronic transport in finite size samples also reveal a similar transport gap, up to 1eV within experimentally achievable $\\sqrt{N_{H}}/N_{C}$ value.

Grassi, Roberto; Low, Tony; Lundstrom, Mark

2011-11-01

130

Superconductivity:  

NASA Astrophysics Data System (ADS)

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

Sacchetti, N.

131

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

NASA Astrophysics Data System (ADS)

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

132

Energy Gaps in Etched Graphene Nanoribbons  

Microsoft Academic Search

Transport measurements on an etched graphene nanoribbon are presented. It is shown that two distinct voltage scales can be experimentally extracted that characterize the parameter region of suppressed conductance at low charge density in the ribbon. One of them is related to the charging energy of localized states, the other to the strength of the disorder potential. The lever arms

C. Stampfer; J. Güttinger; S. Hellmüller; F. Molitor; K. Ensslin; T. Ihn

2009-01-01

133

Dipolon theory of energy gap parameters in high-temperature superconductors at zero temperature  

NASA Astrophysics Data System (ADS)

Many-body field-theoretic techniques involving dipolon propagator and electron Green's function have been used to derive the general expressions at zero temperature for the renormalized energy gap parameter ?(k-->,?), the gap renormalization parameter Z(k-->,?), and energy band renormalization parameter ?(k-->,?) for momentum k--> and frequency ?. The present theory takes into account explicitly the dressed dipolons as mediators of superconductivity, the screened Coulomb repulsion, and nonrigid electron energy bands considering retardation and damping effects and electron-hole asymmetry. For superconducting cuprates it has been shown by symmetry considerations that, in the lowest order approximations, there exists two energy gap parameters, one being antisymmetric (as) with respect to the exchange of the kx and ky components of vector k--> and the other being symmetric (s) with respect to the exchange of kx and ky. The antisymmetric solution is a dx2-y2 wave (i.e., ~ [cos(kx)-cos(ky)]) which changes sign with respect to the exchange of kx and ky, and the symmetric solution which is highly asymmetric s wave or equivalently, a combination of a symmetric s wave and absolute value of dx2-y2 wave (i.e. ~ \\| [cos(kx)-cos(ky)] \\| ) which does not change sign with respect to the exchange of kx and ky. Our self-consistent calculations of the real and imaginary parts of ?(k-->,?), Z(k-->,?), and ?(k-->,?) verify the existence of these two (different) solutions and lead to the conclusion that the antisymmetric solution of the gap parameter corresponds to the observed regular (reg) superconducting energy gap whereas the symmetric solution corresponds to the observed pseudo (pse) energy gap. Calculations have been made for Bi2Sr2CaCu2O8+? as well as Bi2Sr2CaCu2O8. Explicitly, for Bi2Sr2CaCu2O8+? superconductor our calculated values of the antisymmetric and symmetric energy gap parameters are ?as0=22+/-15 meV and ?s1=30+/-10 meV with ?s0=1.5+/-1.5 meV, where ?as(k-->)=?as0 [cos(kx)-cos(ky)] and ?s(k-->)=?s0+?s1\\| [cos(kx)-cos(ky)] \\|, in agreement with the corresponding experimental results ?reg0=16.5+/-1.5 meV, ?pse1~24 meV, and ?pse0=-0.5+/-2.5 meV. For Bi2Sr2CaCu2O8 superconductor our calculated values of the antisymmetric and the symmetric energy gap parameters are ?as0=24+/-13 meV and ?s1=29+/-15 meV with ?s0~0 which also agree with the corresponding experimental results ?reg0=16.5+/-1.5 meV and ?pse1=30-40 meV with ?pse0=-0.5+/-2.5 meV. Our calculations also indicate that the bosonic energy relevant to superconductivity in Bi2Sr2CaCu2O8+? superconductor is about 60 meV arising from O1,2 dipolon excitations and that the broad bands observed in optical experiments are due to O1,1, O1,2, and O3 dipolon excitations. Relative contributions from the various dipolon modes have been analyzed. One finds that the symmetric longitudinal modes of oxygen dipolons contribute dominantly in energy gap parameters. The uncertainties in the calculated values of the various parameters are due to uncertainties in the values of the polarizability particularly of oxygen ions, the shielding parameter, the repulsive Coulomb energy, and due to the calculational errors. The origin of the experimentally deduced T* values has been discussed in terms of the present theory which reveals that T* is greater than Tc and that they have the same physical origin.

Sharma, R. R.

2001-02-01

134

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.

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

135

Quantum-size effects in ultrathin Pb-islands on Si(111): From quantum well states to the reduction of the superconducting gap  

NASA Astrophysics Data System (ADS)

Using low-temperature scanning tunneling spectroscopy at 5 and 50 K, we studied the linewidth of unoccupied quantum-well states in ultrathin Pb islands, grown on Si(111) on two different Pb/Si interfaces. A quantitative analysis of the differential conductance spectra allowed us to determine the electron- electron (e-e), electron-phonon (e-ph), and the interface contributions to the lifetime. Layer-dependent ab initio calculations of the e-ph linewidth contribution are in excellent agreement with the data. Importantly, the sum of the calculated e-e and e-ph lifetime broadening follows the experimentally observed quadratic energy dependence [1]. The energy gap of these superconducting Pb islands, in a thickness range between 60 and 5 monolayer, was found to decrease from its bulk value as a function of inverse island thickness. Corresponding values of the critical temperature Tc, estimated using the bulk gap-to-Tc ratio, are in quantitative agreement with ex-situ magnetic susceptibility measurements, however, in strong contrast to previous scanning probe results. Layer-dependent ab initio density functional calculations for freestanding Pb films show that the e-ph coupling constant, determining Tc, decreases with diminishing film thickness [2].[4pt] [1] I.-P. Hong, C. Brun, F. Patthey, I. Yu. Sklyadneva, X. Zubizarreta, R. Heid, V. M. Silkin, P. M. Echenique, K. P. Bohnen, E. V. Chulkov, and W.-D. Schneider, Phys. Rev. B (RC) 80, 081409 (2009).[0pt] [2] C. Brun, I.-P. Hong, F. Patthey, I. Yu. Sklyadneva, R. Heid, P. M. Echenique, K. P. Bohnen, E. V. Chulkov, and W.-D. Schneider, Phys. Rev. Lett. 102, 207002 (2009).

Schneider, Wolf-Dieter

2010-03-01

136

Tunneling studies on the energy gap evolution of Bi2Sr2CaCu2O8+?  

NASA Astrophysics Data System (ADS)

We report, on the basis of our recent tunneling experiments over wide temperatures (T) and hole-doping (p) ranges in Bi2212/vaccum/Bi2212 junctions fabricated using STM, that in the electronic excitation spectrum, there exists two kinds of pseudogaps (LPG and SPG) with different characteristic energies. The LPG, which is 3 to 4 times larger than the superconducting (SC) gap magnitude 2?0 develops below ~Tmax, where the magnetic susceptibility starts to decrease because of the gradual development of antiferromagnetic spin fluctuations. On the other hand, the SPG, whose magnitude is comparable to 2?0, develops progressively, in addition to the LPG, below the mean-field characteristic temperature Tco for d-wave superconductors, and then evolves into the SC-gap below Tc,suggesting that it will be some kind of precursor of superconditivity. Furthermore, in accordance with the SC transition, the high-energy feature of quasiparticle spectrum outside the SC-gap, changes from a broad hump to a clear dip and hump accompanied by a shift of the hump position toward lower energies, in addition to the rapid growth of SC-gap from SPG. We also report that Tc nearly scales with the product of ?0 and p, kBTc~p?0' the effective SC gap is ~p?0 in high Tc cuprates, instead of ?0 in conventional BCS superconductors.

Oda, Migaku; Momono, Naoki; Ido, Masayuki

2002-09-01

137

Superconducting condensation energy in a diluted Kondo lattice  

NASA Astrophysics Data System (ADS)

Heavy fermion compounds are host to many interesting but poorly understood strong correlation effects, leading in exceptional cases to unconventional superconductivity. CeCoIn5 is such an example of an ambient pressure heavy fermion superconductor with a Tc of 2.3K. Such compounds are best described as a Kondo lattice, where Ce, Yb or U ions form a periodic lattice of magnetic moments coupled to the conduction electrons via antiferromagnetic exchange interaction. Dilution, or substitution, of the Kondo ion with a lanthanide, actinide or alkali-earth element that does not participate in the Kondo lattice, results in the so-called "Kondo hole". The electron scattering off the Kondo hole leads to significant changes in both the normal and superconducting properties. We have investigated the suppression of superconductivity in CeCoIn5 diluted with La, Yb, Y, Ca, Th, Gd, Er, Eu and Lu via specific heat measurements on well characterized single crystals. The suppression of the superconducting condensation energy exhibits a remarkable departure from the Abrikosov-Gorkov impurity pair breaking picture, emphasizing that the Kondo holes are no ordinary pair-breakers.

Capan, C.; Seyfarth, G.; Hurt, D.; Bianchi, A. D.; Fisk, Z.

2011-01-01

138

High energy ion linacs based on superconducting spoke cavities.  

SciTech Connect

The applicability of superconducting TEM-class spoke cavities to high-energy ion linacs is discussed, and detailed designs for two TEM-class, triple-spoke-loaded superconducting niobium resonant cavities are presented. The 345 MHz cavities have a velocity range of 0.4<{beta}<0.75 and a beam aperture of 4 cm. Spoke-loaded cavities offer several advantages compared with the higher-frequency elliptical-cell cavities that are currently being developed for this range of particle velocities. The proposed triple-spoke cavities can provide broader velocity acceptance, more accelerating voltage per cavity, reduced heat-load operation at 4.2 K, and increased longitudinal acceptance through the high-energy section. Application to the proposed U.S. rare-isotope accelerator driver linac is discussed in detail.

Shepard, K. W.; Ostroumov, P. N.; Delayen, J. R.; Physics; Thomas Jefferson National Accleratory Facility

2003-08-01

139

New power-conditioning systems for superconducting magnetic energy storage  

NASA Astrophysics Data System (ADS)

This dissertation presents the development of new power-conditioning systems for superconducting magnetic energy storage (SMES), which can regulate fast and independently the active and reactive powers demanded in the ac network. Three new power-conditioning systems were developed through a systematic approach to match the requirements of the superconducting coil and the ac power network. Each of these new systems is composed of ten 100-MW modules connected in parallel to handle the large current through the superconducting coil. The first system, which was published in the IEEE Transactions on Energy Conversion, consists of line-commutated 24-pulse converter, a thyristor-switched tap-changing transformer, and a thyristor-switched capacitor bank. The second system, which was accepted for publication in the IEEE Transactions on Energy Conversion, consists of a 12-pulse GTO (gate turn-off thyristor) converter and a thyristor-switched tap-changing transformer. The third system, which was submitted to the International Journal of Energy System, consists of a dc chopper and a voltage-source PWM (pulse width modulation) converter. The operational concept of each new system is verified through mathematical analyses and computer simulations. The dynamic interaction of each new system with the ac network and the superconducting coil is analyzed using a simulation model with EMTP (electro-magnetic transients program). The analysis results prove that each new system is feasible and realizable. Each system can regulate the active and reactive powers of the utility network rapidly and independently, and each offer a significant reduction of the system rating by reducing the reactive power demand in the converter. Feasible design for each new system was introduced using a modular design approach based on the 1000 MW/5000 MWH plant, incorporating commercially available components and proven technologies.

Han, Byung Moon

1992-06-01

140

New power-conditioning systems for superconducting magnetic energy storage  

SciTech Connect

This dissertation presents the development of new power-conditioning systems for superconducting magnetic energy storage (SMES), which can regulate fast and independently the active and reactive powers demanded in the ac network. Three new power-conditioning systems were developed through a systematic approach to match the requirements of the superconducting coil and the ac power network. Each of these new systems is composed of ten 100-MW modules connected in parallel to handle the large current through the superconducting coil. The first system, which was published in the IEEE Transactions on EnergyConversion, consists of line-commutated 24-pulse converter, a thyristor-switched tap-changing transformer, and a thyristor-switched capacitor bank. The second system, which was accepted for publication in the IEEE Transactions on Energy Conversion, consists of a 12-pulse GTO (gate turn-off thyristor) converter and a thyristor-switched tap-changing transformer. The third system, which was submitted to the International Journal of Energy System, consists of a dc chopper and a voltage-source PWM (pulse width modulation) converter. The operational concept of each new system is verified through mathematical analyses and computer simulations. The dynamic interaction of each new system with the ac network and the superconducting coil is analyzed using a simulation model with EMTP (electro-magnetic transients program). The analysis results prove that each new system is feasible and realizable. Each system can regulate the active and reactive powers of the utility network rapidly and independently, and each offer a significant reduction of the system rating by reducing the reactive power demand in the converter. Feasible design for each new system was introduced using a modular design approach based on the 1000 MW/5000 MWH plant, incorporating commercially available components and proven technologies.

Han, B.M.

1992-01-01

141

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

142

Photoabsorption and energy band gap of amorphous Se alloy films  

Microsoft Academic Search

Amorphous selenium alloy films have been found to exhibit excellent photosensitive properties from 300 to 700 nm. These films\\u000a constitute the essential part of xerographic photoreceptors. Optical absorption, energy band gap and X-ray structural analysis\\u000a of Se85 Te15 and Se85 As15 films are reported. The effect of annealing on these parameters has also been indicated.

S C K Misra; T P Sharma

1991-01-01

143

Transport and tunnelling measurements in superconducting YNi2B2C  

NASA Astrophysics Data System (ADS)

New transport (resistivity versus temperature) and tunneling (low-temperature STM) measurements are reported on YNi2B2C samples prepared by inductive melting from the pure elements. Estimations of Debye temperature, electron-phonon interaction parameter ?, plasma frequency and superconducting energy gap are given. Normal-state and superconducting data fit in a consistent picture of BCS superconductivity with ?<=1.

Vaglio, R.; Fontana, F.; Andreone, A.; Iavarone, M.; Canepa, F.; Manfrinetti, P.; Palenzona, A.

1995-02-01

144

Electrically alterable read-only memory cell with graded energy band-gap insulator  

Microsoft Academic Search

Low voltage alterability and excellent memory retention have been obtained with a novel EAROM cell that has a graded energy band-gap film as the first insulator of a Floating-Gate type memory. The graded energy band-gap insulator can enhance charge injection without deteriorating memory retention, because the energy band-gap is narrowed only at the silicon substrate interface. A graded energy band-gap

S. Hijiya; T. Ito; T. Nakamura; N. Toyokura; H. Ishikawa

1980-01-01

145

A superconducting linac as the driver of the energy amplifier  

SciTech Connect

Because of the safer and more reliable mode of operation, a Superconducting Linac is proposed here as the proton beam accelerator which drives a nuclear plant based on the concept of the Energy Amplifier. The accelerator has also high electric power efficiency. An example based on the net generation of 400 MW (electric) is described here. This requires a proton beam energy of 1 GeV with a continuous beam current of 10 mA, corresponding to a beam power of 10 MW.

Ruggiero, A.G.

1996-10-11

146

Multilayer Structures Based on Doped Graded-Band-Gap Semiconductors: Features of Energy Band Diagram  

Microsoft Academic Search

The paper theoretically examines the distinctive features of the energy band gap diagram of symmetric multilayer structures based on uniformly doped graded-band-gap semiconductors with constant gradients of energy band gap and electron affinity. By means of analytical and numerical calculations, it is shown that the energy band diagram of such multilayer structures substantially depends on the layer thickness, with its

B. S. Sokolovskii

1997-01-01

147

Evidence for single-gap superconductivity in Mg ( B1-x Cx ) 2 single crystals with x=0.132 from point-contact spectroscopy  

NASA Astrophysics Data System (ADS)

We report the results of the first directional point-contact measurements in Mg(B1-xCx)2 single crystals with 0.047?x?0.132 . The two-gap superconductivity typical of MgB2 persists up to x=0.105 . In this region, the values of the gaps ?? and ?? were determined by fitting the Andreev-reflection conductance curves with a two-band Blonder-Tinkham-Klapwijk (BTK) model, and confirmed by the single-band BTK fit of the ? - and ? -band conductances, separated by means of a magnetic field. At x=0.132 , when Tc=19K , we clearly observed the merging of the two gaps into one of amplitude ??3meV .

Gonnelli, R. S.; Daghero, D.; Calzolari, A.; Ummarino, G. A.; Dellarocca, Valeria; Stepanov, V. A.; Kazakov, S. M.; Zhigadlo, N.; Karpinski, J.

2005-02-01

148

Novel anisotropy in the superconducting gap structure of Bi2Sr2CaCu2O(8+delta) probed by quasiparticle heat transport.  

PubMed

Since the nature of pairing interactions is manifested in the superconducting gap symmetry, the exact gap structure, particularly any deviation from the simple d(x(2)-y(2)) symmetry, would help in elucidating the pairing mechanism in high- T(c) cuprates. Anisotropic heat transport measurement in Bi(2)Sr(2)CaCu(2)O(8+delta) reveals that the quasiparticle populations are different for the two nodal directions and thus the gap structure must be uniquely anisotropic, suggesting that pairing is governed by interactions with a rather complicated anisotropy. Intriguingly, it is found that the "plateau" in the magnetic-field dependence of the thermal conductivity is observed only in the b-axis transport. PMID:11955171

Ando, Yoichi; Takeya, J; Abe, Yasushi; Sun, X F; Lavrov, A N

2002-03-26

149

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

150

Superconducting magnetic bearings for energy storage flywheels  

Microsoft Academic Search

We are investigating the use of flywheels for energy storage. Flywheel devices need to be of high efficiency and an important source of losses is the bearings. In addition, the requirement is for the devices to have long lifetimes with minimal or no maintenance. Conventional rolling element bearings can and have been used, but a noncontact bearing, such as a

T. Coombs; A. M. Campbell; R. Storey; R. Weller

1999-01-01

151

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

152

Energy gap from tunneling and metallic contacts onto MgB{sub 2}: Possible evidence for a weakened surface layer  

SciTech Connect

Point-contact tunnel junctions using a Au tip on sintered MgB{sub 2} pellets reveal a sharp superconducting energy gap that is confirmed by subsequent metallic contacts made on the same sample. The peak in the tunneling conductance and the metallic contact conductance follow the BCS form, but the gap values of 4.3{minus}4.6 meV are less than the weak-coupling BCS value of 5.9 meV for the bulk T{sub c} of 39 K. The low value of {Delta} compared to the BCS value for the bulk T{sub c} is possibly due to chemical reactions at the surface.

Schmidt, Herbert; Zasadzinski, J. F.; Gray, K. E.; Hinks, D. G.

2001-06-01

153

Hybridization and superconducting gaps in heavy-fermion superconductor PuCoGa5 probed via the dynamics of photoinduced quasiparticles  

SciTech Connect

We have examined the relaxation of photoinduced quasiparticles in the heavy-fermion superconductor PuCoGa{sub 5}. The deduced electron-phonon coupling constant is incompatible with the measured superconducting transition temperature T{sub c}, which speaks against phonon-mediated superconducting pairing. Upon lowering the temperature, we observe an order-of-magnitude increase of the quasiparticle relaxation time in agreement with the phonon bottleneck scenario - evidence for the presence of a hybridization gap in the electronic density of states. The modification of photoinduced reflectance in the superconducting state is consistent with the heavy character of the quasiparticles that participate in Cooper pairing. The discovery of relatively high-temperature superconductivity in the Pu-based compounds PuCoGa{sub 5} (T{sub c} = 18.5 K) and PuRhGa{sub 5} (T{sub c} = 8.7 K) has renewed the interest in actinide materials research. The Pu-based superconductors share the HoCoGa{sub 5}-type tetragonal lattice stucture with the Ce-based series of compounds (CeRhIn{sub 5}, CeCoIn{sub 5}, and CeIrIn{sub 5}) commonly referred to as '115' materials. In the Ce-based 115 compounds, CeIrIn{sub 5} (T{sub c} = 0.4 K) and CeCoIn{sub 5} (T{sub c} = 2.3 K), display superconductivity at ambient pressure. Both Ce- and Pu-based 115 compounds display the heavy fermion behavior resulting from the influence of 4f (Ce) and 5f (Pu) electrons. The most intriguing question concerns the origin of superconductivity (SC) in the 115 materials. In the Ce series, the d-wave symmetry of the SC order parameter and the proximity of SC order to magnetism have lead to a widespread belief that the unconventional SC is induced by antiferromagnetic spin fluctuations. In the Pu compounds, two possible scenarios regarding the SC mechanism have been considered: one approach favors a magnetically mediated unconventional SC similar to that in CeCoIn{sub 5}. In the other scenario, the conventional SC is mediated by phonons, where the strength of the electron-phonon (e-ph) coupling {lambda} is the crucial parameter that sets the superconducting transition temperature T{sub c}. In this Letter, we present a measurement of the e-ph coupling constant {lambda} via the pump-probe optical study of the room-temperature relaxation time of photoinduced reflectance. We find that e-ph coupling ({lambda} = 0.2-0.26) is too weak to explain the high T{sub c} of PuCoGa{sub 5} and that phonon-mediated superconductivity is unlikely in this material. Upon lowering the temperature in the normal state (T > T{sub c}), we find an order-of-magnitude increase in the relaxation time consistent with a phonon bottleneck, similar to other heavy-fermion materials, which provides the first optical evidence of the presence of a hybridization gap in the electronic density of states (DOS). Below T{sub c}, the photoinduced response exhibits dramatic changes that we ascribe to the opening of the superconducting (SC) gap at the Fermi level. The observed dynamics confirms that the same quasiparticles detected in the normal state, i.e., the heavy quasiparticles, also participate in the SC pairing. Our study is the first to directly probe the electronic structure of PuCoGa{sub 5} in the SC state and corroborate that fact. Our results are consistent with the theoretical investigations, which find that the electronic structure is dominated by cylindrical sheets of Fermi surfaces with large 5f electron character, suggesting that the delocalized 5f electrons of Pu playa key role in the superconducting pairing.

Talbayev, Diyar [Los Alamos National Laboratory; Trugman, Stuart A [Los Alamos National Laboratory; Zhu, Jian - Xin [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Kennison, John A [Los Alamos National Laboratory; Mitchell, Jeremy N [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Sarrao, John L [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory; Burch, Kenneth S [CANADA; Chia, Elbert E. M. [CANADA

2009-01-01

154

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

155

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

156

Control aspects of the Tacoma superconducting magnetic energy storage project  

SciTech Connect

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

Hauer, J.F.; Boenig, H.J.

1987-05-01

157

Effects of out-of-plane disorder on the nodal quasiparticle and superconducting gap in single-layer Bi2Sr1.6L0.4CuO6+? (L=La,Nd,Gd)  

NASA Astrophysics Data System (ADS)

How out-of-plane disorder affects the electronic structure has been investigated for the single-layer cuprates Bi2Sr1.6L0.4CuO6+? ( L=La , Nd, and 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 quasiparticle width increases, the antinodal 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 antinodal gap and the depression of the superconducting gap in the nodal region.

Hashimoto, M.; Yoshida, T.; Fujimori, A.; Lu, D. H.; Shen, Z.-X.; Kubota, M.; Ono, K.; Ishikado, M.; Fujita, K.; Uchida, S.

2009-04-01

158

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

159

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

160

Can renewable and unconventional energy sources bridge the global energy gap in the 21st century?  

Microsoft Academic Search

Energy experts project that global oil supplies will only meet demand until global oil production has peaked sometime between 2013 and 2020. Declining oil production after peak production will cause a global energy gap to develop, which will have to be bridged by unconventional and renewable energy sources. Nuclear, solar and hydrogen are destined to become major energy sources during

Mamdouh G. Salameh

2003-01-01

161

Weak Spin Fluctuation with Finite Wave Vector and Superconducting Gap Symmetry in KxFe2-ySe2: 77Se Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We report 77Se-nuclear magnetic resonance (NMR) results down to sufficiently low temperatures under magnetic fields parallel to both the ab-plane and the c-axis in a paramagnetic/superconducting (PM/SC) phase of KxFe2-ySe2. The observation of anisotropy in the orbital part of the Knight shift results in the anisotropy of its spin part increasing on approaching the transition temperature. The anisotropy of the Korringa relation suggests the presence of the weak spin fluctuations with a finite wave vector \\mbi{q}, which induce the magnetic fluctuations along the ab-plane at the Se site. Such fluctuations do not correspond to the stripe (?,0) correlation of the Fe moment observed in many Fe-based superconductors, and are not contradictory to weak (?,?) correlations. The nuclear spin--lattice relaxation rate 1/T1 shows a field-independent T1 T˜ const. behavior at low temperatures for H\\parallel ab, which is attributed to the nonzero density of states at the Fermi level and can be explained by the sign-changing order parameter even for nodeless gaps. The temperature dependence of 1/T1 is reproduced well by nodeless models with two isotropic gaps or a single anisotropic gap. The obtained gap magnitude in the isotropic two-gap model is comparable to those obtained in the angle-resolved photoemission spectroscopy experiments.

Kotegawa, Hisashi; Tomita, Yusuke; Tou, Hideki; Mizuguchi, Yoshikazu; Takeya, Hiroyuki; Takano, Yoshihiko

2012-10-01

162

Evidence for nodeless superconducting gap in NaFe1-xCoxAs from low-temperature thermal conductivity measurements  

NASA Astrophysics Data System (ADS)

The thermal conductivity of optimally doped NaFe0.972Co0.028As (Tc ˜ 20 K) and overdoped NaFe0.925Co0.075As (Tc ˜ 11 K) single crystals were measured down to 50 mK. No residual linear term ?0/T is found in zero magnetic field for both compounds. Applying a field H = 3 T (?Hc2/12) does not noticeably increase ?0/T in NaFe1.972Co0.028As. The ?0/T of overdoped NaFe1.925Co0.075As shows a field dependence similar to the optimally doped BaFe1.85Co0.15As2. All these results suggest nodeless superconducting gaps in NaFe1-xCoxAs from the optimal doping to the overdoped regime, with low anisotropy or ratio between the magnitudes of different gaps.

Zhou, S. Y.; Hong, X. C.; Qiu, X.; Pan, B. Y.; Zhang, Z.; Li, X. L.; Dong, W. N.; Wang, A. F.; Luo, X. G.; Chen, X. H.; Li, S. Y.

2013-01-01

163

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

164

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.

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

165

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

166

Survey of domestic research on superconducting magnetic energy storage  

SciTech Connect

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

Dresner, L.

1991-09-01

167

Survey of domestic research on superconducting magnetic energy storage  

SciTech Connect

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

Dresner, L.

1991-09-01

168

Superconducting detectors for particles from atoms to proteins  

NASA Astrophysics Data System (ADS)

Superconducting detectors are ideal for detecting low-energy particles from atoms to proteins of which kinetic energies range from less than 1 keV to ˜30 keV compatible with analytical instruments for ordinary laboratory use. The superconducting detectors have the advantages of detecting low energy quanta, because a threshold equivalent to the gap parameter (?) is extremely small: ˜meV that is one-thousandth of the band gap of semiconductor detectors. Any low-energy quanta including phonons created by individual particle hit-events on the detector surface can be detected through Cooper-pair breaking. Such detectors as superconducting tunnel junctions (STJs) and superconducting stripline detectors (SSLDs) are promising for developing advanced analytical instruments for nuclear physics, basic chemistry, and biology. Especially, mass spectrometry (MS) equipped with the superconducting detectors has been producing the remarkable results, which have never been obtained by conventional MS instruments.

Ohkubo, M.

2008-09-01

169

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

170

The superconducting gaps of C-substituted and Al-substituted MgB2 single crystals by point-contact spectroscopy  

NASA Astrophysics Data System (ADS)

We studied the effects of carbon and aluminum substitutions on the gaps of the two-band superconductor MgB2 by means of point-contact measurements in Mg(B1-xCx)2 and Mg1-yAlyB2 single crystals with 0 x 0.132 and 0 y 0.21. The gap amplitudes, and , were determined by fitting the conductance curves of the point contacts with the standard Blonder-Tinkham-Klapwijk (BTK) model generalized to the two-band case. Whenever possible, their values were confirmed by the independent fit (with a single-band BTK model) of the partial contribution of the two bands to the conductance, separated by means of a suitable magnetic field B*. In C-substituted crystals, the two gaps remain clearly distinct up to x 0.10, but at x = 0.132 we observed for the first time their merging into a single gap 3 meV with a gap ratio 2 = kBTc close to the standard BCS value. In Al-substituted crystals, we found no evidence of this gap merging. Instead, reaches the value 0.4 meV at y = 0.21, where saturates at about 4 meV. These results are compared with other recent experimental findings in polycrystals and with the predictions of the models for multiband superconductivity.

Daghero, D.; Gonnelli, R. S.; Calzolari, A.; Ummarino, G. A.; Dellarocca, Valeria; Stepanov, V. A.; Zhigadlo, N.; Kazakov, S. M.; Karpinski, J.

2005-03-01

171

Energy gap tuning in uniaxial strained zigzag graphene nanoribbons  

Microsoft Academic Search

The band structures of zigzag graphene nanoribbons under uniaxial strain are investigated within the mean-field Hubbard model. In addition to the intrinsic gap modification, the strain can induce two additional gaps in the conduction and valence bands when the compressive strain along the armchair direction or the tensile strain along the zigzag direction is greater than 13%. These band gap

Fei Liu; Xiaoyan Liu; Jinfeng Kang

2011-01-01

172

Length and energy gap dependences of thermoelectricity in nanostructured junctions.  

PubMed

The possibilities of an enhanced thermoelectric figure of merit value, ZT, in a nanostructured junction are examined for a wide range of parameter values in a theoretical model. Our research shows that the figure of merit can take a very large maximum, which depends both on the length and the energy gap values. The maximum of ZT is achieved when the Fermi level of the electrodes is aligned to the edge of the electronic transmission function of the junction, where both the conductance and the Seebeck constant are significantly enhanced. On the basis of our results, we conclude that nanowires and molecular junctions form a special class of systems where a large ZT can be expected in some cases. PMID:23528878

Asai, Yoshihiro

2013-03-25

173

Department of Energy`s Wire Development Workshop - Superconductivity program for electric systems  

SciTech Connect

The 1996 High-Temperature Superconducting Wire Development Workshop was held on January 31--February 1 at the Crown Plaza Tampa Westshore in Tampa, Florida. The meeting was hosted by Tampa Electric Company and sponsored by the Department of Energy`s Superconductivity Program for Electric Systems. The meeting focused on recent high-temperature superconducting wire development activities in the Department of Energy`s Superconductivity Systems program. Tampa Electric`s Greg Ramon began the meeting by giving a perspective on the changes now occurring in the utility sector. Major program wire development accomplishments during the past year were then highlighted, particularly the world record achievements at Los Alamos and Oak Ridge National Laboratories. The meeting then focussed on three priority technical issues: thallium conductors; AC losses in HTS conductors; and coated conductors on textured substrates. Following in-depth presentations, working groups were formed in each technology area to discuss and critique the most important current research and development issues. The working groups identified research areas that have the potential for greatly enhancing the wire development effort. These areas are discussed in the summary reports from each of the working groups. This document is a compilation of the workshop proceedings including all general session presentations and summary reports from the working groups.

NONE

1996-06-01

174

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

SciTech Connect

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

None

2010-10-01

175

Stability and Rate of Superconducting Magnet Winding Transition into Normal State as a Result of Energy Losses During Energy Removal.  

National Technical Information Service (NTIS)

Calculations of the effect of energy losses on stability and rate of superconducting magnet winding transition into normal state under adiabatic conditions during energy removal are conducted. The effects of properties and parameters of conductors on stab...

D. Kabat V. G. Luppov

1982-01-01

176

Gap filling strategies for long term energy flux data sets  

Microsoft Academic Search

At present a network of over 100 field sites are measuring carbon dioxide, water vapor and sensible heat fluxes between the biosphere and atmosphere, on a nearly continuous basis. Gaps in the long term measurements of evaporation and sensible heat flux must be filled before these data can be used for hydrological and meteorological applications. We adapted methods of gap

Eva Falge; Dennis Baldocchi; Richard Olson; Peter Anthoni; Marc Aubinet; Christian Bernhofer; George Burba; Reinhart Ceulemans; Robert Clement; Han Dolman; André Granier; Patrick Gross; Thomas Grünwald; David Hollinger; Niels-Otto Jensen; Gabriel Katul; Petri Keronen; Andrew Kowalski; Chun Ta Lai; Beverley E Law; Tilden Meyers; John Moncrieff; Eddy Moors; J William Munger; Kim Pilegaard; Üllar Rannik; Corinna Rebmann; Andrew Suyker; John Tenhunen; Kevin Tu; Shashi Verma; Timo Vesala; Kell Wilson; Steve Wofsy

2001-01-01

177

Band Gap Energy and Band Lineup of III-V Alloy Semiconductors Incorporating Nitrogen and Boron  

Microsoft Academic Search

The band gap energy and band lineup of 15 binary, 42 ternary and 39 quaternary III-V alloy semiconductors composed of (B, Al, Ga, In)(N, P, As, Sb) are calculated by mean of the dielectric method of Van Vechten and the Harrison model, respectively. The alloys including N are predicted to have negative band gap energy in most of the compositional

Shiro Sakai; Yoshihiro Ueta; Yoji Terauchi

1993-01-01

178

Temperature effects on the band-gap energy in p-type III-V semiconductors  

Microsoft Academic Search

We apply a new expression for the valence-band random-phase-approximation dielectric function of semiconductors with a zinc-blende structure to determine the temperature dependence of the band-gap energy in p-doped GaAs. Our results demonstrate that the electronic contribution to the energy-gap shift is nearly temperature independent.

Witold Bardyszewski; David Yevick

1989-01-01

179

Electronic Specific Heat of La2-xSrxCuO4: Pseudogap Formation and Reduction of the Superconducting Condensation Energy  

NASA Astrophysics Data System (ADS)

To examine the so-called small pseudogap and the superconducting (SC) condensation energy U(0), the electronic specific heat Cel was measured on La2-xSrxCuO4 up to ˜120 K. In samples with doping level p (=x) less than ˜0.2, small pseudogap behavior appears in the ? (=Cel/T) vs T curve around the mean-field critical temperature for a d-wave superconductor Tco (=2?0/(4--5)kB), where ?0 is the maximum gap at T? Tc. The condensation energy U(0) is largely reduced in the pseudogap regime ( p? 0.2). The reduction of U(0) can be well reproduced by introducing an effective SC energy scale {?0}eff=? p?0 (?=4.5) instead of ?0. The effective SC energy scale is discussed in relation to the coherent pairing gap formed over the nodal Fermi arc.

Matsuzaki, Toshiaki; Momono, Naoki; Oda, Migaku; Ido, Masayuki

2004-08-01

180

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

PubMed

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

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

2013-03-21

181

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

182

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

183

Conductance spectrum and superconducting gap structures observed in c-axis FeSe0.46Te0.54/Au junctions  

NASA Astrophysics Data System (ADS)

The electric transport properties of superconducting c-axis FeSe0.46Te0.54/Au (S/N) junctions, fabricated using pulsed laser deposition, have been investigated in the temperature range of 2 K to the superconducting transition temperature Tc (~ 13.5 K) and in the presence of applied magnetic fields from 0 to 9 T. A large zero bias conductance peak has always been observed in every conductance spectrum of several batches of junctions. In addition, we have found several gap-like features. Using the extended BTK theory with the currently favored nodeless S+/--wave symmetry, our conductance spectrum can be reproduced quite well in the low bias range with ?1 = 4 meV and ?2 = 6 meV at 2 K. However, the experimental conductance spectrum is substantially below the one calculated in the high bias range. Furthermore, there is a conductance minimum at approximately 20 meV, which may be the reason for the discrepancy.

Shen, Y. T.; Li, Y. S.; Lin, K. C.; Wu, M. K.; Chi, C. C.

2013-09-01

184

Low-energy physical properties of high- Tc superconducting Cu oxides: A comparison between the resonating valence bond and experiments  

NASA Astrophysics Data System (ADS)

In a recent review by Anderson and co-workers, it was pointed out that an early resonating valence bond (RVB) theory is able to explain a number of unusual properties of high-temperature superconducting (SC) Cu oxides. Here we extend previous calculations to study more systematically the low-energy physical properties of the plain vanilla d -wave RVB state, and to compare the results with the available experiments. We use a renormalized mean-field theory combined with variational Monte Carlo and power Lanczos methods to study the RVB state of an extended t-J model in a square lattice with parameters suitable for the hole-doped Cu oxides. The physical observable quantities we study include the specific heat, the linear residual thermal conductivity, the in-plane magnetic penetration depth, the quasiparticle energy at the antinode (?,0) , the superconducting energy gap, the quasiparticle spectra, and the Drude weights. The traits of nodes (including kF , the Fermi velocity vF , and the velocity along Fermi surface v2 ), and the SC order parameter are studied. Comparisons of the theory and the experiments in cuprates show an overall qualitative agreement, especially on their doping dependences.

Yang, Kai-Yu; Shih, C. T.; Chou, C. P.; Huang, S. M.; Lee, T. K.; Xiang, T.; Zhang, F. C.

2006-06-01

185

Enhanced energy relaxation process of a quantum memory coupled to a superconducting qubit  

NASA Astrophysics Data System (ADS)

For quantum information processing, each physical system has a different advantage as regards implementation, so hybrid systems that benefit from the advantage of several systems would provide a promising approach. One common hybrid approach involves combining a superconducting qubit as a controllable qubit and another quantum system with a long coherence time as a memory qubit. The use of a superconducting qubit gives us excellent controllability of the quantum states, and the memory qubit is capable of storing information for a long time. It has been believed that selective coupling can be realized between a superconducting qubit and a memory qubit by tuning the energy splitting between them. However, we have shown that this detuning approach has a fundamental drawback as regards energy leakage from the memory qubit. Even if the superconducting qubit is effectively separated by reasonable detuning, a non-negligible incoherent energy relaxation in the memory qubit occurs via residual weak coupling when the superconducting qubit is affected by severe dephasing. This energy transport from the memory qubit to the control qubit can be interpreted as the appearance of the anti-quantum Zeno effect induced by the fluctuation in the superconducting qubit. We also discuss possible ways to avoid this energy relaxation process, which is feasible with existing technology.

Matsuzaki, Yuichiro; Nakano, Hayato

2012-11-01

186

Superconductivity in 4 angstrom single-walled carbon nanotubes.  

PubMed

Investigation of the magnetic and transport properties of single-walled small-diameter carbon nanotubes embedded in a zeolite matrix revealed that at temperatures below 20 kelvin, 4 angstrom tubes exhibit superconducting behavior manifest as an anisotropic Meissner effect, with a superconducting gap and fluctuation supercurrent. The measured superconducting characteristics display smooth temperature variations owing to one-dimensional fluctuations, with a mean-field superconducting transition temperature of 15 kelvin. Statistical mechanic calculations based on the Ginzburg-Landau free-energy functional yield predictions that are in excellent agreement with the experiments. PMID:11431560

Tang, Z K; Zhang, L; Wang, N; Zhang, X X; Wen, G H; Li, G D; Wang, J N; Chan, C T; Sheng, P

2001-06-29

187

Superconductive energy storage inductor-converter units for power systems  

Microsoft Academic Search

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

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

1975-01-01

188

Reentrant behavior of superconducting alloys  

NASA Astrophysics Data System (ADS)

A dirty BCS superconductor with magnetic impurities is studied. The asymptotic solution of the thermodynamics of such a superconductor with spin 1/2 and 7/2 magnetic impurities is found. To this end, the system's free energy f(H, ?) is bounded from above and below by mean-field type bounds, which are shown to coalesce almost exactly in the thermodynamic limit, provided the impurity concentration is sufficiently small. The resulting mean-field equations for the gap ? and a parameter ?, characterizing the impurity subsystem, are solved and the solution minimizing f is found for various values of magnetic coupling constant g and impurity concentration x. The phase diagrams of the system are depicted with five distinct phases: the normal phase, unperturbed superconducting phase, perturbed superconducting phase with nonzero gap in the excitation spectrum, perturbed gapless superconducting phase and impurity phase with completely suppressed superconductivity. In the perturbed superconducting phase, superconductivity coexists with magnetic order. The computed phase diagrams are in good agreement with experimental data for Ce1 - xGdxRu2 and for certain pseudoternary systems, e.g. (Er1 - xHox)Rh4B4. Furthermore, evidence of reentrant superconductivity and Jaccarino-Peter compensation is found. The credibility of the theory is verified by testing the dependence of the superconducting transition temperature Tc on x. Very good quantitative agreement with experimental data is obtained for several alloys: (La1 - xCex)Al2, (La1 - xGdx)Al2 and (La0.8 - xY0.20)Cex. The theory presented improves earlier developments in this field.

Borycki, Dawid; Ma?kowiak, Jan

2011-03-01

189

Superconducting gap measurements on Co-doped SrFe2As2 single crystals by point contact spectroscopy  

NASA Astrophysics Data System (ADS)

We present point contact spectroscopy results on single crystal Co-doped SrFe2As2. Two sets of Andreev-like enhancements in conductance are seen with nominally c-axis contacts. For temperatures up to Tc = 14.5 K, the conductance is fit to a Blonder-Tinkham-Klapwijk (BTK) model extended to two independent bands with lifetime broadening [1]. We also consider recently proposed s±-wave extensions to BTK [2,3]. Many recent reports claim multiple gaps in the 122 compounds, however care must be taken to distinguish the presence of Andreev peaks from other excitation modes. We find robust evidence of an SC gap at 6 meV and evidence of another conductance enhancement at 12 mV that tracks the inner gap. The origin of this feature, and of multi-gap features as measured by PCS, are discussed. [1] G. E. Blonder, M. Tinkham, and T. M. Klapwijk, PRB 25, 45154532 (1982). [2] A. A. Golubov, et al. PRL 103, 077003 (2009). [3] I. B. Sperstad, J. Linder, A. Sudbo, PRB 80, 144507 (2009).

Hunt, Cassandra R.; Arham, H. Z.; Park, W. K.; Greene, L. H.; Gillett, J.; Sebastian, S.

2011-03-01

190

Inelastic Neutron Scattering Studies of High-Energy Spin Excitations in Superconducting BaFe1.9Ni0.1As2  

NASA Astrophysics Data System (ADS)

Understanding how the spin fluctuations evolve with doping in iron pnictide superconductors is important because spin fluctuations may mediate electron pairing for superconductivity in these materials. Upon doping, the spin fluctuation persists long after the long-range antiferromagnetism is destroyed. More importantly, spin excitations are coupled to superconductivity in the appearance of a neutron magnetic resonance and a superconductivity-induced spin gap. However, all current neutron scattering results in iron based superconductors are confined to low energy excitations except for the ``11'' FeTe1-xSex system, which shows incommensurate excitations that are not found in other iron pnictide systems. Therefore, how the spin waves in parent compounds of the ``122'' (AFe2As2, A = Ca, Sr, Ba) system will evolve when the system becomes an optimal superconductor is still an open question. We use time-of-flight spectroscopy to determine S (Q,?) at energy regions not accessed before. We compare spin fluctuations of iron arsenide superconductors with those of high-Tc copper oxides and discuss their role in the superconductivity of these materials.

Liu, Mengshu; Abernathy, Douglas; Zhao, Jun; Wang, Meng; Zhang, Chenglin; Wang, Miaoyin; Dai, Pengcheng

2010-03-01

191

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

Microsoft Academic Search

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

H. J. Boenig; J. F. Hauer

1985-01-01

192

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

Microsoft Academic Search

Recent advances on superconducting magnetic bearing (SMB) technologies for flywheel energies storage systems (FESSs) are reviewed based on the results of NEDO flywheel project (2000–2004). We constructed a radial-type SMB model for 100kWh class FESSs and evaluated the bearing characteristics. The SMB model consists of a superconducting stator of YBCO bulks and a NdFeB permanent magnet circuit. The levitation force

N. Koshizuka

2006-01-01

193

Research on the application of superconducting magnetic energy storage in wind\\/photovoltaic generation system  

Microsoft Academic Search

Because of the renewable energy generation (for example wind and photovoltaic) becomes a new research hotspot, people pays more attention to the problem of power fluctuation of wind\\/PV (photovoltaic) generation as the wind velocity and solar insolation intensity are intermittent and unpredictable. To solve the problem, this paper introduced superconducting magnetic energy storage (SMES). Compared with other energy storage, SMES

Hui Zhang; Hai Dou; Jing Ren; Jinqi Li; Hongwei Zhang

2009-01-01

194

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

NASA Astrophysics Data System (ADS)

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. The major features and costs of a jointly developed 5000 MWh SMES plant design are described.

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

195

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

196

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

197

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

Microsoft Academic Search

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

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

1996-01-01

198

A Study of Corona Discharge Rate and Energy Loss in Spark Gaps  

Microsoft Academic Search

A study was carried out on the corona discharge rate and energy loss occurring within artificial cavities. An air gap with metallic electrodes was utilized to simulate the ionization sources within a cable. The corona discharge rates, obtained with varying gap spacings under different vapor pressures, showed marked deviations from the idealized behavior. thhe calculated tangent ¿ values, in terms

R. Bartnikas; G. L. d'Ombrain

1965-01-01

199

Energy-gap modulation of BN ribbons by transverse electric fields: First-principles calculations  

Microsoft Academic Search

Systematic ab initio calculations show that the energy gap of BN nanoribbons (BNNRs) with zigzag or armchair edges can be significantly reduced by a transverse electric field and be completely closed at a critical field which decreases with increasing ribbon width. In addition, a distinct gap modulation in the ribbons with zigzag edges is presented when a reversed electric field

Zhuhua Zhang; Wanlin Guo

2008-01-01

200

New modeling strategy for the fringing energy in magnetic components with air gap  

Microsoft Academic Search

This work presents a new modeling strategy to account for the energy stored in the volume around the air gap in gapped magnetic components. The approach is based on the Schwarz-Christoffel transformation, which has been extended to axisymmetrical magnetic components. The results have been validated by means of comparisons with analytical expressions (no fringing flux consideration), 2D FEA based models

L. M. Escribano; R. Prieto; J. A. Oliver; J. A. Cobos; J. Uceda

2002-01-01

201

Parity effect in a small superconducting particle  

NASA Astrophysics Data System (ADS)

Matveev and Larkin calculated the parity effect on the ground-state energy of a small superconducting particle in the regimes where the mean level spacing ? is either large or small compared to the bulk gap ?. We perform a numerical calculation which extends their results to intermediate values of ?/?.

Berger, S. D.; Halperin, B. I.

1998-09-01

202

Invariant Eigen-Operator Method of Deriving Energy-Level Gap for Noncommutative Quantum Mechanics  

NASA Astrophysics Data System (ADS)

We propose a new method to derive energy-level gap for Hamiltonians in the context of noncommutative quantum mechanics (NCQM). This method relies on finding invariant eigen-operators whose commutators with Hamiltonian are still the operators themselves but with some eigenvalue-like coefficients, which correspond to the energy-level gaps of the systems. Based on this method, only after some simple algebra, we derive the energy-level gaps for several important systems in NCQM, and most of these results have not been reported in literature so far.

Jing, Si-Cong; Fan, Hong-Yi

203

Sensing with Superconducting Point Contacts  

PubMed Central

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

Nurbawono, Argo; Zhang, Chun

2012-01-01

204

Air-gap effects in inductive energy transfer  

Microsoft Academic Search

A transformer with a separation between the primary and secondary windings can be used to transfer power to artificial organs, pacemakers or robot joints without electrical contacts or wires. This paper examines the impact of the gap fringing field in the operation of the dc-dc converter. As has been implied in previous work the power losses and EMI generated by

K. D. Papastergiou; D. E. Macpherson

2008-01-01

205

Finite-size energy gap in weak and strong topological insulators  

NASA Astrophysics Data System (ADS)

The nontrivialness of a topological insulator (TI) is characterized either by a bulk topological invariant or by the existence of a protected metallic surface state. Yet, in realistic samples of finite size, this nontrivialness does not necessarily guarantee the gaplessness of the surface state. Depending on the geometry and on the topological indices, a finite-size energy gap of different nature can appear, and, correspondingly, exhibit various scaling behaviors of the gap. The spin-to-surface locking provides one such gap-opening mechanism, resulting in a power-law scaling of the energy gap. Weak and strong TIs show different degrees of sensitivity to the geometry of the sample. As a noteworthy example, a strong TI nanowire of a rectangular-prism shape is shown to be more gapped than that of a weak TI of precisely the same geometry.

Imura, Ken-Ichiro; Okamoto, Mayuko; Yoshimura, Yukinori; Takane, Yositake; Ohtsuki, Tomi

2012-12-01

206

Pressure Dependence of Energy Gaps and Refractive Indices of Tetrahedrally Bonded Semiconductors.  

National Technical Information Service (NTIS)

The pressure dependence of energy gaps for a number of elemental and compound semiconductors is investigated employing the empirical pseudopotential method. The compressibility and the empirical pseudopotential form factors appropriate for describing the ...

Y. F. Tsay S. S. Mitra B. Bendow

1974-01-01

207

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

208

Optical and thermal band gap energy of chemically deposited bismuth(III) selenide thin films  

Microsoft Academic Search

The band gap energy of bismuth(III) selenide in thin-film form was determined using the optical and thermal methods. The optical band gap energy of 0.35eV was calculated on the basis of the recorded optical spectra in the near-infrared region, within the framework of a parabolic approximation for the dispersion relation, using the equations which arise from Fermi’s golden rule for

Biljana Pejova; Ivan Grozdanov; Atanas Tanuševski

2004-01-01

209

Energy band gap engineering in borate ultraviolet nonlinear optical crystals: ab initio studies  

Microsoft Academic Search

The development of ultraviolet (UV) nonlinear optical (NLO) crystals demands optical materials with wide energy band gaps. Here we report first-principles studies on the electronic structures in several UV NLO borates with representative structures. Combined with model analysis, we find that the oxygen non-bonding 2p orbitals play an important role on the top of valence bands. The energy band gap

Ran He; Z S Lin; Tao Zheng; He Huang; C T Chen

2012-01-01

210

Invariant Eigen-Operator Method of Deriving Energy-Level Gap for Noncommutative Quantum Mechanics  

Microsoft Academic Search

We propose a new method to derive energy-level gap for Hamiltonians in the context of noncommutative quantum mechanics (NCQM). This method relies on finding invariant eigen-operators whose commutators with Hamiltonian are still the operators themselves but with some eigenvalue-like coefficients, which correspond to the energy-level gaps of the systems. Based on this method, only after some simple algebra, we derive

Si-Cong Jing; Hong-Yi Fan

2005-01-01

211

Optical conductivity and kinetic energy of the superconducting state: A cluster dynamical mean field study  

Microsoft Academic Search

We study the evolution of the optical conductivity in the t-J model with temperature and doping using the Cluster Dynamical Mean Field Method. The transition to the superconducting state in the overdoped regime is characterized by an increase in the kinetic energy of the system, in contrast to the underdoped side where kinetic energy of the system decreases upon condensation.

K. Haule; G. Kotliar

2007-01-01

212

Kinetic energy driven superfluidity and superconductivity and the origin of the Meissner effect  

NASA Astrophysics Data System (ADS)

Superfluidity and superconductivity have many elements in common. However, I argue that their most important commonality has been overlooked: that both are kinetic energy driven. Clear evidence that superfluidity in He is kinetic energy driven is the shape of the ? transition and the negative thermal expansion coefficient below T?. Clear evidence that superconductivity is kinetic energy driven is the Meissner effect: I argue that otherwise the Meissner effect would not take place. Associated with this physics I predict that superconductors expel negative charge from the interior to the surface and that a spin current exists in the ground state of superconductors (spin Meissner effect). I propose that this common physics of superconductors and superfluids originates in rotational zero point motion. This view of superconductivity and superfluidity implies that rotational zero-point motion is a fundamental property of the quantum world that is missed in the current understanding.

Hirsch, J. E.

2013-10-01

213

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

214

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

215

Zero-energy modes and gate-tunable gap in graphene on hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

In this article, we derive an effective theory of graphene on a hexagonal boron nitride (h-BN) substrate. We show that the h-BN substrate generically opens a spectral gap in graphene despite the lattice mismatch. The origin of that gap is particularly intuitive in the regime of strong coupling between graphene and its substrate, when the low-energy physics is determined by the topology of a network of zero-energy modes. For twisted graphene bilayers, where inversion symmetry is present, this network percolates through the system and the spectrum is gapless. The breaking of that symmetry by h-BN causes the zero-energy modes to close into rings. The eigenstates of these rings hybridize into flat bands with gaps in between. The size of this band gap can be tuned by a gate voltage and it can reach the order of magnitude needed to confine electrons at room temperature.

Kindermann, M.; Uchoa, Bruno; Miller, D. L.

2012-09-01

216

Simple experimental verification of the relation between the band-gap energy and the energy of photons emitted by LEDs  

Microsoft Academic Search

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 essential simplifications of

Jürgen W Precker

2007-01-01

217

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

SciTech Connect

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

2004-05-03

218

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

219

Superconducting transition detectors for low-energy gamma-ray astrophysics  

NASA Astrophysics Data System (ADS)

A program to investigate superconducting devices such as STDs for use in high-resolution Compton telescopes and coded-aperture detectors is presented. For higher energy applications, techniques are investigated with potential for scaling to large detectors, while also providing excellent energy and positional resolution. STDs are discussed, utilizing a uniform array of spherical granules tens of microns in diameter. The typical temperature-magnetic field phase for a low-temperature superconductor, the signal produced by the superconducting-normal transition in the 32-m diameter Sn granule, and the temperature history of an STD granule following heating by an ionizing particle are illustrated.

Kurfess, James D.; Johnson, W. N.; Fritz, Gilbert G.; Strickman, M. S.; Kinzer, R. L.

1990-08-01

220

Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2  

SciTech Connect

We have performed low-temperature specific heat C and thermal conductivity {kappa} measurements on the Ni-pnictide superconductors BaNi{sub 2}As{sub 2} (T{sub c} = 0.7K) and SrNi{sub 2}P{sub 2} (T{sub c} = 1.4K). The temperature dependences C(T) and {kappa}(T) of the two compounds are similar to the results of a number of s-wave superconductors. Furthermore, the concave field responses of the residual {kappa} for BaNi{sub 2}As{sub 2} rules out the presence of nodes on the Fermi surfaces. We postulate that fully gapped superconductivity could be universal for Ni-pnictide superconductors. Specific heat data on Ba{sub 0.6}La{sub 0.4}Ni{sub 2}As{sub 2} shows a mild suppression of Tc and H{sub c2} relative to BaNi{sub 2}As{sub 2}.

Kurita, N [Los Alamos National Laboratory (LANL); Ronning, F. [Los Alamos National Laboratory (LANL); Miclea, C. F. [Los Alamos National Laboratory (LANL); Tokiwa, Y. [Los Alamos National Laboratory (LANL); Bauer, E. D. [Los Alamos National Laboratory (LANL); Subedi, Alaska P [ORNL; Singh, David J [ORNL; Sakai, H [Japan Atomic Energy Agency (JAEA); Thompson, J. D. [Los Alamos National Laboratory (LANL); Movshovich, R [Los Alamos National Laboratory (LANL)

2011-01-01

221

Excitation of Superconducting Qubits from Hot Nonequilibrium Quasiparticles  

NASA Astrophysics Data System (ADS)

Superconducting qubits probe environmental defects such as nonequilibrium quasiparticles, an important source of decoherence. We show that “hot” nonequilibrium quasiparticles, with energies above the superconducting gap, affect qubits differently from quasiparticles at the gap, implying qubits can probe the dynamic quasiparticle energy distribution. For hot quasiparticles, we predict a non-negligible increase in the qubit excited state probability Pe. By injecting hot quasiparticles into a qubit, we experimentally measure an increase of Pe in semiquantitative agreement with the model and rule out the typically assumed thermal distribution.

Wenner, J.; Yin, Yi; Lucero, Erik; Barends, R.; Chen, Yu; Chiaro, B.; Kelly, J.; Lenander, M.; Mariantoni, Matteo; Megrant, A.; Neill, C.; O'Malley, P. J. J.; Sank, D.; Vainsencher, A.; Wang, H.; White, T. C.; Cleland, A. N.; Martinis, John M.

2013-04-01

222

Photoemission Studies of High Critical Transition Temperature Superconductors: Doping Dependences, Fermi Surfaces, Superconducting Gaps, and Metal-Superconductor Interfaces  

Microsoft Academic Search

Angle-resolved photoemission spectroscopy is one of the most powerful probes of the electronic structure of a solid since it gives direct information about the energy and momentum-dependent occupied density-of-states. We have applied angle-resolved photoemission with very high energy resolution (~35 meV) to the study of the recently discovered high-temperature superconductors. This high energy resolution enables studies of the very low

Daniel Stephen Dessau

1993-01-01

223

Rugged superconducting detector for monitoring infrared energy sources in harsh environments  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

224

A double-superconducting axial bearing system for an energy storage flywheel model  

NASA Astrophysics Data System (ADS)

The bulk high temperature superconductors (HTSCs) with unique flux-pinning property have been applied to fabricate two superconducting axial bearings for an energy storage flywheel model. The two superconducting axial bearings are respectively fixed at two ends of the vertical rotational shaft, whose stator is composed of seven melt-textured YBa2Cu3O7-x (YBCO) bulks with diameter of 30 mm, height of 18 mm and rotor is made of three cylindrical axial-magnetized NdFeB permanent magnets (PM) by superposition with diameter of 63 mm, height of 27 mm. The experimental results show the total levitation and lateral force produced by the two superconducting bearings are enough to levitate and stabilize the 2.4 kg rotational shaft. When the two YBCO stators were both field cooled to the liquid nitrogen temperature at respective axial distances above or below the PM rotor, the shaft could be automatically levitated between the two stators without any contact. In the case of a driving motor, it can be stably rotated along the central axis besides the resonance frequency. This double-superconducting axial bearing system can be used to demonstrate the flux-pinning property of bulk HTSC for stable levitation and suspension and the principle of superconducting flywheel energy storage system to visitors.

Deng, Z.; Lin, Q.; Ma, G.; Zheng, J.; Zhang, Y.; Wang, S.; Wang, J.

2008-02-01

225

Specific heat to Hc2: Evidence for nodes or deep minima in the superconducting gap of underdoped and overdoped Ba(Fe1-xCox)2As2  

NASA Astrophysics Data System (ADS)

Low-temperature specific heat, C, in magnetic fields up to Hc2 is reported for underdoped Ba(Fe0.955Co0.045)2As2 (Tc = 8 K) and for three overdoped samples Ba(Fe1-xCox)2As2 (x = 0.103, 0.13, and 0.15; Tc = 17.2, 16.5, and 11.7 K, respectively). Previous measurements of thermal conductivity (as a function of temperature and field) and penetration depth on comparable-composition samples gave some disagreement as to whether there was fully gapped/nodal behavior in the under-/overdoped materials, respectively. The present work shows that the measured behavior of the specific heat ? (?C/T as T ? 0, i.e., a measure of the electronic density of states at the Fermi energy) as a function of field approximately obeys ? ? H0.5±0.1, similar to the Volovik effect for nodal superconductors, for both the underdoped and the most overdoped Co samples. However, for the two overdoped compositions x = 0.103 and 0.13, the low-field (H ? 10 T) data show a Volovik-like behavior of ? ? H0.3-0.4, followed by an inflection point, followed at higher fields by ? ? H1. We argue that, within the two-band theory of superconductivity, an inflection point may occur if the interband coupling is dominant.

Kim, J. S.; Faeth, B. D.; Wang, Y.; Hirschfeld, P. J.; Stewart, G. R.; Gofryk, K.; Ronning, F.; Sefat, A. S.; Choi, K. Y.; Kim, K. H.

2012-07-01

226

AB INITIO AND DENSITY FUNCTIONAL STUDIES OF POLYTHIOPHENE ENERGY BAND GAP  

Microsoft Academic Search

The energy band gap of intrinsic thiophene monomer and dimer were calculated using Hartree-Fock (HF) and density functional theory (DFT) methods employing various combinations of exchange and correlation functionals with electron core potential (ECP) split valence basis sets. HF overestimates band gap by up to 6.10 eV for thiophene monomers and dimers. DFT calculations with hybrid functionals (B3LYP and B3P86)

Arnold C. Alguno; Wilfredo C. Chung; Rolando V. Bantaculob; Reynaldo M. Vequizob; Hitoshi Miyata; Edgar W. Ignacio; Angelina M. Bacal

227

Electroluminescence at silicon band gap energy from mechanically pressed indium-tin-oxide\\/Si contact  

Microsoft Academic Search

Room temperature electroluminescence (EL) corresponding to Si band gap energy is observed from mechanically pressed indium-tin-oxide (ITO)\\/Si contact. The intensity of luminescence is pressure dependent and highly related to the current-voltage characteristics. Increasing pressure simultaneously reduces the rectification property and the luminescence. The physical reason for EL is attributed to the formation of an air gap between the ITO and

Ching-Fuh Lin; Miin-Jang Chen; Shu-Wei Chang; Peng-Fei Chung; Eih-Zhe Liang; Ting-Wien Su; C. W. Liu

2001-01-01

228

Influence of quasiparticle multi-tunneling on the energy flow through the superconducting tunnel junction  

SciTech Connect

Superconducting tunnel junction (STJ) detector consists of two layers of superconducting material separated by thin insulating barrier. An incident particle produces in superconductor excess nonequilibrium quasiparticles. Each quasiparticle in superconductor should be considered as quantum superposition of electron-like and hole-like excitations. This duality nature of quasiparticle leads to the effect of multi-tunneling. Quasiparticle starts to tunnel back and forth through the insulating barrier. After tunneling from biased electrode quasiparticle loses its energy via phonon emission. Eventually, the energy that equals to the difference in quasiparticle energy between two electrodes is deposited in the signal electrode. Because of the process of multi-tunneling, one quasiparticle can deposit energy more than once. In this work, the theory of branching cascade processes was applied to the process of energy deposition caused by the quasiparticle multi-tunneling. The formulae for the mean value and variance of the energy transferred by one quasiparticle into heat were derived. (authors)

Samedov, V. V.; Tulinov, B. M. [National Research Nuclear Univ. - Moscow Engineering Physics Inst., 31, Kashirskoye Shosse, 115409, Moscow (Russian Federation)

2011-07-01

229

Magnon energy gap and quantum fluctuation in a ferro-anti-ferromagnetic multisublattice system  

NASA Astrophysics Data System (ADS)

Within the framework of the linear spin wave approximation and the retarded Green's function method, the magnetic properties of a ferro-anti-ferromagnetic Heisenberg system are studied. Under certain cases, five magnon energy gaps exist in the energy band. The effects of upper surface anisotropy, spin numbers, exchange coupling, and antiferromagnetic intralayer exchange coupling on magnon energy gaps, as well as the effects of the interlayer exchange couplings on magnetization and quantum fluctuation, are discussed. Results show that antiferromagnetic (ferrimagnetic) interlayer exchange coupling plays a significant role in the magnetic properties of the system.

Zhang, Fan; Jiang, Wei; Guo, An-bang; Wang, Wei; Liu, Li-mei; Deng, Qi

2013-04-01

230

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

PubMed Central

Background Overweight develops gradually as a result of a long term surplus on the balance between energy intake and energy expenditure. Aim of this study was to quantify the positive energy balance responsible for excess body weight gain (energy gap) in young overweight children. Methods Reported data on weight and height were used of 2190 Dutch children participating in the PIAMA birth cohort study. Accumulated body energy was estimated from the weight gain observed between age 2 and age 5-7. Energy gap was calculated as the difference in positive energy balance between children with and without overweight assuming an energy efficiency of 50%. Results Ten percent of the children were overweight at the age of 5-7 years. For these children, median weight gain during 4-years follow-up was 13.3 kg, as compared to 8.5 kg in the group of children who had a normal weight at the end of the study. A daily energy gap of 289-320 kJ (69-77 kcal) was responsible for the excess weight gain or weight maintenance in the majority of the children who were overweight at the age of 5-7 years. The increase in daily energy requirement to maintain the 4.8 kilograms excess weight gain among overweight children at the end of the study was approximately 1371 kJ. Conclusions An energy gap of about 289-320 kJ per day over a number of years can make the difference between normal weight and overweight in young children. Closing the energy gap in overweight children can be achieved by relatively small behavior changes. However, much more effort is required to lose the excess weight gained.

2011-01-01

231

Transport and optical gaps and energy band alignment at organic-inorganic interfaces  

NASA Astrophysics Data System (ADS)

The transport and optical band gaps for the organic semiconductor tin (II) phthalocyanine (SnPc) and the complete energy band profiles have been determined for organic-inorganic interfaces between SnPc and III-V semiconductors. High throughput measurement of interface energetics over timescales comparable to the growth rates was enabled using in situ and real-time photoelectron spectroscopy combined with Organic Molecular Beam Deposition. Energy band alignment at SnPc interfaces with GaAs, GaP, and InP yields interface dipoles varying from -0.08 (GaP) to -0.83 eV (GaAs). Optical and transport gaps for SnPc and CuPc were determined from photoelectron spectroscopy and from optical absorption using spectroscopic ellipsometry to complete the energy band profiles. For SnPc, the difference in energy between the optical and transport gaps indicates an exciton binding energy of (0.6 +/- 0.3) eV.

Evans, D. A.; Vearey-Roberts, A. R.; Roberts, O. R.; Williams, G. T.; Cooil, S. P.; Langstaff, D. P.; Cabailh, G.; McGovern, I. T.; Goss, J. P.

2013-09-01

232

Improvement of synchronous generator damping through superconducting magnetic energy storage systems  

Microsoft Academic Search

Stabilization of a synchronous generator through control of firing angle of the power converters in superconducting magnetic energy storage (SMES) systems is considered. An optimum strategy of the firing angle control is designed so as to eliminate the transients in minimum time. A nonlinear model of a synchronous generator, its governor and exciter systems, and an SMES system connected to

A. H. M. A. Rahim; A. M. Mohammad

1994-01-01

233

Application of superconducting magnetic energy storage unit to improve the damping of synchronous generator  

Microsoft Academic Search

A systematic approach to the design of a controller for superconducting magnetic energy storage (SMES) units to improve the dynamic stability of a power system is presented. The scheme employs a proportional-integral (PI) controller to enhance the damping of the electromechanical mode oscillation of synchronous generators. The parameters of the PI controller are determined by the pole assignment method based

Chi-Jui Wu; Yuang-Shung Lee

1991-01-01

234

Enhancement of Transient Stability of an Industrial Cogeneration System with Superconducting Magnetic Energy Storage Unit  

Microsoft Academic Search

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie-line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an extemal fault of utility power system occurs.

C. T. Hsu

2002-01-01

235

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

Microsoft Academic Search

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

Y. Mitani; K. Tsuji; Y. Murakami

1988-01-01

236

Halbach array superconducting magnetic bearing for a flywheel energy storage system  

Microsoft Academic Search

In order to develop a new magnetic bearing set for a flywheel energy storage prototype, it was designed and simulated some configurations of Permanent Magnetic Bearings (PMB) and Superconducting Magnetic Bearings (SMB). The bearings were assembled with Nd-Fe-B permanent magnets and the simulations were carried out with the Finite Element Method (FEM). The PMB was designed to reduce the load

Guilherme G. Sotelo; Antonio C. Ferreira

2005-01-01

237

Design of superconducting magnetic bearings with high levitating force for flywheel energy storage systems  

Microsoft Academic Search

Hybrid superconducting magnetic bearing (SMB), using YBCO high temperature superconductors (HTS) coupled with permanent magnets, has been implemented into a flywheel energy storage (FES) system prototype. The hybrid SMB design uses permanent magnets to levitate the rotor weighing 19 kg and superconductors to stabilize the inherently unstable magnet-magnet interactions. The SMB bearings are brought into action under convenient field-cooled conditions.

Z. Xia; Q. Y. Chen; K. B. Ma; C. K. McMichael; M. Lamb; R. S. Cooley; P. C. Fowler; W. K. Chu

1995-01-01

238

Production techniques for the superconducting super collider low energy booster quadrupole magnet  

Microsoft Academic Search

The manufacturing techniques used for a prototype quadrupole magnet, developed at Lawrence Berkeley Laboratory (LBL) for the Superconducting Super Collider (SSC) Low Energy Booster (LEB), are described. The SSC LEB Ring employs 96 dipoles and 90 quadrupoles connected in series to form the magnetic lattice, requiring the use of a 21.9 mm x 23.0 mm hollow conductor for the quadrupoles.

Michael E. Morrison; Gerd U. Behrsing; Robert L. Fulton

1994-01-01

239

Design of an accelerating cavity for the Superconducting Super Collider Low-Energy Booster  

Microsoft Academic Search

The authors present the history and status of the design of the accelerator cavity to be incorporated into the Low-Energy Booster (LEB) of the Superconducting Super Collider (SSC). The LEB is a proton synchrotron, 540 m in circumference, and having 108 buckets around the ring. Acceleration programs, each 50-ms long, take place at a rate of 10\\/s. The beta change

C. C. Friedrichs; L. Walling; B. M. Campbell

1991-01-01

240

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

Microsoft Academic Search

As an outgrowth of the Technology Reinvestment Program of the 1990s, an Agreement was formed between BWXT and the DOE to promote the commercialization of Superconducting Magnetic Energy Storage (SMES) technology. Business and marketing studies showed that the performance of electric transmission lines could be improved with this SMES technology by stabilizing the line thereby allowing the reserved stability margin

CHARLES M. WEBER

2008-01-01

241

Dynamic simulation of hybrid wind-diesel power generation system with superconducting magnetic energy storage  

Microsoft Academic Search

In this paper, a systematic method of choosing the gain parameter of the wind turbine generator pitch control is presented, using the Lyapunov technique, that guarantees stability. A comprehensive digital computer model of a hybrid wind-Diesel power generation system, including the Diesel and wind power dynamics with a superconducting magnetic energy storage (SMES) unit, for stability evaluation is developed. The

S. C. Tripathy

1997-01-01

242

For prototype super-conducting magnetic energy storage (SMES) [voltage source convertor control scheme  

Microsoft Academic Search

In this paper, a synchronous frame based control method of voltage source converter (VSC) for superconducting magnetic energy storage (SMES) is presented. The model and the feedforward decoupling method are described. The design of the regulators is depicted in detail. Simulations and experiments are both demonstrate the studies

Liu Ping; Xiong Jian; Kang Yong; Zhang Hui; Chen Jian

2000-01-01

243

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

244

Large high current density superconducting solenoids for use in high energy physics experiments  

Microsoft Academic Search

Very often the study of high energy physics in colliding beam storage-rings requires a large magnetic field volume in order to detect and analyze charged particles which are created from the collision of two particle beams. Large superconducting solenoids which are greater than 1 meter in diameter are required for this kind of physics. In many cases, interesting physics can

M. A. Green; P. H. Eberhard; J. D. Taylor

1976-01-01

245

Beauty physics at the ultrahigh energies of the ELOISATRON (Euroasiatic Long Intersecting Superconducting Accelerator Synchrotron)  

SciTech Connect

The potential for experimentally studying B physics at the proposed INFN 100 TeV ELOISATRON (Euroasiatic Long Intersecting Superconducting Accelerator Synchrotron) is compared with possibilities at 40 TeV at the Superconducting Super Collider. The effect of the increase in center of mass energy on the production and decay of B mesons has been investigated, particularly with respect to the accummulation of large samples of B hadron decays necessary for the detection of CP violating effects. 13 refs., 7 figs., 1 tab.

Cox, B.

1988-02-01

246

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

247

Phase competition in trisected superconducting dome.  

PubMed

A detailed phenomenology of low energy excitations is a crucial starting point for microscopic understanding of complex materials, such as the cuprate high-temperature superconductors. Because of its unique momentum-space discrimination, angle-resolved photoemission spectroscopy (ARPES) is ideally suited for this task in the cuprates, where emergent phases, particularly superconductivity and the pseudogap, have anisotropic gap structure in momentum space. We present a comprehensive doping- and temperature-dependence ARPES study of spectral gaps in Bi(2)Sr(2)CaCu(2)O(8+?), covering much of the superconducting portion of the phase diagram. In the ground state, abrupt changes in near-nodal gap phenomenology give spectroscopic evidence for two potential quantum critical points, p = 0.19 for the pseudogap phase and p = 0.076 for another competing phase. Temperature dependence reveals that the pseudogap is not static below T(c) and exists p > 0.19 at higher temperatures. Our data imply a revised phase diagram that reconciles conflicting reports about the endpoint of the pseudogap in the literature, incorporates phase competition between the superconducting gap and pseudogap, and highlights distinct physics at the edge of the superconducting dome. PMID:23093670

Vishik, I M; Hashimoto, M; He, Rui-Hua; Lee, Wei-Sheng; Schmitt, Felix; Lu, Donghui; Moore, R G; Zhang, C; Meevasana, W; Sasagawa, T; Uchida, S; Fujita, Kazuhiro; Ishida, S; Ishikado, M; Yoshida, Yoshiyuki; Eisaki, Hiroshi; Hussain, Zahid; Devereaux, Thomas P; Shen, Zhi-Xun

2012-10-23

248

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

249

Localized exchange-correlation potential from second-order self-energy for accurate Kohn-Sham energy gap  

NASA Astrophysics Data System (ADS)

A local Kohn-Sham (KS) exchange-correlation potential is derived by localizing the second-order self-energy operator, using approximations to the linear response Sham-Schlüter equation. Thanks to the use of the resolution-of-identity technique for the calculation of the self-energy matrix elements, the method is very efficient and can be applied to large systems. The authors investigate the KS energy gaps and lowest excitation energies of atoms and small- and medium-size molecules. Reference KS energy gaps (from accurate densities) of atoms and small molecules can be reproduced with great accuracy. For larger systems they found that the KS energy gap is smaller than the one obtained from the local-density approximation, showing the importance of an ab initio correlation in the Kohn-Sham potential.

Fabiano, E.; Della Sala, F.

2007-06-01

250

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

251

Household energy studies: the gap between theory and method  

Microsoft Academic Search

At the level of theory it is now widely accepted that energy consumption patterns are a complex technical and socio-cultural phenomenon and to understand this phenomenon, it must be viewed from both engineering and social science perspectives. However, the methodological approaches taken in household energy studies lag behind the theoretical advances made in the last ten or fifteen years. The

Tracey Crosbie

2006-01-01

252

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

253

Conductivity peak, relaxation dynamics, and superconducting gap of YBa{sub 2}Cu{sub 3}O{sub 7} studied by terahertz and femtosecond optical spectroscopies  

SciTech Connect

Recent measurements at microwave, terahertz (THz), and infrared frequencies have revealed a peak in {sigma}{sub 1} below {ital T}{sub {ital c}}. Based on our THz measurements, which were performed on high quality, single crystal films of YBCO (900 and 500 A), we have found that {sigma}{sub 1} features a peak which increases in amplitude and shifts to lower temperatures as frequency changes from 1.2 to 0.4 THz. Although the quasiparticle relaxation time extracted from these results using the two-fluid Drude model exhibits an enhancement below {ital T}{sub {ital c}}, the analysis may not be adequate to account for the strong frequency dependence of the conductivity peak by the competition between the drop in scattering rate and the decreasing normal fluid density with temperature. On the contrary, we were able to account for the frequency dependent {sigma}{sub 1} by fitting with Mattis-Bardeen theory (modified to include scattering) using a slower average rate of increase of the anisotropic gap than for the BCS case as temperature decreases below {ital T}{sub {ital c}}. This is consistent with the higher normal fluid density (higher than Gorter-Casimir values) from the two-fluid model interpretation of our THz results. Thus, we have found evidence of BCS coherence factors in a high-{ital T}{sub {ital c}} superconductor with a slower than BCS gap increase below {ital T}{sub {ital c}}. We have discussed the role of coherence factors to account for the presence of the conductivity peak and the absence of the peak in NMR relaxation rate. Furthermore, we have presented a model for the quasiparticle relaxation time measured by the femtosecond pump-probe spectroscopy. This model allowed us to find a fit to the temperature-dependent energy gap function which is also consistent with the slower gap increase below {ital T}{sub {ital c}}.

Frenkel, A.; Gao, F.; Liu, Y.; Whitaker, J.F.; Uher, C. [Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Hou, S.Y.; Phillips, J.M. [AT& T Bell Laboratory, Murray Hill, New Jersey 07974 (United States)

1996-07-01

254

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

NASA Astrophysics Data System (ADS)

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 magnet bearing (PMB) and superconducting magnetic bearing (SMB). This paper, discusses the design of the permanent magnet bearing (PMB) and the dynamics of the new energy storage flywheel system.

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

2007-04-01

255

Average energy gap in III-V semiconductors and ternary compounds  

Microsoft Academic Search

The average energy gap Eg of IV and III-V type semiconductors is calculated from the E0 and E2 transition energies in relation to the 'one gap Penn model' (1962) and from epsilon 2(E).Eg is given by: Eg=M0\\/( epsilon (0)-1) where M0=(2\\/ pi ) integral 0infinity epsilon 2(E)dE. Taking into account Eg given by Phillips (1970) as Eg2=Eh2+C2, the variation of

C. Ance

1979-01-01

256

Empirical determination of the energy band gap narrowing in highly doped n+ silicon  

NASA Astrophysics Data System (ADS)

Highly doped regions in silicon devices should be analyzed using Fermi-Dirac statistics, taking into account energy band gap narrowing (BGN). An empirical expression for the BGN as a function of dopant concentration is derived here by matching the modeled and measured thermal recombination current densities J0 of a broad range of n+ dopant concentration profiles prepared by phosphorus diffusion. The analysis is repeated with Boltzmann statistics in order to determine a second empirical expression for the apparent energy band gap narrowing, which is found to be in good agreement with previous work.

Yan, Di; Cuevas, Andres

2013-07-01

257

First Beam Halo Calculations for the Superconducting Linear Accelerator of the Energy Amplifier  

NASA Astrophysics Data System (ADS)

For a first analysis of the Halo effect in the superconducting linear accelerator for a Full Scale Energy Amplifier (C. Rubbia and J.A. Rubio, "A Tentative Program Towards a Full Scale Energy Amplifier", CERN/LHC/96-11 (EET), Geneva 15th July 1996.) , a new tracking code based on a core particle model has been developed. The computer code is described and simulation results of nonlinear particle motion in the optimized accelerating structure are presented.

Wrulich, A.

1997-05-01

258

Study on high temperature superconducting magnetic bearing for 10 kWh flywheel energy storage system  

Microsoft Academic Search

Flywheel energy storage systems with high temperature superconducting magnetic bearings are expected for load leveling use. A 1 kWh flywheel of 600 mm diameter was developed and the maximum energy storage of 1.4 kWh at 20,000 RPM was attained. For the development of a large capacity flywheel system, it is necessary to sophisticate the cooling system and improve the performance

Shigeo Nagaya; N. Kashima; M. Minami; H. Kawashima; S. Unisuga

2001-01-01

259

Design and manufacture of a high temperature superconducting magnetic energy storage device  

Microsoft Academic Search

Micro-Superconducting Magnetic Energy Storage (?-SMES) technology has emerged as a method for mitigating voltage sags for smaller scale applications using energy storage capacities of less than 100kJ. These units are designed to mitigate low frequency (<1kHz) voltage sags in power distribution systems extending the lifetime of electronic loads by reducing voltage fluctuations and reducing load outages due to under-voltage trips.

Christopher John Hawley

2005-01-01

260

High-Tc Superconducting Thin- and Thick-Film-Based Coated Conductors for Energy Applications  

SciTech Connect

Although the first epitaxial films of YBCO with high Tc were grown nearly 20 years ago, the understanding and control of the nanostructures responsible for the dissipation-free electrical current transport in high temperature superconductors (HTS) is quite recent. In the last six to seven years, major advances have occurred in the fundamental investigation of low angle grain boundaries, flux-pinning phenomena, growth mode, and atomic-level defect structures of HTS epitaxial films. As a consequence, it has been possible to map and even engineer to some extent the performance of HTS coatings in large regions of the operating H, T, J phase space. With such progress, the future of high temperature superconducting wires looks increasingly promising despite the tremendous challenges offered by these brittle and anisotropic materials. Nevertheless, further performance improvements are necessary for the superconducting technology to become cost-competitive against copper wires and ultimately succeed in revolutionizing the transmission of electricity. This can be achieved by further diminishing the gap between theoretical and experimental values of the critical current density Jc, and/or increasing the thickness of the superconductive layer as much as possible without degrading performance. In addition, further progress in controlling extrinsic and/or intrinsic nano-sized defects within the films is necessary to significantly reduce the anisotropic response of HTS and obtain a nearly constant dependence of the critical current on the magnetic field orientation, which is considered crucial for power applications. This chapter is a review of the challenges still present in the area of superconducting film processing for HTS wires and the approaches currently employed to address them.

Cantoni, Claudia [ORNL; Goyal, Amit [ORNL

2010-01-01

261

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

262

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

263

Alternative Approach for Determination of Energy Band Gap of Semiconductors Through Electrical Analysis  

NASA Astrophysics Data System (ADS)

Traditional way of extracting energy band gap (EG) of semiconductors from UV-Visible transmisson measurement becomes difficult once EG lies below than 1 eV. Instead of optical excitation of electrons from valance to conduction bands, Schockley-Read-Hall statistics was considered to determine EG by electrical analysis. According to the statistics, generation recombination and diffusion mechanisms were expected, differing through activation energy. The first processes become dominant at intermatiate temperature where activation energy would be half of the band gap whereas the second one occurs under high temperature side where activation energy would be equal to the band gap. Based on that ac conductance(capacitance)-temperature-frequency (G(C)-T-?) measurements were performed to obtain energy band gap of semiconductors having narrow EG such as iron silicide, ?-FeSi2, chromium silicide, CrSi2 grown on crystaline silicon substrates. Satisfactory EG results were obtained as 0.85 eV and 0.25 eV for ?-FeSi2 and CrSi2, respectively. At last, the approach was tested on well known MIS (abbreviation of metal-insulator-semiconductor) type structure; the acquired EG convinced that the approach was applicable and reliable.

Özdemİ R, Orhan; Tatar, Beyhan; Yilmazer, Deneb; Gökdemİ R, Pnar; Ürgen, Mustafa; Kutlu, Kubilay

2010-01-01

264

Gap spectroscopy in underdoped YBa2Cu3O6+x from superfluid spectral weight and intrinsic pair tunneling  

NASA Astrophysics Data System (ADS)

Numerous experiments on cuprate high temperature superconductors reveal evidence for two different energy gaps: a normal state pseudogap that grows on underdoping, and a superconducting gap connected to the transition temperature Tc [1]. Here we use two different experiments to probe the superconducting energy gap scale in highly underdoped YBa2Cu3O6+x: intrinsic pair tunneling perpendicular to the CuO2 planes; and measurements of in-plane superfluid spectral weight. The measurements have been carried out on special samples in which doping can be tuned continuously using controlled oxygen annealing at room temperature [2]. We present data for Tc in the range of 3 K to 17 K, and show that the superconducting energy gap is indeed linked to Tc (2?˜4 kBTc), vanishing as Tc->0. [4pt] [1] H"ufner et al. Rep. Prog. Phys. 71, 062501 (2008)[0pt] [2] Broun et al. Phys. Rev. Lett. 99, 237003 (2007)

Huttema, Wendell; Turner, Patrick; Liang, Ruixing; Hardy, Walter; Bonn, Doug; Broun, David

2009-05-01

265

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

National Technical Information Service (NTIS)

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 t...

R. A. Hawsey B. B. Banerjee P. M. Grant

1996-01-01

266

Gaps, barriers and conceptual chasms: theories of technology transfer and energy in buildings  

Microsoft Academic Search

Having shown how much energy might be saved through the use of economically worthwhile measures and technologies, researchers and policy makers then find themselves trying to close the gap between current practice and recognised technical potential. The ensuing process of technology transfer is often seen as a process of overcoming ‘non technical barriers’ which inhibit the realisation of proven technical

Elizabeth Shove

1998-01-01

267

ENERGY BAND GAP AND CONDUCTIVITY MEASUREMENT OF CdSe THIN FILMS  

Microsoft Academic Search

Thin film of CdSe has been deposited onto clean glass substrate by using vacuum evaporation technique. This thin film is characterized through the XRD, which indicates that film is polycrystalline in nature and having preferred orientation along (002) plane in c-direction. Absorption spectra of this thin film has been recorded using spectrophotometer. The energy band gap has been determined using

D. Patidar; K. S. Rathore; N. S. Saxena; Kananbala Sharma; T. P. Sharma

268

Photoemission and density functional theory study of Ir(111); energy band gap mapping  

Microsoft Academic Search

We have performed combined angle-resolved photoemission spectroscopy (ARPES) experiments and density functional theory (DFT) calculations of the electronic structure of the Ir(111) surface, with the focus on the existence of energy band gaps. The investigation was motivated by the experimental results suggesting Ir(111) as an ideal support for the growth of weakly bonded graphene. Therefore, our prime interest was electronic

I. Pletikosic; M. Kralj; D. Sokcevic; R. Brako; P. Lazic; P. Pervan

2010-01-01

269

Determination of energy band gap of nanocrystalline SbSI using diffuse reflectance spectroscopy  

Microsoft Academic Search

Twelve methods of determining energy band gap (Eg) of semiconductors using diffuse reflectance spectroscopy have been applied in investigations of sonochemically produced antimony sulfoiodide (SbSI) consisting of nanowires. It has been proved that the best method of determining Eg is based on simultaneous fitting of many mechanisms of absorption to the spectral dependence of Kubelka-Munk function evaluated from the diffuse

M. Nowak; B. Kauch; P. Szperlich

2009-01-01

270

Elementary technique to measure the energy band gap and diffusion potential of pn junctions  

Microsoft Academic Search

This paper describes three simple experimental exercises suitable for one or more laboratory periods in which the students measure the forward current voltage, the forward rate of change of junction voltage with temperature, and the reverse capacitance voltage characteristics of a pn junction. Using these data the students determine the energy band gap of the semiconductor, the diffusion potential, the

Charles W. Fischer

1982-01-01

271

Compilation of Energy Band Gaps in Elemental and Binary Compound Semiconductors and Insulators  

Microsoft Academic Search

Energy band gaps are tabulated for elemental and binary compound semiconductors and insulators reported in 723 references. The method of measurement, transition, type of sample, and other pertinent information are included for each entry. The determinations believed to be the most reliable are indicated.

W. H. Strehlow; E. L. Cook

1973-01-01

272

Stimulated Raman up conversion of a helicon by band-gap energy plasmons in a semiconductor  

Microsoft Academic Search

Stimulated Raman up conversion of a helicon wave in a semiconductor, where free carrier plasma frequency equals band-gap energy divided by Planck's constant, is investigated. The stimulated electron hole recombination drives a Langmuir wave. The free carrier density oscillations associated with the Langmuir wave couple with the free carrier oscillatory velocities due to the helicon and derive a sum frequency

Pawan Kumar; V. K. Tripathi

2009-01-01

273

Optical fundamental band-gap energy of semiconductors by photoacoustic spectroscopy  

Microsoft Academic Search

The optical band-gap energy of the semiconductors GaAs, CdSe, Cds, ZnSe and Si doped with P at a concentration of 4 x 10~~cm-~, are obtained by photoacoustic spectroscopy technique. Excellent agreements are found with the values recorded in the literature.

J. Caetano de Souza; A. Ferreira da Silva; H. Vargas

1994-01-01

274

Inclusion of technology diffusion in energy-systems models: some gaps and needs  

Microsoft Academic Search

This paper presents some needs and gaps in the representation of technology diffusion in energy-system models. Without intending to be exhaustive, some selected aspects are identified and discussed as follows: the spatial patterns of diffusion and spatial technology spillovers, the role of technology learning and R&D activities, technology clusters and uncertainty. An improved dialogue and exchange between the technology diffusion

Leonardo Barreto; René Kemp

2008-01-01

275

Coherence peak and superconducting energy gap in Rb3C60 observed by muon spin relaxation  

NASA Astrophysics Data System (ADS)

Spin-exchange scattering of endohedral muonium with thermal electronic excitations has been found to result in muon spin relaxation in the fullerene superconductor Rb3C60. The temperature dependence of this T(1) exp -1 muon spin relaxation exhibits a coherence peak just below T(c), and may be characterized in the framework of the Hebel-Slichter (1959) theory for spin-relaxation in a superconductor.

Kiefl, R. F.; Macfarlane, W. A.; Chow, K. H.; Dunsiger, S.; Duty, T. L.; Johnston, T. M. S.; Schneider, J. W.; Sonier, J.; Brard, L.; Strongin, R. M.

1993-06-01

276

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.

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

2011-01-01

277

Measurement of energy band gap using an electrolyte-semiconductor junction: Water-gallium indium arsenide alloys  

Microsoft Academic Search

Energy band gaps of semiconductors are usually obtained by optical transmission measurements through bulk samples. Such measurements on epitaxial layers are difficult due to absorption in the substrate. A technique utilizing the photogeneration of carriers at an electrolyte-semiconductor junction is described for the measurement of the energy gap of epitaxial layers. Results of measurements of the band gap of GaInAs

B. Jayant Baliga; Rajaram Bhat; Sorab K. Ghandhi

1975-01-01

278

Measurement of energy band gap using an electrolyte-semiconductor junction: Water–gallium indium arsenide alloys  

Microsoft Academic Search

Energy band gaps of semiconductors are usually obtained by optical transmission measurements through bulk samples. Such measurements on epitaxial layers are difficult due to absorption in the substrate. A technique utilizing the photogeneration of carriers at an electrolyte-semiconductor junction is described for the measurement of the energy gap of epitaxial layers. Results of measurements of the band gap of GaInAs

B. Jayant Baliga; Rajaram Bhat; Sorab K. Ghandhi

1975-01-01

279

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

280

Energy band and band-gap properties of deformed single-walled silicon nanotubes  

Microsoft Academic Search

The fantastic physical properties of single-walled silicon nanotubes (SWSiNTs) under mechanical strain make them promising\\u000a materials for fabricating nanoscale electronic devices or transducers. Here we investigate the energy band and band-gap properties\\u000a of the SWSiNTs calculated from the tight-binding model approximation. The results show that the band-gap properties are very\\u000a sensitive to the deformation degree and the helicity of the

Guang-Cun Shan; Wei Huang

2010-01-01

281

Energy-resolved detection of single infrared photons with ? = 8 ?m using a superconducting microbolometer  

NASA Astrophysics Data System (ADS)

We report on the detection of single photons with ? = 8 ?m using a superconducting hot-electron microbolometer. The sensing element is a titanium transition-edge sensor with a volume ~0.1 ?m3 fabricated on a silicon substrate. Poisson photon counting statistics including simultaneous detection of 3 photons was observed. The width of the photon-number peaks was 0.11 eV, 70% of the photon energy, at 50-100 mK. This achieved energy resolution is one of the best figures reported so far for superconducting devices. Such devices can be suitable for single-photon calorimetric spectroscopy throughout the mid-infrared and even the far-infrared.

Karasik, Boris S.; Pereverzev, Sergey V.; Soibel, Alexander; Santavicca, Daniel F.; Prober, Daniel E.; Olaya, David; Gershenson, Michael E.

2012-07-01

282

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

283

Alternative Approach for Determination of Energy Band Gap of Semiconductors Through Electrical Analysis  

Microsoft Academic Search

Traditional way of extracting energy band gap (EG) of semiconductors from UV-Visible transmisson measurement becomes difficult once EG lies below than 1 eV. Instead of optical excitation of electrons from valance to conduction bands, Schockley-Read-Hall statistics was considered to determine EG by electrical analysis. According to the statistics, generation recombination and diffusion mechanisms were expected, differing through activation energy. The

Orhan R; Beyhan Tatar; Deneb Yilmazer; Pnar R; Mustafa Ürgen; Kubilay Kutlu

2010-01-01

284

Performance of Small-Gap Undulators at the SLS Intermediate Energy Storage Ring  

NASA Astrophysics Data System (ADS)

The Swiss Light Source (SLS) at the Paul Scherrer Institut (PSI) became the first medium energy synchrotron user facility to rely on the high harmonic operation of small gap, short period undulators to extend high brightness radiation into a regime (3-18 keV) otherwise only accessible using lower brightness wigglers or operation at higher electron beam energy. Today several facilities with beam energy 2-3 GeV follow a similar route. A PSI/SPring-8 collaboration was formed to install and operate the first in-vacuum undulator shortly after commissioning of the SLS storage ring (2.4 GeV) in 2001. The goal of the joint project was to prove that high harmonic operation of small period undulators at small gaps is a valid concept to operate the PX-I beamline at 1 Å under user operation conditions. The performance of the PX-I beamline proved to be excellent and launched the installation of meanwhile 4 new in-vacuum undulators. Having routinely operated such devices for 5 years, our experience confirms that (1) the concept of operating short period undulators (19-24 mm) on higher harmonics (11./13.) is valid, (2) reliable small gap (5-6 mm) undulator operation is feasible in the presence of top-up injection, and (3) during gap scans the photon beam can be stabilized to sub-?rad precision using non-intercepting photon beam monitors.

Ingold, G.; Boege, M.; Bulgheroni, W.; Keller, A.; Krempaski, J.; Schulze-Briese, C.; Schulz, L.; Schmidt, T.; Zimoch, D.; Hara, T.; Tanaka, T.; Kitamura, H.

2007-01-01

285

Specific Heat To Hc2: Evidence for Nodes or Deep Minima in the Superconducting Gap of Under- and Overdoped BaFe2-xCoxAs2  

NASA Astrophysics Data System (ADS)

Low temperature specific heat, C, in magnetic fields up to Hc2 is reported for BaFe1.91Co0.09As2 (underdoped, Hc2 16 T, Tc=8 K), BaFe1.79Co0.21As2 (overdoped, Hc2 27 T, Tc=17 K), and - for comparison - BaFe1.95Ni0.05As2, which should have properties similar to the underdoped Co-sample. Previous measurements of thermal conductivity (as a function of temperature and field) and penetration depth on comparable composition samples gave some disagreement as to whether there was fully gapped/nodal behavior in the under-/overdoped materials respectively. The present work shows that the measured behavior of the specific heat ? ( C/T as T->0, i. e. a measure of the electronic density of states at the Fermi energy) as a function of field obeys ? H^0.6±0.1, similar to the Volovik effect for nodal superconductors, over the entire field range for both under- and overdoped Co samples as well as for the underdoped Ni sample. By comparison to theory, the possibility of two bands, one with line nodes and one fully gapped, being present in these materials is discussed.

Stewart, G. R.; Kim, J. S.; Gofryk, K.; Ronning, F.; Sefat, A. S.; Choi, K. Y.; Kim, K. H.

2012-02-01

286

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

Microsoft Academic Search

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

Zhong-Chao Zhang; Boon-Teck Ooi

1993-01-01

287

DEVELOPMENT OF A PROTOTYPE SUPERCONDUCTING CW CAVITY AND CRYOMODULE FOR ENERGY RECOVERY  

Microsoft Academic Search

Energy Recovery LINAC (ERL) and LINAC-driven FEL proposals and developments are now widespread around the world. Superconducting RF (SRF) cavity advances made over the last 10 years for TESLA\\/TTF at 1.3 GHz, in reliably achieving accelerating gradients >20 MV\\/m, suggest their suitability for these ERL and FEL accelerators. Typically however, photon fluxes are maximised from the associated insertion devices when

P. A. McIntosh; C. D. Beard; D. M. Dykes; B. Todd; S. Belomestnykh; M. Liepe; V. Medjidzade; H. Padamsee; J. Sears; V. D. Shemelin; D. Proch; A. Buechner; P. Michel; J. Teichert; T. Kimura; T. I. Smith; J. Byrd; J. N. Corlett; D. Li

2006-01-01

288

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

289

Engineering prototype of a superconducting flywheel for long term energy storage  

Microsoft Academic Search

We built a flywheel system with superconducting magnetic bearings. The bearing consists of six melt-textured YBCO pellets mounted inside a continuous flow LN2 cryostat. A disk measuring ? 190 mm×30 mm was safely rotated at speeds up to 15000 rpm. The disk was driven by a high speed three phase synchronous homopolar motor\\/generator. Maximum energy capacity was 4.8 Wh, maximum

H. J. Bornemann; Andrea Tonoli; Tobias Ritter; Claus Urban; Oleg Zaitsev; Klaus Weber; Hennann Rietschel

1995-01-01

290

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

291

Production techniques for the Superconducting Super Collider Low Energy Booster quadrupole magnet  

Microsoft Academic Search

The manufacturing techniques used for a prototype quadrupole magnet, developed at Lawrence Berkeley Laboratory (LBL) for the Superconducting Super Collider (SSC) Low Energy Booster (LEB), are described. The SSC LEB Ring employs 96 dipoles and 90 quadrupoles connected in series to form the magnetic lattice, requiring the use of a 21.9 mm×23.0 mm hollow conductor for the quadrupoles. Due to

M. E. Morrison; G. U. Behrsing; R. L. Fulton

1994-01-01

292

Multiple-photon effects in fermion-(anti)fermion scattering at Superconducting Super Collider energies  

Microsoft Academic Search

We use the theory of Yennie, Frautschi, and Suura to realize, via Monte Carlo methods, the process ff(-)-->f'f(-)'+ngamma at energies reached at the Superconducting Super Collider (SSC) and the CERN Large Hadron Collider, where f and f' are quarks or leptons. QED infrared divergences are canceled to all orders in perturbation theory. The resulting Monte Carlo event generator SSC-YFS2 is

D. B. Delaney; S. Jadach; Ch. Shio; G. Siopsis; B. F. L. Ward

1993-01-01

293

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

SciTech Connect

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

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

1984-01-01

294

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

SciTech Connect

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

Bianchi, M. V. A.

2011-11-01

295

Applications of high-energy heavy-ions from superconducting cyclotrons  

SciTech Connect

The superconducting cyclotrons of the National Superconducting Cyclotron Laboratory (NSCL), a major nuclear physics facility, can provide ions of any element from hydrogen to uranium. A major upgrade to the NSCL is underway and will consist of an electron cyclotron resonance (ECR) ion source followed by two large superconducting cyclotrons (K500 and K1200). Ions can be extracted at any point along this chain allowing a large range of energies and charge states. The ion energies range from a few keV to over 20 GeV, and charge states up to fully stripped {sup 197}Au{sup 79+} and two electron {sup 238}U{sup 90+} are possible. The long range of the high-energy heavy-ions allows them to penetrate deeply into a target that is placed in air, outside a vacuum chamber. The ion beams have already been used for a number of applications including; ion implantation, atomic physics, single event effects in integrated circuits, DNA radiation studies, radiation detector studies, flux pinning in high-T{sub c} superconductors, calibration of a space-based spectrometer, isotropic ratio measurements, material wear studies, and continuous positron emission tomography imaging.

Grimm, T. L. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States)

1999-06-10

296

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

297

Spin band gap and emerging low energy excitations in a doped cobaltate perovskite  

NASA Astrophysics Data System (ADS)

We investigated spin dynamics in half doped cobaltate La1.5Sr0.5CoO4, using inelastic neutron scattering. At high temperatures we observe a broad band of continuum antiferromagnetic dynamic spin correlations, extending to energies above 20 meV. As temperature decreases below spin ordering transition (TSO = 30K), a single coherent magnon mode emerges at low energies (bandwith 15 meV), separated by an energy band gap from a broad continuum scattering residing at high energies 20 <=E <=30 meV. This points to an emerging 2D-XY behavior of spins, consistent with the strong planar anisotropy of this material.

Savici, Andrei; Zaliznyak, Igor; Gu, Genda; Chen, Ying; Garlea, Vasile

2007-03-01

298

On the ``massless gap`` adjustment of detected energy for passive material in front of a calorimeter  

SciTech Connect

I have designed a correction scheme for energy losses in passive material in front of a calorimeter based on the ``massless gap`` idea. I use a flexible geometry model of a calorimeter design for SDC outside of a solenoidal coil made of aluminium cylinders of adjustable thickness. The signal from the first radiation length of active calorimetry is scaled dependent on the incoming and observed energies of the shower. A reasonable recovery of the resolution of an unobstructed calorimeter is achieved using correction factors that depend only upon the total thickness of passive material. Thus a useful correction may be built into the hardware by increasing the amount of scintillator in the first radiation length of the active calorimeter. The distribution of correction factors determined event-by-event indicate that an additional dependence on the observed signal in the massless gap and total incident energy is clearly present.

Trost, H.J.

1992-01-31

299

On the massless gap'' adjustment of detected energy for passive material in front of a calorimeter  

SciTech Connect

I have designed a correction scheme for energy losses in passive material in front of a calorimeter based on the massless gap'' idea. I use a flexible geometry model of a calorimeter design for SDC outside of a solenoidal coil made of aluminium cylinders of adjustable thickness. The signal from the first radiation length of active calorimetry is scaled dependent on the incoming and observed energies of the shower. A reasonable recovery of the resolution of an unobstructed calorimeter is achieved using correction factors that depend only upon the total thickness of passive material. Thus a useful correction may be built into the hardware by increasing the amount of scintillator in the first radiation length of the active calorimeter. The distribution of correction factors determined event-by-event indicate that an additional dependence on the observed signal in the massless gap and total incident energy is clearly present.

Trost, H.J.

1992-01-31

300

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

301

Construction of a large superconducting spectrometer magnet  

Microsoft Academic Search

A sector-type superconducting spectrometer magnet for nuclear physics experiments has been constructed. The central magnetic field is 3 T with a magnet gap of 50 cm and a stored energy estimated to be 11.2 MJ. Three-dimensional magnetic field calculations and a stress analysis have been performed to design the coil and supporting structures. The magnet has a flexible helium transfer

T. Shintomi; K. Aoki; Y. Doi; Y. Makida; O. Hashimoto; T. Kitami; T. Miyaji; T. Nagae; M. Sekimoto

1991-01-01

302

Size-dependent energy band gap and dielectric constant within the generalized Penn model applied to a semiconductor nanocrystallite  

Microsoft Academic Search

We calculated size-dependent single particle energy eigenvalues, wave functions, energy band gap, and dielectric constant for a semiconductor nanocrystallite, within the framework of the two band Penn model. The finite size effects are presented as size-dependent correction terms to the energy eigenvalues and the energy band gap of the bulk semiconductor. Ours is a self-consistent calculation within the Penn model

A. C. Sharma

2006-01-01

303

Evidence of two-gap superconductivity in Na0.35CoO2.1.3H2O  

Microsoft Academic Search

The recent discovery of superconductivity in the layered cobalt oxyhydrate Na0.35CoO2.1.3H2O [1] has attracted considerable attention in the scientific community because of its structural similarity to high-Tc cuprates. Although intensive studies have been performed to understand the nature of superconductivity in this compound, no consensus has been reached on many important issues and the symmetry of order parameter still remains

H. Q. Yuan; P. Badica

2005-01-01

304

Superconducting tunneling-junction detectors of X-ray radiation. Issues concerning the energy resolution  

SciTech Connect

The effect of the recombination-and edge-related losses of nonequilibrium quasiparticles on the energy resolution of superconducting tunneling detectors is studied. The dependence of the signal on the energy of X-ray photons is measured and the shape of instrument-related lines is studied for the Ti/Nb/Al/AlO{sub x}/Al/Nb/NbN detectors with the Ti/Nb passive electrode. Experimental data are analyzed using the diffusion-based model of tunneling detectors.

Andrianov, V. A. [Skobel'tsyn Research Institute of Nuclear Physics at the Moscow State University (Russian Federation)], E-mail: andrva22@mail.ru; Gor'kov, V. P. [Moscow State University, Department of Computational Mathematics and Cybernetics (Russian Federation)], E-mail: v-p-gorkov@yandex.ru; Koshelets, V. P., E-mail: valery@hitech.cplire.ru; Filippenko, L. V. [Russian Academy of Sciences, Institute of Radio Engineering and Electronics (Russian Federation)

2007-02-15

305

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

306

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

2012-12-11

307

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

PubMed

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

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

2013-10-06

308

The General Antiparticle Spectrometer (GAPS) - Hunt for dark matter using low energy antideuterons  

Microsoft Academic Search

The GAPS experiment is foreseen to carry out a dark matter search using a novel detection approach to detect low-energy cosmic-ray antideuterons. The theoretically predicted antideuteron flux resulting from secondary interactions of primary cosmic rays with the interstellar medium is very low. So far not a single cosmic antideuteron has been detected by any experiment, but well-motivated theories beyond the

P. von Doetinchem; T. Aramaki; S. Boggs; W. Craig; H. Fuke; F. Gahbauer; C. Hailey; J. Koglin; N. Madden; I. Mognet; K. Mori; R. Ong; T. Yoshida; T. Zhang; J. Zweerink

2010-01-01

309

Double-Loop Josephson-Junction Flux Qubit with Controllable Energy Gap  

Microsoft Academic Search

A double-loop four-Josephson-junction (4-JJ) flux qubit has an advantage over a three-Josephson-junction flux qubit in that the energy gap Delta at the degeneracy point can be controlled in situ by varying the magnetic flux in one of the two loops. We report the results of microwave spectroscopy and ground-state measurements of a 4-JJ qubit. The value of Delta is estimated

Y. Shimazu; Y. Saito; Z. Wada

2009-01-01

310

Spectroscopy of Josephson-Junction Flux Qubit with Controllable Energy Gap  

Microsoft Academic Search

A double-loop four-Josephson-junction (4-JJ) flux qubit has an advantage over a three-Josephson-junction flux qubit in that the energy gap Delta at the symmetry point can be controlled in situ by varying the magnetic flux in one of the two loops. We report the results of a microwave spectroscopy measurement of a 4-JJ qubit. The magnetic fluxes in the two loops

Yoshihiro Shimazu; Yuuki Saito; Zenpei Wada

2009-01-01

311

The Energy Band Gap of AlxGa1-xN  

Microsoft Academic Search

Combining experimental measurements with an analysis of sample strain, we have determined the ``unstrained'' energy band gap, Eg, of AlxGa1-xN for 0 <= x <= 1. Care was taken to grow films with narrow (00.2) and (10.2) X-ray diffraction rocking curve widths, to insure low residual strain in the samples. This is significant because, even for our high quality AlxGa1-xN

Qing S. Paduano; David W. Weyburne; Lionel O. Bouthillette; Shen-Qi Wang; Michael N. Alexander

2002-01-01

312

Energy Band-Gaps of MgxZn1-xSe  

Microsoft Academic Search

Based on a pseudopotential scheme, the composition dependence of energy band-gaps of zinc-blende MgxZn1-xSe ternary alloys in the composition range of 0<=x<=1 are determined. The effect of deviation of lattice constants of the alloys of interest from Vegard's law on the optical bowing parameter and system transition between the direct and indirect structures is discussed.

Z. Charifi; H. Baaziz; N. Bouarissa

2004-01-01

313

Calculation of energy band gaps in quaternary iii\\/v alloys  

Microsoft Academic Search

The dielectric theory of electronegativity is applied to the calculation of the compositional dependence of the energy band gap for quaternary III\\/V alloys of type Al-xBxC1-yDy and A1-x-yBxCyD. The departure from linearity of EG versus x and y is taken to be the sum of two terms, the intrinsic or virtual crystal term and the extrinsic term due to effects

G. B. Stringfellow

1981-01-01

314

Energy band-gap bowing parameter in an AlxGa1 - x N alloy  

Microsoft Academic Search

Optical measurements are performed near the fundamental absorption edge for single-crystal AlxGa1?x N epitaxial layers in the composition range of 0?x?0.4. The dependence of the energy band gap on composition is found to deviate downwards from linearity, the bowing parameter being b=1.0±0.3 eV. The origin of the large bowing is discussed in terms of the pseudopotential of Al and Ga

Y. Koide; H. Itoh; M. R. H. Khan; K. Hiramatu; N. Sawaki; I. Akasaki

1987-01-01

315

Calculation of energy band gaps in quaternary iii\\/v alloys  

Microsoft Academic Search

The dielectric theory of electronegativity is applied to the calculation of the compositional dependence of the energy band\\u000a gap for quaternary III\\/V alloys of type Al-xBxC1-yDy and A1-x-yBxCyD. The departure from linearity of EG versus x and y is taken to be the sum of two terms, the intrinsic or virtual crystal term and the extrinsic term due to effects

G. B. Stringfellow

1981-01-01

316

Electronic structure and energy band gap of poly (9,9-dioctylfluorene) investigated by photoelectron spectroscopy  

Microsoft Academic Search

The electronic structure of poly (9,9-dioctylfluorene) (PFO) film on a Au-coated Si substrate was investigated by ultraviolet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS). From the UPS measurement, we obtained the ionization potential (Ip) of the PFO film, Ip=5.60+\\/-0.05 eV. From the XPS shake-up peaks of the C1s core level, we estimated the electron energy band gap (Eg) of

L. S. Liao; M. K. Fung; C. S. Lee; S. T. Lee; M. Inbasekaran; E. P. Woo; W. W. Wu

2000-01-01

317

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

318

High Energy Gap OLED Host Materials for Green and Blue PHOLED Materials  

Microsoft Academic Search

In this paper, we developed a series of novel arylamino-containing spiro triplet state host materials for green and blue phosphorescent emitters. With high enough energy gap and compatible HOMO, LUMO levels, we demonstrated the green PHOLED with a low driving voltage of 2.5 V and a high power efficiency of 38.5 lm\\/W. We also demonstrated blue PHOLED with a very

Chi-Jen Lin; Heh-Lung Huang; Mei-Rurng Tseng; Chien-Hong Cheng

2009-01-01

319

The Electrical BandGap Energy of Porous Silicon Measured Versus Sample Temperature  

Microsoft Academic Search

Photocurrent measurements have been carried out on a series of samples consisting of porous silicon on top of crystalline silicon, in the temperature range 10–300 K. From the experimental data set, the electrical band-gap energy of porous silicon is deduced to be (1.80 ± 0.01) eV, independent of sample temperature. The results are discussed with the conclusion that for the

J. T. Frederiksen; P. G. Melcher; E. Veje

2000-01-01

320

Energy gaps, magnetism, and electric-field effects in bilayer graphene nanoribbons  

Microsoft Academic Search

Using a first principles density functional electronic structure method, we\\u000astudy the energy gaps and magnetism in bilayer graphene nanoribbons as a\\u000afunction of the ribbon width and the strength of an external electric field\\u000abetween the layers. We assume AB (Bernal) stacking and consider both armchair\\u000aand zigzag edges and two edge alignments distinguished by a 60$^o$ rotation of

Bhagawan Sahu; Hongki Min; Allan. H. MacDonald; Sanjay K. Banerjee

2008-01-01

321

Electroluminescence at Si band gap energy based on metal-oxide-silicon structures  

Microsoft Academic Search

Room-temperature electroluminescence corresponding to Si band gap energy from metal-oxide-semiconductor structures on both p-type and n-type Si is observed. With very thin oxide grown by rapid thermal oxidation, the metal-oxide-semiconductor structures behave like light emitting diodes. Luminescence is observed under forward bias even with a current density as low as 0.67 A\\/cm2. The physical reason for the electroluminescence is discussed

Ching-Fuh Lin; C. W. Liu; Miin-Jang Chen; M. H. Lee; I. C. Lin

2000-01-01

322

Band Gap Energy and Its Temperature Dependence of GaInAsSb Quaternary Alloy Grown by Molecular Beam Epitaxy  

Microsoft Academic Search

Room temperature band gap energies of MBE-grown Ga1-xInxAs1-ySby have been determined from Fourier transform infrared spectroscopy measurements. The results show good agreement with those calculated from a semi-empirical interpolation method. The temperature dependence of band gap energy has also been investigated for an alloy sample with x=0.247 and y=0.907 at temperatures ranging from 10 to 300 K. While the energy

Wen'gang Bi; Aizhen Li

1992-01-01

323

FLYWHEEL ENERGY STORAGE SYSTEMS WITH SUPERCONDUCTING BEARINGS FOR UTILITY APPLICATIONS  

SciTech Connect

This project’s mission was to achieve significant advances in the practical application of bulk high-temperature superconductor (HTS) materials to energy-storage systems. The ultimate product was planned as an operational prototype of a flywheel system on an HTS suspension. While the final prototype flywheel did not complete the final offsite demonstration phase of the program, invaluable lessons learned were captured on the laboratory demonstration units that will lead to the successful deployment of a future HTS-stabilized, composite-flywheel energy-storage system (FESS).

Dr. Michael Strasik; Mr. Arthur Day; Mr. Philip Johnson; Dr. John Hull

2007-10-26

324

On the energy band gap correlation and effective charges of some ternary chalcopyrites and their mixed versions  

Microsoft Academic Search

We have been able to obtain for the first time a correlation of the lowest energy band gap with the average principal quantum number and molecular weight for the ternary chalcopyrites and their mixed versions which in turn helps in estimating the band gap, the latter being a key design parameter for various optoelectronic devices. The agreement of our results

L. K. Samanta; S. Chatterjee

2005-01-01

325

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

326

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

327

Calculation of the composition dependence of the energy band gap in semiconducting solid solutions based on zinc, cadmium, and lead chalcogenides  

Microsoft Academic Search

Our study, based on interpolation methods, looked at the composition dependence of the energy band gap E\\/sub g\\/ in ternary and quaternary semiconducting solid solutions based on zinc, cadmium, and lead chalcogenides. Change in the energy band gap dependent on composition is not linear in most ternary systems. The nonlinear character of the composition dependent energy band gap for solid

F. U. Galeeva; K. D. Tarzimanov; I. K. Akhmetshin

1988-01-01

328

Predictions of anisotropic superconductivity in UIr/sub 3/ and UPt/sub 3/  

SciTech Connect

Anisotropic singlet state superconductivity is predicted for UIr/sub 3/ (an itinerant non-heavy fermion intermetallic) as was done earlier for UPt/sub 3/ (perhaps the prototype heavy fermion system). In both, this arises from strong Uf-Xd hybridization which yields a highly anisotropic Fermi surface (now confirmed by dHvA experiments of Taillefer et al. on UPt/sub 3/), electron - phonon interaction, and superconducting energy gap.

Oguchi, T.; Freeman, A.J.; Crabtree, G.W.

1986-01-01

329

Energy gap of tight-binding electrons on generalized honeycomb lattice  

NASA Astrophysics Data System (ADS)

So as to clearly understand the energy band gap of graphene, we study the energy band of tight-binding electrons on a honeycomb lattice with on-site potentials ?A and ?B on sublattices A and B, nearest-neighbor transfer integrals ta, tb and tc, and next-nearest-neighbor transfer integrals t2a, t2b, t2c, t2d, t2e and t2f, where t2a, t2b and t2C are transfer integrals between sublattice A, and t2d, t2e and t2f are transfer integrals between sublattice B.

Kishigi, Keita; Takeda, Ryuichi; Hasegawa, Yasumasa

2008-10-01

330

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

NASA Astrophysics Data System (ADS)

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

Ayataka Endo,; Chihaya Adachi,

2010-05-01

331

Superconducting magnets  

SciTech Connect

Superconducting dipole magnets for high energy colliders are discussed. As an example, the magnets recently built for the Relativistic Heavy Ion Collider at Brookhaven are reviewed. Their technical performance and the cost for the industry-built production dipoles are given. The cost data is generalized in order to extrapolate the cost of magnets for a new machine.

Willen, E.

1996-12-31

332

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

333

Single-loop-like energy oscillations and staircase vortex occupation in superconducting double networks  

NASA Astrophysics Data System (ADS)

The magnetic-field dependence of the energy and vortex occupation is calculated for the recently realized superconducting double network consisting of two interlaced subnetworks of small and large loops. Two different approaches are employed, both based on the J2 model: Mean-field analysis that minimizes the network energy assuming random-vortex configurations and numerical simulations in which energy is minimized avoiding this assumption. In the mean-field analysis the vortex population in both subnetworks increases linearly with the applied field. In contrast the simulations show that while the population of the large loops increases linearly with field, the occupation of the small loops grows in steps, resembling the behavior of an ensemble of decoupled loops. This decoupling is also reflected in the waveform of the energy versus applied field. A modified mean-field analysis, which introduces decoupling between the small loops, yields results in excellent agreement with the simulations. These findings suggest that the behavior of a single loop is reflected in the double network and thus constitute it as a favorable system for the experimental study of quantization effects in superconducting loops.

Sochnikov, I.; Shokef, Y.; Shaulov, A.; Yeshurun, Y.

2011-07-01

334

Measurement of 10 zJ energy dissipation of adiabatic quantum-flux-parametron logic using a superconducting resonator  

NASA Astrophysics Data System (ADS)

Adiabatic quantum-flux-parametron (AQFP) logic has the potential to operate with an ultimately small bit energy of several zeptojoules; however, this is too small to measure by conventional techniques. We measure such a small energy dissipation by coupling a superconducting resonator with an AQFP gate, where the insertion loss is sensitively varied with the small dissipation due to the very high Q factor of the resonator. We designed and implemented a 5 GHz superconducting resonator coupled with an AQFP gate. Measurement results show that the bit energy of the gate is ~10 zJ at 5 GHz operation.

Takeuchi, N.; Yamanashi, Y.; Yoshikawa, N.

2013-02-01

335

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

336

Manipulation of resonant tunneling by substrate-induced inhomogeneous energy band gaps in graphene with square superlattice potentials  

NASA Astrophysics Data System (ADS)

We investigate the resonant transmission of Dirac electrons through inhomogeneous band gap graphene with square superlattice potentials by transfer matrix method. The effects of the incident angle of the electrons, Fermi energy and substrate-induced Dirac gaps on the transmission are considered. It is found that the Dirac gap of graphene adds another degree of freedom with respect to the incident angle, the Fermi energy and the parameters of periodic superlattice potentials (i.e., the number, width and height of the barriers) for the transmission. In particular, the inhomogeneous Dirac gap induced by staggered substrates can be used to manipulate the transmission. The properties of the conductance and Fano factor at the resonant peaks are found to be affected by the gaps significantly. The results may be helpful for the practical application of graphene-based electronic devices.

Li, Guanqiang; Chen, Guangde; Peng, Ping; Cao, Zhenzhou; Ye, Honggang

2013-11-01

337

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

338

Superconducting tunnel junctions  

NASA Astrophysics Data System (ADS)

The development of superconducting detectors well suited for X-ray spectroscopy in the energy range below 10 keV is considered. Detectors equipped with superconducting thin film absorbers, which are well suited for X-ray spectroscopy in this range, are investigated. Superconducting tunnel junctions are discussed in general and the results along with superconducting X-ray detectors, exploiting quasi particle trapping, are presented. The relative charge output of superconducting tunnel junctions is considered. The epitaxial growth of vanadium absorbers, necessary to obtain detectors of long term stability is also considered.

Kraus, H.; Jochum, J.; Kemmather, B.; Gutsche, M.; Feilitzsch, F. V.; Moessbauer, R. L.

1991-11-01

339

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

SciTech Connect

The Bonneville Power Administration operates the transmission system that joins the Pacific Northwest and southern California. A 30 MJ (8.4 kWh) Superconducting Magnetic Energy Storage (SMES) unit with a 10 MW converter can provide system damping for low frequency oscillations. The unit is scheduled to operate in 1982. Progress during FY 81 is described. The coil is complete. All major components of the electrical and cryogenic systems have been received and testing has begun. Computer control hardware is in place and software development is proceeding. Support system components and dewar lid are being fabricated and foundation design is complete. A contract for dewar fabrication is being negotiated.

Schermer, R.I.

1981-01-01

340

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

SciTech Connect

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

Schermer, R.I.

1981-01-01

341

Production techniques for the superconducting super collider low energy booster quadrupole magnet  

NASA Astrophysics Data System (ADS)

The manufacturing techniques used for a prototype quadrupole magnet, developed at Lawrence Berkeley Laboratory (LBL) for the Superconducting Super Collider (SSC) Low Energy Booster (LEB), are described. The SSC LEB Ring employs 96 dipoles and 90 quadrupoles connected in series to form the magnetic lattice, requiring the use of a 21.9 mm x 23.0 mm hollow conductor for the quadrupoles. Due to the large conductor size and small bend radii required, development of special fixtures was necessary. A unique coil-forming method with close attention paid to tooling design and special assembly procedures was required to manufacture this prototype to stringent specifications.

Morrison, Michael E.; Behrsing, Gerd U.; Fulton, Robert L.

1994-07-01

342

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

343

Switchable superconducting mirrors  

SciTech Connect

This patent describes a reflection apparatus. It comprises a source of electromagnetic radiation emitting a beam of photons of a given wavelength corresponding to a given energy; a superconducting mirror having a reflective surface in a path of the beam and having charge carrying pairs with a respective optical binding energy, the given wavelength being greater than a wavelength at which the photon energy is equal to the optical binding energy, whereby at temperatures below a critical temperature of the superconducting mirror corresponding to a superconductive mode, the surface is reflective to the beam, and the superconducting mirror can be quenched to a nonsuperconductive mode to extinguish reflection of the beam by the surface; and means operatively coupled to the superconducting mirror for selectively quenching the superconducting mirror to the nonsuperconductive mode.

Hed, A.Z.

1991-07-30

344

Strain effects on the energy band-gap in oxygenated CdTe thin films studied by photoreflectance  

Microsoft Academic Search

The incorporation of oxygen during the preparation of sputtered CdTe films produces a strong strain of the zincblende (cubic) lattice. First as a consequence of this, the energy band-gap shifts to lower energies and then, for larger strains, the degeneracy of the hole valence bands splits into two bands at the fundamental band-gap. These two transitions were measured using photoreflectance

L. N. Alejo-Armenta; F. J. Espinoza-Beltrán; C. A. Alejo-Armenta; C. Vazquez-Lopez; H. Arizpe-Chavez; R. Ram??rez-Bon; O. Zelaya-Angel; J. Gonzalez-Hernandez

1999-01-01

345

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

Microsoft Academic Search

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

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

2008-01-01

346

Energy gaps in failed superconductor La1.875Ba0.125CuO4  

Microsoft Academic Search

By angle-resolved photoemission spectroscopy with improved energy and momentum resolution, we find in the normal state of La2-xBaxCuO4 x = 1\\/8 a strong existence of the nodal quasi-particle together with a d-wave energy gap along the underlying Fermi surface extending over a significant range in the momentum space before an abrupt take-off of the gap close to the antinodal region.

R.-H. He; K. Tanaka; S.-K. Mo; T. Sasagawa; M. Fujita; N. Mannella; K. Yamada; Z. Hussain; Z.-X. Shen

2008-01-01

347

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

348

Sensitivity of a superconducting nanowire detector for single ions at low energy  

NASA Astrophysics Data System (ADS)

We report on the characterization of a superconducting nanowire detector for ions at low kinetic energies. We measure the absolute single-particle detection efficiency ? and trace its increase with energy up to ? = 100%. We discuss the influence of noble gas adsorbates on the cryogenic surface and analyze their relevance for the detection of slow massive particles. We apply a recent model for the hot-spot formation to the incidence of atomic ions at energies between 0.2 and 1 keV. We suggest how the differences observed for photons and atoms or molecules can be related to the surface condition of the detector and we propose that the restoration of proper surface conditions may open a new avenue for SSPD-based optical spectroscopy on molecules and nanoparticles.

Sclafani, Michele; Marksteiner, Markus; McLennan Keir, Fraser; Divochiy, Alexander; Korneev, Alexander; Semenov, Alexander; Gol'tsman, Gregory; Arndt, Markus

2012-02-01

349

Tunable Coupling in Circuit Quantum Electrodynamics Using a Superconducting Charge Qubit with a V-Shaped Energy Level Diagram  

NASA Astrophysics Data System (ADS)

We introduce a new type of superconducting charge qubit that has a V-shaped energy spectrum and uses quantum interference to provide independently tunable qubit energy and coherent coupling to a superconducting cavity. Dynamic access to the strong coupling regime is demonstrated by tuning the coupling strength from less than 200 kHz to greater than 40 MHz. This tunable coupling can be used to protect the qubit from cavity-induced relaxation and avoid unwanted qubit-qubit interactions in a multiqubit system.

Srinivasan, S. J.; Hoffman, A. J.; Gambetta, J. M.; Houck, A. A.

2011-02-01

350

Point-contact Andreev reflection tunneling spectroscopy (PCARTS) of the superconducting gap structure in LuNi2B2C  

NASA Astrophysics Data System (ADS)

The PCARTS technique is employed to investigate the gap anisotropy and proposed existence of point-nodes in LuNi2B2C (TC ˜ 16 K). Differential conductance spectra are taken from two different sets of single crystal samples along three major orientations: [001], [110], and [100]. Analyzing using the single-gap Blonder-Tinkham-Klapwijk (BTK) model reproducibly shows the gaps along these directions are 2.4, 2.6, and 2.3 meV, respectively, for one set of samples and 2.4, 2.8, and 2.7 meV, respectively, for the other set. This is smaller than the gap anisotropy reported by other groups[1]. At low temperatures, the single-gap BTK model does not satisfactorily fit our data. Models employing an anisotropic gap are being investigated, as are experiments parameterizing the tunneling cone effect.[1] Y.G. Naidyuk, et al,condmat/0609769(2006); N.L.Bobrov, et al,PRB 71, 014512 (2005); S. Mukhopadhyay, et al,PRB 72, 014545 (2005).

Lu, Xin; Park, W. K.; Greene, L. H.; Yeo, Sunmog; Oh, Kyu-Hwan; Lee, Sung-Ik; Bud'Ko, Sergey L.; Canfield, Paul C.

2008-03-01

351

Superconducting and SDW condensation energies in the 2D Hubbard model and the meaning to the stripe phase  

Microsoft Academic Search

The variational Monte Carlo calculations give a finite bulk-limit value of superconducting (SC) condensation energy Econd in the 2D Hubbard model with next-nearest-site transfer energy t? when electron density ??0.84 with ?0.25?t???0.10; our energy unit is the transfer energy between the nearest-neighbor (n.n.) sites. However, the SDW Econd computed by the same method is larger than the SC one in

K. Yamaji; T. Yanagisawa; S. Koike

2001-01-01

352

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

353

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

SciTech Connect

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

CHARLES M. WEBER

2008-06-24

354

Availability analysis of a 100 kWh superconducting magnetic energy storage  

NASA Astrophysics Data System (ADS)

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

Maekinen, H.; Mikkonen, R.

355

Can the Energy Gap in the Protein-Ligand Binding Energy Landscape Be Used as a Descriptor in Virtual Ligand Screening?  

PubMed Central

The ranking of scores of individual chemicals within a large screening library is a crucial step in virtual screening (VS) for drug discovery. Previous studies showed that the quality of protein-ligand recognition can be improved using spectrum properties and the shape of the binding energy landscape. Here, we investigate whether the energy gap, defined as the difference between the lowest energy pose generated by a docking experiment and the average energy of all other generated poses and inferred to be a measure of the binding energy landscape sharpness, can improve the separation power between true binders and decoys with respect to the use of the best docking score. We performed retrospective single- and multiple-receptor conformation VS experiments in a diverse benchmark of 40 domains from 38 therapeutically relevant protein targets. Also, we tested the performance of the energy gap on 36 protein targets from the Directory of Useful Decoys (DUD). The results indicate that the energy gap outperforms the best docking score in its ability to discriminate between true binders and decoys, and true binders tend to have larger energy gaps than decoys. Furthermore, we used the energy gap as a descriptor to measure the height of the native binding phase and obtained a significant increase in the success rate of near native binding pose identification when the ligand binding conformations within the boundaries of the native binding phase were considered. The performance of the energy gap was also evaluated on an independent test case of VS-identified PKR-like ER-localized eIF2? kinase (PERK) inhibitors. We found that the energy gap was superior to the best docking score in its ability to more highly rank active compounds from inactive ones. These results suggest that the energy gap of the protein-ligand binding energy landscape is a valuable descriptor for use in VS.

Grigoryan, Arsen V.; Wang, Hong; Cardozo, Timothy J.

2012-01-01

356

Operational characteristics of energy storage high temperature superconducting flywheels considering time dependent processes  

NASA Astrophysics Data System (ADS)

Technical and economical feasibilities of short-term energy storage flywheels with high temperature superconducting (HTS) bearing are widely investigated. It is essential to reduce the ac losses caused by magnetic field variations in HTS bulk disks/rings (levitators) used in the magnetic bearings of flywheels. For the HTS bearings the calculation and measurement of the magnetic field distribution were performed. Effects like eccentricity, tilting were measured. Time dependency of the levitation force following a jumpwise movement of the permanent magnet was measured. The results were used to setup an engineering design algorithm for energy storage HTS flywheels. This algorithm was applied to an experimental HTS flywheel model with a disk type permanent magnet motor/generator unit designed and constructed by the authors. A conceptual design of the disk-type motor/generator with radial flux is shown.

Vajda, Istvan; Kohari, Zalan; Porjesz, Tamas; Benko, Laszlo; Meerovich, V.; Sokolovsky; Gawalek, W.

2002-08-01

357

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/cm2. 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 kWh class flywheel energy storage system and investigated the feasibility of active magnetic bearings for the 10 kWh 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

358

Korea's Developmental Program for Superconductivity.  

National Technical Information Service (NTIS)

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 Electri...

1995-01-01

359

Energy band gaps of Zn1-xMgxSySe1-y lattice matched to GaAs  

Microsoft Academic Search

We report on theoretical study of the energy band gaps for the quaternary alloys Zn1-xMgxSySe1-y in conditions of lattice matching to GaAs substrates using simply the empirical pseudopotential method under the virtual crystal approximation which takes into account the effects of compositional disorder. Our results agree generally very well with the available experimental data. It is shown that the band-gap

Z. Charifi; H. Baaziz; N. Bouarissa

2003-01-01

360

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

361

A study of energy band gap versus temperature for Cu 2ZnSnS 4 thin films  

Microsoft Academic Search

The temperature dependent band gap energy of Cu2ZnSnS4 thin film was studied in the temperature range of 77–410K. 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 range.

Prashant K. Sarswat; Michael L. Free

362

Intersubband transitions in conduction band quantum wells: the role of energy band gaps and band off-sets  

Microsoft Academic Search

A new 14-band k·p analysis of optical intersubband transitions in conduction band quantum wells demonstrates the importance of the energy band gap and the band off-sets in determining the strength of such transitions, In particular it is found (1) that a narrow band gap enhances the TE activity, and is therefore desirable, because of the importance of band mixing, and

Lung-Han Peng

1995-01-01

363

Optical constants at and below energy gap of layered ternary Tl compounds  

NASA Astrophysics Data System (ADS)

Incoherent reflection mode of spectroscopic phase modulated ellipsometry (SPME) was firstly applied to quasi-two-dimensional TlInS2, TlGaS2 and TlGaSe2 to obtain uniaxial optical anisotropy of these materials at room temperature. Simulation of the measured SPME signal was performed within uniaxial incoherent reflection model, with a result of perfect match to experimental data for all three compounds. Birefringence in a photon energy range from below the energy gap of each material and down to 0.76eV was reliably determined. Obtained birefringence agrees well with optical anisotropy reported earlier from light figure studies of the above materials in the visible spectral range.

Okada, W.; Shim, Y.; Mamedov, N.

2006-09-01

364

Stochastic Method for the Operation of a Power System With Wind Generators and Superconducting Magnetic Energy Storages (SMESs)  

Microsoft Academic Search

Various energy storage systems have been adopted in power systems for economic and reliability reasons. In order to maintain the reliability of power systems, reserve power needs to be scheduled against possible generation unit outages. The varia- tion of wind power outputs also requires additional reserve power in addition to the reserve for the possible generation unit outages. Superconducting Magnetic

Jaehee Lee; Ji-Hui Kim; Sung-Kwan Joo

2011-01-01

365

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

Microsoft Academic Search

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

Seyed Mohammad; SADEGH ZADEH

2007-01-01

366

Operation of the 30 MJ Superconducting Magnetic Energy Storage System in the Bonneville Power Administration Electrical Grid.  

National Technical Information Service (NTIS)

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...

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

1984-01-01

367

Operation of the 30 MJ superconducting magnetic energy storage system in the Bonneville Power Administration electrical grid  

Microsoft Academic Search

The 30 MJ superconducting magnetic energy storage (SMES) system was installed in the Bonneville Power Administration (BPA) Tacoma Substation in 1982-83. 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.

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

1985-01-01

368

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

Microsoft Academic Search

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

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

1984-01-01

369

Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor  

NASA Astrophysics Data System (ADS)

The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi2Sr2-xLaxCuO6+? system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.

Peng, Yingying; Meng, Jianqiao; Mou, Daixiang; He, Junfeng; Zhao, Lin; Wu, Yue; Liu, Guodong; Dong, Xiaoli; He, Shaolong; Zhang, Jun; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Lee, T. K.; Zhou, X. J.

2013-09-01

370

Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor.  

PubMed

The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi2Sr2-xLaxCuO6+? system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity. PMID:24051514

Peng, Yingying; Meng, Jianqiao; Mou, Daixiang; He, Junfeng; Zhao, Lin; Wu, Yue; Liu, Guodong; Dong, Xiaoli; He, Shaolong; Zhang, Jun; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Lee, T K; Zhou, X J

2013-09-20

371

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

372

Superconductivity sourcebook  

Microsoft Academic Search

The information in this book was compiled from a wide variety of authorities who are specialists in their fields. The following topics are covered in the 14 chapters in this book: overview of superconductivity; superconductivity applications; market potential; commercializing superconductivity; superconductivity definitions; acronyms and abbreviations; periodical literature; journal papers; conference proceedings and papers; superconductivity reference books; information resources; products and

Hunt

1989-01-01

373

Energy calibration of superconducting transition edge sensors for x-ray detection using pulse analysis  

SciTech Connect

Transition edge sensors (TESs) have been developed to be used as high-resolution x-ray detectors. They show excellent energy resolution and can be used in many applications. TESs are a special kind of calorimeters that can determine small temperature changes after x-ray absorption. Such a temperature change causes a strong resistance change (superconducting to normal-conducting phase transition) that can be measured. The energy calibration of a TES based spectrometer is problematic due to the nonlinear behavior of the detector response. In this article, a method is introduced to calibrate the energy scale of TES spectra. This is accomplished by calculating the energy dependence of the response of the detector operated in electrothermal feedback mode. Using this method a calibration accuracy of a few eV for an x-ray energy of 6 keV can be achieved. Examples of energy dispersive x-ray spectroscopy (EDS) measurements demonstrate the high quality of this method for everyday use of TES EDS detectors in material analysis. However, because the method relies only on a few very general assumptions, it should also be useful for other kinds of TES detectors.

Hollerith, C.; Simmnacher, B.; Weiland, R.; Feilitzsch, F. v.; Isaila, C.; Jochum, J.; Potzel, W.; Hoehne, J.; Phelan, K.; Wernicke, D.; May, T. [Infineon Technologies AG, Otto-Hahn-Ring 6, 91739 Munich (Germany); Physik-Department E15, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching (Germany); Vericold Technologies GmbH, Bahnhofstrasse 21, 85737 Ismaning (Germany); Institute for Physical High Technology, Albert-Einstein-Strasse 9, 07702 Jena (Germany)

2006-05-15

374

Superconducting wire fabrication  

Microsoft Academic Search

Experiments were done leading to the fabrication of high-temperature superconducting composite wire. Bulk superconductor was characterized by using optical microscopy, scanning electron microscopy, and energy-dispersive x ray spectroscopy. The chemical compatibility of superconducting materials with a number of metal sheathing candidates was tested, with silver offering the best compatibility. Wire was fabricated by drawing 0.250-inch-diameter silver tubing packed with superconducting

W. E. Glad; G. G. Chase

1990-01-01

375

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

376

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

377

Direct and indirect transitions in the region of the band gap using electron-energy-loss spectroscopy  

Microsoft Academic Search

The momentum and energy dependence of the matrix elements for direct and indirect transitions across the band gap is studied both theoretically and experimentally. The accepted theory for the inelastic scattering cross section of fast electrons by condensed matter is extended to show how the nature of a transition can change the shape of the measured energy-loss spectrum in the

B. Rafferty; L. M. Brown

1998-01-01

378

Novel Gapped Quantum Wire  

NASA Astrophysics Data System (ADS)

High quality state of the art quantum wires (QWRs) can be fabricated by the novel cleaved edge overgrowth technique, proposed by (Pfeiffer et al., 1990). Transverse quantization in these QWRs leads to a succession of nested energy bands. With the lowest two successive energy levels occupied, gapped phases are possible including, e.g, an intersubband charge density wave (ICDW) and a Cooper phase with strong superconducting fluctuations (Starykh et al., 2000). Due to the possibility of density reorganization, in which it becomes favorable for the two lowest subbands to match their densities, the ICDW is usually the most likely state. Recently, by exploiting the valley degeneracy in AlAs, a single QWR has been fabricated with two degenerate nonoverlapping bands separated in k space by half an Umklapp vector (Moser et al. 2004). For low densities this structure is able to access a multiple subband regime that is not subject to the density reorganizing ICDW, leaving the Cooper phase to flourish. Using Abelian bosonization, we explore the relevant interaction terms for this system, including Umklapp assisted Cooper scattering, and discuss the phase diagram.

Datta, Trinanjan

2005-03-01

379

Novel Gapped Quantum Wire  

NASA Astrophysics Data System (ADS)

High quality state of the art quantum wires (QWRs) can be fabricated by the novel Cleaved Edge Overgrowth (CEO) technique, proposed by (Pfeiffer et al, 1990). Transverse quantization in these QWRs leads to a succession of nested energy bands. With the lowest two successive energy levels occupied, gapped phases are possible including, e.g., an intersubband charge density wave (ICDW) and a Cooper phase with strong superconducting fluctuations (Starykh et al, 2000). Due to the possibility of density reorganization, in which it becomes favorable for the two lowest subbands to match their densities, the ICDW is usually the most likely state. Recently, by exploiting the valley degeneracy in AlAs, a single QWR has been fabricated with two degenerate nonoverlapping bands separated in k space by half an Umklapp vector (Moser et al 2004). For low densities the structure is able to access a multiple subband regime that is not subject to the density reorganizing ICDW, leaving a Cooper phase to flourish. Using Abelian bosonization, we explore the relevant interaction terms for this system, including Umklapp assisted Cooper scattering and discuss the phase diagram.

Datta, Trinanjan

2005-04-01

380

Special Photon Energies for Extracting the Bosonic Spectral Function Mediating Superconductivity in Bi2212 via ARPES  

NASA Astrophysics Data System (ADS)

We have carried out extensive simulations of the ARPES photointensity througout the Brillouin zone for exciting states from the bonding as well as the antibonding FS in Bi2212 for a wide range of photon energies(h?). The binding energy range considered is ˜3 times the superconducting energy scale, which should be adequate for treating the mixing of the bosonic glue. The constancy of the ARPES matrix element is analyzed in terms of a simple measure of variations defined by variance as a percentage of the normalized average intensity. The presented results allow us to obtain the specific h?'s where the matrix element remains constant within a particular level of tolerance, and to determine how different regions of the (k_allel,?) space contribute in this regard. Photon energies, where the matrix element displays a weak k_allel and ? dependence provide special windows for applying schemes such as those of Vekhter and Varma [Phys. Rev. Lett. 90, 237003 (2003)], and for investigating self-energy effects more generally via ARPES (e.g. the kink physics). Work supported by the USDOE.

Bansil, A.; Lindroos, M.; Markiewicz, R. S.

2004-03-01

381

Superconducting wire.  

National Technical Information Service (NTIS)

This invention consists of a method of producing superconducting wire by drawing a glass fiber with a melted powder of a superconducting wire inside the glass tube. After drawing, the glass fiber is heated to crystallize the superconducting compound. The ...

D. E. Day J. J. Petrovic F. D. Gac C. S. Ray

1991-01-01

382

Fabrication of Nb/A1 Superconducting Tunnel Junction  

NASA Astrophysics Data System (ADS)

We report the successful fabrication and I--V curve superconductivity test results of the Nb/Al-based superconducting tunnel junctions. STJs with side-lengths of 20, 40, 60 and 80 ?m were fabricated by deposition of polycrystalline Nb/Al/AlOx/Al/Nb 5-layer thin films incorporated on a 3-inch Si wafer. STJ was designed by TannerTM L-Edit 8.3 program, and fabricated in SQUID fabrication facility, KRISS. 5-layer STJ thin-films were fabricated using UV photolithography, DC magnetron sputtering, Reactive ion etching, and CVD(Chemical Vapor Deposition) techniques. Superconducting state test for STJ was succeeded in 4K with liquid helium cooling system. Their performance indicators such as energy gap, normal resistance, normal resistivity, dynamic resistance, dynamic resistivity, and quality factor were measured from I--V curve. Fabricated Nb/Al STJ shows 11% higher FWHM energy resolution than genuine Nb STJ.

Cho, Sung-Ik; Park, Young-Sik; Park, Jang-Hyun; Lee, Yong-Ho; Lee, Sang-Kil; Kim, Sug-Whan; Han, Won-Yong

2004-12-01

383

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

SciTech Connect

The Bonneville Power Administration operates the transmission system that joins the Pacific Northwest and southern California. A 30-MJ (8.4-kWh) Superconducting Magnet Energy Storage (SMES) unit with a 10-MW converter can provide system damping for low frequency oscillations. The unit is scheduled to operate in 1982. Progress during FY 80 is described. The conductor has been fully tested both electrically and mechanically, all of the necessary copper and superconductor has been purchased, and the first production lengths of cable have been fabricated. All major components of the electrical and cryogenic systems except the gas recovery unit have been received, but the refrigerator, converter, and one transformer were damaged during shipment. The dewar is being procured, and the coil support system has been designed. Support work at LASL to prepare for subsystem testing is nearly complete.

Schermer, R.I.

1980-01-01

384

A new power-conditioning system for superconducting magnetic energy storage  

SciTech Connect

A new power-conditioning system for superconducting magnetic energy storage, which can independently regulate the active and reactive power of the utility network, is presented. The conceived system is composed of ten 100-MW modules connected in parallel. Each 100-MW module consists of a tap changing transformer and a 12-pulse, force-commutated converter. This system offers a significant reduction of the system rating by reducing the reactive power demand in the converter with control of the tap-changing ratio and the converter firing angle. The operational concept of this system is verified through mathematical analysis and computer simulation. The dynamic interaction between this system and the ac network is analyzed using a simulation model with EMTP. The analysis results prove that the new system concept is feasible. This system can be built with commercially available components and proven technologies.

Han, B.M.; Karady, G.G. (Arizona State Univ., Tempe, AZ (United States))

1993-06-01

385

A safe, low current, high gradient, superconducting quadrupole magnet for high energy physics beam transport  

SciTech Connect

A superconducting quadrupole magnet has been fabricated and tested that generates a gradient of 60 T/m at a peak operating current of 1100 amperes. The cold bore of the magnet is 12.7 cm in diameter and 2.8 m long, and the unwanted field multipoles sum to 4 parts per thousand of the quadrupole field at a bore radius of 5.0 cm. The magnet operates safely without quench protection and peak coil temperatures following quenches deliberately induced at full field do not exceed 50 K. Testing at the design gradient of 50 T/m indicates a beam energy deposition quench threshold of approximately 5 mJ/cm/sup 3/.

Smith, R.; Gonczy, J.; Kelly, A.; Kim, S.; Krieger, C.; Underwood, D.; Wallace, E.; Wiggins, K.

1983-05-01

386

Superconductivity sourcebook  

SciTech Connect

The information in this book was compiled from a wide variety of authorities who are specialists in their fields. The following topics are covered in the 14 chapters in this book: overview of superconductivity; superconductivity applications; market potential; commercializing superconductivity; superconductivity definitions; acronyms and abbreviations; periodical literature; journal papers; conference proceedings and papers; superconductivity reference books; information resources; products and services; points of contact; and the federal superconductivity initiative.

Hunt, V.D.

1989-01-01

387

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

ERIC Educational Resources Information Center

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

Kuroda, Tsuyoshi; Nakajima, Yoshitaka; Eguchi, Shuntarou

2012-01-01

388

Observation of the Finite Superconducting Gap States in La1.86Sr0.14CuO4-x by Electron Tunneling  

Microsoft Academic Search

In order to investigate symmetry of the Cooper pairing in high-T c superconductors,quasiparticle tunneling studies were carried out by means of micro-break SIS junction which was in situ prepared at the LT-STM\\/STS stage. For La1.86Sr0.14CuO4-x single crystal, a distinct gap structure with a definite bias range of almost zero conductance level was observed on the tunneling spectrum. This result is

Hironaru Murakami; Syuzo Ohbuchi; Ryozo Aoki

1994-01-01

389

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

390

Multiparticle-multihole states around {sup 16}O and correlation-energy effect on the shell gap  

SciTech Connect

Multiparticle-multihole states around {sup 16}O such as the famous 0{sub 2}{sup +} state in {sup 16}O are investigated with a shell-model calculation in the full p-sd model space. It is found that the modification of the N=Z=8 shell gap due to correlation energy is unexpectedly large, which plays an essential role in accounting for those states. We point out that correlation energy affects the shell gap in the opposite way between {sup 16}O and {sup 56}Ni, giving its mechanism in terms of the difference of the L-S and j-j closures.

Utsuno, Yutaka; Chiba, Satoshi [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

2011-02-15

391

Strong-coupling superconductivity in NaFe1-xCoxAs: Validity of Eliashberg theory  

NASA Astrophysics Data System (ADS)

We study the normal-state and superconducting properties of the NaFe1-xCoxAs system by specific heat measurements. Both the normal-state Sommerfeld coefficient and superconducting condensation energy are strongly suppressed in the underdoped and heavily overdoped samples. The low-temperature electronic specific heat can be well fitted by either a one-gap or a two-gap BCS-type function for all the superconducting samples. The ratio ?NTc2/Hc2(0) can nicely associate the neutron spin resonance as the bosons in the standard Eliashberg model. However, the value of ?C/Tc?N near optimal doping is larger than the maximum value the model can obtain. Our results suggest that the high-Tc superconductivity in the Fe-based superconductors may be understood within the framework of boson-exchange mechanism but significant modification may be needed to account for the finite-temperature properties.

Tan, Guotai; Zheng, Ping; Wang, Xiancheng; Chen, Yanchao; Zhang, Xiaotian; Luo, Jianlin; Netherton, Tucker; Song, Yu; Dai, Pengcheng; Zhang, Chenglin; Li, Shiliang

2013-04-01

392

Weak-coupling superconductivity in electron-doped NaFe0.95Co0.05As revealed by ARPES  

NASA Astrophysics Data System (ADS)

We report a systematic study on the electronic structure and superconducting (SC) gaps in electron-doped NaFe0.95Co0.05As superconductor using angle-resolved photoemission spectroscopy. Holelike Fermi sheets are at the zone center and electronlike Fermi sheets are at the zone corner, and are mainly contributed by xz and yz orbital characters. Our results reveal a (?)/(KBTc) in the range of 1.8-2.1, suggesting a weak-coupling superconductivity in these compounds. Gap closing above the transition temperature (Tc) shows the absence of pseudogaps. Gap evolution with temperature follows the BCS gap equation near the ?, Z, and M high symmetry points. Furthermore, an almost isotropic superconductivity along the kz direction in the momentum space is observed by varying the excitation energies.

Thirupathaiah, S.; Evtushinsky, D. V.; Maletz, J.; Zabolotnyy, V. B.; Kordyuk, A. A.; Kim, T. K.; Wurmehl, S.; Roslova, M.; Morozov, I.; Büchner, B.; Borisenko, S. V.

2012-12-01

393

Inelastic energy loss of light particles scattered by solid surfaces at low energy: influence of the `gap'  

NASA Astrophysics Data System (ADS)

The energy spectra of particles scattered by solid surfaces are used to determine the inelastic energy loss at low energy. Assuming the binary collision approximation, a modified TRIM code provides length distributions which are converted to time-of-flight (TOF) spectra by using the friction coefficient as an adjustable parameter. Owing to the nonlinear effects occurring in this energy range, the theoretical value of the electronic stopping power is performed from electron-particle scattering cross-section using a screened potential and so, the phase shifts, obtained self-consistently in the framework of density functional theory (DFT). In the case of He/a:Si interaction at 4 keV, the standard model leads to a largely overestimated value. This fact has been attributed to the presence of the electron energy gap EG and to the structure of the valence band. We verify this assumption in a non-static model involving all electrons of the valence band with a threshold condition ve'2vF2+2EG, where vF is the Fermi velocity and ve the electron velocity after scattering (non-static extended collisional model). The theoretical results agree very well with the experimental ones for He colliding three targets: a:Si, a:Ge and polycrystalline Ni at 4 keV. The calculations performed for the velocity range below 1 a.u. confirm the important role of the gap and the band structure in the lowering of stopping power at low velocity.

Boudjema, M.; D'bichi, N.; Boudouma, Y.; Chami, A. C.; Arezki, B.; Khalal, K.; Benazeth, C.; Benoit-Cattin, P.

2000-04-01

394

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

395

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

396

Superconducting wire  

Microsoft Academic Search

This invention consists of a method of producing superconducting wire by drawing a glass fiber with a melted powder of a superconducting wire inside the glass tube. After drawing, the glass fiber is heated to crystallize the superconducting compound. The diameter of the superconducting wires is controlled by the rate at which the glass fiber s are drawn from the

D. E. Day; J. J. Petrovic; F. D. Gac; C. S. Ray

1991-01-01

397

Superconducting wire  

DOEpatents

This invention consists of a method of producing superconducting wire by drawing a glass fiber with a melted powder of a superconducting wire inside the glass tube. After drawing, the glass fiber is heated to crystallize the superconducting compound. The diameter of the superconducting wires is controlled by the rate at which the glass fiber s are drawn from the glass tube.

Day, D.E.; Petrovic, J.J.; Gac, F.D.; Ray, C.S.

1991-03-05

398

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

399

Tight-binding calculations of energy gaps in (001)-(InAs)n(InSb)m strained superlattices  

NASA Astrophysics Data System (ADS)

Tight-binding calculations of electronic structures for (001)-(InAs)n(InSb)m strained layer superlattices are presented. The dependences of the superlattice band gap on the band offsets between InAs and InSb are examined for three different types of biaxial strains. It is found that the band gap depends strongly on the band offset, and that for m=1 the ordering lowers the band gap with respect to the random alloy. A comparison with the photoluminescence data for the energy gaps of (n×1) strained-layer superlattices is discussed. In addition, the electronic structures of strained InAs quantum wells are calculated, and interpretations are provided for the observed type-I to type-II band alignment transition at n=5 in a quantum well formed by (n×1) strained layer superlattices and AlSb barriers. Changes of energy gaps with layer thicknesses in strained layer superlattices with n=m and n=8-m are also studied.

Lin-Chung, P. J.; Yang, M. J.

2000-05-01

400

Determination of band gap energy (Eg) of Cu2ZnSnSe4 thin films: On the discrepancies of reported band gap values  

NASA Astrophysics Data System (ADS)

We demonstrate experimental data to elucidate the reason for the discrepancies of reported band gap energy (Eg) of Cu2ZnSnSe4 (CZTSe) thin films, i.e., 1.0 or 1.5 eV. Eg of the coevaporated CZTSe film synthesized at substrate temperature (Tsub) of 370 °C, which was apparently phase pure CZTSe confirmed by x-ray diffraction (XRD) and Raman spectroscopy, is found to be around 1 eV regardless of the measurement techniques. However, depth profile of the same sample reveals the formation of ZnSe at CZTSe/Mo interface. On the other hand, Eg of the coevaporated films increases with Tsub due to the ZnSe formation, from which we suggest that the existence of ZnSe, which is hardly distinguishable from CZTSe by XRD, is the possible reason for the overestimation of overall Eg.

Ahn, Sejin; Jung, Sunghun; Gwak, Jihye; Cho, Ara; Shin, Keeshik; Yoon, Kyunghoon; Park, Doyoung; Cheong, Hyonsik; Yun, Jae Ho

2010-07-01

401

Improvement of superconducting properties of old Y Ba Cu O specimens by high-energy heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Superconducting parameters of different, almost 20 years old Y Ba Cu O samples, prepared in 1987 1988 are investigated. The aim of this research is to find out how a heavy ion beam can enhance the superconducting features of very old and originally not always perfect Y-based specimens. As is observed, their electrical and magnetic characteristics are very sensitive to high-energy Bi-ion irradiation, which results in significant increase of the superconducting parameters. The most important one of them is the global critical current density which is calculated with the help of a new method on the basis of experiments. It can be increased by 18 39%, depending on the original, starting conditions of the samples before the irradiation. At the same time, the average values of intragrain critical current density grows by 37 51%. A slight increase in the critical temperature of 1 2 K was also observed. The experiments on AC susceptibility demonstrate that this irradiation causes to develop faster the total diamagnetic state and decreases the loss. The reason of these effects can be found in the better orientation of crystals, enlargement of microcrystalline aggregates, higher homogenization of the material, thus, in the increase of the superconducting component of samples due to the irradiation.

Kirschner, I.; Balogh, A.; Peurla, M.; Laiho, R.; Mészáros, Cs.; Pintér-Csordás, A.

2006-12-01

402

Calculation of the atomic spin densities and energy band gaps of carbon high-spin aromatic (pi) large macromolecular systems  

Microsoft Academic Search

In this work we have calculated the atomic spin densities and energy band gaps of three kinds of large carbon unlocalized high-spin aromatic systems, consisting of 1000 to 10 000 atoms. The selected systems, nanotubes, graphenes, and polyaryls, have obvious theoretical and technical interest. The results obtained for nanotubes and graphenes confirm and expand the ones published by other authors.

J. R. A´lvarez Collado

2008-01-01

403

Field-Induced Insulator to Semimetal Transition and Field Electron Emission of Nanorods of Semiconductors of Wide Energy Band Gaps  

Microsoft Academic Search

Significant field emission is found theoretically possible from nanorods of semiconductors of wide energy band gaps. If the nanorod has a thin surface layer containing a large number of localized states, a part of nanorod can exhibit an insulator-to-semimetal transition under high enough fields of direction parallel to its axis, so that field emission occurs at the apex of the

Zhibing Li; Weiliang Wang; Shaozhi Deng; Ningsheng Xu; Guiyang Huang

2005-01-01

404

A qualitative comparison of energy band gap equations with a focus on temperature and its effect on CNTFETs  

Microsoft Academic Search

The role of temperature in semiconductors has been established as a contributing factor in affecting the energy band gap. However, the temperature in Carbon nanotube field effect transistors (CNTFETs) is said to be negligible and can be ignored as stated in [1]. An investigation on how the temperature would affect these devices is investigated by comparing different equations with a

Jesus A. Torres; Hasina F. Huq

2011-01-01

405

Endogenous implementation of technology gap in energy optimization models—a systematic analysis within TIMES G5 model  

Microsoft Academic Search

Evaluation of global diffusion potential of learning technologies and their timely specific cost development across regions is always a challenging issue for the future technology policy preparation. Further the process of evaluation gains interest especially by endogenous treatment of energy technologies under uncertainty in learning rates with technology gap across the regions in global regional cluster learning approach. This work

Ullash K. Rout; Ulrich Fahl; Uwe Remme; Markus Blesl; Alfred Voß

2009-01-01

406

Superconductivity in a model involving transverse gauge bosons  

NASA Astrophysics Data System (ADS)

It has been known for some time that a system of fermions interacting with transverse gauge bosons does not behave like a Fermi liquid and provides a bona fide model for a non-Fermi liquid. Here we study superconductivity in this model Preliminary calculations show explicitly that a superconducting gap exists only for couplings greater than a threshold. It is hoped that a proper elucidation of this problem would lead to insights that may be useful in developing effective low energy theories of realistic physical problems, such as the normal state of high temperature superconductors, the state of half-filled quantum Hall systems, or the color superconductivity in the quark-gluon system, or even in the effects of disorder in a non-Fermi liquid system that could provide a new paradigm.

Mandal, Ipsita; Chakravarty, Sudip; Chung, Suk Bum

2013-03-01

407

Tests of the 30-MJ superconducting magnetic-energy storage unit  

SciTech Connect

A 30-MJ (8.4 kWh) superconducting magnetic energy storage (SMES) unit with a 10-MW converter was installed during the later months of 1982 at the Bonneville Power Administration (BPA) Tacoma substation in Tacoma, Washington. The unit, which is capable of absorbing and releasing up to 10 MJ of energy at a frequency of 0.35 Hz, was designed to damp the dominant power swing mode of the Pacific AC Intertie. Extensive tests were performed with the unit during the first half of 1983. This paper will review the major components of the storage unit and describe the startup and steady state operating experience with the coil, dewar, refrigerator and converter. The unit has absorbed power up to a level of 11.8 Mw. Real power was modulated following a sinusoidal power demand with frequencies from 0.1 to 1.2 Hz and a power level up to +- 8.3 MW. The unit has performed in accordance with design expectations and no major problems have developed.

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

1983-01-01

408

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

409

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

410

Superconductivity in the system of p electrons  

SciTech Connect

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

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

2012-10-15

411

Formation of the density wave energy gap in Na2Ti2Sb2O: An optical spectroscopy study  

NASA Astrophysics Data System (ADS)

We performed an optical spectroscopy measurement on single crystals of Na2Ti2Sb2O, which is a parent compound for the newly discovered Ti-based superconductors. The study reveals a significant spectral change across the phase transition at 114 K and formation of a density wave type energy gap. The opening of the gap removes most of the free carrier spectral weight and causes a dramatic reduction in the carrier scattering rate. The ratio of 2?/kBTs?14 is considerably larger than the mean-field value based on the weak-coupling BCS theory. The study also reveals a weak correlation effect in the titanium oxypnictides.

Huang, Y.; Wang, H. P.; Wang, W. D.; Shi, Y. G.; Wang, N. L.

2013-03-01

412

Generation of high-energy synchrotron radiation with a 10-T superconducting wiggler installed in the SPring8 storage ring  

Microsoft Academic Search

A three-pole 10-T superconducting wiggler was installed in the 8-GeV electron storage ring at SPring-8 for generating high-energy synchrotron radiation. Beam tests were carried out to check its performance and to investigate the effects on a stored beam. A beam was successfully stored at magnetic fields of the wiggler up to 9.7 T. The beam current was limited to 1

K. Soutome; S. Date; H. Ego; T. Fukui; M. Hara; N. Hosoda; Y. Kawashima; M. Kodera; N. Kumagai; T. Magome; M. Masaki; T. Masuda; S. Matsui; T. Nakamura; T. Noda; Y. Ohashi; T. Ohshima; M. Oishi; H. Saeki; S. Sasaki; M. Shoji; S. Takano; M. Takao; T. Takashima; H. Takebe; K. Tamura; H. Tanaka; Y. Taniuchi; K. Tsumaki; T. Yorita; C. Zhang; H. Yonehara; J. Schimizu; A. Batrakov; G. Karpov; G. Kulipanov; M. Kuzin; V. Shkaruba; A. Skrinsky; N. Mezentsev

2003-01-01

413

Design of the main dipoles and quadrupoles for the SSC Low Energy Booster. [Superconducting Super Collider (SSC)  

Microsoft Academic Search

The Superconducting Super Collider (SSC) Low Energy Booster (LEB) is a synchrotron which accelerates bunches of protons from a momentum of 1.2 Gev\\/c at injection to a momentum of 12.0 Gev\\/c at extraction. The main bending dipoles with a peak field of 1.3 Tesla and the main focusing and defocusing quadrupoles with a peak gradient of about 14.9 Tesla\\/m operate

V. Thiagarajan; X. Wu; R. York; R. D. Schlueter; K. Halbach

1992-01-01

414

Conceptual system design of a 5 MWh\\/100 MW superconducting flywheel energy storage plant for power utility applications  

Microsoft Academic Search

The authors have designed a 5 MWh\\/100 MW superconducting flywheel energy storage plant. The plant consists of 10 flywheel modules rated at 0.5 MWh\\/10 MW each. Module weight is 30 t, size is ? 3.5 m×6.5 m high. A synchronous type motor-generator is used for power input\\/output. Each flywheel system consists of four disk modules made from a carbon fibre

H. J. Bornemann; M. Sander

1997-01-01

415

Theoretical analysis and experimental results on super-conducting magnetic energy storage (SMES) in dynamic simulation test of power system  

Microsoft Academic Search

This paper introduces a double-DSPs controlled power conditioning system (PCS) for superconducting magnetic energy storage (SMES), which is used for experimental study in dynamic simulation tests of power system. Considering of realization, voltage source converter (VSC) with a chopper is adopted in the experimental sample. The VSC in the PCS is a four-quadrant AC\\/DC converter and chopper is a two-quadrant

Hui Zhang; Yong Kang; Pengcheng Zhu; Xuejuan kong; Ping Liu; Jian Chen

2001-01-01

416

Lattice parameter and energy band gap of cubic AlxGayIn1-x-yN quaternary alloys  

Microsoft Academic Search

First-principles total energy calculations, combined with a generalized quasichemical approach to disorder and compositional effects, are used to obtain the lattice parameter and the energy band gap of cubic AlxGayIn1-x-yN quaternary alloys. It is found that the lattice parameter a(x,y) fulfills a Vegard's-like law; that is, it shows a linear dependence on the alloy contents x and y. The range

M. Marques; L. K. Teles; L. M. R. Scolfaro; J. R. Leite; J. Furthmüller; F. Bechstedt

2003-01-01

417

Lattice parameter and energy band gap of cubic AlxGayIn1?x?yN quaternary alloys  

Microsoft Academic Search

First-principles total energy calculations, combined with a generalized quasichemical approach to disorder and compositional effects, are used to obtain the lattice parameter and the energy band gap of cubic AlxGayIn1?x?yN quaternary alloys. It is found that the lattice parameter a(x,y) fulfills a Vegard’s-like law; that is, it shows a linear dependence on the alloy contents x and y. The range

M. Marques; L. K. Teles; L. M. R. Scolfaro; J. R. Leite; F. Bechstedt

2003-01-01

418

Graded or stepped energy band-gap-insulator MIS structures (GI-MIS or SI-MIS)  

Microsoft Academic Search

A new concept in nonvolatile semiconductor memory using graded or stepped energy band-gap insulators under the gate electrode of a metal-insulator-semiconductor type structure is described. With the graded or stepped insulator, electrons or holes can be injected from the gate electrode at low to moderate applied fields. These carriers then flow under the applied voltage bias into a wide energy

D. J. DiMaria

1979-01-01

419

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

420

Restoration of the Derivative Discontinuity in Kohn-Sham Density Functional Theory: An Efficient Scheme for Energy Gap Correction  

NASA Astrophysics Data System (ADS)

From the perspective of perturbation theory, we propose a systematic procedure for the evaluation of the derivative discontinuity (DD) of the exchange-correlation energy functional in Kohn-Sham (KS) density functional theory, wherein the exact DD can in principle be obtained by summing up all the perturbation corrections to infinite order. Truncation of the perturbation series at low order yields an efficient scheme for obtaining the approximate DD. While the zeroth-order theory yields a vanishing DD, the first-order correction to the DD can be expressed as an explicit universal functional of the ground-state density and the KS lowest unoccupied molecular orbital density, allowing the direct evaluation of the DD in the standard KS method without extra computational cost. The fundamental gap can be predicted by adding the estimated DD to the KS gap. This scheme is shown to be accurate in the prediction of the fundamental gaps for a wide variety of atoms and molecules.

Chai, Jeng-Da; Chen, Po-Ta

2013-01-01

421

Far Infrared Studies of Superconducting V sub 3 Si, Nb sub 3 Ge and Nb. Final Report.  

National Technical Information Service (NTIS)

Far infrared spectroscopy between 10 and 250 cm exp -1 is an effective probe of superconductivity because typical gap and phonon energies lie in this region. Between 1979 and 1985, this DOE contract supported far infrared research in homogeneous high-T/su...

S. Perkowitz

1985-01-01

422

Superconducting quantum bits.  

PubMed

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

Clarke, John; Wilhelm, Frank K

2008-06-19

423

Superconductivity in liquid metallic hydrogen  

Microsoft Academic Search

By solving the Eliashberg equations for the gap function, the super-conducting transition temperature of a proposed low-temperature liquid state of metallic hydrogen is found to be comparable to that obtained, with similar approximations, for the solid. This indicates that metallic hydrogen may be a superconducting liquid in the density range 1.6> or =r\\/sub s\\/> or =1.3, where the melting point

J. E. Jaffe; N. W. Ashcroft

1981-01-01

424

Redox Free Energies from Vertical Energy Gaps: Ab Initio Molecular Dynamics Implementation  

Microsoft Academic Search

The development of methods for the exploration of reaction paths in condensed molecular systems (solutions and biopolymers)\\u000a and the computation of the corresponding reaction free energies and kinetic parameters remains at the center of research in\\u000a computational chemistry. Much has happened in recent years. It is the subject of a good number of the chapters in this book,\\u000a which give

J. Blumberger; M. Sprik

2006-01-01

425

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

426

Superconducting magnetic energy storage (SMES) program. Progress report, January 1-December 31, 1984  

SciTech Connect

The 30 MJ, 10 MW superconducting magnetic energy storage (SMES) system was devised to interact in the Western US Power System as an alternate means to damp unstable oscillations at 0.35 Hz on the Pacific HVAC Intertie. The SMES unit was installed at the Tacoma Substation of the Bonneville Power Administration (BPA). The operating limits of the 30 MJ SMES unit were established, and different means of controlling real and reactive power were tested. The unit can follow a sinusoidal power demand signal with an amplitude of up to 8.6 MW with the converter working in a 12 pulse mode. When the converter operates in the constant VAR mode, a time varying real power demand signal of up to 5 MW can be met. Experiments showed that the Pacific ac Intertie has current and reactive power variations of the same frequency as the modulating frequency of the SMES device. Endurance tests were run to assess the reliability of the SMES subsystems with a narrow band noise input, which is characteristic of the modulation signal for stabilizer operation. During the endurance tests, parameters of the ac power system were determined. Converter short circuit tests, load tests under various control conditions, dc breaker tests for coil current interruption, and converter failure mode tests were conducted. The experimental operation of the SMES system was concluded and the operation was terminated in early 1984.

Rogers, J.D. (comp.)

1985-05-01

427

Universality of the Dispersive Spin-Resonance Mode in Superconducting BaFe2As2  

NASA Astrophysics Data System (ADS)

Spin fluctuations in superconducting BaFe2(As1-xPx)2 (x=0.34, Tc=29.5K) are studied using inelastic neutron scattering. Well-defined commensurate magnetic signals are observed at (?, 0), which is consistent with the nesting vector of the Fermi surface. Antiferromagnetic (AFM) spin fluctuations in the normal state exhibit a three-dimensional character reminiscent of the AFM order in nondoped BaFe2As2. A clear spin gap is observed in the superconducting phase forming a peak whose energy is significantly dispersed along the c axis. The bandwidth of dispersion becomes larger with approaching the AFM ordered phase universally in all superconducting BaFe2As2, indicating that the dispersive feature is attributed to three-dimensional AFM correlations. The results suggest a strong relationship between the magnetism and superconductivity.

Lee, C. H.; Steffens, P.; Qureshi, N.; Nakajima, M.; Kihou, K.; Iyo, A.; Eisaki, H.; Braden, M.

2013-10-01

428

Coexistence of superconductivity and ferromagnetism in ferromagnet/superconductor proximity structures  

NASA Astrophysics Data System (ADS)

The Nambu spinor Green's function approach is applied to calculating the density of states (DOS) and superconducting order parameter in normal-metal/insulator/ferromagnet/superconductor (NM/I/FM/SC) junctions. It is found that the s-wave superconductivity and ferromagnetism can coexist near the FM/SC interface, which is induced by proximity effect. On the SC side, the spin-dependent DOS appears both within and without the energy gap. On the FM side, the superconducting order parameter displays a damped oscillation and the DOS exhibits some superconducting behavior. The calculated result for the DOS in FM for “0 state” and “? state” can reproduce recent tunneling spectra in Al/Al2O3/PdNi/Nb tunnel junctions.

Sun, Guoya; Xing, D. Y.; Shen, R.; Lin, H. Q.

2002-11-01

429

Nodes versus minima in the energy gap of iron pnictide superconductors from field-induced anisotropy.  

PubMed

We develop the formalism for computing the oscillations of the specific heat and thermal transport under rotated magnetic field in multiband superconductors with anisotropic gap and apply it to iron-based materials. We show that these oscillations change sign at low temperatures and fields, which strongly influences the experimental conclusions about the gap structure. We find that recent measurements of the specific heat oscillations indicate that the iron-based superconductors possess an anisotropic gap with deep minima or nodes close to the line connecting electron and hole pockets. We predict the behavior of the thermal conductivity that will help distinguish between these cases. PMID:21231129

Vorontsov, A B; Vekhter, I

2010-10-28

430

Conformal GaP layers on Si wire arrays for solar energy applications  

NASA Astrophysics Data System (ADS)

We report conformal, epitaxial growth of GaP layers on arrays of Si microwires. Silicon wires grown using chlorosilane chemical vapor deposition were coated with GaP grown by metal-organic chemical vapor deposition. The crystalline quality of conformal, epitaxial GaP/Si wire arrays was assessed by transmission electron microscopy and x-ray diffraction. Hall measurements and photoluminescence show p- and n-type doping with high electron mobility and bright optical emission. GaP pn homojunction diodes on planar reference samples show photovoltaic response with an open circuit voltage of 660 mV.

Tamboli, Adele C.; Malhotra, Manav; Kimball, Gregory M.; Turner-Evans, Daniel B.; Atwater, Harry A.

2010-11-01

431

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

432

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.

433

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

434

Prospects for the medium- and long-term development of China`s electric power industry and analysis of the potential market for superconductivity technology  

SciTech Connect

First of all, overall economic growth objectives in China are concisely and succinctly specified in this report. Secondly, this report presents a forecast of energy supply and demand for China`s economic growth for 2000--2050. In comparison with the capability of energy construction in China in the future, a gap between supply and demand is one of the important factors hindering the sustainable development of Chain`s economy. The electric power industry is one of China`s most important industries. To adopt energy efficiency through high technology and utilizing energy adequately is an important technological policy for the development of China`s electric power industry in the future. After briefly describing the achievements of China`s electric power industry, this report defines the target areas and policies for the development of hydroelectricity and nuclear electricity in the 2000s in China, presents the strategic position of China`s electric power industry as well as objectives and relevant plans of development for 2000--2050. This report finds that with the discovery of superconducting electricity, the discovery of new high-temperature superconducting (HTS) materials, and progress in materials techniques, the 21st century will be an era of superconductivity. Applications of superconductivity in the energy field, such as superconducting storage, superconducting transmission, superconducting transformers, superconducting motors, its application in Magneto-Hydro-Dynamics (MHD), as well as in nuclear fusion, has unique advantages. Its market prospects are quite promising. 12 figs.

Li, Z. [Bob Lawrence and Associates, Inc., Alexandria, VA (United States)

1998-05-01

435

Evolution from a Nodeless Gap to dx2-y2-Wave in Underdoped La2-xSrxCuO4  

NASA Astrophysics Data System (ADS)

Using angle-resolved photoemission spectroscopy (ARPES), it is revealed that the low-energy electronic excitation spectra of highly underdoped superconducting and nonsuperconducting La2-xSrxCuO4 cuprates are gapped along the entire underlying Fermi surface at low temperatures. We show how the gap function evolves to a dx2-y2 form with increasing temperature or doping, consistent with the vast majority of ARPES studies of cuprates. Our results provide essential information for uncovering the symmetry of the order parameter(s) in strongly underdoped cuprates, which is a prerequisite for understanding the pairing mechanism and how superconductivity emerges from a Mott insulator.

Razzoli, E.; Drachuck, G.; Keren, A.; Radovic, M.; Plumb, N. C.; Chang, J.; Huang, Y.-B.; Ding, H.; Mesot, J.; Shi, M.

2013-01-01

436

Superconductivity and information exchange  

NASA Astrophysics Data System (ADS)

The author was invited to visit several institutions in Europe for the purposes of collaboration, information exchange, and presentation of seminars. Extensive exchanges of information regarding the current state of the field in high-temperature superconductivity took place. Five seminars on the recent work of Klemm and Liu on interlayer pairing were given, and the response was very favorable. A new collaboration on the role of gap anisotropy on the physical properties of high-temperature superconductors was begun.

Klemm, R. A.

1990-08-01

437

Superconducting Transducer.  

National Technical Information Service (NTIS)

The patent application describes a high power density, low frequency superconducting transducer which includes an electro-dynamic drive wherein a superconducting magnet provides the primary driving force for two AC-driven copper coils. Each of the copper ...

M. G. Karamargin

1975-01-01

438

Charge Density Wave and Superconductivity in Anisotropic Materials  

Microsoft Academic Search

The interplay between superconductivity and charge density wave state concomitant with the lattice instability is discussed theoretically based on the partial gapping model appropriate for anisotropic materials. The present calculation aims at supplementing the theory by Bilbro and McMillan on the same partical gapping model. Various thermodynamic quantities such as the specific heat jump at the superconducting transition and anisotropic

Kazushige Machida

1984-01-01

439

Dynamical Model of Elementary Particles Based on an Analogy with Superconductivity. I  

Microsoft Academic Search

It is suggested that the nucleon mass arises largely as a self-energy of some primary fermion field through the same mechanism as the appearance of energy gap in the theory of superconductivity. The idea can be put into a mathematical formulation utilizing a generalized Hartree-Fock approximation which regards real nucleons as quasi-particle excitations. We consider a simplified model of nonlinear

Y. Nambu; G. Jona-Lasinio

1961-01-01

440

Growth and energy band gap of CaSeS thin films prepared by hot-wall epitaxy  

NASA Astrophysics Data System (ADS)

This paper investigates preparation of CaSeS thin films using hot-wall epitaxy. These films can be grown epitaxially on cleaved BaF2(1 1 1) at a substrate temperature of 873 K by tailoring the VI/II flux ratio vaporized from Ca and SeS resources. The optical absorption edge of these films thus tailored can be observed clearly, shifting toward higher photon energy with increasing S content. In particular, the energy band gap of CaSe0.66S0.34, capable of lattice-matching to InP was found to be 4.69 eV, producing considerably large band gap difference of 3.34 eV between the CaSe0.66S0.34 and InP.

Abe, Seishi; Masumoto, Katashi

2007-03-01

441

Temperature and composition dependence of the energy band gap of Pb1- x Mn x S solid solution  

Microsoft Academic Search

Photovoltaic p-n junctions in n-type Pb1-xMn x S x≦0.04, have been made by sulphur diffusion. Current-voltage and resistance-voltage characteristics have been examined at various temperatures. The spectral responses of the diodes have been measured within the temperature range from 5 to 300 K at a zero bias. From these measurements the energy band gap of Pb1- x Mn x S

G. Karczewski; M. Klimkiewicz; I. Glass; A. Szczerbakow; R. Behrendt

1982-01-01

442

The capacitances of aniso-type heterojunctions with continuously varying energy band gap and electron affinity in the transition region†  

Microsoft Academic Search

Using a semi-abrupt model that the energy band gap and the electron affinity vary linearly in the transition region but both the permittivity and the dopant concentration change abruptly in the pseudo-interface, the expressions for the capacitances of aniso-type and iso-type heterojunctions taking into account the effect of mobile carriers have been derived. The validity of this model and the

B. HALIL; K. C. KAO

1972-01-01

443

The effect of elastic strain on energy band gap and lattice parameter in III-V compounds  

Microsoft Academic Search

The elastic and misfit strain in vapor-grown InGaP\\/GaAs crystals was determined by measuring the lattice parameter of the InGaP before and after removal of the GaAs substrate. The energy-band-gap shift as a function of strain was measured in a similar manner using photoluminescence. Up to 70% of the misfit strain was found to be accommodated elastically. The critical resolved shear

G. H. Olsen; C. J. Nuese; R. T. Smith

1978-01-01

444

Surface energy band gap of polycrystalline CuInSe2 thin-films in tunneling spectroscopy  

Microsoft Academic Search

In this paper, the authors demonstrate a tunneling spectroscopic technique to determine energy band gaps of the CuInSe2 thin-film solar cell surfaces. The I-V characteristics are measured with STM in ambient air. Using the well-known theory of tunneling spectroscopy, the normalized differential conductivity corresponding to surface density of states is both evaluated from the measured I-V characteristics and simulated with

Z. Zhang; P. Heuell; M. Kulakov; B. Bullemer

1994-01-01

445

Spin-orbit splittings and energy band gaps calculated with the Heyd-Scuseria-Ernzerhof screened hybrid functional  

Microsoft Academic Search

We assess the Heyd-Scuseria-Ernzerhof (HSE) screened Coulomb hybrid density functional for the calculation of spin-orbit (SO) splittings and energy band gaps. We have employed a set of 23 semiconductors with available experimental data, including group IV elements, and group III-V, II-VI, and IB-VII compounds. The spin-orbit interaction is included in the calculations using relativistic effective core potentials within a second-variation

Juan E. Peralta; Jochen Heyd; Gustavo E. Scuseria; Richard L. Martin

2006-01-01

446

Temperature and composition dependence of the energy band gap of Pb 1? x Mn x S solid solution  

Microsoft Academic Search

Photovoltaicp-n junctions inn-type Pb1-xMnxSx?0.04, have been made by sulphur diffusion. Current-voltage and resistance-voltage characteristics have been examined at various temperatures. The spectral responses of the diodes have been measured within the temperature range from 5 to 300 K at a zero bias. From these measurements the energy band gap of Pb1-xMnxS solid solution has been determined as a function of

G. Karczewski; M. Klimkiewicz; I. Glass; A. Szczerbakow; R. Behrendt

1982-01-01

447

Effect of passivants in energy gap of Si47X24Y36 nano-clusters: A theoretical investigation  

NASA Astrophysics Data System (ADS)

Passivation on the surface of the nano-cluster Si47 core cluster can lead to the formation of Si47X24Y36, where X and Y represent the inner and outer layer passivated positions, respectively. Accordingly, X and Y positions can accommodate one and three passivants, respectively. Herein, the density functional theory (DFT) and B3LYP method with the 6-31G(d) basis set were used to generate the electronic structures (HOMO, LUMO and energy gap between HOMO and LUMO) for two different fully passivated Si nano-clusters of Si47X60 and Si47X24Y36, both with a Td symmetry. The optimized structures were obtained with the local density approximation (LDA) implemented in SIESTA package. For fully passivated Si47X60 nano-clusters (X=-H, -CH3, -OH, -NH2, -F, -SiH3, -SH, -Cl, -C2H5 and -OCH3) alkyl passivants (-CH3 and -C2H5) affect insignificantly the calculated energy gaps while electron-withdrawing passivants give red-shifted electronic spectra. Same investigations were also conducted for the partially hydrogenated Si nano-clusters, inner layer passivated Si47X24H36 and outer layer passivated Si47H24Y36. The calculated energy gaps of Si nano-clusters with inner layer passivation (Si47X24H36) are close to that of Si47X60, both inner and outer layers passivated. Hence, the outer layer passivant effect is insignificant, which is also demonstrated by insignificant changes in energy gaps (?0.5eV) for the Si nano-clusters with outer layer passivation since the difference of the Mülliken charge is ?0.1eV.

Chen, Wen-Hao; Chang, Chih-Hsiang; Chang, Yeong-Sheng; Pan, Jiunn-Hung; Wang, Houng-Wei; Chou, Yu-Ma; Wang, Bo-Cheng

2011-02-01

448

Supernonlinear Shifts of Optical Energy Gaps in InSe and GaSe under Hydrostatic Pressure  

Microsoft Academic Search

Fundamental absorption spectra have been measured in layer compounds InSe and GaSe under hydrostatic pressure up to 4 GPa. The first and the second direct edges exhibit extremely nonlinear behaviors: The energy gap at the former edge decreases first, takes a minimum at 0.5 GPa in InSe and at 1.1 GPa in GaSe, and then increases with pressure, while that

Noritaka Kuroda; Osamu Ueno; Yuichiro Nishina

1986-01-01

449

Effect of d electrons in transition-metal ions on band-gap energies of diluted magnetic semiconductors  

Microsoft Academic Search

We present a theoretical study of the effect of partially filled d electrons in transition-metal ions on the E1 and E1+Delta1 band-gap energies of the diluted magnetic semiconductors. Semiempirical tight-binding calculations were performed to study the effects of interactions arising from the hybridization between the localized d orbitals of a transition-metal impurity and the bulk band states of II-VI semiconductors

Y. D. Kim; Yia-Chung Chang; M. V. Klein

1993-01-01

450

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

451

Magnetic hourglass dispersion and its relation to high-temperature superconductivity in iron-tuned Fe1+yTe0.7Se0.3  

NASA Astrophysics Data System (ADS)

High-temperature superconductivity remains arguably the greatest enigma of condensed matter physics. The discovery of iron-based high-temperature superconductors [1, 2] has renewed the importance of understanding superconductivity in materials susceptible to magnetic order and fluctuations. Intriguingly, they show magnetic fluctuations reminiscent of superconducting (SC) cuprates [3], including a ‘resonance’ and an ‘hourglass’-shaped dispersion [4], which provides an opportunity to gain new insights into the coupling between spin fluctuations and superconductivity. In this paper, we report inelastic neutron scattering data on Fe1+yTe0.7Se0.3 using excess iron concentration to tune between an SC (y = 0.02) and a non-SC (y = 0.05) ground state. We find incommensurate spectra in both the samples but discover that in the one that becomes SC, a constriction toward a commensurate hourglass-shape develops well above Tc. Conversely, a spin gap and a concomitant spectral weight shift happen below Tc. Our results imply that the hourglass-shaped dispersion is most likely a prerequisite for superconductivity, whereas the spin gap and shift of spectral weight are the consequences of superconductivity. We explain this observation by pointing out that an inward dispersion toward the commensurate wave vector is needed for the opening of a spin gap to lower the magnetic exchange energy and hence provide the necessary condensation energy for the SC state to emerge.

Tsyrulin, N.; Viennois, R.; Giannini, E.; Boehm, M.; Jimenez-Ruiz, M.; Omrani, A. A.; Dalla Piazza, B.; Rønnow, H. M.

2012-07-01

452

Spin Dynamics and Magnetic Coherence in the Superconducting State of High-Temperature Superconductors  

NASA Astrophysics Data System (ADS)

Recent inelastic neutron scattering (INS) experiments(T. Mason et al.), Phys. Rev. Lett 77, 1604 (1996); B. Lake et al., Nature 400, 43 (1999). on La_2-xSr_xCuO4 have observed dramatic changes in the incommensurate magnetic response, \\chi'', upon entering the superconducting state (magnetic coherence effect). In particular, they observed a sharpening of the incommensurate peaks which is accompanied by a transfer of spectral weight to higher energies, and an only weakly momentum dependent spin-gap. In this talk I propose a scenario in which the magnetic coherence effect arises from an interplay of incommensurate spin structure, d-wave symmetry of the superconducting gap and the form of the Fermi surface in La_2-xSr_xCuO_4. This scenario is based on the idea that incommensurate spin excitations are a relaxational mode whose frequency dependence is solely determined by its coupling to fermionic quasiparticles. Within the spin-fermion model I show that the opening of the superconducting gap in the electronic spectrum gives rise to the observed transfer of spectral weight, and simultaneously, to a sharpening of the incommensurate peaks. This scenario provides a quantitative explanation for the momentum and frequency dependence of \\chi'' in the superconducting state, as well as for the weak momentum dependence of the spin-gap. I thus argue that magnetic coherence is simply a reflection of electronic coherence in the superconducting phase. Moreover, I demonstrate that INS data in the superconducting state provide insight into the form of the Fermi surface and thus complement angle-resolved photoemission experiments. For La_2-xSr_xCuO_4, the analysis of INS data within the presented scenario suggests a Fermi surface which is closed around (?,?). Finally, I discuss several predictions for the appearance of a similar magnetic coherence effect in other cuprate superconductors which exhibit an incommensurate magnetic response.

Morr, Dirk K.

2000-03-01

453

An extended dead-end elimination algorithm to determine gap-free lists of low energy states.  

PubMed

Proteins are flexible systems and commonly populate several functionally important states. To understand protein function, these states and their energies have to be identified. We introduce an algorithm that allows the determination of a gap-free list of the low energy states. This algorithm is based on the dead-end elimination (DEE) theorem and is termed X-DEE (extended DEE). X-DEE is applicable to discrete systems whose state energy can be formulated as pairwise interaction between sites and their intrinsic energies. In this article, the computational performance of X-DEE is analyzed and discussed. X-DEE is implemented to determine the lowest energy protonation states of proteins, a problem to which DEE has not been applied so far. We use X-DEE to calculate a list of low energy protonation states for two bacteriorhodopsin structures that represent the first proton transfer step of the bacteriorhodopsin photocycle. PMID:17471458

Kloppmann, Edda; Ullmann, G Matthias; Becker, Torsten

2007-11-15

454

Energy band-gap shift with elastic strain in GaxIn1 - xP epitaxial layers on (001) GaAs substrates  

Microsoft Academic Search

It is demonstrated that the energy band gap in epitaxial layers is changed by biaxial elastic strains which are produced by lattice mismatches in heterostructures. The epitaxial layers used in this work were Gax In1?xP layers grown on (001) GaAs substrates by liquid phase epitaxy. The energy band-gap shifts were determined by comparing the photoluminescence peak energies of the as-grown

Hiromitsu Asai; Kunishige Oe

1983-01-01

455

BSCCO superconductors : hole-like fermi surface and doping dependence of the gap function.  

SciTech Connect

We use the gradient of the energy-integrated angle resolved photoemission (ARPES) intensity in order to define precisely the Fermi surface (FS) in BSCCO superconductors. We show that, independent of the photon energy, the FS is a hole barrel centered at ({pi},{pi}), Then, the superconducting gap along the FS is precisely determined from ARPES measurements on over-doped and underdoped samples of Bi2212. As the doping decreases, the maximum gap increases, but the slope of the gap near the nodes decreases. Though consistent with d-wave symmetry, the gap with underdoping cannot be fit by the simple cos(k{sub x})-cos(k{sub y}) form. A comparison of our ARPES results with available penetration depth data indicates that the renormalization of the linear T suppression of the superfluid density at low temperatures due to quasiparticle excitations around the d-wave nodes is large and doping dependent.

Campuzano, J. C.; Ding, H.; Fretwell, H. M.; Kadowaki, K.; Kaminski, A.; Mesot, J.; Mochiku, T.; Norman, M. R.; Paramekanti, A.; Randeria, M.; Sato, T.; Takahashi, T.; Takeuchi, T.; Yokoya, T.

1999-08-18

456

Control of Superconducting Magnetic Energy Storage Units in Multi-Machine Power Systems  

NASA Astrophysics Data System (ADS)

A new scheme, in which a synchronous generator connected to the SMES busbar is used as a feedback generator, is proposed to control superconducting magnetic energy storage (SMES) units in multi-machine power systems, in this dissertation. The speed and the load angle changes of the feedback generator are used to calculate the necessary real power transfers to the SMES, while the necessary reactive power transfers are calculated from the voltage changes of the common busbar. Expressions are derived for the direct and quadrature axis components of the current drawn by the SMES, for unequal firing angles in the converter bridge, and the relationships of the two currents to the total real and reactive power transfers to the SMES are shown. The expressions derived are valid for small or large systems, under steady state or transient conditions, and it is shown through computer simulations in a small power system that, the proposed scheme is quite effective in stabilizing electromechanical oscillations caused by small as well as large disturbances. It is also shown that, the SMES can improve the power output of wind turbine induction generators, and also stabilize the oscillations caused by wind power losses in a steam turbine generator system, and thereby eliminate the need to use diesel turbine generators for the same purpose. Finally, equations are derived to represent the synchronous machine in terms of its d-q circuits, while it is connected to the network which is described by complex quantities, and the formulations done for the proposed scheme are extended to study the use of SMES units with proposed control in power systems of large and complex configurations. The proposed scheme of control is simple, and does not call for a special design of a controller requiring simplifying assumptions such as the presence of an infinite busbar or steady state operating conditions on the system, and therefore, would help in the widespread use of SMES units in electric utilities.

Ranaweera, Aruna

457

Pair breaking versus symmetry breaking: Origin of the Raman modes in superconducting cuprates  

NASA Astrophysics Data System (ADS)

We performed Raman scattering experiments on superconductivity-induced features in Bi2Sr2(Ca1-xYx)Cu2O8+? (Bi-2212), YBa2Cu3O6+x (Y-123), and Tl2Ba2CuO6+? (Tl-2201) single crystals. The results in combination with earlier ones enable us to systematically analyze the spectral features in the doping range 0.07?p?0.24. In B2g (xy) symmetry, we find universal spectra and the maximal gap energy ?0 to scale with the superconducting transition temperature Tc. The B1g (x2-y2) spectra in all three compounds show an anomalous increase of the intensity toward overdoping. The energy scale of the corresponding peak is neither related to the pairing energy nor to the pseudogap, but possibly stems from a symmetry breaking transition at the onset point of superconductivity at psc2?0.27.

Munnikes, N.; Muschler, B.; Venturini, F.; Tassini, L.; Prestel, W.; Ono, Shimpei; Ando, Yoichi; Peets, D. C.; Hardy, W. N.; Liang, Ruixing; Bonn, D. A.; Damascelli, A.; Eisaki, H.; Greven, M.; Erb, A.; Hackl, R.

2011-10-01

458

Photoinduced Melting of Superconductivity in the High-Tc Superconductor La2?xSrxCuO4 Probed by Time-resolved Optical and Terahertz Techniques  

SciTech Connect

The dynamics of depletion and recovery of a superconducting state in La{sub 2-x}Sr{sub x}CuO{sub 4} thin films is investigated utilizing optical pump-probe and optical pump-THz-probe techniques as a function of temperature and excitation fluence. The absorbed energy density required to suppress superconductivity is found to be about eight times higher than the thermodynamically determined condensation energy density and nearly temperature independent between 4 and 25 K. These findings indicate that, during the time when the superconducting state suppression takes place ({approx}0.7 ps), a large part (nearly 90%) of the energy is transferred to the phonons with energy lower than twice the maximum value of the superconducting gap and only 10% is spent on Cooper pair breaking.

Logvenov, G.; Beyer, M.; Staedter, D.; Beck, M.; Schaefer, H.; Kabanov, V.V.; Bozovic, I.; Koren, G.; Demsar, J.

2011-06-13

459

The sensitivity of the energy band gap to changes in the dimensions of the CdSe quantum rods at room temperature: STM and theoretical studies  

Microsoft Academic Search

The energy band gap of a series of different sizes of CdSe quantum rods have been determined by STM technique at room temperature. The results confirm that the band gap of CdSe quantum rods (QRs) depends mainly on the width (the dimension of the electron confinement) and only slightly on the length as shown previously in the literatures. The experimental

H. Talaat; T. Abdallah; M. B. Mohamed; S. Negm; Mostafa A. El-Sayed

2009-01-01

460

Measurements of energy gap at the level anti-crossing region of the photo-excited triplet state of organic molecules  

NASA Astrophysics Data System (ADS)

By the application of zero-field magnetic resonance (ZFMR)/FID technique and fast-field sweeping around the level anti-crossing region with fixed rf frequency, we obtained the (minimum) energy gaps between the two crossing levels as 16.7±2.0 and 14.3±3.7 MHz for pentacene-h 14 in p-terphenyl and pentacene-d 14 in p-terphenyl, respectively, when B0? x. The minimum energy gaps occur at 14 mT for both systems. The hyperfine interaction contributes only partially to the observed energy gap.

Yang, Tran-Chin; Sloop, David J.; Weissman, S. I.; Lin, Tien-Sung

2000-12-01

461

Inter-Layer Superconducting Pairing Induced c-axis Nodal Lines in Iron-based Superconductors  

NASA Astrophysics Data System (ADS)

A layered superconductor with a full pairing energy gap can be driven into a nodal superconducting (SC) state by inter-layer pairing when the SC state becomes more quasi-3D. We propose that this mechanism is responsible for the observed nodal behavior in a class of iron-based SCs. We show that the intra- and inter-layer pairings generally compete and the gap nodes develop on one of the hole Fermi surface pockets as they become larger in the iron-pnictides. Our results provide an explanation of the c-axis gap modulations and gap nodes observed by angle resolved photo emission spectroscopy. In addition, we predict that an anti-correlated c-axis gap modulations on the hole and electron pockets should be observable in the s±-wave pairing state.

Setty, Chandan; Su, Yuehua; Wang, Ziqiang; Hu, Jiangping

2012-02-01

462

Coexistence of antiferromagnetism and d+id superconducting correlations in the graphene bilayer  

NASA Astrophysics Data System (ADS)

We discuss the t-J-U model on a honeycomb monolayer that has the same low-energy description of the kinetic term as the graphene bilayer, and in particular study coexistence of antiferromagnetism and