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1

Influence of Superconducting Leads Energy Gap on Electron Transport Through Double Quantum Dot by Markovian Quantum Master Equation Approach  

NASA Astrophysics Data System (ADS)

The superconducting reservoir effect on the current carrying transport of a double quantum dot in Markovian regime is investigated. For this purpose, a quantum master equation at finite temperature is derived for the many-body density matrix of an open quantum system. The dynamics and the steady-state properties of the double quantum dot system for arbitrary bias are studied. We will show that how the populations and coherencies of the system states are affected by superconducting leads. The energy parameter of system contains essentially four contributions due to dots system-electrodes coupling, intra dot coupling, two quantum dots inter coupling and superconducting gap. The coupling effect of each energy contribution is applied to currents and coherencies results. In addition, the effect of energy gap is studied by considering the amplitude and lifetime of coherencies to get more current through the system.

Afsaneh, E.; Yavari, H.

2014-02-01

2

Doping and temperature dependence of the superconducting energy gap in the electron-doped cuprate Pr 2- xCe xCuO 4- ?  

NASA Astrophysics Data System (ADS)

In hole-doped cuprate superconductors at low carrier concentrations two energy scales are identified: the superconducting energy gap and the pseudogap. The relation between these energy scales is still a puzzle. In these compounds a measurement of the energy gap is not necessarily a probe of the order parameter. In the electron-doped cuprates the pseudogap does not obscure the superconducting state. Consequently, the superconducting gap can be studied directly in a tunneling experiment. Here we show that by studying superconductor/insulator/superconductor planar tunnel junctions we are able to map the behavior of the gap amplitude for the entire (doping-temperature) phase diagram of the electron-doped cuprate superconductor Pr2-xCuO. The superconducting gap, ?, shows a BCS-like temperature dependence even for extremely low carrier concentrations. Moreover, ? follows the doping dependence of planes where d-wave superconductivity takes place [8]. In addition there are changes in the shape of the Fermi surface with doping [9-12]. On the other hand, there are several differences between these compounds, including the temperature dependence of the resistivity above (PCCO) with lead as a counter electrode. We measured the differential conductance at different temperatures and magnetic fields for the entire doping range where superconductivity exists. Fig. 1 presents the normalized (by the conductance at ?0H=10 T) differential conductance at various temperatures of the extremely underdoped x = 0.125. For each temperature we fit the data using a modified BTK model for a non-monotonic d-wave as described elsewhere [17]. From our fit we found that ? goes to zero at the critical temperature in a BCS way for the entire doping range, this is seen in Fig. 2. We made use of the absence of the pseudogap and the accessible upper critical field to measure the low temperature limit of the gap amplitude as a function of doping for the entire superconducting regime [18]. Our results are shown in Fig. 3. For the overdoped and optimally doped regions the gap follows the doping dependence of Tc as found for hole-doped cuprates. Surprisingly, this behavior persists for underdoped samples. For this doping regime, the gap amplitude decreases with decreasing doping, in strong contrast with the celebrated tunneling measurements on hole-doped cuprates [19]. In summary, we present the tunneling spectra of lead/insulator/PCCO junctions over the entire doping range where superconductivity is observed. We found that the gap amplitude follows the BCS-type temperature dependence. In addition, we show that for this cuprate the gap amplitude follows the critical temperature as a function of doping, even for underdoped samples. Our results are therefore consistent with a single superconducting energy scale, in contrast with the hole-doped cuprates. We note that for hole-doped cuprates probed by node sensitive spectroscopies and Andreev-Saint-James reflections one finds an energy scale which decreases with doping in the underdoped regime. This behavior resembles our findings reported here. Assuming that the hole-doped and the electron-doped cuprates share the same mechanism for superconductivity, we can conclude that for hole-doped cuprates the Andreev-Saint-James (and nodal) gap is the superconducting gap, while the pseudogap is a competing order to superconductivity.We are indebted to G. Deutscher, S. Hacohen-Gourgy for fruitful discussions, to M. Karpovski for evaporating lead electrodes. This research was partially supported by the Binational Science Foundation Grant Number 2006385, the Israel Science Foundation Grant Number 1421/08 and by the Wolfson Family Charitable Trust. RLG is partially supported by the NSF DMR0653535.

Diamant, I.; Greene, R. L.; Dagan, Y.

3

Extended Supersymmetry in Gapped and Superconducting Graphene  

E-print Network

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

V. K. Oikonomou

2014-11-30

4

a Proposed New Measurement of the Superconducting Gap in YBa2Cu3O7  

Microsoft Academic Search

The superconducting energy gap of YBa2Cu3O7 (YBCO) varies strongly with ec{k} and from a sheet of the Fermi surface to another. The strong anisotropic superconducting gap in high Tc materials such as YBCO has led to conflicting d-wave and s-wave interpretations. We have utilized electronic wave functions from the ab-initio density functional calculation and the related electron-phonon interaction matrix elements

G. L. Zhao; D. Bagayoko

2007-01-01

5

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

6

Superconducting gap of UCoGe probed by thermal transport  

NASA Astrophysics Data System (ADS)

Thermal conductivity measurements in the superconducting state of the ferromagnet UCoGe were performed at very low temperatures and under magnetic field on samples of different qualities and with the heat current along the three crystallographic axis. This allows one to disentangle intrinsic and extrinsic effects, confirm the situation of multigap superconductivity, and shed new light on the situation expected or claimed for the gap in these ferromagnetic superconductors, such as evidence of the absence of "partially gapped" Fermi surfaces.

Taupin, M.; Howald, L.; Aoki, D.; Brison, J.-P.

2014-11-01

7

The Specific Heat of Na0.3CoO4?1.3H2O: Possible Non-Magnetic Pair Breaking, Two Energy Gaps, and Strong Fluctuations in the Superconducting State  

NASA Astrophysics Data System (ADS)

Two samples of Na0.3CoO2?1.3H2O have very different specific heats reflecting extreme sensitivity to minor differences in sample treatment. They have nearly the same superconducting transition temperatures with strong deviations from BCS behavior and evidence of two energy gaps that are markedly different for the two samples. Non-magnetic scattering centers may have a strong, but unusual, pair-breaking effect.

Phillips, N. E.; Oeschler, N.; Fisher, R. A.; Gordon, J. E.; Foo, M.-L.; Cava, R. J.

2006-09-01

8

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

PubMed

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

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

2015-01-16

9

Specific heat of Na0.3CoO2?1.3H2O : Two energy gaps, nonmagnetic pair breaking, strong fluctuations in the superconducting state, and effects of sample age  

NASA Astrophysics Data System (ADS)

The specific heat of three samples of Na0.3CoO2?1.3H2O shows an evolution of the superconductivity and its eventual disappearance with increasing sample age. The specific heat of two superconducting samples is characteristic of a superconductor with two energy gaps, which implies contributions of two electron bands to the Fermi surface. The changes in the specific heat are associated with a nonmagnetic pair-breaking action that progresses with sample age and acts preferentially in the band with the smaller gap to produce an increasing “residual” electron density of states and a shift in the relative contributions of the bands to the superconducting condensate. For the nonsuperconducting sample the pair breaking has weakened the superconducting-state electron pairing to the point that it has given way to a competing order. The similarity of the time scale for these changes to that recently reported for the formation of O vacancies suggests a relation between the two effects and the identification of the O vacancies as the pair-breaking scattering centers. Together, these effects provide an understanding of the strong sample dependence of the properties of this material. They also suggest an unusual competition between two effects of the O vacancies: enhancement of the superconductivity at low concentrations by adjusting the carrier concentration and destruction of the superconductivity at high concentrations by pair breaking. Comparison of the coefficient of the normal-state conduction-electron specific heat, ?n=16.1mJK-2mol-1 , with band-structure calculations supports the existence of the controversial eg' hole pockets in the Fermi surface, in addition to the well established a1g surface. The onset of the transition to the vortex state is independent of magnetic field, suggesting the presence of unusually strong fluctuation effects. The specific-heat results and their implications for band structure and symmetry of the superconducting-state order parameter are compared with other experimental and theoretical results.

Oeschler, N.; Fisher, R. A.; Phillips, N. E.; Gordon, J. E.; Foo, M.-L.; Cava, R. J.

2008-08-01

10

Energy gaps in high-transition-temperature cuprate superconductors  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

11

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

E-print Network

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

Shuji Watanabe; Ken Kuriyama

2014-11-27

12

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

13

Laser pumped superconductive energy storage system  

Microsoft Academic Search

A superconductive energy storage system comprising a magnetic field surrounding a superconducting coil having large currents circulating therein, cooling said coil to superconducting temperatures, starting said circulating current in said superconducting coil inductively by a small primer coil, transmitting additional energy into said energy storage system utilizing a laser beam, and retaining said energy in said energy storage system until

1983-01-01

14

Superconducting gap structure of the 115s revisited.  

PubMed

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. PMID:22773378

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

2012-07-25

15

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

16

Energy gaps in ?-graphdiyne nanoribbons  

SciTech Connect

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

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

2014-04-14

17

Quasiparticle interference and superconducting gap in Ca2-xNaxCuO2Cl2  

NASA Astrophysics Data System (ADS)

High-transition-temperature (high-Tc) superconductivity is ubiquitous in the cuprates containing CuO2 planes, but each cuprate has its own character. The study of the material dependence of the d-wave superconducting gap (SG) should provide important insights into the mechanism of high-Tc superconductivity. However, because of the `pseudogap' phenomenon, it is often unclear whether the energy gaps observed by spectroscopic techniques really represent the SG. Here, we use scanning tunnelling spectroscopy to image nearly optimally doped Ca2-xNaxCuO2Cl2(Na-CCOC) with Tc=25-28K. It enables us to observe the quasiparticle interference effect in this material, through which we obtain unambiguous information on the SG. Our analysis of quasiparticle interference in Na-CCOC reveals that the SG dispersion near the gap node is almost identical to that of Bi2Sr2CaCu2Oy (Bi2212) at the same doping level, despite the Tc of Bi2212 being three times higher than that of Na-CCOC. We also find that the SG in Na-CCOC is confined in narrower energy and momentum ranges than Bi2212, which explains-at least in part-the remarkable material dependence of Tc.

Hanaguri, T.; Kohsaka, Y.; Davis, J. C.; Lupien, C.; Yamada, I.; Azuma, M.; Takano, M.; Ohishi, K.; Ono, M.; Takagi, H.

2007-12-01

18

Superconducting gap symmetry from repulsive interactions in the spin-singlet state  

Microsoft Academic Search

We obtained the superconducting gap equation in terms of the effective T-scattering matrix. We considered the gap symmetry in both singlet and triplet states as well as in charge and spin channels. We show that the superconducting gap for the repulsive interactions in the spin-singlet state exists in the charge channel only, and the gap has s-wave symmetry (?=0, where

Y. M. Malozovsky; J. D. Fan; D. Bagayoko

2001-01-01

19

Superconducting gap symmetry from repulsive interactions in the spin-singlet state  

Microsoft Academic Search

We obtained the superconducting gap equation in terms of the effective \\/T-scattering matrix. We considered the gap symmetry in both singlet and triplet states as well as in charge and spin channels. We show that the superconducting gap for the repulsive interactions in the spin-singlet state exists in the charge channel only, and the gap has s-wave symmetry (\\/l=0, where

Y. M. Malozovsky; J. D. Fan; D. Bagayoko

2001-01-01

20

Evidence for a cos(4?) modulation of the superconducting energy gap of optimally doped FeTe(0.6)Se(0.4) single crystals using laser angle-resolved photoemission spectroscopy.  

PubMed

We study the superconducting-gap anisotropy of the ?-centered hole Fermi surface in optimally doped FeTe(0.6)Se(0.4) (T(c)=14.5 K), using laser-excited angle-resolved photoemission spectroscopy. We observe sharp superconducting (SC) coherence peaks at T=2.5 K. In contrast to earlier angle-resolved photoemission spectroscopy studies but consistent with thermodynamic results, the momentum dependence shows a cos(4?) modulation of the SC-gap anisotropy. The observed SC-gap anisotropy strongly indicates that the pairing interaction is not a conventional phonon-mediated isotropic one. Instead, the results suggest the importance of second-nearest-neighbor electronic interactions between the iron sites in the framework of s(±)-wave superconductivity. PMID:23368253

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

2012-12-01

21

Superconducting energy storage magnet  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

22

Measurement of a double neutron-spin resonance and an anisotropic energy gap for underdoped superconducting NaFe0.985Co0.015As using inelastic neutron scattering.  

PubMed

We use inelastic neutron scattering to show that superconductivity in electron-underdoped NaFe0.985Co0.015As induces a dispersive sharp resonance near E(r1)=3.25??meV and a broad dispersionless mode at E(r2)=6??meV. However, similar measurements on overdoped superconducting NaFe0.935Co0.045As find only a single sharp resonance at E(r)=7??meV. We connect these results with the observations of angle-resolved photoemission spectroscopy that the superconducting gaps in the electron Fermi pockets are anisotropic in the underdoped material but become isotropic in the overdoped case. Our analysis indicates that both the double neutron spin resonances and gap anisotropy originate from the orbital dependence of the superconducting pairing in the iron pnictides. Our discovery also shows the importance of the inelastic neutron scattering in detecting the multiorbital superconducting gap structures of iron pnictides. PMID:24289703

Zhang, Chenglin; Yu, Rong; Su, Yixi; Song, Yu; Wang, Miaoyin; Tan, Guotai; Egami, Takeshi; Fernandez-Baca, J A; Faulhaber, Enrico; Si, Qimiao; Dai, Pengcheng

2013-11-15

23

A Proposed New Measurement of the Superconducting Gap Around -point in Bi 2 Sr 2 CaCu 2 O 8  

Microsoft Academic Search

In previous publications, Zhao et al. have presented first-principle calculations of the electronic structure, T\\u000a c, and the superconducting energy gaps on the Fermi surfaces of YBa2Cu3O7 (YBCO). However, experimental measurements of the superconducting gaps on the Fermi surfaces of YBCO still face some challenges\\u000a due to surface problems for YBCO samples. Considering the similarities between the crystal structure, electronic

G. L. Zhao; J. Tang; D. Bagayoko

2010-01-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

25

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

PubMed

Ultrafast spectroscopy is an emerging technique with great promise in the study of quantum materials, as it makes it possible to track similarities and correlations that are not evident near equilibrium. Thus far, however, the way in which these processes modify the electron self-energy--a fundamental quantity describing many-body interactions in a material--has been little discussed. Here we use time- and angle-resolved photoemission to directly measure the ultrafast response of self-energy to near-infrared photoexcitation in high-temperature cuprate superconductor. Below the critical temperature of the superconductor, ultrafast excitations trigger a synchronous decrease of electron self-energy and superconducting gap, culminating in a saturation in the weakening of electron-boson coupling when the superconducting gap is fully quenched. In contrast, electron-boson coupling is unresponsive to ultrafast excitations above the critical temperature of the superconductor and in the metallic state of a related material. These findings open a new pathway for studying transient self-energy and correlation effects in solids. PMID:25222844

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

2014-01-01

26

The imaginary part of the gap function in color superconductivity  

E-print Network

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

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

2006-06-12

27

Terahertz time-domain measurement of the conductivity and superconducting band gap in niobium  

NASA Astrophysics Data System (ADS)

We measure the complex conductivity of thin superconducting niobium films using coherent time-domain terahertz spectroscopy. Both real and imaginary part of the conductivity are measured simultaneously without referring to the Kramers-Kronig relations. We also measure the superconducting band gap directly from the onset of absorption and compare our results with theory.

Nuss, Martin C.; Goossen, K. W.; Gordon, J. P.; Mankiewich, P. M.; O'Malley, M. L.; Bhushan, M.

1991-08-01

28

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

E-print Network

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

Shuji Watanabe

2010-06-07

29

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

30

Performance of a K-band superconducting gap-coupled microstrip antenna  

Microsoft Academic Search

Superconducting circular gap-coupled antennas at 26 GHz have been designed and fabricated on lanthanum aluminate substrate using a YBCO high-temperature superconducting thin film. The efficiencies and far-field antenna patterns have been measured and are compared with an identical antenna patterned with gold. The experimental far-field patterns agree well with published models, and efficiency measurements show a maximum improvement of 9%

M. A. Richard; P. C. Claspy

1992-01-01

31

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

NASA Astrophysics Data System (ADS)

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

Margine, E. R.; Giustino, Feliciano

2014-07-01

32

Axionic superconductivity in three dimensional doped narrow gap semiconductors  

E-print Network

We consider the competition between the conventional s-wave and the triplet Balian-Werthamer or the B-phase pairings in the doped three dimensional narrow gap semiconductors, such as $\\mathrm{Cu}_x\\mathrm{Bi}_2\\mathrm{Se}_3$ and $\\mathrm{Sn}_{1-x}\\mathrm{In}_x\\mathrm{Te}$. When the coupling constants of the two contending channels are comparable, we find a simultaneously time-reversal and parity violating $p + is$ state at low temperatures, which provides an example of dynamic axionic state of matter. In contradistinction to the time-reversal invariant, topological B-phase, the $p + is$ state possesses gapped Majorana fermions as the surface Andreev bound states, which give rise to an anomalous surface thermal Hall effect. The anomalous gravitational and electrodynamic responses of the $p+is$ state can be described by the $\\theta$ vacuum structure, where $\\theta \

Pallab Goswami; Bitan Roy

2014-08-07

33

Molecular Pairing and Fully Gapped Superconductivity in Yb-doped CeCoIn5  

NASA Astrophysics Data System (ADS)

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

Erten, Onur; Flint, Rebecca; Coleman, Piers

2015-01-01

34

Molecular Pairing and Fully Gapped Superconductivity in Yb-doped CeCoIn_{5}.  

PubMed

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

Erten, Onur; Flint, Rebecca; Coleman, Piers

2015-01-16

35

Fermi-Dirac function and energy gap  

E-print Network

Medium field method is applied for studying valence electron behavior in metals. When different wave-vector electrons are attracted at low temperatures, distribution function gets discontinued. As a result, a specific energy gap occurs.

Bondarev, Boris

2014-01-01

36

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

37

Energy loss in spark gap switches  

SciTech Connect

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

Oreshkin, V. I., E-mail: oreshkin@ovpe.hcei.tsc.ru; Lavrinovich, I. V. [Institute of High Current Electronics SB RAS, Akademichesky Ave. 2/3, 634055 Tomsk (Russian Federation) [Institute of High Current Electronics SB RAS, Akademichesky Ave. 2/3, 634055 Tomsk (Russian Federation); National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk (Russian Federation)

2014-04-15

38

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

NASA Astrophysics Data System (ADS)

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

Taillefer, Louis

2006-03-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

40

High temperature superconducting magnetic energy storage for future NASA missions  

NASA Technical Reports Server (NTRS)

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

Faymon, Karl A.; Rudnick, Stanley J.

1988-01-01

41

Two-gap superconductivity seen in penetration-depth measurements of Lu2Fe3Si5 single crystals  

NASA Astrophysics Data System (ADS)

A single crystal of superconducting Lu2Fe3Si5 was studied using the tunnel-diode resonator technique in the Meissner and mixed states. The temperature dependence of the superfluid density provides strong evidence for two-gap superconductivity and indicates that there are nearly equal contributions from each gap having magnitudes of ?1/kBTc=1.86 and ?2/kBTc=0.54 . In the vortex state, the pinning strength shows unusually strong temperature dependence and is nonmonotonic with the magnetic field (peak effect). The irreversibility line is sharply defined and quite distant from the Hc2(T) line, which hints at enhanced vortex fluctuations in this two-gap system. Altogether, our findings from electromagnetic measurements provide strong support for the existence of two-gap superconductivity in Lu2Fe3Si5 , as previously suggested from specific-heat measurements.

Gordon, R. T.; Vannette, M. D.; Martin, C.; Nakajima, Y.; Tamegai, T.; Prozorov, R.

2008-07-01

42

Spin-singlet superconductivity with a full gap in locally noncentrosymmetric SrPtAs  

NASA Astrophysics Data System (ADS)

We report Pt-NMR195 and As75 nuclear quadrupole resonance measurements for the locally noncentrosymmetric superconductor SrPtAs where the As-Pt layer breaks inversion symmetry while globally the compound is centrosymmetric. The nuclear spin-lattice relaxation rate 1/T1 shows a well-defined coherence peak below Tc and decreases exponentially at low temperatures. The spin susceptibility measured by the Knight shift also decreases below Tc down to T superconducting state with a full gap. Our results suggest that the spin-orbit coupling due to the local inversion-symmetry breaking is not large enough to bring about an exotic superconducting state, or the interlayer hopping interaction is larger than the spin-orbit coupling.

Matano, K.; Arima, K.; Maeda, S.; Nishikubo, Y.; Kudo, K.; Nohara, M.; Zheng, Guo-qing

2014-04-01

43

Study on the energy criterion of cuprate superconductivity  

E-print Network

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

Gu Jiapu

2007-07-07

44

Energy applications of high-temperature superconductivity  

SciTech Connect

The discovery in 1986 of superconductivity in the range of 35 to 40 K and the subsequent increase in the critical temperature for superconductivity to over 125 K provided strong incentives to look at the opportunities for using these materials in the end-use sector for energy conservation and energy utilization improvements. An assessment was therefore sponsored by the US Department of Energy (DOE) and the Electric Power Research Institute (EPRI) to explore the technical feasibility and utilization of incorporating high-temperature superconductors at liquid nitrogen temperature (77 K) in a number of end-use technologies for technical and economic benefits. The results would provide DOE and EPRI with perspective of the opportunities and with guidance for future research in exploring and developing superconductivity applications. Earlier studies by ANL and ORNL, in a preliminary look at the energy application sector, served to sort out the most useful areas for a more intensive evaluation. The present assessment was conducted by experts at four national laboratories and their subcontractors. The selection of the end-use categories was based on energy consumption, technologies with potential for conversion from oil and gas to electrical energy, and processes and components using magnetic fields and/or large currents. Nine areas were identified for the study: motors, power electronics, transportation, electromagnetic pumping, magnetic heat pumping, materials fabrication, materials production, separation, and lighting. In addition, other energy-production-related concepts uncovered during the assessment are described briefly. Separate from the nine technology oriented assessments, a market-oriented assessment was also performed on four selected applications: motors, magnetic heat pumps (MHPs), transportation (Maglev), and separation. The issues on safety of large magnetic fields and stored energy were also reviewed.

Dale, S.J. (ed.) (Oak Ridge National Lab., TN (USA)); Wolf, S.M. (ed.) (USDOE, Washington, DC (USA)); Schneider, T.R. (ed.) (Electric Power Research Inst., Palo Alto, CA (USA))

1990-01-01

45

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

Microsoft Academic Search

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

G. L. Zhao; D. Bagayoko

2008-01-01

46

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

2011-04-01

47

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

SciTech Connect

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

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

2014-07-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

49

Pushing the Gradient Limitations of Superconducting Photonic Band Gap Structure Cells  

SciTech Connect

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

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

2012-06-07

50

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

51

Type I and Two-Gap Superconductivity in Neutron Star Magnetism  

E-print Network

Neutron-star inner cores with several charged baryonic components are likely to be analogues of the two-gap superconductor which is of current interest in condensed-matter physics. Consequently, type I superconductivity is less probable than type II but may nevertheless be present in some intervals of matter density. The intermediate state structure formed at finite magnetic flux densities after the superconducting transitions is subject to buoyancy, frictional and neutron-vortex interaction forces. These are estimated and it is shown that the most important frictional force is that produced by the stable stratification of neutron-star matter, the irreversible process being diffusion in the normal, finite magnetic-flux density, parts of the structure. The length-scale of the structure, in directions perpendicular to the local magnetic field is of crucial importance. For small scales, the flux comoves with the neutron vortices, as do the proton vortices of a type II superconductor. But for much larger length-scales, flux movement tends to that expected for normal charged Fermi systems.

P B Jones

2006-06-30

52

Energy gaps measured by scanning tunneling microscopy  

SciTech Connect

A scanning tunneling microscope (STM) has been used to measure energy gaps in the charge-density-wave (CDW) phases of the layer-structure dichalcogenides and in the high-temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. Measured values of {Delta}{sub CDW} at 4.2 K for 2{ital H}-TaSe{sub 2}, 2{ital H}-TaS{sub 2}, and 2{ital H}-NbSe{sub 2} are 80, 50, and 34 meV giving values of 2{Delta}{sub CDW}/{ital k}{sub {ital B}T{ital c}} equal to 15.2, 15.4, and 23.9, indicating strong coupling in these CDW systems. Measured values of {Delta}{sub CDW} at 4.2 K in 1{ital T}-TaSe{sub 2} and 1{ital T}-TaS{sub 2} are {approximately}150 meV for both materials giving 2{Delta}{sub CDW}/{ital k}{sub {ital B}T{ital c}}{approx}5.8. STM scans of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} at 4.2 K resolve atoms on the BiO{sub {ital x}} layer and show possible variations in electronic structure. The energy gap determined from {ital I} versus {ital V} and {ital dI}/{ital dV} versus {ital V} curves is in the range 30--35 meV giving values of 2{Delta}/{ital k}{sub {ital B}T{ital c}}{approx}8. Spectroscopy measurements with the STM can exhibit large zero-bias anomalies which complicate the analysis of the energy-gap structure, but adequate separation has been accomplished.

Wang, C.; Giambattista, B.; Slough, C.G.; Coleman, R.V. (Department of Physics, University of Virginia, Charlottesville, VA (USA)); Subramanian, M.A. (Central Research and Development Department, E. I. DuPont DeNemours Company, Wilmington, DE (USA))

1990-11-15

53

Superconducting condensation energy of CeCu2Si2 and theoretical implications  

NASA Astrophysics Data System (ADS)

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

Kirchner, Stefan

2012-02-01

54

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

55

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

56

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

57

Spin-singlet superconductivity with multiple gaps in PrFeAsO0.89F0.11  

NASA Astrophysics Data System (ADS)

We report 75As and 19F NMR studies on the superconducting properties of the newly discovered compound PrFeAsO0.89F0.11 (Tc=45 K). The Knight shift in the direction of Hparab-plane decreases below Tc to almost zero, which indicates spin-singlet pairing. The temperature dependencies of both the Knight shift and the spin lattice relaxation rate indicate that there are two gaps opening below Tc, with nodes in the gap function.

Matano, K.; Ren, Z. A.; Dong, X. L.; Sun, L. L.; Zhao, Z. X.; Zheng, Guo-qing

2008-09-01

58

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

59

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

60

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

61

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

62

Controlling the energy gap of graphene by Fermi velocity engineering  

NASA Astrophysics Data System (ADS)

The electronic structure of a single-layer graphene with a periodic Fermi velocity modulation is investigated by using an effective Dirac-like Hamiltonian. In a gapless graphene or in a graphene with a constant energy gap the modulation of the Fermi velocity, as expected, only changes the dispersion between energy and moment, turning the minibands narrower or less narrow than in the usual graphene depending on how the Fermi velocity is modulated and the energy gap remains the same. However, with a modulated energy gap it is possible to control the energy gap of graphene by Fermi velocity engineering. This is based on a very simple idea that has never been reported so far. The results obtained here reveal a new way of controlling the energy gap of graphene, which can be used in the fabrication of graphene-based devices.

Lima, Jonas R. F.

2015-01-01

63

Superconductivity and fusion energy—the inseparable companions  

NASA Astrophysics Data System (ADS)

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

Bruzzone, Pierluigi

2015-02-01

64

Specific-heat of Na 0.35CoO 2 · 1.3H 2O: Effects of sample age and pair breaking on two-gap superconductivity  

NASA Astrophysics Data System (ADS)

Specific-heat measurements on Na 0.35CoO 2 · 1.3H 2O show an evolution of the superconductivity, and its ultimate disappearance, with increasing sample age. An increase in pair breaking action, which occurs preferentially in an electron band with a small energy-gap, produces a shift in the relative contributions of two electron bands to the superconducting condensation. The similarity of the time scale for these changes to that recently reported for structural changes suggests a relation between the two effects and a basis for understanding the sample dependence of the properties of this material in general.

Phillips, N. E.; Oeschler, N.; Fisher, R. A.; Gordon, J. E.; Foo, M.-L.; Cava, R. J.

2007-09-01

65

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

66

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

SciTech Connect

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

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

2014-06-01

67

Energy Gap in Nuclear Matter. II. BCS Theory  

Microsoft Academic Search

The Bardeen-Cooper-Schrieffer (BCS) theory is employed to study the energy gap in nuclear matter with various internucleonic potentials which fit singlet low-energy scattering data and the s-wave phase shift at 310 MeV. The interactions are expressed as the sum of two terms, each of which is separable, thus admitting exact solutions of the energy-gap equation. The dependence of the energy

R. Kennedy; L. Wilets; E. M. Henley

1964-01-01

68

Scaling up energy efficiency: bridging the action gap  

E-print Network

The Alternative Policy Scenario of the International Energy Agency sets out what could happen were energy security policy #12;objectives related to energy security and global CO2 emissions in the Alternative PolicyScaling up energy efficiency: bridging the action gap 2-3 April 2007 International Energy Agency

69

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

PubMed

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

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

2014-01-01

70

Homolumo gap from dynamical energy levels  

SciTech Connect

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

Andric, I.; Jonke, L.; Jurman, D.; Nielsen, H. B. [Theoretical Physics Division, Rudjer Boskovic Institute, P.O. Box 180, 10002 Zagreb (Croatia); Niels Bohr Institute, Copenhagen DK 2100 (Denmark)

2009-11-15

71

Toroidal constant-tension superconducting magnetic energy storage units  

DOEpatents

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

Herring, J. Stephen (Idaho Falls, ID)

1992-01-01

72

Controlling the band gap energy of cluster-assembled materials.  

PubMed

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

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

2013-11-19

73

Tunneling spectroscopy of the superconducting state of URu2Si2  

NASA Astrophysics Data System (ADS)

We present measurements of the superconducting gap of URu2Si2 made with scanning tunneling microscopy using a superconducting tip of Al. We find tunneling conductance curves with a finite value at the Fermi level. The density of states is V shaped at low energies, and the quasiparticle peaks are located at values close to the expected superconducting gap from weak-coupling BCS theory. Our results point to rather opened gap structures and gap nodes on the Fermi surface.

Maldonado, A.; Guillamon, I.; Rodrigo, J. G.; Suderow, H.; Vieira, S.; Aoki, D.; Flouquet, J.

2012-06-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

75

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

E-print Network

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

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

2015-01-15

76

Angular Position of Nodes in the Superconducting Gap of Quasi2D Heavy-Fermion Superconductor CeCoIn5  

Microsoft Academic Search

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 Hc2, indicating a Pauli limited superconducting

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

2001-01-01

77

Is There an Energy Efficiency Gap?  

E-print Network

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

Allcott, Hunt Volney

78

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

E-print Network

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

Monneau, Régis

79

Doping dependence of low-energy quasiparticle excitations in superconducting Bi2212  

PubMed Central

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

2013-01-01

80

Superconducting gap induced barrier enhancement in a BiFeO3-based heterostructure  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

81

Is There an Energy Efficiency Gap?  

Microsoft Academic Search

Many analysts have argued that energy efficiency investments offer an enormous “win-win” opportunity to both reduce negative externalities and save money. This overview paper presents a simple model of investment in energy-using capital stock with two types of market failures: first, uninternalized externalities from energy consumption, and second, forces such as imperfect information that cause consumers and firms not to

Hunt Allcott; Michael Greenstone

2012-01-01

82

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

83

Charge-order-maximized momentum-dependent superconductivity  

E-print Network

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

Loss, Daniel

84

Is There An Energy Efficiency Gap?  

E-print Network

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

Allcott, Hunt

2012-01-17

85

Is There an Energy Efficiency Gap?  

E-print Network

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

Alcott, Hunt

2012-01-17

86

Which Way to the Energy Gap?  

ERIC Educational Resources Information Center

The higher cost of energy in the future might well dampen the current ardour for industrialization. Cheap sources are the ones most likely to disappear, pointing to a further disparity between industrialized and nonindustrialized societies. (BL)

Loftas, Tony

1973-01-01

87

Impact of superconductive magnetic energy storage on electric power transmission  

Microsoft Academic Search

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

K.-S. Tam; P. Kumar

1990-01-01

88

Discovery Fusion Energy Science using a Superconducting Laboratory  

E-print Network

Discovery Fusion Energy Science using a Superconducting Laboratory Magnetosphere M. E. Mauel, D Plasma Science & Fusion Center Administration Computers & Networks Calendar Safety Plasma Science University, New York, NY Plasma Science and Fusion Center, MIT, Cambridge, MA Outline · Linking space science

Mauel, Michael E.

89

Toroidal constant-tension superconducting magnetic energy storage units  

DOEpatents

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

Herring, J.S.

1992-11-03

90

Boson wavefunction and condensation energy in the superconducting state of doped semiconductors  

SciTech Connect

The superconducting state of doped semiconductors, in which a superconducting gap opens in the spectrum of one-particle states formed (upon doping) in the region of the initial energy gap, is studied within the framework of the Holstein-Anderson model. The wavefunction of the relative motion of a pair of particles in the bound state is determined. The dependence of the size of this wavefunction on the level of doping in the overdoping region of the phase diagram is consistent with the published experimental data for La{sub 2-x}Sr{sub x}CuO{sub 4}. Variation of the temperature in the range of T < T{sub c} only influences the natural normalization of the boson wavefunction (normalized to the boson density), while the size of the wavefunction is independent of the temperature. Theoretical values of the condensation energy and the heat capacity jump upon the superconductor-metal transition in the region of optimal doping agree with the experimental data for La{sub 2-x}Sr{sub x}CuO{sub 4}.

Agafonov, A. I., E-mail: aai@isssph.kiae.ru; Manykin, E. A. [Russian Research Centre Kurchatov Institute (Russian Federation)

2006-05-15

91

STRIPES AND SUPERCONDUCTIVITY IN CUPRATE SUPERCONDUCTORS  

SciTech Connect

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

TRANQUADA, J.M.

2005-08-22

92

Low energy multicycle injection in a superconducting electron storage ring  

Microsoft Academic Search

It is shown that multicycle injection in an electron storage ring with a superconducting bending magnet can, in principle, be possible at low energy because of short radiation damping time and long Touschek life time due to beam enlargement. We estimated possible beam current by multicycle injection for a circular ring: radius=0.5 m; field index=0.5; injection energy=15 MeV; injector current=50

K. Nakayama; Y. Gomei

1989-01-01

93

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.

94

Superconductivity  

SciTech Connect

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

Rosen, J.

1988-06-01

95

Energy gap of some alkaline halate crystals by optical methods  

NASA Astrophysics Data System (ADS)

Applying four optical methods i.e. Faraday rotation, optical absorption, diffuse reflection and refractive index dispersion the energy gap was calculated for LiIO 3, NaBrO 3 and NaClO 3 crystals. Preliminary discussion of electronic band structure of the crystals studied is given.

Koralewski, M.; Szafra?ski, M.

1986-03-01

96

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

SciTech Connect

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

He, R.

2010-05-04

97

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

PubMed Central

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

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

2014-01-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

99

Heat transport in RbFe2As2 single crystals: Evidence for nodal superconducting gap  

NASA Astrophysics Data System (ADS)

The in-plane thermal conductivity of iron-based superconductor RbFe2As2 single crystal (Tc? 2.1 K) was measured down to 100 mK. In zero field, the observation of a significant residual linear term ?0/T = 0.65 mW K-2 cm-1 provides clear evidence for nodal superdonducting gap. The field dependence of ?0/T is similar to that of its sister compound CsFe2As2 with comparable residual resistivity ?0 and lies between the dirty and clean KFe2As2 . These results suggest that the (K, Rb, Cs)Fe2As2 serial superconductors have a common nodal gap structure.

Zhang, Z.; Wang, A. F.; Hong, X. C.; Zhang, J.; Pan, B. Y.; Pan, J.; Xu, Y.; Luo, X. G.; Chen, X. H.; Li, S. Y.

2015-01-01

100

Superconducting magnetic energy storage apparatus structural support system  

DOEpatents

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

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

1992-01-01

101

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

E-print Network

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

Chapman, Jon

102

Controllable generation of two-mode-entangled states in two-resonator circuit QED with a single gap-tunable superconducting qubit  

NASA Astrophysics Data System (ADS)

We study controllable generation of two-mode-entangled states in a circuit QED setup, which consists of two spatially separated superconducting transmission line resonators and a single gap-tunable superconducting qubit. Two sharp coupling sidebands are induced when the artificial atom is suitably driven by a bichromatic microwave field. The two resonators can have squeezing-type interactions with the qubit via the coupling sidebands. If the two resonators are not degenerate, we show that the two resonators can be cooled down into the two-mode squeezed vacuum via dissipation of the qubit. The generation of the two-mode squeezed state is based on a dissipative state-engineering process, which explores the energy relaxation of the qubit as a resource. Moreover, the scheme does not need both the specific preparation of the initial state and the designed special dynamical process of the system. If the resonators are degenerate, we show that entangled coherent states of the resonators can be generated by use of the unitary dynamical evolution process of the system and the state-projection measurement. Moreover, macro entangled coherent states of the resonators with huge photons can in principle be created if the resonators and the qubit have sufficiently long lifetimes. The present scheme has two remarkable features: (1) only a single qubit is used in the generation of the two-mode squeezed state; and (2) the ultrastrong coupling condition and initializing the resonators in coherent states are not required. These make the present scheme more simple and feasible in experimental implementation.

Ma, Sheng-Li; Li, Zhen; Fang, Ai-Ping; Li, Peng-Bo; Gao, Shao-Yan; Li, Fu-Li

2014-12-01

103

A universal theorem of energy discretization - its implication in a promising mechanism of all superconductivities[1  

NASA Astrophysics Data System (ADS)

We report on a theorem stating that discretization of wavevector hence energy would universally result, if the motion of a quantum particle is spatially prohibited. The prohibition to electrons in a metal can be effectuated by such as a tight binding effect or a large resistivity. On identification of the resultant energy quanta as the superconducting gap, and, in combining this with the simple theory of metals, we correctly predict that good "normal conductors" such as Cu are not superconductors, or vice verse; and the estimated T_c's for the superconductors fall within the right magnitudes. Work supported by the Swedish Natural Science Research Council. With thanks to Prof B Johansson, Prof V Heine, Prof K-F Berggren, Prof M Springford, Dr B Sernulius for useful discussions. [1] Paper presented at The XXII Int Conf on Low Temp Phys (1999) Finland; also: Abst, pp307.

Zheng-Johansson, J. X.; Johansson, P.-I.

2000-03-01

104

Photonic Band Gap resonators for high energy accelerators  

SciTech Connect

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

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

1993-12-31

105

Design optimization of superconducting magnetic energy storage coil  

NASA Astrophysics Data System (ADS)

An optimization formulation has been developed for a superconducting magnetic energy storage (SMES) solenoid-type coil with niobium titanium (Nb-Ti) based Rutherford-type cable that minimizes the cryogenic refrigeration load into the cryostat. Minimization of refrigeration load reduces the operating cost and opens up the possibility to adopt helium re-condensing system using cryo-cooler especially for small-scale SMES system. Dynamic refrigeration load during charging or discharging operational mode of the coil dominates over steady state load. The paper outlines design optimization with practical design constraints like actual critical characteristics of the superconducting cable, maximum allowable hoop stress on winding, etc., with the objective to minimize refrigeration load into the SMES cryostat. Effect of design parameters on refrigeration load is also investigated.

Bhunia, Uttam; Saha, Subimal; Chakrabarti, Alok

2014-05-01

106

The dx2 y2-wave superconducting gap in Bi2Sr2CaCu2O8: scanning tunnelling microscope spectroscopy  

Microsoft Academic Search

We have carried out electron tunnelling spectroscopy on Bi2Sr2CaCu2O8 single crystals with the use of a scanning tunnelling microscope at 4.2 K. A conductance peak structure was observed near zero bias voltage for the tunnelling along the Cu-O bonding direction. A clear superconducting gap was observed for the tunnelling along the Cu-Cu direction. Curves along the Cu-O and Cu-Cu directions

Koji Suzuki; Koichi Ichimura; Kazushige Nomura; Shunji Takekawa

107

Impact of superconductive magnetic energy storage on electric power transmission  

SciTech Connect

This paper demonstrates that a superconductive magnetic energy storage (SMES) system can provide a significant positive impact on electric power transmission. Through the use of SMES, transmission line loadings during heavy load hours can be reduced. Transmission losses as well as the fuel cost for these losses over a 24-hour period can also be decreased. A new SMES scheme, the SMES/dc link, is introduced in this paper for energy storage and control of power flow. The operation of this scheme and the benefits it provides are presented in this paper.

Tam, K.S.; Kumar, P. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (USA). Dept. of Electrical Engineering)

1990-09-01

108

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

109

Superconductivity near a ferromagnetic quantum critical point  

NASA Astrophysics Data System (ADS)

We study the superconducting instability against spin fluctuations in weak and nearly ferromagnetic metals in the vicinity of the zero temperature magnetic transition. A set of Eliasberg equations for p-wave pairing is solved to determine the normal state quasiparticle self energy and the superconducting transition temperature T_c. We find that superconductivity close to the quantum critical point results from the competition between the magnetic fluctuation mediated pairing interaction and the pair-breaking, non-Fermi liquid self energy effects. We obtain Tc and the superconducting gap as a function of the distance to the ferromagnetic transition.

Wang, Ziqiang; Mao, Wenjin; Kevin, Bedell

2001-03-01

110

Superconducting cables: Long distance energy transmission. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the design, development, and evaluation of superconducting cables and power transmission lines for long distance energy transmission. Topics include methods of cryogenic refrigeration and electrical insulation, fabrication and development of niobium alloy conductors, energy loss analysis, and dielectric design of superconducting power transmission systems. Government research reports on superconducting technology for electric power transmission and distribution are also reviewed.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1996-02-01

111

Superconducting cables: Long distance energy transmission. (Latest citations from the NTIS bibliographic database). NewSearch  

SciTech Connect

The bibliography contains citations concerning the design, development, and evaluation of superconducting cables and power transmission lines for long distance energy transmission. Topics include methods of cryogenic refrigeration and electrical insulation, fabrication and development of niobium alloy conductors, energy loss analysis, and dielectric design of superconducting power transmission systems. Government research reports on superconducting technology for electric power transmission and distribution are also reviewed. (Contains a minimum of 106 citations and includes a subject term index and title list.)

Not Available

1994-11-01

112

Superconducting cables: Long distance energy transmission. (Latest citations from the NTIS Bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the design, development, and evaluation of superconducting cables and power transmission lines for long distance energy transmission. Topics include methods of cryogenic refrigeration and electrical insulation, fabrication and development of niobium alloy conductors, energy loss analysis, and dielectric design of superconducting power transmission systems. Government research reports on superconducting technology for electric power transmission and distribution are also reviewed. (Contains a minimum of 105 citations and includes a subject term index and title list.)

Not Available

1993-12-01

113

Superconducting cables: Long distance energy transmission. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the design, development, and evaluation of superconducting cables and power transmission lines for long distance energy transmission. Topics include methods of cryogenic refrigeration and electrical insulation, fabrication and development of niobium alloy conductors, energy loss analysis, and dielectric design of superconducting power transmission systems. Government research reports on superconducting technology for electric power transmission and distribution are also reviewed.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1997-06-01

114

Superconducting cables: Long distance energy transmission. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning the design, development, and evaluation of superconducting cables and power transmission lines for long distance energy transmission. Topics include methods of cryogenic refrigeration and electrical insulation, fabrication and development of niobium alloy conductors, energy loss analysis, and dielectric design of superconducting power transmission systems. Government research reports on superconducting technology for electric power transmission and distribution are also reviewed. (Contains a minimum of 105 citations and includes a subject term index and title list.)

Not Available

1993-08-01

115

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

116

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

117

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

118

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

119

Momentum-resolved superconducting gap in the bulk of Ba1-xKxFe2As2 from combined ARPES and ?SR measurements  

NASA Astrophysics Data System (ADS)

Here we present a calculation of the temperature-dependent London penetration depth, ?(T), in Ba1-xKxFe2As2 (BKFA) on the basis of the electronic band structure (Zabolotnyy et al 2009 Nature 457 569, Zabolotnyy et al 2009 Physica C 469 448) and momentum-dependent superconducting gap (Evtushinsky et al 2009 Phys. Rev. B 79 054517) extracted from angle-resolved photoemission spectroscopy (ARPES) data. The results are compared to the direct measurements of ?(T) by muon spin rotation (?SR) (Khasanov et al 2009 Phys. Rev. Lett. 102 187005). The value of ?(T=0), calculated with no adjustable parameters, equals 270 nm, while the directly measured one is 320 nm; the temperature dependence ?(T) is also easily reproduced. Such agreement between the two completely different approaches allows us to conclude that ARPES studies of BKFA are bulk-representative. Our review of the available experimental studies of the superconducting gap in the new iron-based superconductors in general allows us to state that most of them bear two nearly isotropic gaps with coupling constants 2?/kBTc=2.5±1.5 and 7±2.

Evtushinsky, D. V.; Inosov, D. S.; Zabolotnyy, V. B.; Viazovska, M. S.; Khasanov, R.; Amato, A.; Klauss, H.-H.; Luetkens, H.; Niedermayer, Ch; Sun, G. L.; Hinkov, V.; Lin, C. T.; Varykhalov, A.; Koitzsch, A.; Knupfer, M.; Büchner, B.; Kordyuk, A. A.; Borisenko, S. V.

2009-05-01

120

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

121

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

122

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

PubMed Central

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

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

2013-01-01

123

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

124

Analysis of the rapidity gap probability at CERN collider energies  

NASA Astrophysics Data System (ADS)

The rapidity gap probability, i.e., the probability of detecting no particles in a given rapidity interval is investigated in proton-antiproton collisions at CERN collider energies. A scaling behaviour is found in the central rapidity domain, similar to the scaling of the void probability in the Perseus-Pisces supercluster region of galaxies. This observation confirms that the recently proposed linked-pair approximation for the N-particle cumulant correlation functions holds valid to high order with linking coefficients slightly smaller than the negative binomial values. In the outer region of rapidity deviations are found from the scaling law which possibly is caused by the violation of translation invariance of the correlation functions. The correspondence to the clan production picture of hadronization is outlined: it is shown that the clan-model parameters can be obtained directly from the ``hole probability''.

Hegyi, S.

1992-01-01

125

Energy resolution of superconducting tunnel diodes in low-energy radiation detection  

Microsoft Academic Search

In this paper, we obtain an expression for the energy resolution of superconducting tunnel diodes for detection of low-energy\\u000a x-rays. We show that the major contribution to the energy resolution comes from the relative variance of the probability that\\u000a a quasielectron tunnels from one layer to another, which is due to the spatial dependence of the probability of interaction\\u000a between

V. V. Samedov

1998-01-01

126

A new boson-fermion model of superconductivity  

E-print Network

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

Tian De Cao

2010-10-17

127

Damping subsynchronous resonance using superconducting magnetic energy storage unit  

SciTech Connect

A novel damping scheme using superconducting magnetic energy storage (SMES) unit is proposed in this paper to damp subsynchronous resonance (SSR) of the IEEE Second Benchmark Model, system-1 which is a widely employed standard model for computer simulation of SSR. The studied system contains a turbine-generator set connected to an infinite bus through two parallel transmission lines, one of which is series-capacitor compensated. In order to stabilize all SSR modes, simultaneous active and reactive power modulation and a proportional-integral-derivative (PID) damping controller designed by modal control theory are proposed for the SMES unit. Frequency-domain approach based on eigenvalue analysis and time-domain approach based on nonlinear-model simulations are performed to validate the effectiveness of the damping method. It can be concluded from the simulation results that the proposed damping scheme can effectively suppress SSR of the studied system.

Wang, L.; Lee, S.M.; Huang, C.L. (National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Electrical Engineering)

1994-12-01

128

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

129

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

130

Breakdown of the energy gap law in molecular lanthanoid luminescence: the smallest energy gap is not universally relevant for nonradiative deactivation.  

PubMed

For several decades, the energy gap law has been the prevalent theoretical framework for the discussion of nonradiative deactivation of lanthanoid luminescence in molecular coordination chemistry. Here we show experimentally on samarium and dysprosium model complexes that the size of the energy gap ?E between a lanthanoid emitting state and the next-lower electronic state cannot be considered a reliable and accurate predictor of the quantitative extent of nonradiative deactivation by aromatic C-H and C-D oscillator overtones. Because the energy gap is the central pillar for the entire conceptual framework of the energy gap law, this finding amounts to largely invalidating this theory for the quantitative description of molecular multiphonon relaxation. PMID:24665884

Doffek, Christine; Wahsner, Jessica; Kreidt, Elisabeth; Seitz, Michael

2014-04-01

131

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

E-print Network

," Proc. Ninth Int. Cryo. Eng. Conf., Kobe, 1982, pp. 731 744. 8. Eyssa, Y.M. et al., "Axially Rippled Two-Layer Solenoid for Superconductive Magnetic Energy Storage," Proceedings of the 9th International Conference on Magnet Technology, Zurich...

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

132

Topological superconductivity induced by ferromagnetic metal chains  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

133

Superconducting gamma and fast-neutron spectrometers with high energy resolution  

DOEpatents

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

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

2008-11-04

134

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

NASA Astrophysics Data System (ADS)

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

Onari, Seiichiro; Saito, Tetsuro; Kontani, Hiroshi

2012-02-01

135

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

E-print Network

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

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

2014-10-14

136

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

137

Ph.D. in Physics Seoul National University, Seoul, Korea 2003 2010 Thesis: "Direct observation of two-gap superconductivity in SrFe1.85Co0.15As2 single crystals  

E-print Network

observation of two-gap superconductivity in SrFe1.85Co0.15As2 single crystals by scanning tunneling microscopy of graphene-related nanostructures, such as epitaxial graphene on SiC, graphene on metal surface, and hybrid single crystals by scanning tunneling microscopy and spectroscopy", New Journal of Physics, 13, 033005

Pennycook, Steve

138

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

139

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

140

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

141

Coexistence of ferromagnetism and superconductivity in Ni/Bi bilayers.  

PubMed

In spite of a lack of superconductivity in bulk crystalline Bi, thin film Bi deposited on thin Ni underlayers are strong-coupled superconductors below approximately 4 K. We unambiguously demonstrate that by tuning the Ni thickness the competition between ferromagnetism and superconductivity in the Ni/Bi can be tailored. For a narrow range of Ni thicknesses, the coexistence of both a superconducting energy gap and conduction electron spin polarization are visible within the Ni side of the Ni/Bi bilayers, independent of any particular theoretical model. We believe that this represents one of the clearest observations of superconductivity and ferromagnetism coexisting. PMID:15698312

LeClair, P; Moodera, J S; Philip, J; Heiman, D

2005-01-28

142

Experimental study of a transformer with superconducting elements for fault current limitation and energy redistribution  

NASA Astrophysics Data System (ADS)

Numerous proposed and developed superconducting fault current limiters and self-limiting transformers limit successfully fault currents but do not provide uninterrupted supplying of consumers. A design investigated in the work combines the functions of a conventional transformer with the functions of fast energy redistribution and fault protection. The device constitutes a transformer containing an additional high-temperature superconducting (HTS) coil short-circuited by a thin film HTS switching element. Fault current limitation and redistribution of the power flow to a standby line are achieved as a result of a fast transition of the superconducting switching element from the superconducting into the normal state. Transient and steady-state characteristics were experimentally investigated. A mathematical model of the device operation was proposed, and the calculated results were found to be in good agreement with the experimental data. The application field and basic requirements to such devices were discussed and it was shown that the proposed device meets these requirements.

Meerovich, V.; Sokolovsky, V.

2005-08-01

143

Holographic Superconductivity with Gauss-Bonnet gravity  

E-print Network

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

Ruth Gregory

2010-12-07

144

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

E-print Network

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

Weston, Ken

145

Electric energy by direct conversion from gravitational energy: a gift from superconductivity  

E-print Network

We theoretically demonstrate that electromagnetic energy can be obtained by direct, lossless, conversion from gravitational and kinetic energies. For this purpose we discuss the properties of an electromechanical system which consists of a superconducting coil submitted to a constant external force and to magnetic fields. The coil oscillates and has induced in it a rectified electrical current whose magnitude may reach hundreds of Ampere. There is no need for an external electrical power source for the system to start out and it can be kept working continuously if linked to large capacitors. We extensively discuss the issue of energy dissipation in superconductors and show that the losses for such a system can be made extremely small for certain operational conditions, so that by reaching and keeping resonance the system main application should be in magnetic energy storage and transmission.

Osvaldo F. Schilling

2003-09-01

146

Effects of edge magnetism and external electric field on energy gaps in multilayer graphene nanoribbons  

NASA Astrophysics Data System (ADS)

Using first-principles density-functional theory, we study the electronic structure of multilayer graphene nanoribbons as a function of the ribbon width and the external electric field, applied perpendicular to the ribbon layers. We consider two types of edges (armchair and zigzag), each with two edge alignments (referred to as ? and ? alignments). We show that, as in monolayer and bilayer armchair nanoribbons, multilayer armchair nanoribbons exhibit three classes of energy gaps which decrease with increasing width. Nonmagnetic multilayer zigzag nanoribbons have band structures that are sensitive to the edge alignments and the number of layers, indicating different magnetic properties and resulting energy gaps. We find that energy gaps can be induced in ABC -stacked ribbons with a perpendicular external electric field while in other stacking sequences, the gaps decrease or remain closed as the external electric field increases.

Sahu, Bhagawan; Min, Hongki; Banerjee, Sanjay K.

2010-09-01

147

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

NASA Astrophysics Data System (ADS)

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

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

148

Superconductivity and the BCS-Bogoliubov Theory  

E-print Network

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

Shuji Watanabe

2010-06-07

149

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

150

Superconductivity for Electric Systems  

E-print Network

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

151

Superconductivity for Electric Systems  

E-print Network

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

152

Superconductivity for Electric Systems  

E-print Network

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

153

A Study on Optimal Sizing of Superconducting Magnetic Energy Storage in Distribution Power System  

Microsoft Academic Search

This paper proposes a method to determine the optimal size of superconducting magnetic energy storage (SMES) to improve the stability of distribution power system with photovoltaic (PV) generation. The output power of PV system fluctuates according to changing weather conditions. Then, the system is subject to be unstable. In order to improve its stability, the SMES is applied. In general,

Byung-Kwan Kang; Seung-Tak Kim; Byung-Chul Sung; Jung-Wook Park

2012-01-01

154

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

155

Determination of the Temperature Dependence of the Band Gap Energy of Semiconductors from Transmission Spectra  

NASA Astrophysics Data System (ADS)

A method to determine the temperature dependence of the band gap energy, E g( T), of semiconductors from their measured transmission spectra is described. A relationship between the band gap energy and the energy corresponding to the peak of the spectral derivative is found for InAs and validated for III-V and II-VI binary semiconductors (InAs, InP, GaAs, GaP, ZnSe, and CdTe). Band gap energies obtained using this method are within 1% of previously published results over a temperature range of 80 K to 650 K. The same method was also applied to two bulk ternary semiconductor alloys (In x Ga1- x As and InAs1- y P y ) for several compositions. Predicted results compared well with thin-film measurements available in the literature. A separate technique for determining E g is also reported, using thickness-dependent transmission spectra. Finally, the thermooptic coefficient (d n/d T) is determined using the derivative of the band gap energy with respect to temperature (d E g/d T) and is compared with direct experimental measured results.

Wei, Jean; Murray, Joel M.; Barnes, Jacob; Gonzalez, Leonel P.; Guha, Shekhar

2012-10-01

156

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

157

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

1985-02-01

159

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

NASA Astrophysics Data System (ADS)

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

Al-Talibi, A. Adhim

160

Space applications of superconductivity  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

161

Power-saving circuits of railway traction power supply based on superconducting inductive energy storage  

Microsoft Academic Search

Primary technical power losses in the system of railway traction power supply are described that may be reduced by means of\\u000a superconducting inductive energy storage (SIES). Main SIES construction elements and its operation principle are described.\\u000a Based on data from experiments and imitation modeling, values on the order of the SIES energy capacity, as well as its mass\\u000a and overall

M. V. Shevlyugin

2008-01-01

162

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

PubMed Central

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

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

2014-01-01

163

Energy gap in the aetiology of body weight gain and obesity: a challenging concept with a complex evaluation and pitfalls.  

PubMed

The concept of energy gap(s) is useful for understanding the consequence of a small daily, weekly, or monthly positive energy balance and the inconspicuous shift in weight gain ultimately leading to overweight and obesity. Energy gap is a dynamic concept: an initial positive energy gap incurred via an increase in energy intake (or a decrease in physical activity) is not constant, may fade out with time if the initial conditions are maintained, and depends on the 'efficiency' with which the readjustment of the energy imbalance gap occurs with time. The metabolic response to an energy imbalance gap and the magnitude of the energy gap(s) can be estimated by at least two methods, i.e. i) assessment by longitudinal overfeeding studies, imposing (by design) an initial positive energy imbalance gap; ii) retrospective assessment based on epidemiological surveys, whereby the accumulated endogenous energy storage per unit of time is calculated from the change in body weight and body composition. In order to illustrate the difficulty of accurately assessing an energy gap we have used, as an illustrative example, a recent epidemiological study which tracked changes in total energy intake (estimated by gross food availability) and body weight over 3 decades in the US, combined with total energy expenditure prediction from body weight using doubly labelled water data. At the population level, the study attempted to assess the cause of the energy gap purported to be entirely due to increased food intake. Based on an estimate of change in energy intake judged to be more reliable (i.e. in the same study population) and together with calculations of simple energetic indices, our analysis suggests that conclusions about the fundamental causes of obesity development in a population (excess intake vs. low physical activity or both) is clouded by a high level of uncertainty. PMID:24457473

Schutz, Yves; Byrne, Nuala M; Dulloo, Abdul; Hills, Andrew P

2014-01-01

164

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

Microsoft Academic Search

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

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

1994-01-01

165

Use of a High-Temperature Superconducting Coil for Magnetic Energy Storage  

NASA Astrophysics Data System (ADS)

A high temperature superconducting magnetic energy storage device (SMES) has been realised using a 350 m-long BSCCO tape wound as a ''pancake'' coil. The coil is mounted on a cryocooler allowing temperatures down to 17.2 K to be achieved. The temperature dependence of coil electrical resistance R(T) shows a superconducting transition at T = 102.5 K. Measurements of the V(I) characteristics were performed at several temperatures between 17.2 K and 101.5 K to obtain the temperature dependence of the critical current (using a 1 µV/cm criterion). Critical currents were found to exceed 100 A for T < 30 K. An electronic DC-DC converter was built in order to control the energy flow in and out of the superconducting coil. The converter consists of a MOS transistor bridge switching at a 80 kHz frequency and controlled with standard Pulse Width Modulation (PWM) techniques. The system was tested using a 30 V squared wave power supply as bridge input voltage. The coil current, the bridge input and output voltages were recorded simultaneously. Using a 10 A setpoint current in the superconducting coil, the whole system (coil + DC-DC converter) can provide a stable output voltage showing uninterruptible power supply (UPS) capabilities over 1 s.

Fagnard, J.-F.; Crate, D.; Jamoye, J.-F.; Laurent, Ph; Mattivi, B.; Cloots, R.; Ausloos, M.; Genon, A.; Vanderbemden, Ph

2006-06-01

166

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

167

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

168

Energy gaps and elementary excitations for certain VBS-quantum antiferromagnets  

SciTech Connect

It is shown for a class of antiferromagnetic Hamiltonians how one can get lower bounds for the energy gap above the ground state by diagonalizing a finite system. This method is applied to certain spin chains (including a spin-1 chain). Trial wave functions are proposed for the elementary excitations and are tested in the case of the spin-1 chain.

Knabe, S.

1988-08-01

169

Energy gaps and elementary excitations for certain VBS-quantum antiferromagnets  

Microsoft Academic Search

It is shown for a class of antiferromagnetic Hamiltonians how one can get lower bounds for the energy gap above the ground state by diagonalizing a finite system. This method is applied to certain spin chains (including a spin-1 chain). Trial wave functons are proposed for the elementary excitations and are tested in the case of the spin-1 chain.

Stefan Knabe

1988-01-01

170

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

SciTech Connect

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

Rogers, J.D. (comp.)

1981-03-01

171

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

Microsoft Academic Search

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

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

1992-01-01

172

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

E-print Network

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

173

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

174

Energy Flow and Rapidity Gaps Between Jets in Photoproduction at HERA  

E-print Network

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

Adloff, C

2002-01-01

175

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

E-print Network

Renewable Energy Desalination: An Emerging Solution to Close MENA's Water Gap 56th Annual NM Water Conf., New Water New Energy: A Conference Linking Desalination and Renewable Energy 45 Renewable Energy and renewable energy to climate change impacts on water and agriculture sectors. Dr. Debele has published

Johnson, Eric E.

176

Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

177

Hermetically sealed superconducting magnet motor  

DOEpatents

A hermetically sealed superconducting magnet motor includes a rotor separated from a stator by either a radial gap, an axial gap, or a combined axial and radial gap. Dual conically shaped stators are used in one embodiment to levitate a disc-shaped rotor made of superconducting material within a conduit for moving cryogenic fluid. As the rotor is caused to rotate when the field stator is energized, the fluid is pumped through the conduit. 6 figs.

DeVault, R.C.; McConnell, B.W.; Phillips, B.A.

1996-07-02

178

Hermetically sealed superconducting magnet motor  

DOEpatents

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

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

1996-01-01

179

Free energy surfaces in the superconducting mixed state  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

180

Femtosecond optical diagnostics of interlevel energy relaxation in the band gap of silver iodide nanocrystals  

NASA Astrophysics Data System (ADS)

The kinetics of the relaxation processes in silver iodide nanocrystals synthesized in a nanoporous silicate glass matrix and excited by femtosecond laser pulses has been experimentally studied. A short-lived characteristic transmission band is found to be formed in the spectral range of exciton absorption of nanocrystals. The specific features of photoexcited-carrier relaxation, which are due to the energy redistribution of captured carriers over levels in the band gap of silver iodide nanocrystals, are considered. The energy transfer relaxation rates are estimated and possible mechanisms of the energy transfer are discussed.

Andreeva, O. V.; Buganov, O. V.; Kim, A. A.; Nikonorov, N. V.; Sidorov, A. I.; Stasel'ko, D. I.; Tikhomirov, S. A.

2012-04-01

181

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

E-print Network

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

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

2008-06-27

182

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

PubMed

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

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

2012-12-14

183

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

184

Enhancing the design of a superconducting coil for magnetic energy storage systems  

NASA Astrophysics Data System (ADS)

Study and analysis of a coil for Superconducting Magnetic Energy Storage (SMES) system is presented in this paper. Generally, high magnetic flux density is adapted in the design of superconducting coil of SMES to reduce the size of the coil and to increase its energy density. With high magnetic flux density, critical current density of the coil is degraded and so the coil is wound with High Temperature Superconductors (HTS) made of different materials. A comparative study is made to emphasize the relationship between the energy storage and length of the coil wound by Bi2223, SF12100, SCS12100 and YBCO tapes. Recently for the construction of HTS magnets, YBCO tapes have been used. Simulation models for various designs have been developed to analyze the magnetic field distribution for the optimum design of energy storage. The design which gives the maximum stored energy in the coil has been used with a certain length of second-generation HTS. The performance analysis and the results of comparative study are done.

Indira, Gomathinayagam; UmaMaheswaraRao, Theru; Chandramohan, Sankaralingam

2015-01-01

185

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

186

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

SciTech Connect

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

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

2009-09-11

187

Large gap magnetic suspension system  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

188

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

189

Investigation of the superconducting gap structure in SrFe2(As0.7P0.3)2 by magnetic penetration depth and flux flow resistivity analysis  

NASA Astrophysics Data System (ADS)

We measured the microwave surface impedances and obtained the superfluid density and flux flow resistivity in single crystals of a phosphor-doped iron-based superconductor SrFe2(As1-xPx)2 single crystals (x=0.30, Tc=25K). At low temperatures, the superfluid density, ns(T)/ns(0), obeys a power law, ns(T)/ns(0)=1-C(T/Tc)n, with a fractional exponent of n=1.5-1.6. The flux flow resistivity was significantly enhanced at low magnetic fields. These features are consistent with the presence of line nodes on at least one band and modulated nodeless gap with deep minimum on the same bands and/or other bands. The remarkable difference observed in the superconducting gap structure between SrFe2(As1-xPx)2 and BaFe2(As1-xPx)2 in our experiments is important for clarifying the mechanism of iron-based superconductivity in the 122 system.

Takahashi, Hideyuki; Okada, Tatsunori; Imai, Yoshinori; Kitagawa, Kentaro; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Maeda, Atsutaka

2012-10-01

190

Superconducting cables: long-distance energy transmission. January 1973-February 1988 (Citations from the NTIS data base). Report for January 1973-February 1988  

SciTech Connect

This bibliography contains citations concerning the design, development, and evaluation of superconducting cables and power-transmission lines for long-distance energy transmission. Topics include methods of cryogenic refrigeration and electrical insulation, fabrication and development of niobium-alloy conductors, energy-loss analysis, and dielectric-design techniques for superconducting power-transmission systems. Government research project reports on superconducting technology for electric-power transmission and distribution are included. (Contains 129 citations fully indexed and including a title list.)

Not Available

1988-03-01

191

Spin-orbit coupling, anisotropic magnetic fluctuations and nodeless energy gap in iron-pnictides revealed by NMR  

NASA Astrophysics Data System (ADS)

We report on the pairing symmetry and the spin correlations in the Fe(Ni)-based superconductors RFe(Ni)AsO1-xFx (R=Pr, La), LiFeAs and Ba1-xKxFe2As2 single crystals, based on our extensive nuclear magnetic resonance and nuclear quadrupole resonance measurements. The spin susceptibility measured by the Knight shift decreases below Tc along all crystal directions, which indicates spin-singlet pairing. Evidence for multiple gaps is given. We find that the antiferromagnetic spin fluctuation is anisotropic in the spin space due to spin-orbit coupling, but becomes isotropic in the zero temperature limit, which points to spin-singlet superconductivity with nodeless gap.

Li, Z.; Yang, J.; Zheng, Guo-qing

2012-12-01

192

Superconducting magnetic energy storage. (Latest citations from the INSPEC database). Published Search  

SciTech Connect

The bibliography contains citations concerning research, development, and assessment of superconducting magnetic energy storage (SMES) technology. References discuss the design and performance of toroidal and solenoid type SMES systems for military, space mission, and electric utility applications. Topics include active and reactive power control, power system stability and diagnosis, power supply quality, uninterruptible power supplies, and SMES systems for critical industrial and military uses. Cost analysis and optimization, marketing, and environmental issues are reviewed. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1997-10-01

193

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

194

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

195

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

196

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

PubMed

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

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

2015-01-01

197

Ground state energy and scaling behaviour of spin gap in the XXZ spin-12 antiferromagnetic chain in longitudinal staggered field  

NASA Astrophysics Data System (ADS)

The ground state energy and the spin gap of a spin-12 Heisenberg antiferromagnetic XXZ chain in the presence of longitudinal staggered field (hz) have been estimated by using Jordan-Wigner representation, exact diagonalization and perturbative analysis. All those quantities have been obtained for a region of anisotropic parameter (?) defined by 0???1. For ?=0, the exact value of ground state energy is found for finite values of hz. The spin gap is found to develop as soon as the staggered field is switched on. The magnitude of spin gap is compared with the field induced gap measured in magnetic compounds CuBenzoate and Yb4As3 when ?=1. The dependence of spin gap on both ? and hz has been found which gives rise to scaling laws associated with hz. Scaling exponents obtained in two different cases show excellent agreements with the previously determined values. The variation of scaling exponents with ? can be fitted with a regular function.

Paul, Susobhan; Ghosh, Asim Kumar

2014-08-01

198

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

SciTech Connect

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

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

1997-12-01

199

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

PubMed

Energy drinks are relatively new to the United States but are the fastest growing segment of the beverage market. Humans have a long history of consuming caffeine in traditional beverages, such as cocoa, coffee, tea, and yerba maté, but 2 workshops held at the Institute of Medicine (http://www.iom.edu/Activities/Nutrition/PotentialHazardsCaffeineSupplements/2013-AUG-05.aspx) and the NIH (http://ods.od.nih.gov/News/EnergyDrinksWorkshop2013.aspx) in 2013 highlighted many critical gaps in understanding the biologic and behavioral effects of the mixtures of caffeine, vitamins, herbs, sugar or other sweeteners, and other ingredients that typify caffeine-containing energy drinks (CCEDs). For example, different surveys over the same 2010–2012 timeframe report discrepant prevalence of CCED use by teenagers, ranging from 10.3% in 13–17 y olds to >30% of those in grades 10 and 12. Understanding of functional interactions between CCED ingredients, drivers of use, and biologic and behavioral effects is limited. The 4 speakers in the Experimental Biology 2014 symposium titled “Energy Drinks: Current Knowledge and Critical Research Gaps” described recent progress by their groups in extending our understanding of prevalence of CCED use, sources of caffeine in the United States, drivers of CCED use, and behavioral correlations and effects of CCEDs, including effects on attractiveness of both alcoholic and non-alcoholic beverages. PMID:25513313

Sorkin, Barbara C; Coates, Paul M

2014-09-01

200

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

PubMed

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

Sorkin, Barbara C; Coates, Paul M

2014-09-01

201

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

E-print Network

in ordinary metals, electronic spin fluctuations are widely believed to be critical to superconductivity, Sendai 980-8578, Japan 3 TRiP, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan 4 Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan #12;Abstract

Hu, Jiangping

202

Existence of an energy gap in a one-dimensional Lesanovsky model  

NASA Astrophysics Data System (ADS)

We study the quantum lattice gas model in one dimension introduced by Lesanovsky Lesanovsky, Phys. Rev. Lett. 108, 105301 (2012), 10.1103/PhysRevLett.108.105301], who showed that the exact ground state and a couple of excited states can be obtained analytically. The Hamiltonian of the model depends solely on the parameter z, the meaning of which is a fugacity in the corresponding classical lattice gas model. For small z (0energy gap between the ground state and the excited states by applying Knabe's method Knabe, J. Stat. Phys. 52, 627 (1988), 10.1007/BF01019721].

Katsura, Hosho

2013-12-01

203

High Temperature Superconductivity in Cuprates: a model  

E-print Network

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

P. R. Silva

2010-07-16

204

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

E-print Network

scattering leads both to a decrease of Tc and to an ?isotropization? of the gap with vanishing nodes. We do not know any direct measurement of gap aniso- tropy involving the Andreev reflection.12 The STM tunnel- ling measurements at 4 K report a gap of 2... distribution which corresponds well to the recent STM measurements.19 PHYSICAL REVIEW B 71, 014512 s2005d 1098-0121/2005/71s1d/014512s9d/$23.00 ?2005 The American Physical Society014512-1 II. EXPERIMENTAL TECHNIQUE The point contact measurement...

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

2005-01-01

205

Estimation of energy dissipated during superconducting wire motion in a magnetic field  

Microsoft Academic Search

An experiment was carried out to study the motion of superconducting wire under the influence of electromagnetic force. Experiments were conducted at 4.2K by varying the experimental conditions such as tension to the superconducting wire, current ramp rate, and the use of different insulating materials at the interface of the superconducting wire. We were able to examine in detail the

K. Ruwali; A. Yamanaka; K. Hosoyama

2010-01-01

206

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

PubMed Central

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

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

2014-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2002-10-01

208

Calculation of the Band Gap Energy and Study of Cross Luminescence in Alkaline-Earth Dihalide Crystals  

NASA Astrophysics Data System (ADS)

The band gap energy as well as the possibility of cross luminescence processesin alkaline-earth dihalide crystals have been calculated using the ab initio Perturbed-Ion (PI) model.The gap is calculated in several ways: as adifference between one-electron energy eigenvalues and as adifference between total energies of appropriate electronic states of thecrystal, both at the HF level and with inclusion of Coulomb correlation effects.In order to study the possibility of ocurrence of cross luminescence in thesematerials, the energy differencebetween the valence band and the outermost core band for somerepresentative crystals has been calculated.Both calculated band gap energies and cross luminescence predictions comparevery well with the available experimental and theoretical results.

Aguado, Andrés; Ayuela, Andrés; López, José; Alonso, Julio

1999-08-01

209

Applied High-Tc Superconducting Power Machines  

Microsoft Academic Search

Superconductivity is key technology for 21st century. To suppress emission of green house effect gas, applied superconductivity is important. In this paper, the current status of superconducting power machines such as generator, magnetic bearing and motor are described. Most of all studies are the step of demonstration of idea and possibility. There are large gap between physical idea and actual

Tsutomu Hoshino

210

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

211

A fuzzy set theory based control of superconductive magnetic energy storage unit to improve power system dynamic performance  

Microsoft Academic Search

At present fuzzy logic control is receiving increasing emphasis in process control applications. The paper describes the application of fuzzy logic control in a power system that uses a 12-pulse bridge converter associated with superconductive magnetic energy storage (SMES) unit. The fuzzy control is used in both the frequency and voltage control loops, replacing the conventional control method. The control

M. G. Rabbani; J. B. X. Devotta; S. Elangovan

1997-01-01

212

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

PubMed Central

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

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

2014-01-01

213

Phase Structure and Instability Problem in Color Superconductivity  

E-print Network

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

Kenji Fukushima

2005-10-22

214

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

215

Unconventional superconductivity in a two-dimensional repulsive gas of fermions with spin-orbit coupling  

NASA Astrophysics Data System (ADS)

We investigate the superconducting instability of a two-dimensional repulsive Fermi gas with Rashba spin-orbit coupling ?R. Using renormalization group approach, we find the superconducting transition temperature as a function of the dimensionless ratio ?=1}/{2}m?R2/EF where EF = 0 when the smaller Fermi surface shrinks to a (Dirac) point. The general trend is that superconductivity is enhanced as ? increases, but in an intermediate regime ? ? 0.1, a dome-like behavior appears. At a very small value of ?, the angular momentum channel jz in which superconductivity occurs is quite high. With increasing ?, jz decreases with a step of 2 down to jz = 6, after which we find the sequence jz = 6, 4, 6, 2, the last value of which continues to ? ? ?. In an extended range of ?, the superconducting gap predominantly resides on the large Fermi surface, while Josephson coupling induces a much smaller gap on the small Fermi surface. Below the superconducting transition temperature, we apply mean field theory to derive the self-consistent equations and find the condensation energies. The state with the lowest condensation energy is an unconventional superconducting state which breaks time-reversal symmetry, and in which singlet and triplet pairings are mixed. In general, these states are topologically nontrivial, and the Chern number of the state with total angular momentum jz is C = 2jz.

Wang, Luyang; Vafek, Oskar

2014-02-01

216

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

217

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

SciTech Connect

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

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

2014-02-21

218

Spin-bag mechanism of high-temperature superconductivity  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

219

Surface energy band gap of polycrystalline CuInSe{sub 2} thin-films in tunneling spectroscopy  

SciTech Connect

In this paper the authors demonstrate a tunneling spectroscopic technique to determine energy band gaps of the CuInSe{sub 2} thin-film 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 evaluates from the measured I-V characteristics and simulated with help of two gap models with and without additional localized state tails in the gap. The poorly defined gap edges are explained by additional localized states near the top of the valence band and the bottom of the conduction band. These additional localized states could be true surface defect states or originate from deep atomic layers underneath the surfaces due to band bending.

Zhang, Z.; Heuell, P.; Kulakov, M.; Bullemer, B. [Federal Armed Forces Univ. Munich, Neubiberg (Germany). Inst. of Physics

1994-12-31

220

Energy losses in superconductive DC-electromagnets due to ferromagnetic movement  

SciTech Connect

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

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

1996-05-01

221

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

222

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

223

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

224

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

SciTech Connect

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

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

2014-05-28

225

Narrow energy gap between triplet and singlet excited states of Sn2+ in borate glass.  

PubMed

Transparent inorganic luminescent materials have attracted considerable scientific and industrial attention recently because of their high chemical durability and formability. However, photoluminescence dynamics of ns(2)-type ions in oxide glasses has not been well examined, even though they can exhibit high quantum efficiency. We report on the emission property of Sn(2+)-doped strontium borate glasses. Photoluminescence dynamics studies show that the peak energy of the emission spectrum changes with time because of site distribution of emission centre in glass. It is also found that the emission decay of the present glass consists of two processes: a faster S1-S0 transition and a slower T1-S0 relaxation, and also that the energy difference between T1 and S1 states was found to be much smaller than that of (Sn, Sr)B6O10 crystals. We emphasize that the narrow energy gap between the S1 and T1 states provides the glass phosphor a high quantum efficiency, comparable to commercial crystalline phosphors. PMID:24345869

Masai, Hirokazu; Yamada, Yasuhiro; Suzuki, Yuto; Teramura, Kentaro; Kanemitsu, Yoshihiko; Yoko, Toshinobu

2013-01-01

226

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

E-print Network

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

Zhihao Ge; Ruihua Li

2014-12-25

227

Coherent suppression of electromagnetic dissipation due to superconducting quasiparticles.  

PubMed

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

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

2014-04-17

228

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

E-print Network

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

Vodhanel, Mark E

2005-01-01

229

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

230

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

PubMed

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

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

2014-01-01

231

Specific heat of YBa 2Cu 3O 7-?: paramagnetic centers; evidence for line nodes in the energy gap  

NASA Astrophysics Data System (ADS)

Specific-heat data on YBa 2Cu 3O 7-?, O < ? < 0.2, have been analyzed to show the presence of spin-2, as well as spin-1/2, paramagnetic centers. Evidence of line nodes in the energy gap, including conformity to a predicted scaling relation, is reported.

Phillips, N. E.; Fisher, R. A.; Emerson, J. P.; Gordon, J. E.; Woodfield, B. F.; Wright, D. A.

2000-11-01

232

Electron Energy Loss Spectroscopy Measurement of the Optical Gaps on Individual Boron Nitride Single-Walled and Multiwalled Nanotubes  

E-print Network

Electron Energy Loss Spectroscopy Measurement of the Optical Gaps on Individual Boron Nitride spectroscopy experiments have been performed in an electron microscope on several individual boron nitride (BN and close to that for hexagonal boron nitride (h-BN). Very little is experimentally known on the electronic

233

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

NASA Technical Reports Server (NTRS)

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

Lacy, L. L.

1972-01-01

234

A quantum galvanometer with high-energy resolution based on a superconducting interferometer circuit  

SciTech Connect

The authors make a comprehensive analysis of principles of constructing measurement systems based on the superconducting quantum interferometer (SQUID) implemented in integrated form. They note trends of promising applications for galvanometric measurement systems. They describe the two types of SQUID, one-junction and two junction. They analyze the processing and formation of superconducting ion chemical signals and structures. And they present their results in a series of charts and diagrams. They conclude that quantum galvanometry using superconducting microcircuits allows one to propose new experimental studies in microelectronics, the techniques of high-precision measurements, and equipment for metrological work.

Bakhtin, P.A.; Makhov, V.I.; Masalov, V.V.; Sretenskii, V.N.; Tyablikov, A.V.; Vasenkov, A.A.

1985-07-01

235

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

SciTech Connect

We report the surface, structural, electronic, and optical properties of the epitaxial ZnO thin films grown on (0001) sapphire substrate at 600 deg. C by an electron-beam deposition technique. ZnO thin films have been deposited in an oxygen environment and post-deposition annealed to improve the stoichiometry and the crystal quality. In order to investigate the free exciton binding energy and the temperature dependence of the energy bandgap, we carried out variable temperature (78-450 K) transmittance measurements on ZnO thin films. The absorption data below the energy bandgap have been modeled with the Urbach tail and a free exciton, while the data above the gap have been modeled with the charge transfer excitations. The exciton binding energy is measured to be E{sub 0}= 64 {+-} 7 meV, and the energy band gaps of the ZnO film are measured to be E{sub g}-tilde 3.51 and 3.48 eV at 78 and 300 K, respectively. The temperature dependence of the energy gap has been fitted with the Varshni model to extract the fitting parameters {alpha}= 0.00020 {+-} 0.00002 eV/K, {beta}= 325 {+-} 20 K, and E{sub g} (T = 0 K) = 3.516 {+-} 0.0002 eV.

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

2012-04-01

236

Energy gaps in disordered systems: II. Alloys This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Energy gaps in disordered systems: II. Alloys This article has been downloaded from IOPscience. SOC., 1967,VOL. 90. PRINTED I N GREAT BRITAIN Energy gaps in disordered systems 11. Alloys P. L in another, then no state exists in the region of overlap in any alloy of the two, provided only

Taylor, Philip L.

237

Biological effects of magnetic fields from superconducting magnetic energy storage systems  

SciTech Connect

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

Tenforde, T.S.

1989-12-01

238

Superconducting pairing mediated by spin fluctuations from first principles  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

239

Multiband superconductivity in HoNi 2B 2C  

NASA Astrophysics Data System (ADS)

HoNi 2B 2C single crystals prepared by the floating zone method were investigated by resistivity, magnetization, specific heat and point-contact measurements. The coexistence of superconductivity (SC) and antiferromagnetism (AFM) in HoNi 2B 2C is considered experimentally and theoretically for commensurate (C), incommensurate (IC) and metamagnetic magnetic structures within the multiband picture of Fermi surface sheets (FSS) obtained within full potential FPLO-LDA calculations. Special attention is paid to the admixture of Ho 5d states which mediate the pair breaking exchange between the Ho 4f derived local moments and the conduction electrons bearing the superconductivity. Within the paramagnetic and the uniform IC spiral phases, anisotropic multiband SC coexists with magnetism. Within the C-phase (below TN = 5.3 K) single band isotropic SC survives at a single FSS free of Ho 5d states in accord with isotropic standard WHH shaped upper critical fields Hc2( T). The superconducting energy gap obtained from point-contact data was found to disappear at a slightly higher temperature T? = 5.6 K which is also observed in specific heat measurements. Using the experimental values for the energy gap ?(0) and Hc2(0) at zero temperature, the characteristic phonon frequency, the electron-phonon coupling constant and the Fermi velocity of the residual superconducting phase were estimated from the standard isotropic single band model.

Müller, Karl-Hartmut; Fuchs, Günter; Drechsler, Stefan-Ludwig; Opahle, Ingo; Eschrig, Helmut; Schultz, Ludwig; Behr, Günter; Löser, Wolfgang; Souptel, Dmitri; Wälte, Andreas; Nenkov, Konstantin; Naidyuk, Yuri; Rosner, Helge

2007-09-01

240

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

241

Proximity-induced superconductivity in topological Bi2Te2Se and Bi2Se3 films: Robust zero-energy bound state possibly due to Majorana fermions  

NASA Astrophysics Data System (ADS)

Point contact conductance measurements on topological Bi2Te2Se and Bi2Se3 films reveal a signature of superconductivity below 2-3 K. In particular, critical current dips and a robust zero-bias conductance peak are observed. The latter suggests the presence of zero-energy bound states that could be assigned to Majorana fermions in an unconventional topological superconductor. We attribute these observations to proximity-induced local superconductivity in the films by small amounts of superconducting Bi inclusions or segregation to the surface, and provide supportive evidence for these effects.

Koren, G.; Kirzhner, T.; Lahoud, E.; Chashka, K. B.; Kanigel, A.

2011-12-01

242

Electromagnetically Induced Transparency and Autler-Townes Splitting in a Superconducting Quantum Circuit with a Four-Level V-Type Energy Spectrum  

NASA Astrophysics Data System (ADS)

We investigate electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) in a superconducting quantum circuit with a four-level V-type energy spectrum constructed by two coupled superconducting charge qubits. We show that it is possible for this four-level superconducting system to exhibit multiple dips in the absorption spectrum of a probe field, with at most three dips resulting from a combination of two ATS subsystems, which indicates the breakdown of the traditional correspondence between a -level system and dips. It is also shown that the switching from EIT to ATS can be realized in a three-level ladder-type subsystem.

Li, Haichao; Ge, Guoqin; Liao, Lingmin; Feng, Shunbin

2015-02-01

243

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

SciTech Connect

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

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

2014-01-29

244

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

245

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

SciTech Connect

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

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

2013-11-15

246

Superconducting magnet of Aurora  

NASA Astrophysics Data System (ADS)

The AURORA superconducting magnet system is composed of a cylindrical single-body magnet and a refrigeration system for superconducting coils. The magnet generates Bz=1 T on the central orbit at the 150 MeV electron beam injection energy and Bz=4.3 T at the 650 MeV storage energy. The diameter of the central orbit is 1 m. Iron poles and yokes are used for shielding the magnetic field, reducing the electromagnetic force between superconducting coils, and making the magnetic field distribution adequate for beam injection and storage.

Takayama, T.; SHI Accelerator Research Group

1989-07-01

247

Influence of losses on the stability of a high current density superconducting magnet winding during the energy removal process  

NASA Astrophysics Data System (ADS)

The possibility of a high-current-density superconducting magnet winding quench due to losses generated during energy removal from the magnet is demonstrated using a computer program to calculate the specific losses and temperature rise of a composite superconductor. The experiments carried out on a laboratory solenoid with a nearly adiabatically insulated winding and a storage energy of 50 kJ at critical current are in good agreement with theory. It is shown that under certain conditions, the quench magnetic field level is independent of the magnetic field decay velocity.

Luppov, V. G.; Kabat, D.; Shishov, Y. A.; Datskov, V. I.

1980-10-01

248

Superconducting properties of Ca3Ir4Sn13: a ?SR study  

NASA Astrophysics Data System (ADS)

Muon spin relaxation and rotation (?SR) measurements have been performed to study the superconducting properties of Ca3Ir4Sn13. Zero-field ?SR data shows no sign of any magnetic anomaly in Ca3Ir4Sn13 at the superlattice transition temperature, T* or in the superconducting ground state. Transverse-field ?SR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth ?. The dependence of ??2 with temperature is consistent with the existence of a single s-wave energy gap in the superconducting state of Ca3Ir4Sn13 with a gap value of 1.51(5) meV at absolute zero temperature. The magnetic penetration depth at zero temperature ?(0) is 351(4) nm. The ratio ?(0)/kBTc = 2.41(8) indicates that Ca3Ir4Sn13 is a strong-coupling superconductor.

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

2014-12-01

249

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

E-print Network

The general antiparticle spectrometer (GAPS) experiment is a proposed indirect dark matter search focusing on antiparticles produced by WIMP (weakly interacting massive particle) annihilation and decay in the Galactic halo. In addition to the very powerful search channel provided by antideuterons, GAPS has a strong capability to measure low-energy antiprotons (0.07 $\\le$ E $\\le$ 0.25 GeV) as dark matter signatures. This is an especially effective means for probing light dark matter, whose existence has been hinted at in the direct dark matter searches, including the recent result from the CDMS-II experiment. While severely constrained by LUX and other direct dark matter searches, light dark matter candidates are still viable in an isospin-violating dark matter scenario and halo-independent analysis. Along with the excellent antideuteron sensitivity, GAPS will be able to detect an order of magnitude more low-energy antiprotons, compared to BESS, PAMELA and AMS-02, providing a precision measurement of low-energy antiproton flux and a unique channel for probing light dark matter models. Additionally, dark matter signatures from gravitinos and Kaluza-Klein right-handed neutrinos as well as evidence of primordial black hole evaporation can be observed through low-energy antiproton search.

T. Aramaki; S. E. Boggs; P. von Doetinchem; H. Fuke; C. J. Hailey; S. A. I. Mognet; R. A. Ong; K. M. Perez; J. Zweerink

2014-04-02

250

Elementary energy bands in the band structure of the narrow-band-gap semiconductor CdSb  

NASA Astrophysics Data System (ADS)

Based upon the example of a narrow band gap covalent CdSb crystal (D2h16) , it is shown that a spatial electron density distribution in the unit cell is related to the Zak’s elementary energy bands creating the valence band and to the corresponding Wyckoff positions. A role of particular electronic states in the creation of the elementary energy bands was analyzed by conducting ab initio band structure calculations of CdSb. The investigations of the topology of the elementrary energy bands allows one to predict the nature of chemical bondings in rhombic crystals.

Bercha, D. M.; Slipukhina, I. V.; Sznajder, M.; Rushchanskii, K. Z.

2004-12-01

251

Reduction of the energy gap pressure coefficient of GaN due to the constraining presence of the sapphire substrate  

SciTech Connect

We have performed a detailed investigation of the photoluminescence pressure dependence of heteroepitaxial GaN thin films on sapphire substrates. A comparison between as grown GaN on sapphire and free-standing GaN membranes, created using a laser assisted substrate liftoff process, revealed that the presence of the sapphire substrate leads to an energy gap pressure coefficient reduction of approximately 5{percent}. This result agrees with the numerical simulations presented in this article. We established that the linear pressure coefficient of free-standing GaN is 41.4{plus_minus}0.2 meV/GPa, and that the deformation potential of the energy gap is {minus}9.36{plus_minus}0.04 eV. Our results also suggest a new, lower value of the pressure derivative for the bulk modulus of GaN (B{sup {prime}}=3.5). {copyright} {ital 1999 American Institute of Physics.}

Perlin, P.; Mattos, L.; Shapiro, N.A.; Kruger, J. [Lawrence Berkeley National Laboratory and University of California at Berkeley, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory and University of California at Berkeley, 1 Cyclotron Road, Berkeley, California 94720 (United States); Wong, W.S.; Sands, T. [Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720 (United States)] [Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720 (United States); Cheung, N.W. [Department of Electrical Engineering and Computer Science, University of California, Berkeley, California 94720 (United States)] [Department of Electrical Engineering and Computer Science, University of California, Berkeley, California 94720 (United States); Weber, E.R. [Lawrence Berkeley National Laboratory and University of California at Berkeley, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Lawrence Berkeley National Laboratory and University of California at Berkeley, 1 Cyclotron Road, Berkeley, California 94720 (United States)

1999-02-01

252

Effect of electron divergence in air gaps on the measurement of the energy of cascades in emulsion chambers  

NASA Technical Reports Server (NTRS)

The effect of an increase in electron density in the vicinity of the cascade axis caused by an avalanche passing through the gap between lead filters of the emulsion chamber was investigated experimentally. Optical densities were measured in three X-ray films spaced at 400, 800 and 1200 micrometer from the filter surface having a thickness of 6 cascade units. The optical densities of blackening spots caused by electron photon cascades of 1 to 2, 2 to 7 and greater than 7 BeV energies were measured. The results prove the presence of a gap between the filter and the nuclear emulsion which results in the underestimation of energy by several tenths of a percent.

Apanasenko, A. V.; Baradzey, L. T.; Kanevskaya, Y. A.; Smorodin, Y. A.

1975-01-01

253

Self-Consistent Calculation of the correct BandGap and Low Energy Conduction Bands in Gallium-Nitride  

Microsoft Academic Search

The III-V nitrides are viewed as new semiconductors for optoelectronic applications in the blue and UV wavelengths and, more recently, as high-power, high-temperature electronic devices. However, a reliable prediction of the band gap and the low energy conduction bands had, until now, remained a problem in ab initio computations. A spurious effect of the variational procedure and of basis sets

G. L. Zhao; D. Bagayoko; J. D. Fan

1998-01-01

254

Weak-coupling theory of high-temperature superconductivity in the antiferromagnetically correlated copper oxides  

NASA Astrophysics Data System (ADS)

We show that the retarded interaction between quasiparticles on a two dimensional square lattice induced by the exchange of antiferromagnetic paramagnons leads uniquely to a transition to a superconducting state with d2x-y2 symmetry. We find that the effective quasiparticle interaction responsible for superconductivity possesses considerable structure in both momentum and frequency space, and show, by explicit calculations, that if one wishes to obtain quantitatively meaningful results it is essential to allow for that structure in solving the full integral equations that determine the superconducting transition temperature and the superconducting properties. With a spin-excitation spectrum and a quasiparticle-paramagnon coupling determined by fits to normal-state experiments, we obtain high transition temperatures and energy-gap behaviors comparable to those measured for YBa2Cu3O7, YBa2Cu3O6.63, and La1.85Sr0.15CuO4.

Monthoux, P.; Balatsky, A. V.; Pines, D.

1992-12-01

255

Universality of the dispersive spin-resonance mode in superconducting BaFe2As2.  

PubMed

Spin fluctuations in superconducting BaFe2(As(1-x)P(x))2 (x=0.34, T(c)=29.5 K) 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. PMID:24182293

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

2013-10-18

256

Position-dependent effect of non-magnetic impurities on superconducting properties of nanowires  

NASA Astrophysics Data System (ADS)

Anderson's theorem states that non-magnetic impurities do not change the bulk properties of conventional superconductors. However, as the dimensionality is reduced, the effect of impurities becomes more significant. Here we investigate superconducting nanowires with diameter comparable to the Fermi wavelength ?F (which is less than the superconducting coherence length) by using a microscopic description based on the Bogoliubov-de Gennes method. We find that: 1) impurities strongly affect the superconducting properties, 2) the effect is impurity position dependent, and 3) it exhibits opposite behavior for resonant and off-resonant wire widths. We show that this is due to the interplay between the shape resonances of the order parameter and the subband energy spectrum induced by the lateral quantum confinement. These effects can be used to manipulate the Josephson current, filter electrons by subband and investigate the symmetries of the superconducting subband gaps.

Zhang, L.-F.; Covaci, L.; Peeters, F. M.

2015-01-01

257

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

258

Enhancement of magnetic flux distribution in a DC superconducting electric motor  

NASA Astrophysics Data System (ADS)

Most motor designs require an air gap between the rotor and stator to enable the armature to rotate freely. The interaction of magnetic flux from rotor and stator within the air gap will provide the thrust for rotational motion. Thus, the understanding of magnetic flux in the vicinity of the air gap is very important to mathematically calculate the magnetic flux generated in the area. In this work, a finite element analysis was employed to study the behavior of the magnetic flux in view of designing a synchronous DC superconducting electric motor. The analysis provides an ideal magnetic flux distribution within the components of the motor. From the flux plot analysis, it indicates that flux losses are mainly in the forms of leakage and fringe effect. The analysis also shows that the flux density is high at the area around the air gap and the rotor. The high flux density will provide a high force area that enables the rotor to rotate. In contrast, the other parts of the motor body do not show high flux density indicating low distribution of flux. Consequently, a bench top model of a DC superconducting motor was developed where by motor with a 2-pole type winding was chosen. Each field coil was designed with a racetrack-shaped double pancake wound using DI-BSCCO Bi-2223 superconducting tapes. The performance and energy efficiency of the superconducting motor was superior when compared to the conventional motor with similar capacity.

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

2013-06-01

259

Superconductive wire  

DOEpatents

A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity. 2 figs.

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

1995-07-18

260

Superconductive wire  

DOEpatents

A superconductive article is made by inserting a rigid mandrel into an internal cavity of a first metallic tube, said tube having an interior surface and an exterior surface, said interior surface defining the interior cavity, forming a layer of a superconductive material or superconductive precursor upon the exterior surface of said first metallic tube, machining the layer of superconductive material or superconductive precursor to a predetermined diameter to form an intermediate article configured for insertion into a second metallic tube having an interior diameter corresponding to the predetermined diameter, inserting the machined intermediate article into a second metallic tube having an internal diameter corresponding to the predetermined diameter of the intermediate article to form a composite intermediate article, reducing or ironing the composite intermediate article to a predetermined cross-sectional diameter, and sintering the reduced or ironed composite intermediate article at temperatures and for time sufficient for the superconductive material or superconductive precursor to exhibit superconductivity.

Korzekwa, David A. (Los Alamos, NM); Bingert, John F. (Jemez Springs, NM); Peterson, Dean E. (Los Alamos, NM); Sheinberg, Haskell (Santa Fe, NM)

1995-01-01

261

Finite-temperature signatures of gap anisotropy in optical conductivity of ferropnictides  

NASA Astrophysics Data System (ADS)

The low-temperature optical conductivity in the superconducting state of the ferropnictides shows increased absorption at low energies not expected for an isotropic s-wave gap. This may indicate that the gap on one or more of the several bands involved is quite anisotropic. A possible candidate is the gap on the electron pocket at the M point in the Brillouin zone. We calculate the optical response of an extended s-wave superconductor with emphasis on its temperature evolution. An aim is to study the difference in signatures, both in temperature and frequency, expected in the crossover region between a gap with nodes and that with a small gap. Results are also presented for a two-band case with microscopic parameters chosen specific to the ferropnictides. We add their respective conductivities and, thus, neglect any interband contributions.

Schachinger, E.; Carbotte, J. P.

2011-10-01

262

Ten questions and answers about superconductivity  

E-print Network

This work answers the basic questions of superconductivity in a question-and-answer format. We extend a basic hypothesis to various superconductors. This hypothesis is that superconductivity requires that the pairing gap locates around the Fermi level. On the basis of this hypothesis our calculations give the so-called three factor theory with which some key problems of the high temperature superconductivity are explained.

Tian De Cao

2010-06-29

263

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

264

Electronic Characterization of Defects in Narrow Gap Semiconductors-Comparison of Electronic Energy Levels and Formation Energies in Mercury Cadmium Telluride, Mercury Zinc Telluride, and Mercury Zinc Selenide  

NASA Technical Reports Server (NTRS)

We have used a Green's function technique to calculate the energy levels and formation energy of deep defects in the narrow gap semiconductors mercury cadmium telluride (MCT), mercury zinc telluride (MZT) and mercury zinc selenide (MZS). The formation energy is calculated from the difference between the total energy with an impurity cluster and the total energy for the perfect crystal. Substitutional (including antisite), interstitial (self and foreign), and vacancy deep defects are considered. Relaxation effects are calculated (with molecular dynamics). By use of a pseudopotential, we generalize the ideal vacancy model so as to be able to consider relaxation for vacancies. Different charge states are considered and the charged state energy shift (as computed by a modified Haldane-Anderson model) can be twice that due to relaxation. Different charged states for vacancies were not calculated to have much effect on the formation energy. For all cases we find deep defects in the energy gap only for cation site s-like orbitals or anion site p-like orbitals, and for the substitutional case only the latter are appreciably effected by relaxation. For most cases for MCT, MZT, MZS, we consider x (the concentration of Cd or Zn) in the range appropriate for a band gap of 0.1 eV. For defect energy levels, the absolute accuracy of our results is limited, but the precision is good, and hence chemical trends are accurately predicted. For the same reason, defect formation energies are more accurately predicted than energy level position. We attempt, in Appendix B, to calculate vacancy formation energies using relatively simple chemical bonding ideas due to Harrison. However, these results are only marginally accurate for estimating vacancy binding energies. Appendix C lists all written reports and publications produced for the grant. We include abstracts and a complete paper that summarizes our work which is not yet available.

Patterson, James D.

1996-01-01

265

Magnetic-field dependence of energy levels of superconducting nano-scale mettalic grains with strong spin-orbit scattering  

NASA Astrophysics Data System (ADS)

We study the Zeeman splitting of discrete energy levels of superconducting nano-scale metallic grains whose single-electron dynamics is chaotic [1]. In the absence of spin-orbit scattering the Zeeman splitting of a single-electron level is trivial; it is the same for all levels and linear in magnetic field. Spin-orbit coupling suppresses this splitting, induces level-to-level fluctuations and non-linear corrections to the energies. We investigate the combined effect of pairing correlations, which lead to superconductivity in the bulk limit, and spin-orbit scattering on the many-electron energy levels in a weak magnetic field. In particular, we focus our studies on the linear (g-factor) and quadratic (zero-field level curvature) corrections and their mesoscopic fluctuations. The single-electron part of the Hamiltonian follows the statistics of the Gaussian symplectic ensemble of random matrix theory, which is applicable in the limit of strong spin-orbit scattering and a large dimensionless Thouless conductance. The interaction is given by a BCS-like pairing term and the magnetic field coupling is described by a Zeeman term. [1] K. Nesterov and Y. Alhassid, to be published.

Nesterov, Konstantin; Alhassid, Yoram

2012-02-01

266

Progress in Superconducting Metamaterials  

E-print Network

We review progress in the development and applications of superconducting metamaterials. The review is organized in terms of several distinct advantages and unique properties brought to the metamaterials field by superconductivity. These include the low-loss nature of the meta-atoms, their compact structure, their extraordinary degree of nonlinearity and tunability, magnetic flux quantization and the Josephson effect, quantum effects in which photons interact with quantized energy levels in the meta-atom, as well as strong diamagnetism.

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

2014-03-25

267

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

SciTech Connect

We present angle-resolved photoemission spectroscopy (ARPES) studies of the cuprate high-temperature superconductors which elucidate the relation between superconductivity and the pseudogap and highlight low-energy quasiparticle dynamics in the superconducting state. Our experiments suggest that the pseudogap and superconducting gap represent distinct states, which coexist below T{sub c}. Studies on Bi-2212 demonstrate that the near-nodal and near-antinodal regions behave differently as a function of temperature and doping, implying that different orders dominate in different momentum-space regions. However, the ubiquity of sharp quasiparticles all around the Fermi surface in Bi-2212 indicates that superconductivity extends into the momentum-space region dominated by the pseudogap, revealing subtlety in this dichotomy. In Bi-2201, the temperature dependence of antinodal spectra reveals particle-hole asymmetry and anomalous spectral broadening, which may constrain the explanation for the pseudogap. Recognizing that electron-boson coupling is an important aspect of cuprate physics, we close with a discussion of the multiple 'kinks' in the nodal dispersion. Understanding these may be important to establishing which excitations are important to superconductivity.

Vishik, Inna

2011-06-23

268

Development of High Gradient Superconducting Radio Frequency Cavities for International Linear Collider and Energy Recovery Linear Accelerator  

NASA Astrophysics Data System (ADS)

Superconducting radio frequency (SRF) cavities were used for storage rings like TRISTAN at KEK, HERA at DESY and LEP-II at CERN in 1990-2000. This technology has been accepted as a common accelerator technology. In August 2004, ITPR recommended an electron/positron linear collider based on SRF technology for the future high energy physics. ICFA accepted the recommendation and named it ILC (International Linear Collider). SRF cavities have a very unique feature due to its very small surface resistance. Energy recovery is another very exciting application. Many laboratories are proposing ERL (Energy Recovery LINAC) as a next bright photon source. In these accelerators, production of SRF cavities with reliably high performance is the most important issue. In this paper the activities of ILC high gradient cavities will be introduced. ERL activity will be briefly presented.

Saito, Kenji; Furuta, Fumio; Saeki, Takayuki

269

Procedures for Filling Short Gaps in Energy Use and Weather Data  

E-print Network

methods for filling data gaps will be compared using the same statistical parameters (MBE, RMSE, CV-SAE and SSE) to evaluate the prediction error of each model (polynomial, Lagrange, linear interpolation and single variable regression). METHODOLOGY... error (MBE), the coefficient of variation of the root mean square error (CV-RMSE), the coefficient of variation of the ratio of the sum of the absolute errors to the sum of measured data points (CV-SAE) and the coefficient of multiple determination...

Chen, H.; Claridge, D. E.

2000-01-01

270

Far infrared spectroscopy of superconducting and antiferromagnetic materials  

SciTech Connect

Far infrared (FIR) spectroscopy is used to probe low energy electronic excitations in both the superconducting and antiferromagnetic insulating phases of several rare-earth cuprate materials, as well as the organic superconductor K[sub 3]C[sub 60]. Magnetic ordering in the undoped high-Tc parent compounds (RE)[sub 2]CuO[sub 4], where (RE) represents a rare-earth ion, is investigated by exciting the antiferromagnetic resonance (AFMR) modes in the FIR. These studies provide information about the exchange coupling among the spins, and the effects of crystalline anisotropy. The superconducting phases are examined by FIR transmission measurements, which probe the superconducting carrier density and energy gap. The quasi-2D nature of the conductivity in the hole and electron doped high-Tc cuprates La[sub 2[minus]x]Sr[sub x]CuO[sub 4[minus]y], Nd[sub 2[minus]x]Ce[sub x]CuO[sub 4], and Bi[sub 4]Ca[sub 3]Sr[sub 3]Cu[sub 4]O[sub z] is found to produce a c-axis polarized FIR sphere resonance in small isolated superconducting particles of these materials. An analysis of the La[sub 2[minus]x]Sr[sub x]CuO[sub 4[minus]x] data yields a lower limit of 3.0 k[sub B] Tc for the c-axis gap energy, and provides an estimate of [approximately]6 [mu] for the London penetration depth along the c-axis. The isotropic conductivity in K[sub 3]C[sub 60] does not produce such a resonance, and this material is studied by FIR transmission of polycrystalline films of K[sub x]C[sub 60]. The spectra of these films can be modeled with a distribution of Tc's and associated BCS-like gaps, which are thought to be related to sample inhomogeneity. The superconducting energy gap of K[sub 3]C[sub 60] is estimated to be in the range 2-5 k[sub B]Tc. The antiferromagnetic high-Tc parent compounds (RE)[sub 2]CuO[sub 4], with (RE) = La, Sm, Gd, and Nd, are examined in polycrystalline and single crystal form.

Kaplan, S.G.

1993-01-01

271

Design of high-energy high-current linac with focusing by superconducting solenoids  

Microsoft Academic Search

The advancement of MRTI design for 1.5 GeV and 250 mA ion CW linac is presented in the report. In new linac version all the way from input to output the ions are focused by magnetic fields of superconducting solenoids. The ion limit current is far beyond the needed value. The linac focusing channel offers major advantages over the more

Guennady I. Batskikh; Vladimir M. Belugin; Boris I. Bondarev; Arkady P. Fedotov; Alexander P. Durkin; Yury D. Ivanov; Vladimir N. Mikhailov; Boris P. Murin; Kharis Kh. Mustafin; Igor V. Shumakov; Nikolay I. Uksusov

1995-01-01

272

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

E-print Network

losses. Thus, the superconducting transmission and distribu- tion system would allow more electricity to reach consumers with no increase in fossil fuel-related CO2 emissions, using smaller sized equipment. It is estimated that 40 percent of US’s total... .A. Coombs, Numerical analysis and finite element modelling of an HTS synchronous motor, Physica C, issue 450, pp. 1752-1755, 2010 Contents 1 Introduction 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Thesis purpose...

Yuan, Weijia

2010-11-16

273

Design of 57.5 MHz cw RFQ for medium energy heavy ion superconducting linac  

Microsoft Academic Search

The nuclear science community considers the construction of the Rare Isotope Accelerator (RIA) facility as a top priority. The RIA includes a 1.4 GV superconducting linac for production of 400 kW cw heavy ion beams. The initial acceleration of heavy ions delivered from an electron cyclotron resonance ion source can be effectively performed by a 57.5 MHz 4-m long room

P. N. Ostroumov; A. A. Kolomiets; D. A. Kashinsky; S. A. Minaev; V. I. Pershin; T. E. Tretyakova; S. G. Yaramishev

2002-01-01

274

Superconducting thermoelectric generator  

DOEpatents

An apparatus and method for producing electricity from heat. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device.

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

1996-01-01

275

Superconducting thermoelectric generator  

DOEpatents

An apparatus and method for producing electricity from heat. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device.

Metzger, John D. (Eaton's Neck, NY); El-Genk, Mohamed S. (Albuquerque, NM)

1998-01-01

276

Superconducting thermoelectric generator  

DOEpatents

An apparatus and method for producing electricity from heat is disclosed. The present invention is a thermoelectric generator that uses materials with substantially no electrical resistance, often called superconductors, to efficiently convert heat into electrical energy without resistive losses. Preferably, an array of superconducting elements is encased within a second material with a high thermal conductivity. The second material is preferably a semiconductor. Alternatively, the superconducting material can be doped on a base semiconducting material, or the superconducting material and the semiconducting material can exist as alternating, interleaved layers of waferlike materials. A temperature gradient imposed across the boundary of the two materials establishes an electrical potential related to the magnitude of the temperature gradient. The superconducting material carries the resulting electrical current at zero resistivity, thereby eliminating resistive losses. The elimination of resistive losses significantly increases the conversion efficiency of the thermoelectric device. 4 figs.

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

1998-05-05

277

The next-to-leading order vertex for a forward jet plus a rapidity gap at high energies  

NASA Astrophysics Data System (ADS)

We present the results for the calculation of the forward jet vertex associated to a rapidity gap (coupling of a hard pomeron to the jet) in the Balitsky-Fadin-Kuraev-Lipatov (BFKL) formalism at next-to-leading order (NLO). We handle the real emission contributions making use of the high energy effective action proposed by Lipatov, valid for multi-Regge and quasi-multi-Regge kinematics. This result is important since it allows, together with the NLO non-forward gluon Green function, to perform NLO studies of jet production in diffractive events (Mueller-Tang dijets, as a well-known example).

Hentschinski, M.; Madrigal Martínez, J. D.; Murdaca, B.; Sabio Vera, A.

2014-07-01

278

Enhancing the Superconducting Transition Temperature of CeRh1-xIrxIn5 due to the Strong-Coupling Effects of Antiferromagnetic Spin Fluctuations: An In115 Nuclear Quadrupole Resonance Study  

Microsoft Academic Search

We report on systematic evolutions of antiferromagnetic (AFM) spin fluctuations and unconventional superconductivity (SC) in heavy-fermion (HF) compounds CeRh1-xIrxIn5 via an In115 nuclear-quadrupole-resonance experiment. The nuclear spin-lattice relaxation rate 1\\/T1 has revealed the marked development of AFM spin fluctuations as approaching an AFM ordered state. Concomitantly, the superconducting transition temperature Tc and the energy gap Delta0 increase drastically from Tc=0.4K

Shinji Kawasaki; Mitsuharu Yashima; Yoichi Mugino; Hidekazu Mukuda; Yoshio Kitaoka; Hiroaki Shishido; Yoshichika Onuki

2006-01-01

279

BCS superconductivity in quantum critical metals  

Microsoft Academic Search

We consider the superconducting transition in fermionic quantum critical systems. Assuming the validity of Migdal theorem, the gap equation can be written in terms of the retarded pair susceptibility. Instead of the usual BCS form, the pair susceptibility is now subject to scale invariance. The gap and transition temperature is thus of the algebraic form, totally different from the exponential

Jian-Huang She; Jan Zaanen

2010-01-01

280

Cosmic Sparks from Superconducting Strings  

SciTech Connect

We investigate cosmic sparks from cusps on superconducting cosmic strings in light of the recently discovered millisecond radio burst by Lorimer et al.. We find that the observed duration, fluence, spectrum, and event rate can be reasonably explained by grand unification scale superconducting cosmic strings that carry currents {approx}10{sup 5} GeV. The superconducting string model predicts an event rate that falls off only as S{sup -1/2}, where S is the energy flux, and hence predicts a population of very bright bursts. Other surveys, with different observational parameters, are shown to impose tight constraints on the superconducting string model.

Vachaspati, Tanmay [Institute for Advanced Study, Princeton, New Jersey 08540 (United States); CERCA, Physics Department, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106-7079 (United States)

2008-10-03

281

Multiple Superconducting Phases in New Heavy Fermion Superconductor PrOs4Sb12  

Microsoft Academic Search

The superconducting gap structure of recently discovered heavy fermion superconductor PrOs4Sb12 was investigated by using thermal transport measurements in magnetic field rotated relative to the crystal axes. We demonstrate that a novel change in the symmetry of the superconducting gap function occurs deep inside the superconducting state, giving a clear indication of the presence of two distinct superconducting phases with

K. Izawa; Y. Nakajima; J. Goryo; Y. Matsuda; S. Osaki; H. Sugawara; H. Sato; P. Thalmeier; K. Maki

2003-01-01

282

Coexistence of the spini-density-wave and superconductivity in the Ba1-xKxFe2As2  

SciTech Connect

The relation between the spin-density-wave (SDW) and superconducting order is a central topic in current research on the FeAs-based high T{sub c} superconductors. Conflicting results exist in the LaFeAs(O,F)-class of materials, for which whether the SDW and superconductivity are mutually exclusive or they can coexist has not been settled. Here we show that for the (Ba,K)Fe{sub 2}As{sub 2} system, the SDW and superconductivity can coexist in an extended range of compositions. The availability of single crystalline samples and high value of the energy gaps would make the materials a model system to investigate the high T{sub c} ferropnictide superconductivity.

Bao, Wei [Los Alamos National Laboratory; Chen, H [HEFEI NAT. LAB; Ren, Y [ANL; Qiu, Y [NIST CENTER FOR NEUTRON; Liu, R [HEFEI NAT. LAB.; Wu, G H [HEFEI NAT. LAB; Wu, T [HEFEI NAT. LAB.; Xie, Y L [HEFEI NAT. LAB; Wang, F [HEFEI NAT. LAB.; Huang, Q [NIST CENTER FOR NEUTRON; Chen, X H [HEFEI NAT. LAB

2008-01-01

283

Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius  

E-print Network

We have carried out optical-absorption and reflectance measurements at room temperature in single crystals of AWO4 tungstates (A = Ba, Ca, Cd, Cu, Pb, Sr, and Zn). From the experimental results their band-gap energy has been determined to be 5.26 eV (BaWO4), 5.08 eV (SrWO4), 4.94 eV (CaWO4), 4.15 eV (CdWO4), 3.9-4.4 eV (ZnWO4), 3.8-4.2 eV (PbWO4), and 2.3 eV (CuWO4). The results are discussed in terms of the electronic structure of the studied tungstates. It has been found that those compounds where only the s electron states of the A2+ cation hybridize with the O 2p and W 5d states (e.g BaWO4) have larger band-gap energies than those where also p, d, and f states of the A2+ cation contribute to the top of the valence band and the bottom of the conduction band (e.g. PbWO4). The results are of importance in view of the large discrepancies existent in prevoiusly published data.

Lacomba-Perales, R; Errandonea, D; Martinez-Garcia, D; Segura, A

2008-01-01

284

Anomalous Energy Gaps of the Odd Denominator Fractional Quantum Hall States in Different Spin Branches of the Second Landau Level  

NASA Astrophysics Data System (ADS)

The nature of the fractional quantum Hall states forming in the second Landau level, including those with odd denominator Landau level filling factors, remain unknown. Conjectures of nonconventional origins have lead to the investigation of several odd denominator states in the lower spin branch of the second Landau level, such as the ones at ?=2+1/3 and 2+2/3. We report first measurements of the energy gaps in the upper spin branch of the second Landau level at ?=3+1/3, 3+2/3, 3+1/5 and 3+4/5. A comparison of the energy gaps of these states to those of their counterparts in the lower spin branch reveals a surprising reversal in the relative magnitudes of the states at partial filling factors 1/3 and 1/5. We explore possible explanations of this unusual observation. The work at Purdue was supported by the DOE BES contract no. DE-SC0006671. K.K. West and L.N. Pfeiffer acknowledge the support of the Princeton NSF-MRSEC and the Moore Foundation.

Kleinbaum, Ethan; Kumar, Ashwani; Manfra, Michael; Pfeiffer, Loren; West, Ken; Csathy, Gabor

2013-03-01

285

Suppression of activation energy and superconductivity by the addition of Al2O3 nanoparticles in CuTl-1223 matrix  

NASA Astrophysics Data System (ADS)

Low anisotropic (Cu0.5Tl0.5)Ba2Ca2Cu3O10-? (CuTl-1223) high Tc superconducting matrix was synthesized by solid-state reaction and Al2O3 nanoparticles were prepared separately by co-precipitation method. Al2O3 nanoparticles were added with different concentrations during the final sintering cycle of CuTl-1223 superconducting matrix to get the required (Al2O3)y/CuTl-1223, y = 0.0, 0.5, 0.7, 1.0, and 1.5 wt. %, composites. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray, and dc-resistivity (?) measurements. The activation energy and superconductivity were suppressed with increasing concentration of Al2O3 nanoparticles in (CuTl-1223) matrix. The XRD analysis showed that the addition of Al2O3 nanoparticles did not affect the crystal structure of the parent CuTl-1223 superconducting phase. The suppression of activation energy and superconducting properties is most probably due to weak flux pinning in the samples. The possible reason of weak flux pinning is reduction of weak links and enhanced inter-grain coupling due to the presence of Al2O3 nanoparticles at the grain boundaries. The presence of Al2O3 nanoparticles at the grain boundaries possibly reduced the number of flux pinning centers, which were present in the form of weak links in the pure CuTl-1223 superconducting matrix. The increase in the values of inter-grain coupling (?) deduced from the fluctuation induced conductivity analysis with the increased concentration of Al2O3 nanoparticles is a theoretical evidence of improved inter-grain coupling.

Jabbar, Abdul; Qasim, Irfan; Mumtaz, M.; Zubair, M.; Nadeem, K.; Khurram, A. A.

2014-05-01

286

Color superconductivity with determinant interaction in strange quark matter  

E-print Network

We investigate the effect of six fermion determinant interaction on color superconductivity as well as on chiral symmetry breaking. Coupled mass gap equations and the superconducting gap equation are derived through the minimisation of the thermodynamic potential. The effect of nonzero quark -- antiquark condensates on the superconducting gap is derived. This becomes particularly relevant for the case of 2-flavor superconducting matter with unpaired strange quarks in the diquark channel. While the effect of six fermion interaction leads to an enhancement of u-d superconductivity, due to nonvanishing strange quark--antiquark condensates, such an enhancement will be absent at higher densities for u-s or d-s superconductivity due to early (almost) vanishing of light quark-- antiquark condensates.

Amruta Mishra; Hiranmaya Mishra

2006-05-21

287

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

SciTech Connect

Among the accelerator projects under construction at the Relativistic Heavy Ion Collider (RHIC) is an R and D energy recovery LINAC (ERL) test facility. The ERL includes both a five-cell superconducting cavity as well as a superconducting, photoinjector electron gun. Because of the high-charge and high-current demands, effective higher-order mode (HOM) damping is essential, and several strategies are being pursued. Among these is the use of the fundamental power couplers as a means for damping some HOMs. Simulation studies have shown that the power couplers can play a substantial role in damping certain HOMs, and this presentation discusses these studies along with measurements.

Hammons, L.; Hahn, H.

2011-03-28

288

The gap function in YBa[sub 2]Cu[sub 3]O[sub 7  

SciTech Connect

The authors have solved the four-dimensional anisotropic Eliashberg gap equation for YBa[sub 2]Cu[sub 3]O[sub 7] (YBCO) using the calculated electronic structure and the electron-phonon interaction matrix elements. The calculated [Tc] for YBCO is about 89 K for [mu][sup *] = 0.1. At or slightly above the transition temperature [Tc], the real part of the gap function [Delta]([kappa], 0), for all the [kappa]-points on the Fermi surface, becomes zero and the material is not superconducting. However, the energy gap function [Delta]([kappa], [omega]) is still nonzero for [omega] > 0 for some electronic states, leading to a pseudo-gap behavior in YBCO.

Zhao, G.L.; Bagayoko, D. (Southern Univ. and A and M College, Baton Rouge, LA (United States). Physics Dept.)

1998-12-20

289

Effective interactions and superfluid energy gaps for low density neutron matter  

NASA Astrophysics Data System (ADS)

We use a polarization potential approach to calculate properties of neutron matter at sub-nuclear densities with particular attention to the superfluid pairing interaction. Our model divides the quasi-particle scattering amplitude at the Fermi surface into two distinct parts: a direct particle-hole irreducible piece and an induced particle-hole reducible contribution. The direct part is constructed from realistic two-nucleon potentials. Short-range correlations are taken into account phenomenologically by modifying the potentials at short distances. The induced contribution is generated as a self-consistent summation of particle-hole reducible diagrams. The resulting quasi-particle scattering amplitude is fully antisymmetric for all moment 0? q?2 kF. Realistic bounds on the s-wave pairing gap are given and consequences for the dynamics of rotating neutron stars are briefly discussed.

Ainsworth, T. L.; Wambach, J.; Pines, D.

1989-05-01

290

Ab-Initio Calculations of Superconducting Properties of YBa2Cu3 O7  

Microsoft Academic Search

We present ab-initio calculations for the electronic structure and superconducting properties of YBa2 Cu3O7 (YBCO). The electronic structure was calculated using a self-consistent ab-initio LCAO method. We solved the anisotropic Eliashberg gap equation numerically. The strong coupling of the high energy optical phonons around 60-73 meV, with the electrons at the Fermi surface, leads to a high Tc in YBCO.

G. L. Zhao; D. Bagayoko

1999-01-01

291

Superconducting phases of Bi and Ga induced by deposition on a Ni sublayer  

Microsoft Academic Search

Thin films of Bi and Ga deposited at 300 K on thin Ni underlayers are strongly coupled superconductors at liquid-helium temperature. A layer of 0.1-5.0 nm of Ni apparently seeds a superconducting phase in each of these metals. For Bi films Tc<=4 K, with an energy gap 2Delta<=1.30 meV; for Ga films Tc<=7 K and 2Delta<=2.30 meV. For both elements

J. S. Moodera; R. Meservey

1990-01-01

292

Direct evidence for efficient energy transfer from N-related defects to PGa antisite complexes in GaP from optically detected magnetic resonance  

Microsoft Academic Search

The first direct evidence for highly efficient energy migration from N-related ``shallow'' defects to ``deep'' antisite-related complexes in GaP is presented. The efficiency of excitation-transfer processes is studied via the dye-laser-excited excitation spectra of the resonance signals observed in optically detected magnetic resonance (ODMR). On the basis of such ODMR excitation spectra, it is proved directly that the green GaP

W. M. Chen; M. Godlewski; B. Monemar

1987-01-01

293

Superconducting Microelectronics.  

ERIC Educational Resources Information Center

Discusses superconducting microelectronics based on the Josephson effect and its advantages over conventional integrated circuits in speed and sensitivity. Considers present uses in standards laboratories (voltage) and in measuring weak magnetic fields. Also considers future applications in superfast computer circuitry using Superconducting

Henry, Richard W.

1984-01-01

294

Superconducting structure  

DOEpatents

A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

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

2003-04-01

295

Superconducting Structure  

DOEpatents

A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

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

2005-09-13

296

Electronic characterization of defects in narrow gap semiconductors: Comparison of electronic energy levels and formation energies in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide  

NASA Technical Reports Server (NTRS)

The project has evolved to that of using Green's functions to predict properties of deep defects in narrow gap materials. Deep defects are now defined as originating from short range potentials and are often located near the middle of the energy gap. They are important because they affect the lifetime of charge carriers and hence the switching time of transistors. We are now moving into the arena of predicting formation energies of deep defects. This will also allow us to make predictions about the relative concentrations of the defects that could be expected at a given temperature. The narrow gap materials mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS) are of interest to NASA because they have commercial value for infrared detecting materials, and because there is a good possibility that they can be grown better in a microgravity environment. The uniform growth of these crystals on earth is difficult because of convection (caused by solute depletion just ahead of the growing interface, and also due to thermal gradients). In general it is very difficult to grow crystals with both radial and axial homogeneity.

Patterson, James D.; Li, Wei-Gang

1995-01-01

297

Picosecond hot-electron energy relaxation in NbN superconducting photodetectors  

NASA Astrophysics Data System (ADS)

We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron-phonon scattering time ?e-ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time ?es decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, ?e-ph and ?es, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of ?e-ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/-3) GHz if one eliminates the bolometric phonon-heating effect.

Il'in, K. S.; Lindgren, M.; Currie, M.; Semenov, A. D.; Gol'tsman, G. N.; Sobolewski, Roman; Cherednichenko, S. I.; Gershenzon, E. M.

2000-05-01

298

Superconducting terahertz metamaterials  

SciTech Connect

During the past ten years subwavelength metallic structures have enabled metamaterials exhibiting exotic physical properties that are not possible or difficult to realize using naturally occurring materials, This bottom-up metamaterial approach is particularly attractive in the terahertz (THz) frequency range, where the THz gap is inherently associated with the lack of materials with appropriate reponse. In fact THz metamaterial devices have accomplished unprecedented performance towards practical applications. In these devices, the key is to incorporate natural materials, e,g, semiconductors, as the metamaterial substrates or integration parts of metamaterial structures. The active or dynamic tunability of metamaterials is through the application of external stimuli such as temperature, photoexcitation, or electric field. to modify the capacitive gaps in split-ring resonators (SRRs), It becomes clear that we would not be able to do much on the metallic SRRs, i.e. the metal conductivity and therefore the inductance largely remain constant not affected by external stimuli. Recently, there has been increasing interest in superconducting metamaterials towards loss reduction. Significant Joule losses have often prevented resonant metal metamaterials from achieving proposed applications. particularly in the optical frequency range. At low temperatures, superconducting materials possess superior conductivity than metals at frequencies up to THz. and therefore it is expected that superconducting melamaterials will have a lower loss than metal metamatetials, More interestingly, superconductors exhibit tunable complex conductivity over a wide range of values through change of temperature and application of photoexcitation, electrical currents and magnetic fields. Therefore, we would expect correspondingly tunable metamaterials. which originate from the superconducting materials composing the metamaterial, in contrast to tuning the metamaterial embedded environment.

Chen, Hou-tong [Los Alamos National Laboratory; Singh, Ranjan [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Azad, Abul K [Los Alamos National Laboratory; Trugman, Stuart A [Los Alamos National Laboratory; Jia, Quanxi [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory

2010-01-01

299

Large-gap magnetic suspension systems  

NASA Technical Reports Server (NTRS)

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

Britcher, Colin P.

1992-01-01

300

Superconducting accelerating structures for very low velocity ion beams  

SciTech Connect

This paper presents designs for four types of very-low-velocity superconducting accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006 < v/c < 0.06. Superconducting TEM-class cavities have been widely applied to CW acceleration of ion beams. SC linacs can be formed as an array of independently-phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the US and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front-end of such linacs, particularly for the post-acceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008 < {beta} = v/c < 0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

Xu, J.; Shepard, K.W.; Ostroumov, P.N.; Fuerst, J.D.; Waldschmidt, G.; /Argonne; Gonin, I.V.; /Fermilab

2008-01-01

301

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

USGS Publications Warehouse

To investigate the behavior of the fracture energy associated with expanding the rupture zone of an earthquake, we have used the results of a large-scale, biaxial stick-slip friction experiment to set the parameters of an equivalent dynamic rupture model. This model is determined by matching the fault slip, the static stress drop and the apparent stress. After confirming that the fracture energy associated with this model earthquake is in reasonable agreement with corresponding laboratory values, we can use it to determine fracture energies for earthquakes as functions of stress drop, rupture velocity and fault slip. If we take account of the state of stress at seismogenic depths, the model extrapolation to larger fault slips yields fracture energies that agree with independent estimates by others based on dynamic rupture models for large earthquakes. For fixed stress drop and rupture speed, the fracture energy scales linearly with fault slip.

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

2004-01-01

302

Method for obtaining large levitation pressure in superconducting magnetic bearings  

DOEpatents

A method and apparatus are disclosed for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap. 4 figs.

Hull, J.R.

1996-10-08

303

Method for obtaining large levitation pressure in superconducting magnetic bearings  

DOEpatents

A method and apparatus for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap.

Hull, John R. (Hinsdale, IL)

1996-01-01

304

Interpretation of the temperature dependence of conductivity in superconducting oxides  

SciTech Connect

The diverse variations of the conductivities vs. temperature observed in oxide superconductors can be interpreted with a model based on microcanonical ensembles of a semiconductor and a semimetal originally derived for organic radical cation salts. The equation for the model transverses, through the variations of the Fermi and gap energies and a scattering factor, the range from a semiconductor to a semimetal and defines quantitatively the boundary between the two corresponding to the optimum superconducting state. Therein it describes quantitatively the roles of composition and pressure in determining the onset of the superconducting state. An examination of the published resistivity curves vs. temperature for La/sub 2-x/A/sub x/CuO/sub 4-delta/ and YBa/sub 2/Cu/sub 3/O/sub 6.5 + delta/ yield information consistent with the model and relevant to the defects and range of homogeneity needed for phase diagrams. 5 figs., 22 refs.

Thorn, R.J.

1987-01-01

305

New theory of superconductivity. Method of equilibrium density matrix  

E-print Network

A new variational method for studying the equilibrium states of an interacting particles system has been proposed. The statistical description of the system is realized by means of a density matrix. This method is used for description of conduction electrons in metals. An integral equation for the electron distribution function over wave vectors has been obtained. The solutions of this equation have been found for those cases where the single-particle Hamiltonian and the electron interaction Hamiltonian can be approximated by a quite simple expression. It is shown that the distribution function at temperatures below the critical value possesses previously unknown features which allow to explain the superconductivity of metals and presence of a gap in the energy spectrum of superconducting electrons.

Bondarev, Boris

2014-01-01

306

Gap Junctions  

PubMed Central

Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

2013-01-01

307

Superconductivity and the Pseudogap in the 2d Hubbard model  

NASA Astrophysics Data System (ADS)

Using a numerically exact continuous-time quantum Monte Carlo impurity solver and the DCA cluster dynamical mean field method with cluster sizes up to 16, we have been able to access the superconducting phase of the two dimensional Hubbard model for parameters believed to be relevant to high temperature copper oxide superconductivity. We present results for the phase diagram, the gap to transition temperature ratio, and the interplay of the pseudogap and the superconducting gap. The gap results are obtained by direct inference from imaginary frequency data and analytically continued spectral functions.

Gull, Emanuel; Parcollet, Olivier; Millis, Andrew J.

2012-02-01

308

Fermi Liquid Theory on Transport Phenomena in the Superconducting State  

NASA Astrophysics Data System (ADS)

Transport phenomena in the superconducting state are discussed microscopically on the basis of Fermi liquid theory. In this paper we put an emphasis on many body effects. The optical conductivity is shown to have the correction to a current vertex which is explicitly temperature dependent. This current vertex cannot be identified with the velocity of quasiparticles as in the normal state. From these arguments it is concluded that validity of applying results obtained in the normal state simply to the superconducting state is an issue to be carefully studied and not guaranteed in some cases. Several quantities basic in Fermi liquid theory (the renormalization factor, the velocity of quasiparticles and the relation which holds in Galilean invariant case) which have been assumed to hold and given as external parameters in previous works are derived by using Ward-Takahashi identities. These derivations justify the arguments based on the Fermi liquid theory. The many body effect on magnetic field penetration depth is also discussed and an emphasis is put on the difference between this quantity and the superconducting carrier density. By putting together the results obtained for the electromagnetic response case, it is shown that the weight of coherent part which couples to the electromagnetic field is conserved from the normal state to the superconducting state. Thermal conductivity is derived microscopically and the current vertex is shown to be written by the energy current of Bogoliubov quasiparticles. This fact is important for superconductors with anisotropic gaps.

Jujo, Takanobu

2001-05-01

309

Thin superconducting film characterization by surface acoustic waves  

NASA Astrophysics Data System (ADS)

Both the dc electrical resistivity and the attenuation of surface acoustic waves (SAW) were measured in the superconducting state of a granular lead film as a function of an applied magnetic field normal to the film plane. At 4.2 K the data appear to yield an upper critical of about 60 K Gauss and a lower critical field of about 20 K Gauss. A theoretical model that takes into account renormalization has been developed for explaining the SAW attenuation in a superconducting NbN film with a sheet resistivity of 30 k ohms/sq. Bulk ultrasonic measurements in the ferromagnetic superconductors Er(x)Ho(1-x)Rh4B4 indicate that spin phonon interaction increases in the superconducting state of these ternary compounds. Ultrasonic measurements in very pure vanadium single crystals provide low temperature data which yield a zero temperature energy gap 2 Delta(0) that is very close to the BCS value of 3.5 kT sub c but the data close to the superconducting transition temperature T sub c would yield 2 Delta (0) = 4.2 kT sub c. A theoretical model is being investigated to ascertain if it will resolve this apparent discrepancy.

Levy, M.

1985-04-01

310

Comparison of predictions of interpolation equations with experimental values of lattice parameter and energy gap for some multicomponent alloys  

NASA Astrophysics Data System (ADS)

The interpolation equations which may be used to predict properties of two composition variable semiconductor alloys such as (A1-xBx)(C1-yDy) and (AxByC1-x-y)D are reviewed and the former developed to cover the case of three variable alloys of the form (A1-xBx)(C1-yDy) (E1-zFz). The predictions of these various equations are then compared with experimental values of lattice parameters and energy gaps in the alloy systems (Cu1-xAg)(Ga1-yIny)(Se1-zTez)2 and (CdxZnyMn1-x-y)Te. The fit and appropriateness of each equation is discussed.

Avon, Julie E.; Donofrio, Tom; Woolley, John C.

1984-04-01

311

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

Microsoft Academic Search

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

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

2000-01-01

312

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

NASA Astrophysics Data System (ADS)

The thickness dependence of the superconducting energy gap ?La of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ?La and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

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

2014-10-01

313

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

PubMed

The thickness dependence of the superconducting energy gap ?La of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ?La and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here. PMID:25272968

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

2014-10-22

314

Evidence of multiband superconductivity in the ?-phase Mo1?xRex alloys  

NASA Astrophysics Data System (ADS)

We present a detailed study of the superconducting properties in the ?-phase Mo1?xRex (x = 0.25 and 0.4) solid solution alloys pursued through magnetization and heat capacity measurements. The temperature dependence of the upper critical field HC2(T) in these binary alloys shows a deviation from the prediction of the Werthamer–Helfand–Hohenberg (WHH) theory. The temperature dependence of superfluid density estimated from the variation of lower critical field HC1 with temperature, cannot be explained within the framework of a single superconducting energy gap. The heat capacity also shows an anomalous feature in its temperature dependence. All these results can be reasonably explained by considering the existence of two superconducting energy gaps in these Mo1?xRex alloys. Initial results of electronic structure calculations and resonant photoelectron spectroscopy measurements support this possibility and suggest that the Re-5d like states at the Fermi level may not intermix with the Mo-5p and 5s like states in the ?-phase Mo1?xRex alloys and contribute quite distinctly to the superconductivity of these alloys.

Sundar, Shyam; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Roy, S. B.

2015-02-01

315

Evidence of multiband superconductivity in the ?-phase Mo1-xRex alloys.  

PubMed

We present a detailed study of the superconducting properties in the ?-phase Mo1-xRex (x = 0.25 and 0.4) solid solution alloys pursued through magnetization and heat capacity measurements. The temperature dependence of the upper critical field HC2(T) in these binary alloys shows a deviation from the prediction of the Werthamer-Helfand-Hohenberg (WHH) theory. The temperature dependence of superfluid density estimated from the variation of lower critical field HC1 with temperature, cannot be explained within the framework of a single superconducting energy gap. The heat capacity also shows an anomalous feature in its temperature dependence. All these results can be reasonably explained by considering the existence of two superconducting energy gaps in these Mo1-xRex alloys. Initial results of electronic structure calculations and resonant photoelectron spectroscopy measurements support this possibility and suggest that the Re-5d like states at the Fermi level may not intermix with the Mo-5p and 5s like states in the ?-phase Mo1-xRex alloys and contribute quite distinctly to the superconductivity of these alloys. PMID:25563211

Sundar, Shyam; Sharath Chandra, L S; Chattopadhyay, M K; Roy, S B

2015-02-01

316

Imaging the Electron-Boson Coupling in Superconducting FeSe Films Using a Scanning Tunneling Microscope  

NASA Astrophysics Data System (ADS)

Scanning tunneling spectroscopy has been used to reveal signatures of a bosonic mode in the local quasiparticle density of states of superconducting FeSe films. The mode appears below Tc as a "dip-hump" feature at energy ? ˜4.7kBTc beyond the superconducting gap ?. Spectra on strained regions of the FeSe films reveal simultaneous decreases in ? and ?. This contrasts with all previous reports on other high-Tc superconductors, where ? locally anticorrelates with ?. A local strong coupling model is found to reconcile the discrepancy well, and to provide a unified picture of the electron-boson coupling in unconventional superconductors.

Song, Can-Li; Wang, Yi-Lin; Jiang, Ye-Ping; Li, Zhi; Wang, Lili; He, Ke; Chen, Xi; Hoffman, Jennifer E.; Ma, Xu-Cun; Xue, Qi-Kun

2014-02-01

317

Proximity-induced superconductivity effect in a double-stranded DNA  

SciTech Connect

We study the proximity-induced superconductivity effect in a double-stranded DNA by solving the Bogoliubov-de Gennes equations and taking into account the effect of thermal fluctuations of the twist angle between neighboring base pairs. We show that the electron conductance is spin-dependent and the conductance of spin up (down) increases (decreases) due to the spin-orbit coupling (SOC). It is found that, for T?gap energy is temperature-independent and it decreases due to the SOC. In addition, by solving the Bogoliubov-de Gennes equations and local gap parameter equation self-consistently, we find the critical temperature at which transition to superconductivity can take place.

Simchi, Hamidreza, E-mail: simchi@iust.ac.ir [Department of Physics, Iran University of Science and Technology, Narrmak, Tehran 16844 (Iran, Islamic Republic of); Semiconductor Technology Center, Tehran (Iran, Islamic Republic of); Esmaeilzadeh, Mahdi, E-mail: mahdi@iust.ac.ir; Mazidabadi, Hossein [Department of Physics, Iran University of Science and Technology, Narrmak, Tehran 16844 (Iran, Islamic Republic of)

2014-02-07

318

Modulating Sub-THz Radiation with Current in Superconducting Metamaterial  

NASA Astrophysics Data System (ADS)

We show that subterahertz transmission of the superconducting metamaterial, an interlinked two-dimensional network of subwavelength resonators connected by a continuous superconducting wire loop, can be dynamically modulated by passing electrical current through it. We have identified the main mechanisms of modulation that correspond to the suppression of the superconductivity in the network by magnetic field and heat dissipation. Using the metamaterial fabricated from thin niobium film, we were able to demonstrate a transmission modulation depth of up to 45% and a bandwidth of at least 100 kHz. The demonstrated approach may be implemented with other superconducting materials at frequencies below the superconducting gap in the THz and subterahertz bands.

Savinov, V.; Fedotov, V. A.; Anlage, S. M.; de Groot, P. A. J.; Zheludev, N. I.

2012-12-01

319

Physica E 32 (2006) 1416 Tuning the cross-gap transition energy of a quantum dot  

E-print Network

Available online 3 February 2006 Abstract We show that a piezoelectric actuator can be used to apply energy by using uniaxial strain. The strain is applied by glueing the sample to a piezoelectric actuator resistance bridge circuit in combination with a lock in amplifier is used to measure the change in resistance

Ludwig-Maximilians-Universität, München

320

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

SciTech Connect

Here we present Spitzer Space Telescope imaging of Cyg A with the Infrared Array Camera at 4.5 {micro}m and 8.0 {micro}m, resulting in the detection of the high-energy tails or cut-offs in the synchrotron spectra for all four hotspots of this archetype radio galaxy. When combined with the other data collected (and re-analyzed) from the literature, our observations allow for detailed modeling of the broad-band (radio-to-X-ray) emission for the brightest spots A and D. We confirm that the X-ray flux detected previously from these features is consistent with the synchrotron self-Compton radiation for the magnetic field intensity B {approx} 170 {micro}G in spot A, and B {approx} 270 {micro}G in spot D. We also find that the energy density of the emitting electrons is most likely larger by a factor of a few than the energy density of the hotspots magnetic field. We construct energy spectra of the radiating ultrarelativistic electrons. We find that for both hotspots A and D these spectra are consistent with a broken power-law extending from at least 100MeV up to {approx} 100GeV, and that the spectral break corresponds almost exactly to the proton rest energy of {approx} 1GeV. We argue that the shape of the electron continuum most likely reflects two different regimes of the electron acceleration process taking place at mildly relativistic shocks, rather than resulting from radiative cooling and/or absorption e.ects. In this picture the protons inertia defines the critical energy for the hotspot electrons above which Fermi-type acceleration processes may play a major role, but below which the operating acceleration mechanism has to be of a different type. At energies {approx}> 100 GeV, the electron spectra cut-off/steepen again, most likely as a result of spectral aging due to radiative loss effects. We discuss several implications of the presented analysis for the physics of extragalactic jets.

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

2007-03-06

321

Novel triplet host materials with high energy gap and thermal stability for organic electrophosphorescent devices  

NASA Astrophysics Data System (ADS)

Organic electrophosphorescent materials and devices are the prime focus of organic light-emitting diodes research due to their high external quantum efficiency and power efficiency. The host materials with both high triplet energy level and high thermal stability are especially formidable for blue phosphorescent emitters. Herewith we report a novel triplet host material based on fluorene, 9,9-bis(4'-carbazol-phenyl)fluorene (CPF), in which two phenyl-carbazole moieties are connected to C9 carbon of the fluorene. This compound possesses not only desirably high triplet (2.9 eV) energies, but also extremely high glass transition temperature (Tg = 165 °C) and thermal stability. By using CPF as the host material, blue-emitting phosphorescent devices exhibited much higher efficiency and longer lifetime than those with CBP host.

Qiao, Juan; Wang, Li D.; Qiu, Yong

2006-04-01

322

Flavor Superconductivity & Superfluidity  

E-print Network

In these lecture notes we derive a generic holographic string theory realization of a p-wave superconductor and superfluid. For this purpose we also review basic D-brane physics, gauge/gravity methods at finite temperature, key concepts of superconductivity and recent progress in distinct realizations of holographic superconductors and superfluids. Then we focus on a D3/D7-brane construction yielding a superconducting or superfluid vector-condensate. The corresponding gauge theory is 3+1-dimensional N=2 supersymmetric Yang-Mills theory with SU(N) color and SU(2) flavor symmetry. It shows a second order phase transition to a phase in which a U(1) subgroup of the SU(2) symmetry is spontaneously broken and typical superconductivity signatures emerge, such as a conductivity (pseudo-)gap and the Meissner-Ochsenfeld effect. Condensates of this nature are comparable to those recently found experimentally in p-wave superconductors such as a ruthenate compound. A string picture of the pairing mechanism and condensation is given using the exact knowledge of the corresponding field theory degrees of freedom.

Matthias Kaminski

2010-02-25

323

Design of 57.5 MHz CW RFQ for medium energy heavy ion superconducting linac.  

SciTech Connect

The nuclear science community considers the construction of the Rare Isotope Accelerator (RIA) facility as a top priority. The RIA includes a 1.4 GV superconducting linac for production of 400 kW cw heavy ion beams. The initial acceleration of heavy ions delivered from an electron cyclotron resonance ion source can be effectively performed by a 57.5 MHz 4-m long room temperature RFQ. The principal specifications of the RFQ are (i) formation of extremely low longitudinal emittance, (ii) stable operation over a wide range of voltage for acceleration of various ion species needed for RIA operation, and (iii) simultaneous acceleration of two-charge states of uranium ions. cw operation of an accelerating structure leads to a number of requirements for the resonators such as high shunt impedance, efficient water cooling of all parts of the resonant cavity, mechanical stability together with precise alignment, reliable rf contacts, a stable operating mode, and fine tuning of the resonant frequency during operation. To satisfy these requirements a new resonant structure has been developed. This paper discusses the beam dynamics and electrodynamics design of the RFQ cavity, as well as some aspects of the mechanical design of the low-frequency cw RFQ.

Ostroumov, P. N.; Kolomiets, A. A.; Kashinsky, D. A.; Minaev, S. A.; Pershin, V. I.; Tretyakova, T. E.; Yaramishev, S. G.; Physics; Inst. of Theoretical and Experimental Physics

2002-06-01

324

Superconducting dipole magnet requirements for the Fermilab Phase 3 upgrade, SSC high energy booster, and Fermilab independent collider  

SciTech Connect

In July 1988 a small working group was formed to develop a conceptual design for a high field superconducting dipole magnet suitable for use in the Phase III upgrade at Fermilab. The Phase III upgrade calls for replacement of the existing Tevatron with higher field magnets to boost the energy of the fixed target program to 1.5 TeV and to add a 1.8 TeV collider program. As the work of this group evolved it became clear that the resulting design might be applicable to more than just the proposed upgrade. In particular, it seemed plausible that the work might be applicable to the high energy booster (HEB) for the SSC. At the Breckenridge Workshop in August 1989 interest in a third project began to surface, namely the revamping of an earlier proposal for a dedicated collider at Fermilab. We refer to this proposal as the FNAL Independent Collider. The requirements for the dipole magnets for this independent collider appear to be remarkably similar to those proposed for the Phase III upgrade and the SSC HEB. The purpose of this report is to compare the conceptual design of the dipoles developed for the Phase III proposal with the requirements of those for the SSC HEB, the FNAL Independent Collider, and a hybrid design which could serve the needs of both. The Phase III design will be used as the reference point for parameter scaling. 4 figs., 3 tabs.

Nicol, T.H.; Kerby, J.S.

1989-09-01

325

Numerical simulation and analysis of energy loss in a nanosecond spark gap switch  

NASA Astrophysics Data System (ADS)

A system of differential equations for the RLC circuit of a capacitor-switch assembly was derived being supplemented with an equation for the spark resistance of the switch in accordance with the Braginsky model. The parameters that affect the solutions of equations for the circuit with parallel or series connection of several capacitor-switch assemblies to a common inductive load were determined. Based on numerical solution of the system of equations, a dependence of the energy ES released in the spark within the first halfperiod on the discharge circuit and switch parameters was found.

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

2014-11-01

326

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

USGS Publications Warehouse

Adult blueback herring Alosa aestivalis (N = 116) were collected during the 1999, 2000, and 2002-2004 spawning runs from sites on the Hudson and Mohawk rivers, and gut contents were analyzed. Thirty-four fish (33% of those examined) were found to contain food material. Food items were present in 41% of Mohawk River samples and 11% of Hudson River samples; all Hudson River fish containing food were captured in small tributaries above the head of tide. Hudson River fish predominantly consumed zooplankton, while Mohawk River fish consumed benthic aquatic insects in large quantities, including Baetidae, Ephemeridae, and Chironomidae. Using stable isotope analysis and a mixing model, we found that fish collected later in the season had significantly decreased marine-derived C. Condition indices of later-season fish were equal to or greater than those of fish collected earlier in the season. Blueback herring in this system may face increased energy requirements as they migrate farther upstream during spawning runs, and feeding may provide energy subsidies needed to maintain fitness over their expanded migratory range. ?? Copyright by the American Fisheries Society 2007.

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

2007-01-01

327

Superconducting Storage Cavity for RHIC  

SciTech Connect

This document provides a top-level description of a superconducting cavity designed to store hadron beams in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It refers to more detailed documents covering the various issues in designing, constructing and operating this cavity. The superconducting storage cavity is designed to operate at a harmonic of the bunch frequency of RHIC at a relatively low frequency of 56 MHz. The current storage cavities of RHIC operate at 197 MHz and are normal-conducting. The use of a superconducting cavity allows for a high gap voltage, over 2 MV. The combination of a high voltage and low frequency provides various advantages stemming from the resulting large longitudinal acceptance bucket.

Ben-Zvi,I.

2009-01-02

328

Band gaps and band offsets in the SiO2/Si interface calculated by including the self-energy of electrons and holes  

NASA Astrophysics Data System (ADS)

Density Functional theory, as formulated by Kohn and Sham (Phys. Rev. 140, A1133 (1965)), is insufficient when it comes to the calculation of one-particle excitations (electrons and holes). In this case, one has to include the self-energy of the particle (see for instance R. G'omez- Abal. et al Phys. Rev. Lett. 101, 106404 (2008)). This self-energy is mostly the classical electrostatic self-energy of the particle charge density but has an important contribution from exchange and correlation. In a recent paper (L. G. Ferreira et al, Phys. Rev. B 78, 125116 (2008)), it is shown that the self-energy can be calculated with the help of a ``self-energy potential'', wholly derived from pure atomic calculations. The band gaps calculated with those self-energies are precise, in no way worse than the GW band gaps, and yet the calculation is very simple and fast. Next challenge we faced was the calculation of the band-offsets of the all important Si/SiO2 system. Notice that the ``self-energy potential'' is centered between two covalent bonded atoms in the Si side and centered at the O in the SiO2 side. Then the question is whether these self-energy potential perturbations create a wrong charge density at the interface. The answer is that both gaps and band offsets were calculated with outstanding quality.

Ferreira, Luiz; Fonseca, Leonardo; Ribeiro, Mauro, Jr.

2009-03-01

329

Making Superconducting Welds between Superconducting Wires  

NASA Technical Reports Server (NTRS)

A technique for making superconducting joints between wires made of dissimilar superconducting metals has been devised. The technique is especially suitable for fabrication of superconducting circuits needed to support persistent electric currents in electromagnets in diverse cryogenic applications. Examples of such electromagnets include those in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) systems and in superconducting quantum interference devices (SQUIDs). Sometimes, it is desirable to fabricate different parts of a persistent-current-supporting superconducting loop from different metals. For example, a sensory coil in a SQUID might be made of Pb, a Pb/Sn alloy, or a Cu wire plated with Pb/Sn, while the connections to the sensory coil might be made via Nb or Nb/Ti wires. Conventional wire-bonding techniques, including resistance spot welding and pressed contact, are not workable because of large differences between the hardnesses and melting temperatures of the different metals. The present technique is not subject to this limitation. The present technique involves the use (1) of a cheap, miniature, easy-to-operate, capacitor-discharging welding apparatus that has an Nb or Nb/Ti tip and operates with a continuous local flow of gaseous helium and (2) preparation of a joint in a special spark-discharge welding geometry. In a typical application, a piece of Nb foil about 25 m thick is rolled to form a tube, into which is inserted a wire that one seeks to weld to the tube (see figure). The tube can be slightly crimped for mechanical stability. Then a spark weld is made by use of the aforementioned apparatus with energy and time settings chosen to melt a small section of the niobium foil. The energy setting corresponds to the setting of a voltage to which the capacitor is charged. In an experiment, the technique was used to weld an Nb foil to a copper wire coated with a Pb/Sn soft solder, which is superconducting. The joint was evaluated as part of a persistent-current circuit having an inductance of 1 mH. A current was induced in a loop, and no attenuation of the current after a time interval 1,000 s was discernible in a measurement having a fractional accuracy of 10(exp -4): This observation supports the conclusion that the weld had an electrical resistance <10(exp -10) omega.

Penanen, Konstantin I.; Eom, Byeong Ho

2008-01-01

330

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

E-print Network

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

Goddard III, William A.

331

J. Phys. Chem. 1990, 94, 6963-6969 6963 Singlet-Triplet Energy Gaps in Chlorine-Substituted Methylenes and Silylenest  

E-print Network

J. Phys. Chem. 1990, 94, 6963-6969 6963 Singlet-Triplet Energy Gaps in Chlorine: August 11. 1989; In Final Form: March 12, 1990) The singlet-triplet splittingsof chlorine-consistentconfiguration interaction (DCCI) method. All chlorine-substituted methylenes and silylenes have singlet ground states

Goddard III, William A.

332

Superconductivity and magnetism and their interplay in quaternary borocarbides RNi2B2C  

NASA Astrophysics Data System (ADS)

Since 1986, most of the interest in superconductivity became focused on high-Tc cuprates. The discovery of the superconducting quaternary borocarbide system Y Ni B C with Tc as high as?˜12?K inspired research into intermetallic superconductors (IMS) once again. Several reasons can be attributed to this revival of interest in IMS: (i) In the tetragonal quaternary magnetic superconductors RNi2B2C, superconductivity and magnetism occur with Tc and TN?˜?10?K, thereby allowing studies of exotic phenomena associated with, and arising from, the interplay of superconductivity and magnetism. (ii) High TN's and a variety of commensurate and incommensurate magnetic structures in RNi2B2C (Fermi surface nesting playing a central role) strongly suggest that R-spins are coupled via the RKKY-exchange interaction. Hence, unlike in most other magnetic superconductors known so far, conduction electrons take part in superconductivity and magnetism. (iii) Quaternary borocarbides open up new pathways to try and synthesize multicomponent intermetallic superconductors. Their remarkable intrinsic superconducting and magnetic properties and the availability of high quality samples (bulk polycrystalline, large single crystals and thin films) make RNi2B2C particularly special to investigate. Several unusual phenomena have been reported, such as, to name a few, dramatic phonon mode softening at Tc, Hc2(T) exhibiting a positive curvature near Tc and a four-fold anisotropy in the basal plane; a variety of exceptional and fascinating flux line lattice (FLL) related effects — FLL-symmetry transformations and alignments with the underlying crystal lattice as a function of applied field (manifestation of nonlocal electrodynamics despite high ??˜?10, and thermal fluctuation effects even though Tc,?˜?16?K, is not too high) and a four-fold symmetric star-shaped (in real space) vortex core. RNi2B2C are strong coupling s-wave BCS superconductors and, remarkably, have a superconducting gap with extreme anisotropy. Strong experimental evidence shows that the four-fold symmetric superconducting gap has point nodes along the 100- and 10-directions, a feature that has been shown consistent with (s?+?g)-Cooper pairing. An energy gap with such strong anisotropy is unusual for an s-wave superconductor and, hence, calls for a pairing mechanism different from conventional electron phonon coupling. Antiferromagnetic fluctuations possibly play an important role in the mechanism. Magnetic superconductors RNi2B2C (R?=?Dy, Ho, Er, Tm) reveal several phenomena, not observed earlier, associated with the interplay of superconductivity and magnetism. Microscopic evidence (via square FLL interacting with magnetism) of the coexistence of magnetism and superconductivity; intrinsic FLL-pinning by magnetic ions; weak ferromagnetism (local moment) coexisting with superconductivity (down to the lowest temperature) and the spontaneous vortex phase (ErNi2B2C); superconductivity setting in an already magnetically ordered lattice (DyNi2B2C) and pair-breaking by nonmagnetic ions in such materials; rich and complex magnetic structures and double (nearly) re-entrant superconductivity (HoNi2B2C) and changes in the FLL-symmetry in the vicinity of magnetic transition (TmNi2B2C) and 4f-quadrupole ordering (TmNi2B2C) are several exciting phenomena that magnetic superconductors RNi2B2C exhibit.

At the end of this review are indicated some possible further studies in quaternary borocarbide superconductors. These studies may turn out to be important not only with respect to borocarbides themselves but also from the standpoint of superconductivity in general.

Gupta, L. C.

2006-12-01

333

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

NASA Astrophysics Data System (ADS)

An energy recovery LINAC (ERL) is being constructed at Brookhaven National Laboratory that will involve a superconducting LINAC along with a superconducting electron gun, all operating at 703.75 MHz. The ERL will serve as a testbed for the concepts and technologies required to implement future upgrades in the Relativistic Heavy Ion Collider (RHIC). Because of the high current and high charge requirements of the ERL, effective higher-order mode (HOM) damping is an essential component of the ERL research and development program. This thesis focuses on three areas of HOM characterization and damping development: damping of HOMs in the five-cell LINAC, use of the electron gun fundamental power couplers (FPCs) to damp HOMs, and the development of a ceramic/ferrite damper for the electron gun. The five-cell LINAC uses an HOM load lined with ferrite and attached to the beampipe on either side of the cavity. These studies characterized the frequency-dependent nature of the ferrite absorbing material and derived a set of "portable" ferrite parameters that simplified simulation work. Using these "portable" parameters, it was determined that the ferrite absorber is effective in damping the HOMs of the five-cell cavity over a range of frequencies. In addition, higher-order mode damping in the electron gun was studied using the fundamental power couplers. The gun cavity is a superconducting half-cell structure designed to accelerate electrons to an energy of 2.5 MeV and features dual fundamental power couplers. The HOMs of the gun cavity were studied along with the damping capabilities of the FPCs. Simulation studies determined that the FPCs couple strongly to many of the HOMs studied. However, the transition between the coaxial FPCs and the waveguide that feeds power to the FPCs is a "doorknob" type transition, and it was found that this component shows the best transmission qualities between 1 and 2 GHz, thus limiting the damping capabilities of the FPCs to this bandwidth. It remains to be seen how the FPCs will perform under actual conditions. Finally, the development of a ceramic/ferrite damper was described for the electron gun. The damper features a lossless alumina ceramic break surrounded by a ferrite load and was designed to isolate the vacuum chamber from the ferrite tiles. Various studies were conducted using simulation and prototype designs, and it was determined that the ceramic/ferrite load can be effective in damping higher-order modes of the gun cavity. Analytical calculations along with simulation show that the ceramic tends to alter the field distribution of higher-order modes and change the damping qualities depending on the frequency. The effectiveness of the damping for a given mode depends on a variety of factors including the thickness of the ceramic, the spacing between the ceramic and ferrite layers, and the diameter of the inner ceramic surface.

Hammons, Lee Reginald, III

334

Superconducting frustration bit  

NASA Astrophysics Data System (ADS)

A basic design is proposed for a classical bit element of a superconducting circuit that mimics a frustrated multiband superconductor and is composed of an array of ?-Josephson junctions (?-junction). The phase shift of ? provides the lowest energy for one ?-junction, but neither a ? nor a zero phase shift gives the lowest energy for an assembly of ?-junctions. There are two chiral states that can be used to store one bit information. The energy scale for reading and writing to memory is of the same order as the junction energy, and is thus in the same order of the driving energy of the circuit. In addition, random access is also possible.

Tanaka, Y.

2014-10-01

335

Estimating the energy of electric breakdown in air gap between electrolyte and metal electrode  

NASA Astrophysics Data System (ADS)

The influence of induced electric charge (localized on the surface of a suspended copper rod) on the formation of a protrusion (Taylor cone) on the inducing liquid (aqueous solution) surface is considered. At an applied voltage of U ? 12 kV, the protrusion height in the interval of pre-breakdown voltages ( U < U P) is limited by the electric field strength. At U > U P, the growth of protrusion is terminated by an electric discharge, which drives the liquid to oscillate in a broad range of applied voltages U at almost constant multiple frequencies f = f 0 n, which are resonantly switched at certain fixed U values. By measuring the amount of evaporated liquid, the energy (27.8 × 10-3 J) and current (64.9 A) of single discharge were evaluated and the electric capacitance (7.6 × 10-10 F) of a system comprising the water surface and suspended copper electrode was estimated. Serial connection of an additional capacitor (100 ?F) to the copper electrode with induced electric charge leads to a threefold increase in these parameters.

Orlov, A. M.; Yavtushenko, I. O.; Churilov, M. V.

2010-07-01

336

Quantum Tunneling and Heterodyne Detection in Superconducting Tunnel Junctions  

Microsoft Academic Search

The quasiparticle susceptance and conductance of a superconducting tunnel junction was measured including the singularity in the quasiparticle susceptance at the gap voltage. Results are compared to existing theories of superconductive tunneling, and the results agree well with theory. An analogy to a two-level atomic system is developed to explain the photon assisted tunneling process and its dependence on the

Nuray George Ugras

1993-01-01

337

Pseudogap The underdoped region of the temperature doping phase diagram from which cuprate superconductivity  

E-print Network

superconductivity emerges is referred to as the `pseudogap' because evidence exists for partial gapping the masking effects of superconductivity. Quantum Critical Point ­ This identifies the pseudogap in YBa2Cu3O6 is such that it terminates at zero temperature inside the superconducting dome. This indicates that quantum criticality

Weston, Ken

338

Raman spectroscopy on the zigzag graphene nanoribbon Interplay of Antiferromagnetsm and Superconductivity  

E-print Network

and Superconductivity in Bilayer Superconductors Optimal observation time window for forecasting the next earthquake description by two phase variables #12;Topological interference of superconductivity in Pb/Ru/Sr2RuO4-universal superconducting gap structure in iron-pnictides revealed by magnetic penetration depth measurements Quantum

339

Superconducting thermoelectric generator  

DOEpatents

Thermoelectricity is produced by applying a temperature differential to dissimilar electrically conducting or semiconducting materials, thereby producing a voltage that is proportional to the temperature difference. Thermoelectric generators use this effect to directly convert heat into electricity; however, presently-known generators have low efficiencies due to the production of high currents which in turn cause large resistive heating losses. Some thermoelectric generators operate at efficiencies between 4% and 7% in the 800{degrees} to 1200{degrees}C range. According to its major aspects and bradly stated, the present invention is an apparatus and method for producing electricity from heat. In particular, the invention is a thermoelectric generator that juxtaposes a superconducting material and a semiconducting material - so that the superconducting and the semiconducting materials touch - to convert heat energy into electrical energy without resistive losses in the temperature range below the critical temperature of the superconducting material. Preferably, an array of superconducting material is encased in one of several possible configurations within a second material having a high thermal conductivity, preferably a semiconductor, to form a thermoelectric generator.

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

1994-01-01

340

Report of the DOE Office of Energy Research review committee on the Solenoidal Detector Collaboration of the Superconducting Super Collider  

SciTech Connect

At the request of Dr. James F. Decker, Deputy Director of DOE`s Office of Energy Research, a technical review committee was assembled to perform a peer review of the Solenoidal Detector Collaboration (SDC) from October 26 to October 30, 1992, at the Superconducting Super Collider Laboratory (SSCL). The Energy Research Review Committee (ERC) evaluated the technical feasibility, the estimated cost, the proposed construction schedule, and the management arrangements for the SDC detector as documented in the SDC Technical Design Report, SDC Project Cost/Schedule Summary Book, SDC draft Project Management Plan, and other materials prepared for and presented to the Committee by the SDC management. The SDC detector is one of two major detector facilities anticipated at the SSC. The SDC project will be carried out by a worldwide collaboration of almost 1000 scientists, engineers, and managers from over 100 universities, national laboratories, and industries. The SDC will construct a state-of-the-art, general-purpose detector weighing over 26,000 tons and the size of an eight-story building, to perform a broad class of high energy physics experiments at the SSC beginning in the fall of 1999. The design of the SSC detector emphasizes tracking in a strong solenoidal magnetic field to measure charged-particle momenta and to assist in providing good electron and muon identification; identification of neutrinos and other penetrating particles using a hermetic calorimeter; studies of jets of hadrons using both calorimeter and tracking systems; and studies of short-lived particles, such as B mesons, and pattern recognition within complex events using a silicon-based vertex tracking system. These capabilities are the result of the intensive research, development, and design activities undertaken since 1989 by this very large and capable collaboration.

Not Available

1992-11-01

341

Report of the DOE Office of Energy Research review committee on the Solenoidal Detector Collaboration of the Superconducting Super Collider  

SciTech Connect

At the request of Dr. James F. Decker, Deputy Director of DOE's Office of Energy Research, a technical review committee was assembled to perform a peer review of the Solenoidal Detector Collaboration (SDC) from October 26 to October 30, 1992, at the Superconducting Super Collider Laboratory (SSCL). The Energy Research Review Committee (ERC) evaluated the technical feasibility, the estimated cost, the proposed construction schedule, and the management arrangements for the SDC detector as documented in the SDC Technical Design Report, SDC Project Cost/Schedule Summary Book, SDC draft Project Management Plan, and other materials prepared for and presented to the Committee by the SDC management. The SDC detector is one of two major detector facilities anticipated at the SSC. The SDC project will be carried out by a worldwide collaboration of almost 1000 scientists, engineers, and managers from over 100 universities, national laboratories, and industries. The SDC will construct a state-of-the-art, general-purpose detector weighing over 26,000 tons and the size of an eight-story building, to perform a broad class of high energy physics experiments at the SSC beginning in the fall of 1999. The design of the SSC detector emphasizes tracking in a strong solenoidal magnetic field to measure charged-particle momenta and to assist in providing good electron and muon identification; identification of neutrinos and other penetrating particles using a hermetic calorimeter; studies of jets of hadrons using both calorimeter and tracking systems; and studies of short-lived particles, such as B mesons, and pattern recognition within complex events using a silicon-based vertex tracking system. These capabilities are the result of the intensive research, development, and design activities undertaken since 1989 by this very large and capable collaboration.

Not Available

1992-11-01

342

Superconducting magnets  

SciTech Connect

This report provides a self-consistent description of a magnetic field in the aperture of a superconducting magnet and details how this field can be calculated in a magnet with cos theta current distribution in the coils. A description of an apparatus that can be used to measure the field uniformity in the aperture has been given. Finally, a detailed description of the magnet being developed for use in the Superconducting Super Collider is given. When this machine is built, it will be by far the largest application of superconductivity to date and promises to make possible the experimental discoveries needed to understand the basic laws of nature governing the world in which we live.

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

1985-01-01

343

Weak superconductivity  

SciTech Connect

This Proceedings consist of invited papers and contributions presented at the Fifth Czechoslovak Symposium on Weak Superconductivity (5CSSWS) held at Smolenice Castle from May 29 to June 2, 1989. This five-days meeting was organized by the Institute of Electrical Engineering, Electro-Physical Research Center, Slovak Academy of Sciences, Bratislava, in cooperation with the Institute of Measurement and Measuring Techniques, EPRC, SAS, Bratislava and the Institute of Physics, CSAS, in Prague. From the beginning the Czechoslovak activities in weak superconductivity were concerned with preparation and study of properties of weak links based on superconducting thin films of Pb, Nb, and Nb{sub 3}Sn, as well as bulk point contacts and rf SQUIDs for magnetometry. The possibility of application of superconducting weak links with tunnel and bridge junctions in measuring techniques, magnetometry, medicine, metrology, radiometry, etc., were studied. Some of these activities are still in progress. These Proceedings include contributions on the properties of tunnel junctions, electrodynamics of SQUIDs, computer simulation of interferometers, multi-channel magnetometry for biomagnetic applications, etc. The discovery of high T{sub c} superconductivity influenced strongly the topics of 5CSSWS. Most contributions of this volume are devoted to the preparation of high T{sub c} superconductor thin films by vacuum deposition techniques because of their dominant role in technology of cryoelectronic microcircuits. Further, results in the study of physical properties of high T{sub c} superconducting thin films by means of both dc and rf methods, tunnel and microcontact spectroscopy, are documented. Other contributions deal with preparation of rf SQUIDs, radiation detectors, etc.

Benacka, S.; Kedro, M.

1990-01-01

344

Mesoscopic superconductivity in ultrasmall metallic grains  

E-print Network

A nano-scale metallic grain (nanoparticle) with irregular boundaries in which the single-particle dynamics are chaotic is a zero-dimensional system described by the so-called universal Hamiltonian in the limit of a large number of electrons. The interaction part of this Hamiltonian includes a superconducting pairing term and a ferromagnetic exchange term. Spin-orbit scattering breaks spin symmetry and suppresses the exchange interaction term. Of particular interest is the fluctuation-dominated regime, typical of the smallest grains in the experiments, in which the bulk pairing gap is comparable to or smaller than the single-particle mean-level spacing, and the Bardeen-Cooper-Schrieffer (BCS) mean-field theory of superconductivity is no longer valid. Here we study the crossover between the BCS and fluctuation-dominated regimes in two limits. In the absence of spin-orbit scattering, the pairing and exchange interaction terms compete with each other. We describe the signatures of this competition in thermodynamic observables, the heat capacity and spin susceptibility. In the presence of strong spin-orbit scattering, the exchange interaction term can be ignored. We discuss how the magnetic-field response of discrete energy levels in such a nanoparticle is affected by pairing correlations. We identify signatures of pairing correlations in this response, which are detectable even in the fluctuation-dominated regime.

Y. Alhassid; K. N. Nesterov

2014-07-31

345

PREFACE: Superconducting materials Superconducting materials  

NASA Astrophysics Data System (ADS)

The discovery of superconductivity in 1911 was a great milestone in condensed matter physics. This discovery has resulted in an enormous amount of research activity. Collaboration among chemists and physicists, as well as experimentalists and theoreticians has given rise to very rich physics with significant potential applications ranging from electric power transmission to quantum information. Several superconducting materials have been synthesized. Crucial progress was made in 1987 with the discovery of high temperature superconductivity in copper-based compounds (cuprates) which have revealed new fascinating properties. Innovative theoretical tools have been developed to understand the striking features of cuprates which have remained for three decades the 'blue-eyed boy' for researchers in superconductor physics. The history of superconducting materials has been notably marked by the discovery of other compounds, particularly organic superconductors which despite their low critical temperature continue to attract great interest regarding their exotic properties. Last but not least, the recent observation of superconductivity in iron-based materials (pnictides) has renewed hope in reaching room temperature superconductivity. However, despite intense worldwide studies, several features related to this phenomenon remain unveiled. One of the fundamental key questions is the mechanism by which superconductivity takes place. Superconductors continue to hide their 'secret garden'. The new trends in the physics of superconductivity have been one of the two basic topics of the International Conference on Conducting Materials (ICoCoM2010) held in Sousse,Tunisia on 3-7 November 2010 and organized by the Tunisian Physical Society. The conference was a nice opportunity to bring together participants from multidisciplinary domains in the physics of superconductivity. This special section contains papers submitted by participants who gave an oral contribution at ICoCoM2010 and by invited authors selected by the editor. We are grateful to IUPAP, ICTP and the European Office of Aerospace Research and Development, Air Force Office of Scientific Research, United States Air Force Laboratory. We would like to acknowledge the authors for their careful work, and finally we thank Dr L Smith the publisher of Journal of Physics: Condensed Matter for her patience and help. Superconducting materials contents Raman spectrum in the pseudogap phase of the underdoped cuprates: effect of phase coherence and the signature of the KT-type superconducting transitionTao Li and Haijun Liao Pressure effects on Dirac fermions in ?-(BEDT-TTF)2I3Takahiro Himura, Takao Morinari and Takami Tohyama Effect of Zn doping in hole-type 1111 phase (Pr, Sr)FeAsOXiao Lin, Chenyi Shen, Chen Lv, Jianjian Miao, Hao Tan, Guanghan Cao and Zhu-An Xu Superconductivity and ferromagnetism in EuFe2(As1 - xPx)2*Guanghan Cao, Shenggao Xu, Zhi Ren, Shuai Jiang, Chunmu Feng and Zhu'an Xu OInhomogeneous superconductivity in organic conductors: the role of disorder and magnetic fieldS Haddad, S Charfi-Kaddour and J-P Pouget

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

2011-11-01

346

Computer simulation of the energy gap in ZnO- and TiO{sub 2}-based semiconductor photocatalysts  

SciTech Connect

Ab initio calculations of the electronic structures of binary ZnO- and TiO{sub 2}-based oxides are performed to search for optimum dopants for efficient absorption of the visible part of solar radiation. Light elements B, C, and N are chosen for anion substitution. Cation substitution is simulated by 3d elements (Cr, Mn, Fe, Co) and heavy metals (Sn, Sb, Pb, Bi). The electronic structures are calculated by the full-potential linearized augmented plane wave method using the modified Becke-Johnson exchange-correlation potential. Doping is simulated by calculating supercells Zn{sub 15}D{sub 1}O{sub 16}, Zn{sub 16}O{sub 15}D{sub 1}, Ti{sub 15}D{sub 1}O{sub 32}, and Ti{sub 8}O{sub 15}D{sub 1}, where one-sixteenth of the metal (Ti, Zn) or oxygen atoms is replaced by dopant atoms. Carbon and antimony are found to be most effective dopants for ZnO: they form an energy gap {Delta}E = 1.78 and 1.67 eV, respectively. For TiO{sub 2}, nitrogen is the most effective dopant ({Delta}E = 1.76 eV).

Skorikov, N. A., E-mail: nskorikov@gmail.com; Korotin, M. A.; Kurmaev, E. Z. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Cholakh, S. O. [Ural Federal University (Russian Federation)

2012-12-15

347

An approach to control of band gap energy and photoluminescence upon band gap excitation in Pr(3+)-doped perovskites La(1/3)MO3 (M=Nb, Ta):Pr3+.  

PubMed

We synthesized polycrystalline pristine and Pr(3+)-doped perovskites La(1/3)MO(3) (M = Nb, Ta):Pr(3+) and investigated their crystal structure, optical absorption, and luminescence properties. The optical band gap of La(1/3)NbO(3) (3.2 eV) is smaller than that of La(1/3)TaO(3) (3.9 eV), which is primarily due to the difference in electronegativity between Nb and Ta. In La(1/3)NbO(3):Pr(3+), the red emission assigned to the f-f transition of Pr(3+) from the excited (1)D(2) level to the ground (3)H(4) state upon band gap photoexcitation (near-UV) was observed, whereas the f-f transition of Pr(3+) with blue-green emission from the excited (3)P(0) level to the ground (3)H(4) state was quenched. On the other hand, in La(1/3)TaO(3):Pr(3+), the blue-green emission upon band gap photoexcitation was observed. Their differences in emission behavior are attributed to the energy level of the ground and excited states of 4f(2) for Pr(3+), relative to the energy levels of the conduction and valence bands, and the trapped electron state, which mediates the relaxation of electron from the conduction band to the excited state of Pr(3+). La(1/3)NbO(3):Pr(3+) is a candidate red phosphor utilizing near-UV LED chips (e.g., ? = 375 nm) as an excitation source. PMID:21604725

Inaguma, Yoshiyuki; Muronoi, Tsunehiro; Sano, Keiko; Tsuchiya, Takeshi; Mori, Yuki; Katsumata, Tetsuhiro; Mori, Daisuke

2011-06-20

348

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

SciTech Connect

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

Piekarz, Henryk; /Fermilab

2008-02-01

349

Operational Merits of Maritime Superconductivity  

NASA Astrophysics Data System (ADS)

The perspective of superconductivity to transfer currents without loss is very appealing in high power applications. In the maritime sector many machines and systems exist in the roughly 1-100 MW range and the losses are well over 50%, which calls for dramatic efficiency improvements. This paper reports on three studies that aimed at the perspectives of superconductivity in the maritime sector. It is important to realize that the introduction of superconductivity comprises two technology transitions namely firstly electrification i.e. the transition from mechanical drives to electric drives and secondly the transition from normal to superconductive electrical machinery. It is concluded that superconductivity does reduce losses, but its impact on the total energy chain is of little significance compared to the investments and the risk of introducing a very promising but as yet not proven technology in the harsh maritime environment. The main reason of the little impact is that the largest losses are imposed on the system by the fossil fueled generators as prime movers that generate the electricity through mechanical torque. Unless electric power is supplied by an efficient and reliable technology that does not involve mechanical torque with the present losses both normal as well as superconductive electrification of the propulsion will hardly improve energy efficiency or may even reduce it. One exception may be the application of degaussing coils. Still appealing merits of superconductivity do exist, but they are rather related to the behavior of superconductive machines and strong magnetic fields and consequently reduction in volume and mass of machinery or (sometimes radically) better performance. The merits are rather convenience, design flexibility as well as novel applications and capabilities which together yield more adequate systems. These may yield lower operational costs in the long run, but at present the added value of superconductivity rather seems more adequate than cheaper systems.

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

350

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

NASA Technical Reports Server (NTRS)

When energy is deposited in a thin-film cryogenic detector, such as from the absorption of an X-ray, an important feature that determines the energy resolution is the amount of athermal energy that can be lost to the heat bath prior to the elementary excitation systems coming into thermal equilibrium. This form of energy loss will be position-dependent and therefore can limit the detector energy resolution. An understanding of the physical processes that occur when elementary excitations are generated in metal films on dielectric substrates is important for the design and optimization of a number of different types of low temperature detector. We have measured the total energy loss in one relatively simple geometry that allows us to study these processes and compare measurements with calculation based upon a model for the various di.erent processes. We have modeled the athermal phonon energy loss in this device by finding an evolving phonon distribution function that solves the system of kinetic equations for the interacting system of electrons and phonons. Using measurements of device parameters such as the Debye energy and the thermal di.usivity we have calculated the expected energy loss from this detector geometry, and also the position-dependent variation of this loss. We have also calculated the predicted impact on measured spectral line-shapes, and shown that they agree well with measurements. In addition, we have tested this model by using it to predict the performance of a number of other types of detector with di.erent geometries, where good agreement is also found.

Kozorezov, Alexander G.; Lambert, Colin J.; Bandler, Simon R.; Balvin, Manuel A.; Busch, Sarah E.; Sagler, Peter N.; Porst, Jan-Patrick; Smith, Stephen J.; Stevenson, Thomas R.; Sadleir, John E.

2013-01-01

351

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

Padamsee, Hasan S.

2014-10-01

352

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

PubMed

The interface between transition metal compounds provides a rich playground for emergent phenomena. Recently, significantly enhanced superconductivity has been reported for single-layer FeSe on Nb-doped SrTiO3 substrate. Yet it remains mysterious how the interface affects the superconductivity. Here we use in situ angle-resolved photoemission spectroscopy to investigate various FeSe-based heterostructures grown by molecular beam epitaxy, and uncover that electronic correlations and superconducting gap-closing temperature (Tg) are tuned by interfacial effects. Tg up to 75?K is observed in extremely tensile-strained single-layer FeSe on Nb-doped BaTiO3, which sets a record high pairing temperature for both Fe-based superconductor and monolayer-thick films, providing a promising prospect on realizing more cost-effective superconducting device. Moreover, our results exclude the direct correlation between superconductivity and tensile strain or the energy of an interfacial phonon mode, and highlight the critical and non-trivial role of FeSe/oxide interface on the high Tg, which provides new clues for understanding its origin. PMID:25256736

Peng, R; Xu, H C; Tan, S Y; Cao, H Y; Xia, M; Shen, X P; Huang, Z C; Wen, C H P; Song, Q; Zhang, T; Xie, B P; Gong, X G; Feng, D L

2014-01-01

353

Hall conductivity in the normal and superconducting phases of the Rashba system with Zeeman field  

NASA Astrophysics Data System (ADS)

We study the intrinsic Hall conductivity of the ordinary and topological superconducting phases of a Rashba metal in a perpendicular Zeeman field. In this system, the normal metal breaks time reversal symmetry while the superconducting order parameter does not, in contrast to the chiral p -wave superconducting state predicted in the monolayer strontium ruthenate (Sr2RuO4) whose Hall conductivity has been studied extensively. We study the effects of intraband and interband pairing and find there is qualitatively larger change in the intrinsic Hall conductivity when there is interband pairing, with the change in magnitude linear in the pairing gap. We argue that interband pairing leads in general to higher energy costs for the topological phase compared to the topologically trivial phase and thus that the qualitative behavior of the intrinsic Hall conductivity with superconductivity in these systems could provide important clues about the nature of pairing in the superconducting phase and even some hints of whether it is topological or not.

Chung, Suk Bum; Roy, Rahul

2014-12-01

354

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

NASA Astrophysics Data System (ADS)

The universe when the temperature closest to the Big Bang the temperature should be nuclear. Because, after the big bang, instant formation of atoms, nuclei and electrons between the absolute vacuum, the nucleus can not emit energy. (Radioactive elements, except in fact, radiation Yuan Su limited power emitted) which causes atomic nuclei and external temperature difference are so enormous that a large temperature difference reasons, all external particles became closer to the nucleus, affect the motion of electrons. When the conductor conductivity and thus affect the conductivity, the formation of resistance. Assumption that no particles affect the motion of electrons (except outside the nucleus) to form a potential difference will not change after the vector form, is now talking about the phenomenon of superconductivity, and then to introduce general, the gap between atoms in molecules or between small, valence electron number of high temperature superconducting conductors. This theory of atomic nuclei, but also explain the atomic and hydrogen bombs can remain after an explosion Why can release enormous energy reasons. Can also explain the ``super flow'' phenomenon. natural world. Tel 13241375685

Yongquan, Han

2010-10-01

355

Competing effects of surface phonon softening and quantum size effects on the superconducting properties of nanostructured Pb.  

PubMed

The superconducting transition temperature (T(C)) in nanostructured Pb decreases from 7.24 to 6.4 K as the particle size is reduced from 65 to 7 nm, below which superconductivity is lost rather abruptly. In contrast, there is a large enhancement in the upper critical field (H(C2)) in the same size regime. We explore the origin of the unusual robustness of T(C) over such a large particle size range in nanostructured Pb by measuring the temperature dependence of the superconducting energy gap in planar tunnel junctions of Al/Al(2)O(3)/nano-Pb. We show that below 22 nm, the electron-phonon coupling strength increases monotonically with decreasing particle size, and almost exactly compensates for the quantum size effect, which is expected to suppress T(C). PMID:21825535

Bose, Sangita; Galande, Charudatta; Chockalingam, S P; Banerjee, Rajarshi; Raychaudhuri, Pratap; Ayyub, Pushan

2009-05-20

356

Competing effects of surface phonon softening and quantum size effects on the superconducting properties of nanostructured Pb  

NASA Astrophysics Data System (ADS)

The superconducting transition temperature (TC) in nanostructured Pb decreases from 7.24 to 6.4 K as the particle size is reduced from 65 to 7 nm, below which superconductivity is lost rather abruptly. In contrast, there is a large enhancement in the upper critical field (HC2) in the same size regime. We explore the origin of the unusual robustness of TC over such a large particle size range in nanostructured Pb by measuring the temperature dependence of the superconducting energy gap in planar tunnel junctions of Al/Al2O3/nano-Pb. We show that below 22 nm, the electron-phonon coupling strength increases monotonically with decreasing particle size, and almost exactly compensates for the quantum size effect, which is expected to suppress TC.

Bose, Sangita; Galande, Charudatta; Chockalingam, S. P.; Banerjee, Rajarshi; Raychaudhuri, Pratap; Ayyub, Pushan

2009-05-01

357

Effect of a Quartic Anisotropy Energy on the Spiral Magnetic Coexistence State of Superconductivity and Ferromagnetism  

E-print Network

, Department of Physics, Texas A&M University, College Station, Texas ??843 (Received 26 June 1987} The effect of three types of "quartic" anisotropy energy (i.e., in the M term of the magnetic Ginzburg-Landau free energy} on the polarization of the "spiral... the principal axes in the basal plane. This last case studied provides a plausible explanation for the linear polarization observed in the coexistence state of ErRh484. I. INTRODUCTION AND SUMMARY Using an isotropic Ginzburg-Landau theory to investi- gate...

ROSE, GH; Hu, Chia-Ren.

1988-01-01

358

Journal of Superconductivity: Incorporating Novel Magnetism, Vol. 17, No. 1, February 2004 ( C 2004) Energy Scales in the High-Tc Superconductor YBa2Cu3O6+x  

E-print Network

­doped materials the superconductivity could arise from a lowering of the kinetic rather than the potential energy the energy scale for convergence is considerably higher ( 0.6 eV). This difference is discussed in terms s = c2 /2 L, and L is the London penetration depth. The BCS theory holds that while the kinetic energy

Homes, Christopher C.

359

Superconducting radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40)

Harry L. Phillips; Thomas S. Elliott

1997-01-01

360

Superconductive radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron

H. L. Phillips; T. S. Elliott

1998-01-01

361

Superconducting radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron

H. L. Phillips; T. S. Elliott

1997-01-01

362

Superconductive radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40)

Harry Lawrence Phillips; Thomas S. Elliott

1998-01-01

363

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

SciTech Connect

The overall objective of this project was to determine the state-of-the-art and to what extent existing SMES is a viable option in meeting the needs of utilities and their customers for improving electric service power quality. By defining and analyzing SMES electrical/mechanical performance characteristics, and comparing SMES application benefits with competitive stored energy systems, industry will be able to determine SMES unique applications and potential market penetration. Building on this information base, it would also be possible to evaluate the impact of high temperature superconductors (77 K and 20-35 K) on SMES technology applications. The authors of this report constructed a network of industry contacts and research consultants that were used to collect, update, and analyze ongoing SMES R&D and marketing activities in industries, utilities, and equipment manufacturers. These key resources were utilized to assemble performance characteristics on existing SMES, battery, capacitor, flywheel, and high temperature superconductor (HTS) stored energy technologies. From this information, preliminary stored energy system comparisons were accomplished. In this way, the electric load needs would be readily comparable to the potential solutions and applications offered by each aforementioned energy storage technology.

Ferraro, R.J. [Ferraro, Oliver, and Associates, Inc., Knoxville, TN (United States); McConnell, B.W. [Oak Ridge National Lab., TN (United States)

1993-06-01

364

Equilibrium Distributions and Superconductivity  

E-print Network

In this article two models for charges distributions are discussed. On the basis of our consideration we put different points of view for stationary state. We prove that only finite energy model for charges' distribution and well-known variation principle explain some well-known experimental results. A new model for superconductivity was suggested, too. In frame of that model some characteristic experimental results for superconductors is possible to explain.

Ashot Vagharshakyan

2011-06-07

365

Uncertainties in Gapped Graphene  

E-print Network

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

Eylee Jung; Kwang S. Kim; DaeKil Park

2011-07-27

366

Determination of the first satellite valley energy in the conduction band of wurtzite GaN by near-band-gap photoemission spectroscopy  

NASA Astrophysics Data System (ADS)

The position of the first satellite valley in wurtzite GaN is directly determined by near-band-gap photoemission spectroscopy of p-doped GaN activated to negative electron affinity. The photoemission spectra exhibit two structures, with fixed energy position, which originate from electrons accumulated in the conduction band valleys of the bulk material. We assigned the two observed features respectively to ? and L valleys and obtain an intervalley energy separation of 0.90±0.08 eV, well below the theoretical values of the lowest subsidiary valley energy provided by ab initio calculations.

Piccardo, Marco; Martinelli, Lucio; Iveland, Justin; Young, Nathan; DenBaars, Steven P.; Nakamura, Shuji; Speck, James S.; Weisbuch, Claude; Peretti, Jacques

2014-06-01

367

Theory of spin-fluctuation induced superconductivity in iron-based superconductors  

SciTech Connect

In this dissertation we focus on the investigation of the pairing mechanism in the recently discovered high-temperature superconductor, iron pnictides. Due to the proximity to magnetic instability of the system, we considered short-range spin fluctuations as the major mediating source to induce superconductivity. Our calculation supports the magnetic fluctuations as a strong candidate that drives Cooper-pair formation in this material. We find the corresponding order parameter to be of the so-called ss-wave type and show its evolution with temperature as well as the capability of supporting high transition temperature up to several tens of Kelvin. On the other hand, our itinerant model calculation shows pronounced spin correlation at the observed antiferromagnetic ordering wave vector, indicating the underlying electronic structure in favor of antiferromagnetic state. Therefore, the electronic degrees of freedom could participate both in the magnetic and in the superconducting properties. Our work shows that the interplay between magnetism and superconductivity plays an important role to the understanding of the rich physics in this material. The magnetic-excitation spectrum carries important information on the nature of magnetism and the characteristics of superconductivity. We analyze the spin excitation spectrum in the normal and superconducting states of iron pnictides in the magnetic scenario. As a consequence of the sign-reversed gap structure obtained in the above, a spin resonance mode appears below the superconducting transition temperature. The calculated resonance energy, scaled with the gap magnitude and the magnetic correlation length, agrees well with the inelastic neutron scattering (INS) measurements. More interestingly, we find a common feature of those short-range spin fluctuations that are capable of inducing a fully gapped ss state is the momentum anisotropy with elongated span along the direction transverse to the antiferromagnetic momentum transfer. This calculated intrinsic anisotropy exists both in the normal and in the superconducting state, which naturally explains the elliptically shaped magnetic responses observed in INS experiments. Our detailed calculation further shows that the magnetic resonance mode exhibits an upward dispersion-relation pattern but anisotropic along the transverse and longitudinal directions. We also perform a qualitative analysis on the relationship between the anisotropic momentum structure of the magnetic fluctuations and the stability of superconducting phase by intraorbital but interband pair scattering to show the consistency of the magnetic mechanism for superconductivity. As discussed for cuprates, an important identification of the mediating boson is from the fermionic spectrum. We study the spectral function in the normal and superconducting state. Not only do we extract the gap magnitude on the electron- and hole-pockets to show the momentum structure of the gap, but also find a peak-dip-hump feature in the electron spectrum, which reflects the feedback from the spin excitations on fermions. This serves as an interpretation of the kink structure observed in ARPES measurements.

Zhang, Junhua

2011-08-15

368

Cutting-Edge Technology of Bismuth-Based High-Temperature Superconducting Wires for Application in Energy- and Environment-Related Fields  

NASA Astrophysics Data System (ADS)

The first bismuth-based superconductor was discovered by Dr. Maeda of National Research Institute for Metals (currently, National Institute for Materials Science) in 1988. Since then, Sumitomo Electric Industries, Ltd., has been attempting to improve the fabrication method of superconducting wires and to develop products applying bismuth-based superconductors. As a result, the length of wires that can be fabricated has steadily increased as well as the wire performance, and these achievements have led to the practical use of prototype products and demonstration projects worldwide. Bismuth-based superconducting wires were established as an industrial material along with the development of an over pressure sintering method. In addition to this industrial accomplishment, these wires are now ready for practical use in application fields such as power cables and large-scale motors for ships. Superconductivity is an ultimate energy-saving technology, and its practical utilization is expected to contribute to the reduction of CO2 emission and the prevention of global warming.

Hayashi, Kazuhiko

2011-08-01

369

Globally optimal superconducting magnets Part I: Minimum stored energy (MSE) current density map  

NASA Astrophysics Data System (ADS)

An optimal current density map is crucial in magnet design to provide the initial values within search spaces in an optimization process for determining the final coil arrangement of the magnet. A strategy for obtaining globally optimal current density maps for the purpose of designing magnets with coaxial cylindrical coils in which the stored energy is minimized within a constrained domain is outlined. The current density maps obtained utilising the proposed method suggests that peak current densities occur around the perimeter of the magnet domain, where the adjacent peaks have alternating current directions for the most compact designs. As the dimensions of the domain are increased, the current density maps yield traditional magnet designs of positive current alone. These unique current density maps are obtained by minimizing the stored magnetic energy cost function and therefore suggest magnet coil designs of minimal system energy. Current density maps are provided for a number of different domain arrangements to illustrate the flexibility of the method and the quality of the achievable designs.

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

2009-01-01

370

Non-BCS Superconductivity in Cuprates from Attraction of Spin Vortices  

NASA Astrophysics Data System (ADS)

We propose a non-BCS mechanism for superconductivity (SC) in hole-underdoped cuprates based on a gauge approach to the t-J model. The gluing force is a long-range attraction between spin vortices centered on the empty sites of two opposite Néel sublattices, leading to pairing of charge carriers (spinless holons). In the presence of these pairs, a gauge force coming from the single occupancy constraint induces, in turn, a RVB pairing of the spin carriers (spinons), gapped by scattering against spin-vortices. This gives rise to a finite density of incoherent hole pairs, precursor to superconductivity, supporting a Nernst signal whose anticipated contour plot is qualitatively consistent with experiments. The true superconducting transition occurs at an even lower temperature via a planar XY-type transition and it involves a kinetic energy gain due to lowering of the spinon gap. Since the short-range antiferromagnetic (AF) order and the holon pairing originate from the same term of the t-J model, this approach incorporates a strong interplay between AF and SC, giving rise to a universal relation between the energy of the resonance mode (bound state of spinons) and Tc, as observed in neutron scattering experiments.

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

2012-12-01

371

ASC 84: applied superconductivity conference. Final program and abstracts  

SciTech Connect

Abstracts are given of presentations covering: superconducting device fabrication; applications of rf superconductivity; conductor stability and losses; detectors and signal processing; fusion magnets; A15 and Nb-Ti conductors; stability, losses, and various conductors; SQUID applications; new applications of superconductivity; advanced conductor materials; high energy physics applications of superconductivity; electronic materials and characterization; general superconducting electronics; ac machinery and new applications; digital devices; fusion and other large scale applications; in-situ and powder process conductors; ac applications; synthesis, properties, and characterization of conductors; superconducting microelectronics. (LEW)

Not Available

1984-01-01

372

Superconductivity-enhanced conductance fluctuations in few-layer graphene  

NASA Astrophysics Data System (ADS)

We investigate the mesoscopic disorder induced rms conductance variance ?G in short few-layer graphene (FLG) flakes contacted by two superconducting (S) Ti/Al contacts. By sweeping the back-gate voltage, we observe pronounced conductance fluctuations superimposed on a linear background of the two-terminal conductance G. The linear gate voltage induced response can be modelled by a set of interlayer and intralayer capacitances. ?G depends on temperature T and source-drain voltage Vsd. ?G increases with decreasing T and |Vsd|. When lowering |Vsd|, a pronounced cross-over at a voltage corresponding to the superconducting energy gap ? is observed. For |V_{\\mathrm {sd}}|\\lesssim \\Delta the fluctuations are markedly enhanced. Expressed in the conductance variance GGS of one graphene-superconductor (G-S) interface, values of 0.58e2/h are obtained at the base temperature of 230 mK. The conductance variance in the sub-gap region is larger by up to a factor of 1.4-1.8 compared to the normal state. The observed strong enhancement is due to phase coherent charge transfer caused by Andreev reflection at the G-S interface.

Trbovic, J.; Minder, N.; Freitag, F.; Schönenberger, C.

2010-07-01

373

How uncertainty in gap-filled meteorological input forcing at eddy covariance sites impacts modeled carbon and energy flux (Invited)  

NASA Astrophysics Data System (ADS)

In the North American Carbon Program (NACP) Site-level Interim Synthesis, gap-filled meteorological forcing data are provided to drive over 20 terrestrial carbon cycle models at over 40 eddy covariance towers using a standard simulation protocol. The meteorological gap-filling method ingests data from nearby towers or climate stations and uses simple interpolation techniques to fill missing half-hourly data values. These gap-filled forcing datasets are uncertain because of the gap-filling technique and because of potential biases in the tower observations such as the underestimation of precipitation or poor calibration of radiometers. Here we examine the effects of uncertainty in this forcing dataset at selected sites with two models. For each site, an ensemble of 10 forcing datasets is created using varying methods of bias correction, interpolation, and selection of nearby sites for gap-filling. We include the North American Regional Reanalysis (NARR) dataset as one of the ensemble members to quantify uncertainties caused by using reanalysis data. We examine the effects of forcing uncertainty on net ecosystem exchange (NEE), gross primary productivity (GPP), ecosystem respiration (Re) and latent heat (LE) at multiple timescales, with a particular focus on the interannual variability of these flux variables. We also examine the sensitivity of fluxes at each site to individual uncertainties in three variables: temperature, precipitation and photosynthetically active radiation (PAR).

Ricciuto, D. M.; Thornton, P. E.; Schaefer, K.; Cook, R. B.; Davis, K. J.; Synthesis, N.

2009-12-01

374

Advanced superconducting power conditioning system with SMES for effective use of renewable energy  

NASA Astrophysics Data System (ADS)

Since it is an urgent issue to reduce the global Carbon-dioxide in the world, renewable energy should be supplied as a large amount of the electric power. However, if a large amount of fluctuating renewable energy becomes more than adjustable amount of a utility grid capacity, instabilities such as frequency deviation might occur. We propose a system that is composed of SMES and FC-H2-Electrolyzer and also installed adjacent to Liquid Hydrogen station to cool down the SMES. Since the SMES has potentials of quick response and large I/O power, and Fuel Cell has potentials of slow response and steady power supplied from a large amount of hydrogen, we combine both storage devices and apply them to suppress the fluctuating power. We convert the fluctuating power to the constant power by using a developed prediction technology of Kalman filter to predict a trend of the fluctuating power. While the trend power should be supplied by FC or absorbed by the electrolyzer to produce hydrogen, the power difference between the renewable power and the trend power should be stored by the SMES. We simulate the power balance and analyze the required SMES capacity, design the concept of the SMES, and propose an operation algorithm for the SMES to estimate the electric efficiency of the system. It is found that the electric efficiency of the ASPCS can become greater than that of a pumped hydro-machine.

Hamajima, T.; Tsuda, M.; Miyagi, D.; Amata, H.; Iwasaki, T.; Son, K.; Atomura, N.; Shintomi, T.; Makida, Y.; Takao, T.; Munakata, K.; Kajiwara, M.

375

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

NASA Astrophysics Data System (ADS)

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

Sasca, Viorel; Popa, Alexandru

2013-10-01

376

Melt formed superconducting joint between superconducting tapes  

SciTech Connect

This patent describes a superconducting joint between contiguous superconducting tapes having an inner laminate comprised of a parent-metal layer selected from the group niobium, tantalum, technetium, and vanadium, a superconductive intermetallic compound layer on the parent-metal layer, a reactive-metal layer that is capable of combining with the parent-metal and forming the superconductive intermetallic compound, the joint comprising: a continuous precipitate of the superconductive intermetallic compound fused to the tapes forming a continuous superconducting path between the tapes.

Benz, M.G.; Knudsen, B.A.; Rumaner, L.E.; Zaabala, R.J.

1992-07-28

377

Significant reduction in NiO band gap upon formation of Lix Ni1-x O alloys: applications to solar energy conversion.  

PubMed

Long-term sustainable solar energy conversion relies on identifying economical and versatile semiconductor materials with appropriate band structures for photovoltaic and photocatalytic applications (e.g., band gaps of ? 1.5-2.0 eV). Nickel oxide (NiO) is an inexpensive yet highly promising candidate. Its charge-transfer character may lead to longer carrier lifetimes needed for higher efficiencies, and its conduction band edge is suitable for driving hydrogen evolution via water-splitting. However, NiO's large band gap (? 4 eV) severely limits its use in practical applications. Our first-principles quantum mechanics calculations show band gaps dramatically decrease to ? 2.0 eV when NiO is alloyed with Li2O. We show that Lix Ni1-x O alloys (with x=0.125 and 0.25) are p-type semiconductors, contain states with no impurity levels in the gap and maintain NiO's desirable charge-transfer character. Lastly, we show that the alloys have potential for photoelectrochemical applications, with band edges well-placed for photocatalytic hydrogen production and CO2 reduction, as well as in tandem dye-sensitized solar cells as a photocathode. PMID:24265209

Alidoust, Nima; Toroker, Maytal Caspary; Keith, John A; Carter, Emily A

2014-01-01

378

Slater half-occupation technique revisited: the LDA-1/2 and GGA-1/2 approaches for atomic ionization energies and band gaps in semiconductors  

NASA Astrophysics Data System (ADS)

The very old and successful density-functional technique of half-occupation is revisited [J. C. Slater, Adv. Quant. Chem. 6, 1 (1972)]. We use it together with the modern exchange-correlation approximations to calculate atomic ionization energies and band gaps in semiconductors [L. G. Ferreira et al., Phys. Rev. B 78, 125116 (2008)]. Here we enlarge the results of the previous paper, add to its understandability, and show when the technique might fail. Even in this latter circumstance, the calculated band gaps are far better than those of simple LDA or GGA. As before, the difference between the Kohn-Sham ground state one-particle eigenvalues and the half-occupation eigenvalues is simply interpreted as the self-energy (not self-interaction) of the particle excitation. In both cases, that of atomic ionization energies and semiconductor band gaps, the technique is proven to be very worthy, because not only the results can be very precise but the calculations are fast and very simple.

Ferreira, Luiz G.; Marques, Marcelo; Teles, Lara K.

2011-09-01

379

The Study of Energy Band Gap of AlxInyGa1-x-yN Quaternary Alloys Using UV-VIS Spectroscopy  

NASA Astrophysics Data System (ADS)

Optical characterizations have been performed on high-quality quaternary AlxInyGa1-x-yN thin films using UV-VIS spectroscopy at room temperature. The AlxInyGa1-x-yN films were grown on c-plane (0001) sapphire substrates with AlN as buffer layers using molecular beam epitaxy (MBE) technique with aluminum (Al) mole fraction x ranging from 0.0 to 0.2 and constant indium (In) mole fraction y = 0.1. The UV-VIS measurements indicated that the energy band gap of the quaternary films increases with increasing Al composition from 0.05 to 0.2. This trend is expected since the incorporation of Al increases the energy band gap of ternary In0.1Ga0.90N (3.004eV). We have also investigated the bowing parameter of the variation of energy band gaps and found it to be very sensitive on Al content. A value of b=7 eV has been obtained for our quaternary AlxInyGa1-x-yN alloys.

Abid, M. A.; Hassan, H. Abu; Hassan, Z.; Ng, S. S.; Raof, N. H. Abd.; Bakhori, S. K. Mohd

2010-07-01

380

Superconducting magnet  

NASA Technical Reports Server (NTRS)

Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

1985-01-01

381

Temperature Dependent Hybridization Gaps  

NASA Astrophysics Data System (ADS)

A number of heavy-fermion/mixed-valent materials show hybridization gaps either at the Fermi-energy or close to the Fermi-energy. In the former case, a heavy-fermion semiconducting state ensues and in the later case, the system remains metallic at low temperatures. In either case, the electronic structure is extremely temperature-dependent. It has been observed that the gap closes and the heavy quasiparticle bands disappear at high temperatures. The magnitude of the gaps scale with effective quasiparticle masses. A phenomenological model is presented that exhibits a temperature-dependence which is consistent with the above behavior. The model is based on a periodic array of Anderson impurities in which the electron correlations are represented by the coupling to bosons with an Einstein spectra. The model can be solved via systematic approximation. The solution describes the temperature- dependence of coherent and incoherent structures in the electronic excitation spectra. The predicted hybridization gaps for the metallic case are compared with data from photoemission experiments on UPd2Al3.

Riseborough, Peter

2011-03-01

382

Superconducting pipes and levitating magnets.  

PubMed

Motivated by a beautiful demonstration of the Faraday and the Lenz laws in which a small neodymium magnet falls slowly through a conducting nonferromagnetic tube, we consider the dynamics of a magnet falling coaxially through a superconducting pipe. Unlike the case of normal conducting pipes, in which the magnet quickly reaches the terminal velocity, inside a superconducting tube the magnet falls freely. On the other hand, to enter the pipe the magnet must overcome a large electromagnetic energy barrier. For sufficiently strong magnets, the barrier is so large that the magnet will not be able to penetrate it and will be levitated over the mouth of the pipe. We calculate the work that must done to force the magnet to enter a superconducting tube. The calculations show that superconducting pipes are very efficient at screening magnetic fields. For example, the magnetic field of a dipole at the center of a short pipe of radius a and length L approximately > a decays, in the axial direction, with a characteristic length xi approximately 0.26a. The efficient screening of the magnetic field might be useful for shielding highly sensitive superconducting quantum interference devices. Finally, the motion of the magnet through a superconducting pipe is compared and contrasted to the flow of ions through a trans-membrane channel. PMID:17280160

Levin, Yan; Rizzato, Felipe B

2006-12-01

383

Efficient energy transfer from peripheral chromophores to the self-assembled zinc chlorin rod antenna: a bioinspired light-harvesting system to bridge the "green gap".  

PubMed

An artificial light-harvesting rod aggregate based on zinc chlorin and covalently linked naphthalene bisimide chromophore has been realized by self-assembly. Efficient energy transfer (phiET >/= 0.99) takes place upon excitation at 620 nm from peripheral naphthalene bisimides to the zinc chlorin rod aggregate backbone. The appended naphthalene bisimide dyes improve the total LH efficiency of the rod aggregate by 26%. Thus, the present bioinspired antenna system is promising for application in nanodevices for the effective utilization of solar energy by bridging the "green gap". PMID:16704238

Röger, Cornelia; Müller, Marc G; Lysetska, Marina; Miloslavina, Yulia; Holzwarth, Alfred R; Würthner, Frank

2006-05-24

384

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

E-print Network

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

Gruner, Daniel S.

385

Absence of a {open_quote}{open_quote}Threshold Effect{close_quote}{close_quote} in the Energy Loss of Slow Protons Traversing Large-Band-Gap Insulators  

SciTech Connect

The electronic stopping cross section {var_epsilon} of slow hydrogen projectiles in large-band-gap insulators has been measured at energies of a few keV. Even at velocities as low as v{sub 0}/3 (v{sub 0}=c/137) , we find no influence of the band gap on the velocity dependence of {var_epsilon} , contrary to the case of gaseous targets with similar minimum excitation energy. The magnitude of {var_epsilon} and its essentially linear velocity dependence allow us to arrive at the following conclusion: Electron promotion processes contribute substantially to stopping due to formation of molecular orbitals. This points towards the existence of a bound electron state at a proton that moves slowly in an insulator. A simple model based on the calculation of molecular orbital correlation diagrams for the H/LiF collision system supports the idea of local reduction of the band gap of an insulating target. {copyright} {ital 1997} {ital The American Physical Society}

Eder, K.; Semrad, D.; Bauer, P. [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet Linz, A-4040 Linz (Austria)] [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet Linz, A-4040 Linz (Austria); Golser, R. [Institut fuer Radiumforschung und Kernphysik, Universitaet Wien, A-1090 Wien (Austria)] [Institut fuer Radiumforschung und Kernphysik, Universitaet Wien, A-1090 Wien (Austria); Maier-Komor, P. [Target Laboratory, Technical University Munich, D-85748 Garching (Germany)] [Target Laboratory, Technical University Munich, D-85748 Garching (Germany); Aumayr, F. [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Wien (Austria)] [Institut fuer Allgemeine Physik, Technische Universitaet Wien, A-1040 Wien (Austria); Penalba, M. [Departamento de Fisica Aplicada I, E.T.S.I.I. y T., Universidad del Pais Vasco, Bilbao (Spain)] [Departamento de Fisica Aplicada I, E.T.S.I.I. y T., Universidad del Pais Vasco, Bilbao (Spain); Arnau, A.; Ugalde, J.M.; Echenique, P.M. [Departamento de Fisica de Materiales, Universidad del Pais Vasco, Apartado 1072, San Sebastian 20080 (Spain)] [Departamento de Fisica de Materiales, Universidad del Pais Vasco, Apartado 1072, San Sebastian 20080 (Spain)

1997-11-01

386

Spatial Variations in the Superconducting Order Parameter of Bi_2Sr_2CaCu_2O_8+? as Revealed by Low Temperature Scanning Tunneling Spectroscopy  

NASA Astrophysics Data System (ADS)

Scanning tunneling spectroscopy was performed on Zn- and Ni-doped Bi_2Sr_2CaCu_2O_8+? single crystals. Reproducible spectroscopy shows atomic scale spatial variations in the energy and magnitude of the superconducting coherence peaks. We report the results of a statistical analysis of this data and discuss the potential ramifications on spatially averaged measurements. We also consider some possible explanations for such rapid gap magnitude variations.

Madhavan, Vidya; Lang, K. M.; Hudson, E. W.; Pan, S. H.; Eisaki, H.; Uchida, S.; Davis, J. C.

2000-03-01

387

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

388

Superconducting gravimeter  

NASA Technical Reports Server (NTRS)

The superconducting gravimeter was developed and applied to field measurements. The stability of the instrument yielded the highest precision measurements of the Earth tides ever attained. It revealed unprecedented details about the effect of the atmosphere on gravity. Secular variations in gravity and the stability of the instruments were measured by comparing records from co-located instruments. These efforts have resulted in substantial reductions in the noise level at very low frequencies so that the peak differences between two instruments at the same location can be reduced to 0.1 micron gal.

Goodkind, J. M.

1982-01-01

389

seshadri@mrl Superconductivity  

E-print Network

seshadri@mrl Superconductivity Ram Seshadri Materials Department Department of Chemistry Semiconductors and departures from Ohm's law The need for low temperatures and liquid He Superconductivity in Hg The superconducting elements The Meissner effect and superconducting levitation Type I and type II superconductors

Akhmedov, Azer

390

Space applications of superconductivity - High field magnets  

NASA Technical Reports Server (NTRS)

The paper discusses developments in superconducting magnets and their applications in space technology. Superconducting magnets are characterized by high fields (to 15T and higher) and high current densities combined with low mass and small size. The superconducting materials and coil design are being improved and new high-strength composites are being used for magnet structural components. Such problems as maintaining low cooling temperatures (near 4 K) for long periods of time and degradation of existing high-field superconductors at low strain levels can be remedied by research and engineering. Some of the proposed space applications of superconducting magnets include: cosmic ray analysis with magnetic spectrometers, energy storage and conversion, energy generation by magnetohydrodynamic and thermonuclear fusion techniques, and propulsion. Several operational superconducting magnet systems are detailed.

Fickett, F. R.

1979-01-01

391

Field-Angle-Dependent Low-Energy Excitations around a Vortex in the Superconducting Topological Insulator CuxBi2Se3  

NASA Astrophysics Data System (ADS)

We study the quasiparticle excitations around a single vortex in the superconducting topological insulator CuxBi2Se3, focusing on a superconducting state with point nodes. Inspired by the recent Knight shift measurements, we propose two ways to detect the positions of point nodes, using an explicit formula of the density of states with Kramer–Pesch approximation in the quasiclassical treatment. The zero-energy local density of states around a vortex parallel to the c-axis has a twofold shape and splits along the nodal direction with increasing energy; these behaviors can be detected by the scanning tunneling microscopy. An angular dependence of the density of states with a rotating magnetic field on the a–b plane has deep minima when the magnetic field is parallel to the directions of point nodes, which can be detected by angular-resolved heat capacity and thermal conductivity measurements. All the theoretical predictions are detectable via standard experimental techniques in magnetic fields.

Nagai, Yuki

2014-06-01

392

Disorder induced weak and strong localization and their influence on superconductivity in underdoped Bi2+xSr2-xCuO6  

NASA Astrophysics Data System (ADS)

In-plane resistivity and magnetoresistance(MR) measurements were carried out on high-quality underdoped Bi2+xSr2-xCuO6+? (0.1<=x<=0.4) single crystals. The results show that the superconductivity and the normal state MR behaviors strongly rely on the doping level of samples. In the slightly doping level of Bi, a metallic normal state and a finite superconducting transition temperature are observed, and there is always a positive MR in the normal state which is explained by the fluctuating superconductivity mixed with the transport of quasiparticles. With further doping, the low temperature resistivity shows an up turn together with a negative MR. Detailed analysis on the negative MR in this region may suggest that weak localization effect is dominant. As the superconductivity is depressed by more doping and thus more disorders, the delocalization gets much harder and the spin-order contribution may be involved in MR. Moreover, in the heavily underdoped doping, the superconductivity is suppressed completely and resistivity evolves into a strong localization behavior with a Coulomb gap opening at the Fermi energy. After summarizing the doping dependence of MR, we construct a new phase diagram to illustrate how does the disorder give the influence both on the superconductivity and magnetoresistance.

Luo, Huiqian; Cheng, Peng; Wen, Hai-Hu

2008-03-01

393

computational group theory with GAP 1 GAP in Sage  

E-print Network

computational group theory with GAP 1 GAP in Sage the GAP system combinatorics and list 2013 1 / 44 #12;computational group theory with GAP 1 GAP in Sage the GAP system combinatorics and list explicitly in Sage via 1 the class Gap, do help(gap); or 2 opening a Terminal Session with GAP, type gap

Verschelde, Jan

394

Recent Advances in the 5f-Relevant Electronic States and Unconventional Superconductivity of Actinide Compounds  

NASA Astrophysics Data System (ADS)

Recent advances in the understanding of the 5f-relevant electronic states and unconventional superconducting properties are reviewed in actinide compounds of UPd2Al3, UPt3, URu2Si2, UGe2, and PuRhGa5. These are based on the experimental results carried out on high-quality single crystal samples, including transuranium compounds, which were grown by using combined techniques. The paring state and the gap structure of these superconductors are discussed, especially for the corresponding Fermi surfaces which were clarified by the de Haas-van Alphen experiment and the energy band calculations. A detailed systematic study using the NQR/NMR spectroscopy reveals the d-wave superconductivity in PhRhGa5 and the difference of magnetic excitations due to the difference of ground states in U-, Np-, and Pu-based AnTGa5 (T: transition metal) compounds.

Haga, Yoshinori; Sakai, Hironori; Kambe, Shinsaku

2007-05-01

395

Berezinskii-Kosterlitz-Thouless transition to the superconducting state of heavy-fermion superlattices.  

PubMed

We propose an explanation of the superconducting transitions discovered in the heavy-fermion superlattices by Mizukami et al. [Nature Phys. 7, 849 (2011)] in terms of Berezinskii-Kosterlitz-Thouless (BKT) transition. We observe that the effective mass mismatch between the heavy-fermion superconductor and the normal metal regions provides an effective barrier that enables quasi-2D superconductivity in such systems. We show that the resistivity data, both with and without magnetic field, are consistent with BKT transition. Furthermore, we study the influence of a nearby magnetic quantum critical point on the vortex system and find that the vortex core energy can be significantly reduced due to magnetic fluctuations. Further reduction of the gap with decreasing number of layers is understood as a result of pair breaking effect of Yb ions at the interface. PMID:23006395

She, Jian-Huang; Balatsky, Alexander V

2012-08-17

396

Ab-Initio Calculations of Electronic Properties of InP and GaP  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

397

Toward a theory of high-temperature superconductivity in the antiferromagnetically correlated cuprate oxides  

NASA Astrophysics Data System (ADS)

We show that the retarded interaction between quasiparticiles on a 2D square lattice induced by the exchange of antiferromagnetic paramagnons leads uniquely to a transition to a superconducting state with d2x-y2 symmetry. With a spin-excitation spectrum and a quasiparticle-paramagnon coupling determined by fits to normal-state experiments, we obtain high transition temperatures and energy-gap behaviors comparable to those measured for YBa2Cu3O7, YBa2Cu3O6.63, and La1.85Sr0.15CuO4.

Monthoux, P.; Balatsky, A. V.; Pines, D.

1991-12-01

398

Effects of hole doping and chemical pressure on the average superconducting kinetic energy of YBa2Cu3O7-? single crystals  

NASA Astrophysics Data System (ADS)

We reported on MZFC(T) and MFCC(T) reversible dc magnetizations of YBa2Cu3O7-?, Y0.99Ca0.01Ba2Cu3O7-? and YBa1.75Sra0.25Cu3O7-? single crystals with a strong focus on the effects of Ca and Sr doping on the average superconducting kinetic energy density, k(T) of the YBa2Cu3O7-? The k(T) is used as a relevant tool to provide physical information about the HTSC paring mechanism. The determination of the k(T) from MZFC(T) and MFCC(T) data is supported by virial theorem of superconductivity [k(T) = – MB]. The MZFC(T) and MFCC(T) measurements were performed with a SQUID magnetometer to H <= 50kOe applied parallel to the c axis of the samples. The results show that the samples present a common k(T) behavior that is characterized by a maximum value for T <= Tc that gradually decreases as the temperature rises towards to the Tc, becoming null to T <= Tc. The magnetic field affects smoothly the k(T) data behavior. The k(T) results contrasting of our samples shows that the Ca and Sr doping promotes a reduction of its amplitude. A possible explanation to this feature could be associated to the fact that the hole doping character promoted by Ca doping and the chemical pressure effect motivated by Sr doping affects considerably the superconducting paring mechanism of the YBa2Cu3O7-?.

Vieira, V. N.; Mendonça, A. P. A.; Dias, F. T.; da Silva, D. L.; Pureur, P.; Schaf, J.; Hneda, M. L.; Mesquita, F.

2014-12-01

399

Superconductivity in oxygen doped iron telluride by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

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

Zheng, Mao

400

Spatially Varying Energy Gap in the CuO Chains of YBa2Cu3O7-x Detected by Scanning Tunneling Spectroscopy  

Microsoft Academic Search

Current-imaging tunneling spectroscopy (CITS) was performed on cold-cleaved single crystals of YBa2Cu3O7-x at 20 K. CITS data include I\\\\(V\\\\) curves taken simultaneously with a topographic scanning tunneling microscopic image. I\\\\(V\\\\) curves taken on CuO chains show an energy gap of about 20 meV which disappears near oxygen vacancies. We explain several features of large-junction I\\\\(V\\\\) measurements, photoemission spectroscopy, and single-point

H. L. Edwards; D. J. Derro; A. L. Barr; J. T. Markert; A. L. de Lozanne

1995-01-01

401

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

SciTech Connect

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

Chatrchyan, Serguei; et al.

2012-01-01

402

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

403

Color Superconductivity and Tsallis Statistics  

E-print Network

The generalized non-extensive statistics proposed by Tsallis have been successfully utilized in many systems where long range interactions are present. For high density quark matter an attractive long range interaction arising from single gluon exchange suggests the formation of a diquark condensate. We study the effects on this color superconducting phase for two quark flavors due to a change to Tsallis statistics. By numerically solving the gap equation we obtain a generalization of the universality condition, $\\frac{2\\phi_{0}}{T_{C}}\\approx 3.52$ and determine the temperature dependence of the gap. For the Tsallis parameter $q\\approx 1$ the specific heat is exponential becoming more linear as q increases. This suggests that for larger values of q s-wave color superconductors behave like high $T_c$ superconductors rather than weak superconductors.

Justin M. Conroy; H. G. Miller

2008-01-02

404

Color Superconductivity and Tsallis Statistics  

E-print Network

The generalized non-extensive statistics proposed by Tsallis have been successfully utilized in many systems where long range interactions are present. For high density quark matter an attractive long range interaction arising from single gluon exchange suggests the formation of a diquark condensate. We study the effects on this color superconducting phase for two quark flavors due to a change to Tsallis statistics. By numerically solving the gap equation we obtain a generalization of the universality condition, $\\frac{2\\phi_{0}}{T_{C}}\\approx 3.52$ and determine the temperature dependence of the gap. For the Tsallis parameter $q\\approx 1$ the specific heat is exponential becoming more linear as q increases. This suggests that for larger values of q s-wave color superconductors behave like high $T_c$ superconductors rather than weak superconductors.

Conroy, Justin M

2008-01-01

405

Superconducting Magnets for RIA  

SciTech Connect

The highest priority for new construction for the nuclear physics community is the Rare Isotope Accelerator. This project's goal is to produce up to 400 kW of beams from protons to uranium. Beam transport at the high-energy end has to deal with high radiation fields and high beam rigidities. Superconducting magnets are being designed to fulfill both these requirements. The quadrupoles in the fragment separator will use superferric design with pole tip fields of up to 2.5 T to produce the required gradients in the large apertures. Several techniques are presented that deal with making the magnets radiation resistant.

Zeller, A.F. [National Superconducting Cyclotron Lab, Michigan State University, E. Lansing, MI 48824 (United States)

2004-06-23

406

Electronic Structure of Kinetic Energy Driven Cuprate Superconductors  

NASA Astrophysics Data System (ADS)

In this paper, we review the low energy electronic structure of the kinetic energy driven d-wave cuprate superconductors. We give a general description of the charge-spin separation fermion-spin theory, where the constrained electron is decoupled as the gauge invariant dressed holon and spin. In particular, we show that under the decoupling scheme, the charge-spin separation fermion-spin representation is a natural representation of the constrained electron defined in a restricted Hilbert space without double electron occupancy. Based on the charge-spin separation fermion-spin theory, we have developed the kinetic energy driven superconducting mechanism, where the superconducting state is controlled by both superconducting gap parameter and quasiparticle coherence. Within this kinetic energy driven superconductivity, we have discussed the low energy electronic structure of the single layer and bilayer cuprate superconductors in both superconducting and normal states, and qualitatively reproduced all main features of the angle-resolved photoemission spectroscopy measurements on the single layer and bilayer cuprate superconductors. We show that the superconducting state in cuprate superconductors is the conventional Bardeen-Cooper-Schrieffer like with the d-wave symmetry, so that the basic Bardeen-Cooper-Schrieffer formalism with the d-wave gap function is still valid in discussions of the low energy electronic structure of cuprate superconductors, although the pairing mechanism is driven by the kinetic energy by exchanging spin excitations. We also show that the well-pronounced peak-dip-hump structure of the bilayer cuprate superconductors in the superconducting state and double-peak structure in the normal state are mainly caused by the bilayer splitting.

Feng, Shiping; Guo, Huaiming; Lan, Yu; Cheng, Li

407

Multigap superconductivity in doped p-type cuprates  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

408

High field superconducting magnets  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

409

A Superconducting Proton Storage Ring for PEP  

Microsoft Academic Search

In order to provide for electron-proton collisions in the PEP system, plans for a high-energy superconducting proton storage ring are being explored. The energy is constrained to 300 GeV by the radius of the PEP tunnel (350 meters) and the field strength (7 tesla) expected to be available in practical superconducting magnets. A new configuration has been developed in which

A. A. Garren; E. L. Molishever; J. M. Peterson; R. C. Sah

1979-01-01

410

Free-standing oxide superconducting articles  

DOEpatents

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

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

1993-01-01

411

Observations of the whole bell-shaped energy gap law in the intra-molecular charge separation (CS) from S2 state of directly linked Zn-porphyrin-imide dyads: Examinations of wider range of energy gap (-[Delta]GCS) for the CS rates in normal regions  

Microsoft Academic Search

Very recently, we have succeeded in the first observation of the whole bell-shaped energy gap law (EGL) of photoinduced charge separation (CS) reaction, examining the ultrafast reaction from the S2 state of Zn-porphyrin-imide dyads with the fs fluorescence dynamics measurements, which showed EGL including both normal and inverted regimes considerably broader than the result in our previous investigations. We have

Noboru Mataga; Seiji Taniguchi; Haik Chosrowjan; Astuhiro Osuka; Kei Kurotobi

2005-01-01

412

Nodal liquid and s -wave superconductivity in transition metal dichalcogenides  

Microsoft Academic Search

We explore the physical properties of a unified microscopic theory for the coexistence of superconductivity and charge-density waves (CDWs) in two-dimensional transition-metal dichalcogenides. In the case of particle-hole symmetry, the elementary particles are Dirac fermions at the nodes of the charge density wave gap. When particle-hole symmetry is broken, electron (hole) pockets are formed around the Fermi surface. The superconducting

B. Uchoa; G. G. Cabrera; A. H. Castro Neto

2005-01-01

413

Thermopower of three-terminal topological superconducting systems  

NASA Astrophysics Data System (ADS)

We study the thermopower of a three-terminal setup composed of a quantum dot attached to three electrodes, one of which is a topological superconductor. In the model, superconductivity is explicitly taken into account. We compare the results for s -wave (trivial) and p -wave (topological) superconductors and observe that for small temperatures the thermopower has different sign in the two cases. This behavior is strongly dependent on temperature and we estimate an energy scale that controls the sign in the p -wave case, which results proportional to the square root of the gap and the coupling to superconductor. The analytical results obtained with a simple 1D model are confirmed by a more realistic tight-binding model.

Valentini, Stefano; Fazio, Rosario; Giovannetti, Vittorio; Taddei, Fabio

2015-01-01

414

Optimization of the AGS superconducting helical partial snake strength.  

SciTech Connect

Two helical partial snakes, one super-conducting (a.k.a cold snake) and one normal conducting (a.k.a warm snake), have preserved the polarization of proton beam up to 65% in the Brookhaven Alternating Gradient Synchrotron (AGS) at the extraction energy from 85% at injection. In order to overcome spin resonances, stronger partial snakes would be required. However, the stronger the partial snake, the more the stable spin direction tilted producing a stronger horizontal intrinsic resonance. The balance between increasing the spin tune gap generated by the snakes and reducing the tilted stable spin direction has to be considered to maintain the polarization. Because the magnetic field of the warm snake has to be a constant, only the cold snake with a maximum 3T magnetic field can be varied to find out the optimum snake strength. This paper presents simulation results by spin tracking with different cold snake magnetic fields. Some experimental data are also analyzed.

Lin,F.; Huang, H.; Luccio, A.U.; Roser, T.

2008-06-23

415

Preparation of Semiconducting Materials in the Laboratory, Part 2: Microscale Chemical Bath Deposition of Materials with Band Gap Energies in the UV, VIS, and IR  

NASA Astrophysics Data System (ADS)

The technique of chemical bath deposition (CBD), based upon the controlled precipitation of an insoluble compound, is used in the laboratory for the student production of thin films of three inorganic semiconducting sulfides: ZnS, CdS and Bi2S3 which have their band gap energy values (Eg) in the UV, VIS and IR regions of the electromagnetic spectrum, respectively. Here, a saturated solution of an electrolyte in contact with its own solid phase originates a well defined numerical relationship (Ksp) among the concentrations (or activities) of the ions in solution. Precipitation occurs when this product is exceeded. However, this precipitation is usually massive and the solid formed does not grow in a defined, homogeneous pattern. In order to achieve a controlled precipitation one can often add a complexing agent (L) as to form a stable complex (MnLp) with the metallic ion (M) that controls its concentration. The band gap energies, Eg of these semiconducting films produced on glass or polymer slides are then estimated from their absorbance spectra at the corresponding wavelengths, lg (i.e. Eg = hc/lg). Typical student values (in eV) are: 3.7, 2.3 and 1.4 for ZnS, CdS and Bi2S3, respectively which compare well to the literature values of 3.4, 2.42 and 1.47 eV.

Ibanez, Jorge G.; Gomez, Flora; Konik, Ivonne; Lozano, Diana E.; Mugica, Alejandra; Singh, Mono M.; Szafran, Zvi; Pike, Ronald M.

1997-10-01

416

Nodes in the gap structure of the iron arsenide superconductor Ba(Fe1-xCox)2As2 from c-axis heat transport measurements  

E-print Network

,12 and tunneling studies in K-Ba122 detect two full superconducting gaps.13 The magnitude of the gaps in ARPES and deep minima on the remaining, quasi-two-dimensional sheets. DOI: 10.1103/PhysRevB.82.064501 PACS number hand, angle- resolved photoemission spectroscopy ARPES detects a nodeless, isotropic superconducting

Taillefer, Louis

417

Superconducting properties of BaBi3  

NASA Astrophysics Data System (ADS)

We report the superconducting properties of single crystals of the intermetallic compound BaBi3, whose crystal structure is perovskite related. The superconducting transition temperature ({{T}_{c}}=5.82 K) was obtained from heat capacity measurements. Using the measured values for the critical fields {{H}_{c1}},{{H}_{c2}}, and the specific heat C, we estimate the thermodynamic critical field H c (0), coherence length ?(0), Debye temperature {{\\Theta }_{D}} and coupling constant ?ep. \\Delta C/\\gamma {{T}_{c}} and ?ep suggest that BaBi3 is a weakly coupled superconductor. Electronic band structure calculations show a complex Fermi surface and a moderately high DOS at the Fermi level. Further analysis of the electronic specific heat shows that the superconducting properties are dominated by s-wave gap.

Haldolaarachchige, Neel; Kushwaha, S. K.; Gibson, Quinn; Cava, R. J.

2014-10-01

418

Superconductivity in Bulk, Hole-Doped Diamond  

NASA Astrophysics Data System (ADS)

Diamonds, synthesized at high pressure (9 GPa) and high temperature (2500-2800 K) in the systems boron carbide-graphite and boron-graphite, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds were characterized by: X-ray diffraction, Raman scattering, NMR, SQUID magnetometry, calorimetry, Hall effect, resistivity and magnetic susceptibility measurements. They show an expanded (˜1 % in volume) lattice with a softened zone-centre optical phonon mode and reduced Debye temperature, and exhibit bulk superconductivity below Tc ˜4 K. Upper critical field, specific heat and resistivity measurements provide a consistent set of materials parameters that favor a conventional, weak coupling electron-phonon interpretation of the superconducting mechanism at high hole doping. Preliminary measurements of conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below Tc.

Sidorov, Vladimir

2005-03-01

419

BCS superconductivity in quantum critical metals  

NASA Astrophysics Data System (ADS)

We consider the superconducting transition in fermionic quantum critical systems. Assuming the validity of Migdal theorem, the gap equation can be written in terms of the retarded pair susceptibility. Instead of the usual BCS form, the pair susceptibility is now subject to scale invariance. The gap and transition temperature is thus of the algebraic form, totally different from the exponential behavior in BCS theory. Consequently, with reasonably small glue strength, we can get very large gap and transition temperature comparable to those discovered in cuprates. The ratio of the gap to retardation gets boosted by increasing retardation. We also find the upper critical field has a different scaling with the critical temperature. With a non-Lorentzian dynamical exponent, the upper critical field is greatly enhanced when approaching the critical point, though the critical temperature only changes modestly, in agreement with recent experiments on heavy fermions.

She, Jian-Huang; Zaanen, Jan

420

BCS superconductivity in quantum critical metals  

NASA Astrophysics Data System (ADS)

We consider the superconducting transition in fermionic quantum critical systems. Assuming the validity of Migdal theorem, the gap equation can be written in terms of the retarded pair susceptibility. Instead of the usual BCS form, the pair susceptibility is now subject to scale invariance. The gap and transition temperature is thus of the algebraic form, totally different from the exponential behavior in BCS theory. Consequently, with reasonably small glue strength, we can get very large gap and transition temperature comparable to those discovered in cuprates. The ratio of the gap to retardation gets boosted by increasing retardation. We also find the upper critical field has a different scaling with the critical temperature. With a non-Lorentzian dynamical exponent, the upper critical field is greatly enhanced when approaching the critical point, though the critical temperature only changes modestly, in agreement with recent experiments on heavy fermions.

She, Jian-Huang; Zaanen, Jan

2010-12-01

421

Superconductivity in heavily boron-doped silicon carbide  

NASA Astrophysics Data System (ADS)

The discoveries of superconductivity in heavily boron-doped diamond in 2004 and silicon in 2006 have renewed the interest in the superconducting state of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a metallic phase from which upon further doping superconductivity can emerge. Recently, we discovered superconductivity in a closely related system: heavily boron-doped silicon carbide. The sample used for that study consisted of cubic and hexagonal SiC phase fractions and hence this led to the question which of them participated in the superconductivity. Here we studied a hexagonal SiC sample, free from cubic SiC phase by means of x-ray diffraction, resistivity, and ac susceptibility.

Kriener, Markus; Muranaka, Takahiro; Kato, Junya; Ren, Zhi-An; Akimitsu, Jun; Maeno, Yoshiteru

2008-12-01

422

Discovery of a Superconducting High-Entropy Alloy  

NASA Astrophysics Data System (ADS)

High-entropy alloys (HEAs) are multicomponent mixtures of elements in similar concentrations, where the high entropy of mixing can stabilize disordered solid-solution phases with simple structures like a body-centered cubic or a face-centered cubic, in competition with ordered crystalline intermetallic phases. We have synthesized an HEA with the composition Ta34Nb33Hf8Zr14Ti11 (in at. %), which possesses an average body-centered cubic structure of lattice parameter a =3.36 Å. The measurements of the electrical resistivity, the magnetization and magnetic susceptibility, and the specific heat revealed that the Ta34Nb33Hf8Zr14Ti11 HEA is a type II superconductor with a transition temperature Tc?7.3 K, an upper critical field ?0Hc2?8.2 T, a lower critical field ?0Hc1?32 mT, and an energy gap in the electronic density of states (DOS) at the Fermi level of 2? ?2.2 meV. The investigated HEA is close to a BCS-type phonon-mediated superconductor in the weak electron-phonon coupling limit, classifying it as a "dirty" superconductor. We show that the lattice degrees of freedom obey Vegard's rule of mixtures, indicating completely random mixing of the elements on the HEA lattice, whereas the electronic degrees of freedom do not obey this rule even approximately so that the electronic properties of a HEA are not a "cocktail" of properties of the constituent elements. The formation of a superconducting gap contributes to the electronic stabilization of the HEA state at low temperatures, where the entropic stabilization is ineffective, but the electronic energy gain due to the superconducting transition is too small for the global stabilization of the disordered state, which remains metastable.

Koželj, P.; Vrtnik, S.; Jelen, A.; Jazbec, S.; Jagli?i?, Z.; Maiti, S.; Feuerbacher, M.; Steurer, W.; Dolinšek, J.

2014-09-01

423

Discovery of a superconducting high-entropy alloy.  

PubMed

High-entropy alloys (HEAs) are multicomponent mixtures of elements in similar concentrations, where the high entropy of mixing can stabilize disordered solid-solution phases with simple structures like a body-centered cubic or a face-centered cubic, in competition with ordered crystalline intermetallic phases. We have synthesized an HEA with the composition Ta34Nb33Hf8Zr14Ti11 (in at.?%), which possesses an average body-centered cubic structure of lattice parameter a=3.36??Å. The measurements of the electrical resistivity, the magnetization and magnetic susceptibility, and the specific heat revealed that the Ta34Nb33Hf8Zr14Ti11 HEA is a type II superconductor with a transition temperature Tc?7.3??K, an upper critical field ?0H_c2?8.2??T, a lower critical field ?0Hc1?32??mT, and an energy gap in the electronic density of states (DOS) at the Fermi level of 2??2.2??meV. The investigated HEA is close to a BCS-type phonon-mediated superconductor in the weak electron-phonon coupling limit, classifying it as a "dirty" superconductor. We show that the lattice degrees of freedom obey Vegard's rule of mixtures, indicating completely random mixing of the elements on the HEA lattice, whereas the electronic degrees of freedom do not obey this rule even approximately so that the electronic properties of a HEA are not a "cocktail" of properties of the constituent elements. The formation of a superconducting gap contributes to the electronic stabilization of the HEA state at low temperatures, where the entropic stabilization is ineffective, but the electronic energy gain due to the superconducting transition is too small for the global stabilization of the disordered state, which remains metastable. PMID:25238377

Koželj, P; Vrtnik, S; Jelen, A; Jazbec, S; Jagli?i?, Z; Maiti, S; Feuerbacher, M; Steurer, W; Dolinšek, J

2014-09-01

424

Aerospace Applications Of High Temperature Superconductivity  

NASA Astrophysics Data System (ADS)

The existence of superconductors with TcOOK (which implies device operating temper-atures the order of Top ?45K) opens up a variety of potential applications within the aerospace/defense industry. This is partly due to the existence of well developed cooler technologies to reach this temperature regime and partly due to the present operation of some specialized components at cryogenic temperatures. In particular, LWIR focal planes may operate at 10K with some of the signal processing electronics at an intermediate temperature of 40K. Addition of high Tc superconducting components in the latter system may be "free" in the sense of additional system complexity required. The established techniques for cooling in the 20K to 50K temperature regime are either open cycle, expendable material (stored gas with Joule-Thomson expansion, liquid cryogen or solid cryogen) or mechanical refrigerators (Stirling cycle, Brayton cycle or closed cycle Joule-Thomson). The high Tc materials may also contribute to the development of coolers through magnetically levitated bearings or providing the field for a stage of magnetic refrigeration. The discovery of materials with Tc, 90K has generated a veritable shopping list of applications. The superconductor properties which are of interest for applications are (1) zero resistance, (2) Meissner effect, (3) phase coherence and (4) existence of an energy gap. The zero resistance property is significant in the development of high field magnets requiring neglible power to maintain the field. In addition to the publicized applications to rail guns and electromagnetic launcher, we can think of space born magnets for charged particle shielding or whistler mode propagation through a plasma sheath. Conductor losses dominate attenuation and dispersion in microstrip transmission lines. While the surface impedance of a superconductor is non vanishing, significant improvements in signal transmission may be obtained. The Meissner effect may be utilized for some magnetic shielding applications but the penetration depth and high frequency effects will have to be considered. Phase coherence forms the basis for Josephson junction devices which, in turn are used for mixers, detectors and parametric amplifiers in the microwave/millimeter wave regime and for A/D converters, sampling and switching circuits and voltage standards in electronics. The energy gap has been the basis of optical and IR detection through modulation of the order parameter (or gap energy) by generation of quasi particles.

Anderson, W. W.

1988-05-01

425

Band Gap Energy of Chalcopyrite Thin Film Solar Cell Absorbers Determined by Soft X-Ray Emission and Absorption Spectroscopy  

SciTech Connect

The chemical and electronic structure of high efficiency chalcopyrite thin film solar cell absorbers significantly differs between the surface and the bulk. While it is widely accepted that the absorber surface exhibits a Cu-poor surface phase with increased band gap (Eg), a direct access to the crucial information of the depth-dependency of Eg is still missing. In this paper, we demonstrate that a combination of x-ray emission and absorption spectroscopy allows a determination of Eg in the surface-near bulk and thus complements the established surface- and bulk-sensitive techniques of Eg determination. As an example, we discuss the determination of Eg for a Cu(In,Ga)Se2 absorber [(1.52 +- 0.20) eV].

Bar, M.; Weinhardt, L.; Pookpanratana, S.; Heske, C.; Nishiwaki, S.; Shafarman, W.; Fuchs, O.; Blum, M.; Yang, W.; Denlinger, J.D.

2008-05-11

426

Miscibility Gap Systems  

NASA Technical Reports Server (NTRS)

Immiscible droplets embedded in a host fluid in which a temperature gradient exists migrate toward the hot end of the host fluid because of the temperature dependence of the interfacial energy of the droplet. This thermocapillary migration effect was exploited in the design of a controllable heat valve which is the thermal analog of the electronic vacuum triode. Studies have also been made of test cells that could use thermocapillary migration to facilitate the study of condensation and dissolution kinetics in miscibility-gap solutions.

Schmid, L. A.

1985-01-01

427

Suppressed Critical Current in Superconducting Nanowire Single-Photon Detectors With High Fill-Factors  

E-print Network

In this work we present a new fabrication process that enabled the fabrication of superconducting nanowire single photon detectors SNSPD with fill-factors as high as 88% with gaps between nanowires as small as 12 nm. This ...

Yang, Joel K. W.

428

Low-energy spectroscopic mapping studies in optimally-doped Ca 2- xNa xCuO 2Cl 2  

NASA Astrophysics Data System (ADS)

We performed high-resolution scanning tunneling microscopy/spectroscopy on an optimally-doped Ca 2- xNa xCuO 2Cl 2 crystal with Tc ? 25 K. The so-called “checkerboard” local-density-of-state modulation previously found in heavily underdoped regime also manifests in the spectroscopic map of the optimally-doped sample. In addition, spatially-inhomogeneous energy gap with peaks at the gap edges is observed below about 10 meV. The gap tends to be buried at elevated temperatures and correlates with the checkerboard modulation. These results suggest that the gap is related to superconductivity which coexists with the checkerboard modulation.

Hanaguri, T.; Kohsaka, Y.; Séamus Davis, J. C.; Lupien, C.; Yamada, I.; Azuma, M.; Takano, M.; Ohishi, K.; Takagi, H.

2007-09-01

429

Application of simultaneous active and reactive power modulation of superconducting magnetic energy storage unit to damp turbine-generator subsynchronous oscillations  

SciTech Connect

An active and reactive power (P-Q) simultaneous control scheme which is based on a superconducting magnetic energy storage (SMES) unit is designed to damp out the subsynchronous resonant (SSR) oscillations of a turbine-generator unit. In order to suppress unstable torsional mode oscillations, a proportional-integral-derivative (PID) controller is employed to modulate the active and reactive power input/output of the SMES unit according to speed deviation of the generator shaft. The gains of the proposed PID controller are determined by pole assignment approach based on modal control theory. Eigenvalue analysis of the studied system shows that the PID controller is quite effective over a wide range of operating conditions. Dynamic simulations using the nonlinear system model are also performed to demonstrate the damping effect of the proposed control scheme under disturbance conditions.

Wu, Chijui; Lee, Yuangshung (National Taiwan Inst. of Tech., Taipie (Taiwan, Province of China))

1993-03-01

430

Micro-mechanical and Structural Properties and Activation Energy Calculation of Nd2O3 Added Bi2Sr2Ca1Cu2Oy Superconducting System  

NASA Astrophysics Data System (ADS)

Nd added Bi-2212 superconducting samples with x=0, 0.001, 0.005, 0.01, 0.05 and 0.1 were prepared by conventional solid state reaction method and annealed at 840^oC for 72 h. For the comparison, an undoped sample was produced to the same conditions. The effects of Nd addition on structural and micromechanical properties were systematically investigated. The volume fraction, lattice parameters, crystal structure and grain size of the samples were characterized using the X-ray diffractometer and Scanning Electron Microscope. In addition, this study includes determination of the activation energy of Nd in the Bi-2212 system using the magnetoresistivity measurements. And also, we were investigated the mechanical properties for all samples using the Vickers microhardness measurements. Microhardness values of the samples decrease with increasing adding and applied load. The Vickers hardness of the samples studied, exhibits the typical indentation size effect (ISE).

Ozturk, Ozgur; Asikuzun, Elif; Coskunyurek, Murat; Kaya, Seydanur; Yilmazlar, Mustafa; Yildirim, Gurcan; Terzioglu, Cabir

2013-03-01

431

COLOR SUPERCONDUCTIVITY IN COLD, DENSE, QUARK MATTER.  

SciTech Connect

We review what is different and what is similar in a color superconductor as compared to an ordinary BCS superconductor. The parametric dependence of the zero-temperature gap, {phi}{sub 0}, on the coupling constant differs in QCD from that in BCS theory. On the other hand, the transition temperature to the superconducting phase, T{sub c}, is related to the zero-temperature gap in the same way in QCD as in BCS theory, T{sub c}/{phi}{sub 0} {approx_equal} 0.567.

RISCHKE,D.H.; PISARSKI,R.D.

2000-01-03

432

BCS superconductivity in quantum critical metals  

NASA Astrophysics Data System (ADS)

We consider the superconducting transition in fermionic quantum critical systems. Assuming the validity of Migdal theorem, the gap equation can be written in terms of the retarded pair susceptibility. Scale invariance leads to an algebraic gap equation, instead of the BCS exponential form. With reasonably small glue strength, we can get very large transition temperatures comparable to those observed in cuprates. We get nice dome structures around the QCP for a wide range of parameters. With a non-Lorentzian dynamical exponent, the upper critical field is greatly enhanced when approaching the critical point, while the transition temperature only changes modestly, in agreement with recent experiments on heavy fermions.

She, Jian-Huang; Zaanen, Jan

2010-03-01

433

Superconducting magnet  

DOEpatents

A superconducting magnet designed to produce magnetic flux densities of the order of 4 to 5 Webers per square meter is constructed by first forming a cable of a plurality of matrixed superconductor wires with each wire of the plurality insulated from each other one. The cable is shaped into a rectangular cross-section and is wound with tape in an open spiral to create cooling channels. Coils are wound in a calculated pattern in saddle shapes to produce desired fields, such as dipoles, quadrupoles, and the like. Wedges are inserted between adjacent cables as needed to maintain substantially radial placement of the long dimensions of cross sections of the cables. After winding, individual strands in each of the cables are brought out to terminals and are interconnected to place all of the strands in series and to maximize the propagation of a quench by alternating conduction from an inner layer to an outer layer and from top half to bottom half as often as possible. Individual layers are separated from others by spiraled aluminum spacers to facilitate cooling. The wound coil is wrapped with an epoxy tape that is cured by heat and then machined to an interference fit with an outer aluminum pipe which is then affixed securely to the assembled coil by heating it to make a shrink fit. In an alternate embodiment, one wire of the cable is made of copper or the like to be heated externally to propagate a quench.

Satti, John A. (Naperville, IL)

1980-01-01

434

Superconducting microfabricated ion traps  

E-print Network

We fabricate superconducting ion traps with niobium and niobium nitride and trap single [superscript 88]Sr ions at cryogenic temperatures. The superconducting transition is verified and characterized by measuring the ...

Wang, Shannon Xuanyue

435

Magnetic properties of new Haldane gap materials  

NASA Astrophysics Data System (ADS)

High-field magnetization and susceptibility measurements have been performed on the linear-chain Heisenberg antiferromagnets Ni(dmpn) 2N 3(CIO 4) and catena-(?-N 3)?Ni(323-tet)](CIO 4). These compounds have an energy gap at low temperatures, and the values of energy gap, crystalline field constants are estimated from the high-field magnetization data.

Takeuchi, T.; Yosida, T.; Inoue, K.; Yamashita, M.; Kumada, T.; Kindo, K.; Merah, S.; Verdaguer, M.; Renard, J. P.

1995-02-01

436

Cutoff-independent regularization of four-fermion interactions for color superconductivity  

E-print Network

We implement a cutoff-independent regularization of four-fermion interactions to calculate the color-superconducting gap parameter in quark matter. The traditional cutoff regularization has difficulties for chemical potentials \\mu of the order of the cutoff \\Lambda, predicting in particular a vanishing gap at \\mu \\sim \\Lambda. The proposed cutoff-independent regularization predicts a finite gap at high densities and indicates a smooth matching with the weak coupling QCD prediction for the gap at asymptotically high densities.

R. L. S. Farias; G. Dallabona; G. Krein; O. A. Battistel

2005-10-11

437

Simple Superconducting "Permanent" Electromagnet  

NASA Technical Reports Server (NTRS)

Proposed short tube of high-temperature-superconducting material like YBa2Cu3O7 acts as strong electromagnet that flows as long as magnetic field remains below critical value and temperature of cylinder maintained sufficiently below superconducting-transition temperature. Design exploits maximally anisotropy of high-temperature-superconducting material.

Israelson, Ulf E.; Strayer, Donald M.

1992-01-01

438

Superconducting Magnet Division  

E-print Network

Superconducting Magnet Division Ramesh Gupta, BNL, HTS Magnets for Accelerator and Other;Superconducting Magnet Division Ramesh Gupta, BNL, HTS Magnets for Accelerator and Other Applications, March 30 active in HTS magnet R&D for well over a decade #12;Superconducting Magnet Division Ramesh Gupta, BNL

Gupta, Ramesh

439

Macroscopic Models of Superconductivity  

E-print Network

Macroscopic Models of Superconductivity S. J. Chapman, St. Catherine's College, Oxford. Thesis-boundary model for the destruction of superconductivity by an applied magnetic field, under isothermal then describe the Ginzburg-Landau theory of superconductivity, in which the sharp interface is `smoothed out

Chapman, Jon

440

Basic principle of superconductivity  

E-print Network

The basic principle of superconductivity is suggested in this paper. There have been two vital wrong suggestions on the basic principle, one is the relation between superconductivity and the Bose-Einstein condensation (BEC), and another is the relation between superconductivity and pseudogap.

Tian De Cao

2007-08-23

441

Experimental superconducting unipolar machine  

Microsoft Academic Search

Basic design and preliminary test results of an experimental superconducting unipolar machine are presented. The inductor is a superconducting axisymmetric coil placed in a helium tank. The inductor winding consists of twisted multifiber Nb-Ti superconductors with copper matrix, and consists of series-connected sections having different diameters of the superconducting cable. Modeling considerations for extrapolating results to larger systems are discussed.

B. L. Alievskii; A. M. Oktiabrskii; V. L. Orlov

1979-01-01

442

k.p based closed form energy band gap and transport electron effective mass model for [1 0 0] and [1 1 0] relaxed and strained Silicon nanowire  

NASA Astrophysics Data System (ADS)

In this paper, we address a physics based closed form model for the energy band gap (Eg) and the transport electron effective mass in relaxed and strained [1 0 0] and [1 1 0] oriented rectangular Silicon Nanowire (SiNW). Our proposed analytical model along [1 0 0] and [1 1 0] directions are based on the k.p formalism of the conduction band energy dispersion relation through an appropriate rotation of the Hamiltonian of the electrons in the bulk crystal along [0 0 1] direction followed by the inclusion of a 4 × 4 Lüttinger Hamiltonian for the description of the valance band structure. Using this, we demonstrate the variation in Eg and the transport electron effective mass as function of the cross-sectional dimensions in a relaxed [1 0 0] and [1 1 0] oriented SiNW. The behaviour of these two parameters in [1 0 0] oriented SiNW has further been studied with the inclusion of a uniaxial strain along the transport direction and a biaxial strain, which is assumed to be decomposed from a hydrostatic deformation along [0 0 1] with the former one. In addition, the energy band gap and the effective mass of a strained [1 1 0] oriented SiNW has also been formulated. Using this, we compare our analytical model with that of the extracted data using the nearest neighbour empirical tight binding sp3d5s? method based simulations and has been found to agree well over a wide range of device dimensions and applied strain.

Ghosh, Ram Krishna; Bhattacharya, Sitangshu; Mahapatra, Santanu

2013-02-01

443

Nb-Pb Superconducting RF Gun  

SciTech Connect

We report on the status of an electron RF-gun made of two superconductors: niobium and lead. The presented design combines the advantages of the RF performance of bulk niobium superconducting cavities and the reasonably high quantum efficiency of lead, as compared to other superconducting metals. The concept, mentioned in a previous paper, follows the attractive approach of all niobium superconducting RF-gun as it has been proposed by the BNL group. Measured values of quantum efficiency for lead at various photon energies, analysis of recombination time of photon-broken Cooper pairs for lead and niobium, and preliminary cold test results are discussed in this paper.

Sekutowicz, J.; Iversen, J.; Kreps, G.; Moller, W.D.; Singer, W.; Singer, X.; /DESY; Ben-Zvi, I.; Burrill, A.; Smedley, J.; Rao, T.; /Brookhaven; Ferrario, M.; /Frascati; Kneisel, P.; /Jefferson Lab; Langner, J.; Strzyzewski, P.; /Warsaw, Inst. Nucl. Studies; Lefferts, R.; Lipski, A.; /SUNY, Stony Brook; Szalowski, K.; /Lodz U.; Ko, K.; Xiao, L.; /SLAC

2006-03-29

444

Nb-Pb superconducting RF gun  

SciTech Connect

We report on the status of an electron RF-gun made of two superconductors: niobium and lead. The presented design combines the advantages of the RF performance of bulk niobium superconducting cavities and the reasonably high quantum efficiency of lead, as compared to other superconducting metals. The concept, mentioned in a previous paper, follows the attractive approach of all niobium superconducting RF-gun as it has been proposed by the BNL group. Measured values of quantum efficiency for lead at various photon energies, analysis of recombination time of photon-broken Cooper pairs for lead and niobium, and preliminary cold test results are discussed in this paper.

J. Sekutowicz; J. Iversen; G. Kreps; W.D. Moller; W. Singer; X. Singer; I. Ben-Zvi; A. Burrill; J. Smedley; T. Rao; M. Ferrario; P. Kneisel; J. Langner; P. Strzyzewski; R. Lefferts; A. Lipski; K. Szalowski; K. Ko; L. Xiao

2006-04-14

445

Superconducting proximity effect in topological metals  

NASA Astrophysics Data System (ADS)

Much interest in the superconducting proximity effect in three-dimensional (3D) topological insulators (TIs) has been driven by the potential to induce Majorana bound states a