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Physics

Condensed matter

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Displaying 1026 - 1050 of 1253

Many-Pole Model of Inelastic Losses Applied to Calculations of XANES

December 16, 2009
Author(s)
Eric L. Shirley, Joshua J. Kas, J. T. Vinson, N. Trcera, D. Cabaret, John J. Rehr
Conventional Kohn-Sham band-structure methods for calculating deep-core x-ray spectra typically neglect photo-electron self-energy effects, which give rise to an energy dependent shift and broadening of the spectra. Here an a posteriori procedure is

Ultrafast Demagnetization Dynamics at the M Edges of Magnetic Elements Observed Using a Tabletop High-Harmonic Soft X-Ray Source

December 15, 2009
Author(s)
Thomas J. Silva, Justin Shaw, Hans Nembach, Chan La-O-Vorakiat, Mark Siemens, Margaret M. Murnane, Henry C. Kapteyn, Stefan Mathias, Martin Aeschlimann, Patrik Grychtol, Roman Adam, Claus M. Schneider
We use few-femtosecond soft x-ray pulses from high-harmonic generation to extract element-specific demagnetization dynamics and hysteresis loops of a compound material for the first time. Using a geometry where high-harmonic beams are reflected from a

The effect of strain on grains and grain boundaries in YBa2Cu3O7-d coated conductors

December 9, 2009
Author(s)
Daniel C. van der Laan, John (Jack) W. Ekin, Timothy J. Haugan, Paul N. Barnes, Dmytro Abraimov, Fumitake Kametani, David C. Larbalestier, Marty Rupich
The role of grains and grain boundaries in producing reversible strain effects on the transport current critical current (Ic) of YBa2Cu3O7-δ coated conductors was investigated by comparing the strain ε dependence of full-width coated conductors with that

Electrical Characterization of Soluble Anthradithiophene Derivatives

November 19, 2009
Author(s)
Brad Conrad, Calvin Chan, Marsha A. Loth, John E. Anthony, David J. Gundlach
Organic semiconductors remain an active subject for device physics and material science because of their varied electrical properties and potential for low-cost, high-throughput roll-to-roll processing. Several high-mobility oligomers, such as pentacene

Effect of Surface Modes on Photon Propagation through Dielectric Bandgaps

October 28, 2009
Author(s)
Natalia Malkova, Sergey V. Polyakov, Alan L. Migdall, Garnett W. Bryant
We investigate the Hartman saturation effect of photons traveling through barriers created by bandgaps of multilayer stacks. In particular, we investigate theoretically the recently observed jumps in photon transversal times due to adding a single layer

Energy Decay in Josephson Qubits from Non-equilibrium Quasiparticles

August 26, 2009
Author(s)
Jose A. Aumentado, John M. Martinis, M Ansmann
We calculate the energy decay rate of Josephson qubits and superconducting resonators from non-equilibrium quasiparticles. The decay rates from experiments are shown to be consistent with our predictions based on a prior measurement of the quasiparticle

Coupled magnetic and ferroelectric hysteresis in multiferroic Ni ^ d3 ^ V ^ d2 ^ O ^ d8 ^

August 18, 2009
Author(s)
I. Cabrera, M. Kenzelmann, Wangchun Chen, Ross Erwin, Thomas R. Gentile, Juscelino Leao, Jeffrey W. Lynn, N. Rogado, R. J. Cava, C. Broholm, G. Lawes, Ying Chen
Electric control of spin chirality in a magnetically frustrated multiferroic is demonstrated through polarized magnetic neutron diffraction. Cooling to the cycloidal multiferroic phase of Ni ^ d3 ^ V ^ d2 ^ O ^ d8 ^ in an electric field causes the

Anomalous thermal behavior in microcalorimeter gamma-ray detectors

July 20, 2009
Author(s)
Robert D. Horansky, James A. Beall, Kent D. Irwin, Joel N. Ullom
Improving the resolution of gamma-ray detectors is important for many fields, including determinations of the Lamb shift in atoms with high atomic numbers , nuclear treaty verification , and environmental monitoring. High-purity germanium detectors are

The-Final-State Symmetry of Na 1s Core-shell Excitons in NaCl and NaF

July 8, 2009
Author(s)
Eric L. Shirley, K. P. Nagle, G T. Seidler, T. T. Fister, J. A. Bradley, F. C. Brown
We report measurements of the Na 1s contribution to the nonresonant inelastic x-ray scattering (NRIXS) from NaCl and NaF. Prior x-ray absorption studies have observed two pre-edge excitons in both materials. The momentum transfer-dependence (q-dependence)

Inter-Laboratory Comparisons of NbTi Critical Current Measurements

June 22, 2009
Author(s)
Arno Godeke, D. Turrioni, T. Boutboul, Najib Cheggour, A. K. Ghosh, Loren F. Goodrich, M Meinesz, A. den Ouden
We report on a multi-institute comparison of critical current data, measured on a modern Large Hadron Collider (LHC) NbTi wire that has shown a standard deviation below 1% in critical current density spread in more than 1500 measurements. Inter-laboratory

Internal tin Nb3Sn conductors engineered for fusion and particle accelerator applications

June 22, 2009
Author(s)
Jeffrey Parrell, Y. Zhang, Michael Field, M Meinesz, Yonghua Huang, H Miao, Seungok Hong, Najib Cheggour, Loren F. Goodrich
The critical current density (Jc) of Nb3Sn strand has been significantly improved over the last several years. For most magnet applications, high Jc internal tin has displaced bronze process strand. The highest Jc values are obtained from distributed

Number Fluctuations and Energy Dissipation in Sodium Spinor Condensates

June 5, 2009
Author(s)
Yingmei Liu, Eduardo N. Gomez, Stephen E. Maxwell, Lincoln D. Turner, Eite Tiesinga, Paul D. Lett
We characterize fluctuations in atom number and spin populations in F = 1 sodium spinor condensates. The time evolution of the population fluctuations shows a maximum. We interpret this as evidence of a dissipation-driven separatrix crossing in phase space

Topological Insulators and Metals in Atomic Optical Lattices

May 28, 2009
Author(s)
Tudor Stanescu, Victor Galitski, Jay Vaishnav, Charles W. Clark, Sankar Das Sarma
We propose the realization of topological quantum states with cold atoms trapped in an optical lattice. We discuss an experimental setup that generates a two-dimensional hexagonal lattice in the presence of a light-induced periodic vector potential, which

Observing the Quantization of Zero Mass Carriers in Graphene

May 15, 2009
Author(s)
Joseph A. Stroscio, Gregory M. Rutter, D. L. Miller, K. Kubista, W. A. de Heer, Phillip N. First
Application of a magnetic field to conductors causes the charge carriers to circulate in cyclotron orbits with quantized energies called Landau levels (LLs). These are equally spaced in normal metals and two-dimensional electron gases. In graphene, however

Time domain measurement of phase noise in a spin torque oscillator

May 13, 2009
Author(s)
Mark W. Keller, Anthony B. Kos, Thomas J. Silva, William H. Rippard, Matthew R. Pufall
We measure phase noise from the zero crossings of the voltage vs. time waveform of a spin torque nanocontact oscillating in a vortex mode. The power spectrum of the phase noise varies with Fourier frequency f as 1/f 2, consistent with frequency

Phonon softening and anomalous mode near the x c = 0.5 quantum critical point inCa 2-x Sr x RuO 4

May 4, 2009
Author(s)
R. G. Moore, M. D. Lumsden, M. B. Stone, Jiandi Zhang, Ying Chen, Jeffrey Lynn, R. Jin, D Mandrus, E. W. Plummer
Inelastic neutron scattering is used to measure the temperature-dependent phonon dispersion in Ca2−xSrxRuO4(x=0.4,0.6). The in-plane Σ4 octahedral tilt mode softens significantly at the zone boundary of the high-temperature tetragonal (HTT) I41/acd

Itinerant spin excitations near the hidden order transition in URu2Si2

April 22, 2009
Author(s)
J. A. Janik, H. D. Zhou, Y.-J. Jo, L. Balicas, G. J. MacDougall, G. M. Luke, J. D. Garrett, K. J. McClellan, E. D. Bauer, J. L. Sarrao, Yiming Qiu, John R. Copley, Z. Yamani, W. J. Buyers, C. R. Wiebe
By means of neutron scattering we show that the high-temperature precursor to the hidden order state of the heavy fermion superconductor URu 2Si 2 exhibits heavily damped incommensurate paramagnons whose strong energy dispersion is very similar to that of

Cryocoolers: State of the art and recent developments

March 31, 2009
Author(s)
Ray Radebaugh
Cryocooler performance and reliability are continually improving. Consequently, they are more and more frequently implemented by physicists in their laboratory experiments or for commercial and space applications. The five types of cryocoolers most
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