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1. Superconductivity at 18 K in potassium-doped C60

Author

D. W. Murphy, A. P. Ramirez, Robert C. Haddon, Matthew J. Rosseinsky, Arthur F. Hebard, Thomas Palstra, A. R. Kortan, S. H. Glarum, and Zernike Institute for Advanced Materials

Subjects
Superconductivity, Multidisciplinary, Fullerene, Condensed matter physics, Chemistry, Transition temperature, Doping, Condensed Matter::Materials Science, Meissner effect, Electrical resistivity and conductivity, Condensed Matter::Superconductivity, Physics::Atomic and Molecular Clusters, Diamagnetism, Thin film
Abstract

THE synthesis of macroscopic amounts of C60 and C70 (fullerenes)1 has stimulated a variety of studies on their chemical and physical properties2,3. We recently demonstrated that C60 and C70 become conductive when doped with alkali metals4. Here we describe low-temperature studies of potassium-doped C60 both as films and bulk samples, and demonstrate that this material becomes superconducting. Superconductivity is demonstrated by microwave, resistivity and Meissner-effect measurements. Both polycrystalline powders and thin-film samples were studied. A thin film showed a resistance transition with an onset temperature of 16 K and essentially zero resistance near 5 K. Bulk samples showed a well-defined Meissner effect and magnetic-field-dependent microwave absorption beginning at 18 K. The onset of superconductivity at 18 K is the highest yet observed for a molecular superconductor.

Published
1991

2. An X-Ray Imaging Survey of Quasar Jets: The Complete Survey.

Author

H. L. Marshall, J. M. Gelbord, D. M. Worrall, M. Birkinshaw, D. A. Schwartz, D. L. Jauncey, G. Griffiths, D. W. Murphy, J. E. J. Lovell, E. S. Perlman, and L. Godfrey

Subjects
X-ray imaging, QUASARS, ASTRONOMICAL observations, ASTROPHYSICS, COSMIC background radiation
Abstract

We present Chandra X-ray imaging of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like structure. X-rays are detected from 59% of 56 jets. No counter-jets were detected. The core spectra are fitted by power-law spectra with a photon index Γx, whose distribution is consistent with a normal distribution, with a mean of 1.61+0.04−0.05 and dispersion of 0.15+0.04−0.03. We show that the distribution of αrx, the spectral index between the X-ray and radio band jet fluxes, fits a Gaussian with a mean of 0.974 ± 0.012 and dispersion of 0.077 ± 0.008. We test the model in which kiloparsec-scale X-rays result from inverse Compton scattering of cosmic microwave background photons off the jet’s relativistic electrons (the IC-CMB model). In the IC-CMB model, a quantity Q computed from observed fluxes and the apparent size of the emission region depends on redshift as (1 + z)3+α. We fit Q ∝ (1 + z)a, finding a = 0.88 ± 0.90, and reject at 99.5% confidence the hypothesis that the average αrx depends on redshift in the manner expected in the IC-CMB model. This conclusion is mitigated by a lack of detailed knowledge of the emission region geometry, which requires deeper or higher resolution X-ray observations. Furthermore, if the IC-CMB model is valid for X-ray emission from kiloparsec-scale jets, then the jets must decelerate on average: bulk Lorentz factors should drop from about 15 to 2–3 between parsec and kiloparsec scales. Our results compound the problems that the IC-CMB model has in explaining the X-ray emission of kiloparsec-scale jets. [ABSTRACT FROM AUTHOR]

Published
2018
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3. Fullerenes

Author

GEORGE S. HAMMOND, VALERIE J. KUCK, James R. Heath, R. M. Fleming, B. Hessen, T. Siegrist, A. R. Kortan, P. Marsh, R. Tycko, G. Dabbagh, R. C. Haddon, Sergiu M. Gorun, Mark A. Greaney, Victor W. Day, Cynthia S. Day, Roger M. Upton, Clive E. Briant, John E. Fischer, Paul A. Heiney, David E. Luzzi, David E. Cox, A. F. Hebard, M. J. Rosseinsky, D. W. Murphy, S. H. Glarum, T. T. M. Palstra, A. P. Ramirez, S. J. Duclos, Joel M. Hawkins, Axel Meyer, Timothy A. Lewis, Stefan Loren, Robert D. Johnson, Costantino S. Yannoni, Jesse R. Salem, Gerard Meijer, Donald S. Bethune, Donald M. Cox, Rexford D. Sherwood, Paul Tindall, Kathleen M. Creegan, William Anderson, David J. Martella, Ripudaman Malhotra, Donald C. Lorents, Young K. Bae, Christopher H. Becker, Doris S. Tse, Leonard E. Jusinski, Eric D. Wachsman, R. E. Smalley, F. Wudl, A. Hirsch, K. C. Khemani, T. Suzuki, P.-M. Allemand, A. Koch, H. Eckert, G. Srdanov, H. M. Webb, Paul J. Fagan, Joseph C. Calabrese, Brian Malone, GEORGE S. HAMMOND, VALERIE J. KUCK, James R. Heath, R. M. Fleming, B. Hessen, T. Siegrist, A. R. Kortan, P. Marsh, R. Tycko, G. Dabbagh, R. C. Haddon, Sergiu M. Gorun, Mark A. Greaney, Victor W. Day, Cynthia S. Day, Roger M. Upton, Clive E. Briant, John E. Fischer, Paul A. Heiney, David E. Luzzi, David E. Cox, A. F. Hebard, M. J. Rosseinsky, D. W. Murphy, S. H. Glarum, T. T. M. Palstra, A. P. Ramirez, S. J. Duclos, Joel M. Hawkins, Axel Meyer, Timothy A. Lewis, Stefan Loren, Robert D. Johnson, Costantino S. Yannoni, Jesse R. Salem, Gerard Meijer, Donald S. Bethune, Donald M. Cox, Rexford D. Sherwood, Paul Tindall, Kathleen M. Creegan, William Anderson, David J. Martella, Ripudaman Malhotra, Donald C. Lorents, Young K. Bae, Christopher H. Becker, Doris S. Tse, Leonard E. Jusinski, Eric D. Wachsman, R. E. Smalley, F. Wudl, A. Hirsch, K. C. Khemani, T. Suzuki, P.-M. Allemand, A. Koch, H. Eckert, G. Srdanov, H. M. Webb, Paul J. Fagan, Joseph C. Calabrese, and Brian Malone

Subjects
Fullerenes--Congresses, Buckminsterfullerene--Congresses
Published
1992

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