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Physics

Condensed matter

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Displaying 926 - 950 of 1242

Electronic properties of multilayer graphene

March 31, 2012
Author(s)
Hongki Min
In this chapter, we study the electronic structure of arbitrarily stacked multilayer graphene in the absence or presence of magnetic field. Energy band structure and Landau level spectrum are obtained using a pi-orbital continuum model with nearest

Stress propagation in a colloidal suspension under shear

March 1, 2012
Author(s)
William L. George, Pascal Hebraud, Didier Lootens, Mouhamad Khalil, Nicos Martys
The stress propagation in a concentrated attractive colloidal suspension, under shear, is studied using mumerical simulations. A novel way of describing the intercolloidal stress field is proposed and its spatial correlations are studied. An inertia-like

Advanced Code-Division Multiplexers for Superconducting Detector Arrays

February 11, 2012
Author(s)
Kent D. Irwin, Hsiao-Mei Cho, William B. Doriese, Joseph W. Fowler, Gene C. Hilton, Michael D. Niemack, Carl D. Reintsema, Daniel R. Schmidt, Joel N. Ullom, Leila R. Vale
Multiplexers based on the modulation of superconducting quantum interference devices are now regularly used in multi-kilopixel arrays of superconducting detectors for astrophysics, cosmology, and materials analysis. Over the next decade, much larger arrays

Double-Focusing Thermal Triple-Axis Spectrometer at the NCNR

February 2, 2012
Author(s)
Y. Chen, Sung Chang, Yang Zhao, Songxue Chi, William D. Ratcliff, B. G. Ueland, Ross Erwin
The new thermal triple-axis spectrometer at the NIST Center for Neutron Research (NCNR) is located at the BT-7 beam port. The 165 mm diameter reactor beam is equipped with a selection of Söller collimators, beam-limiters, and pyrolytic graphite (PG) filter

Dispersion-Strengthened Silver Alumina for Sheathing Bi2Sr2CaCu2O8+x Multifilamentary Wire

February 1, 2012
Author(s)
Amir Kajbafvala, William Nachtrab, Xifeng Lu, Frank Hunte, Xiaotao Liu, Najib Cheggour, Terence Wong, Justin Schwartz
High strength, high modulus dispersion strengthened (DS) silver-aluminum alloys are studied for sheathing Bi 2Sr 2CaCu 2O8 +x (Bi2212) round wire. Dispersion strengthening is an effective method for producing a fine grain metallurgical structure that is

Probing the timescale of the exchange interaction in a ferromagnetic alloy

January 27, 2012
Author(s)
Justin M. Shaw, Stefan Mathias, Chan La-O-Vorakiat, Hans T. Nembach, Thomas J. Silva, Mark Siemens, Henry Kapteyn, Margaret Murnane
The underlying physics of all ferromagnetic behavior is the cooperative interaction between individual atomic magnetic moments that results in a macroscopic magnetization. In this work, we use extreme ultraviolet pulses from high-harmonic generation as an

Ultrafast Demagnetization Measurements using Extreme Ultraviolet Light: Comparison of Electronic and Magnetic Contributions

January 23, 2012
Author(s)
Thomas J. Silva, Justin M. Shaw, Hans T. Nembach, Margaret M. Murnane, Henry C. Kapteyn, Chan La-O-Vorakiat, Stefan Mathias, Emrah Turgut, Teale A. Carson, Martin Aeschlimann, Claus M. Schneider
Ultrashort pulses of extreme ultraviolet light from high-harmonic generation are a new tool for probing coupled charge, spin, and phonon dynamics with element specificity, attosecond pump-probe synchronization, and time resolution of a few-femtoseconds in

Beyond s-wave scattering for ultracold atoms

January 20, 2012
Author(s)
Ross A. Williams, Lindsay J. LeBlanc, Karina K. Jimenez Garcia, Matthew C. Beeler, Abigail R. Perry, William D. Phillips, Ian B. Spielman
Interactions between particles can be strongly altered by their environment. Here we demonstrate a technique for modifying interactions between ultracold atoms by dressing the bare atomic states with light, creating a screened interaction of vastly

Spin-Charge-Density Wave in a Squircle-Like Fermi Surface for Ultracold Atoms

January 20, 2012
Author(s)
Ian B. Spielman, Dima Makogon, Christiane de Morais Smith
We derive and discuss an experimentally realistic model describing ultracold atoms in an optical lattice including a commensurate, but staggered, Zeeman field. The resulting band structure is quite exotic; fermions in the third band have an unusual rounded

Effect of elastic deformation on frictional properties of few-layer graphene

January 9, 2012
Author(s)
Alexander Y. Smolyanitsky, Jason P. Killgore, Vinod K. Tewary
We describe the results of Brownian dynamics (BD) simulations of an AFM tip scanned on locally suspended few-layer graphene. The effects of surface compliance and sample relaxation are directly related to the observed friction force. We demonstrate that

Chern Numbers Hiding in Time-of-Flight Images

December 21, 2011
Author(s)
Ian B. Spielman, Erhai Zhao, Noah Bray-Ali, Carl J. Williams, Indubala Satija
We present a novel technique for detecting topological invariants -- Chern numbers -- from time-of-flight images of ultra-cold neutral atoms. The Chern number of fermions in a lattice potential depends on magnetic field (for neutral atoms, generated by an

Correlation between in-plane grain orientation and the reversible strain effect on flux pinning in RE-Ba 2 Cu 3 O 7-d coated conductors

December 16, 2011
Author(s)
Daniel C. van der Laan, Loren F. Goodrich, Fraser Douglas, R. Semerad, M Bauer
The pressure dependence of the critical temperature causes a reversible effect of strain on the critical current density and flux pinning strength in many high-temperature superconductors. Recent experiments on patterned coated conductor bridges have shown

Correlation Between the Pressure Dependence of the Critical Temperature and the Reversible Strain Effect on the Critical Current and Pinning Force in Bi 2 Sr 2 CaCu 2 O 8+x Wires

December 16, 2011
Author(s)
Xifeng Lu, Loren F. Goodrich, Daniel C. van der Laan, Jolene D. Splett, Najib Cheggour, T G. Holesinger, F J. Baca
Bi 2Sr 2CaCu 2O 8+x round wires are among the most promising high-temperature superconductor candidates for making high-field magnets that operate at fields above 20 Tesla. Owing to the brittle nature of high-temperature superconductors, their electro

Insensitivity of Sub-Kelvin Electron-Phonon Coupling to Substrate Properties

December 16, 2011
Author(s)
Jason M. Underwood, Peter J. Lowell, Galen C. O'Neil, Joel N. Ullom
We have examined the role of the substrate on electron-phonon coupling in normal metal films of Mn-doped Al at temperatures below 1 K. Normal metal-insulator-superconductor junctions were used to measure the electron temperature in thin metal films as a

Quantum Hall effect on centimeter scale chemical vapor deposited graphene films

December 7, 2011
Author(s)
Tian T. Shen, Wei Wu, Qingkai Yu, Curt A. Richter, Randolph E. Elmquist, David B. Newell, Yong P. Chen
We report observations of well developed half integer quantum Hall effect on mono layer graphene films of 7 mm × 7 mm in size. The graphene films are grown by chemical vapor deposition on copper, then transferred to SiO2/Si substrates, with typical carrier

Reversible effect of strain on transport critical current in Bi 2 Sr 2 CaCu 2 O 8+x superconducting wires: A modified descriptive strain model

December 5, 2011
Author(s)
Najib Cheggour, Xifeng Lu, T G. Holesinger, Theodore C. Stauffer, J Jiang, Loren F. Goodrich
A reversible strain effect on transport critical current I c was found in Bi 2Sr 2CaCu 2O 8+x (Bi-2212) high-temperature superconducting round wires. I c showed unambiguous reversibility at 4 K and 16 T up to an irreversible strain limit of about 0.3 % in

Viewpoint: Topological Invariants Made Manifest

November 28, 2011
Author(s)
Ian B. Spielman, Gediminas Juzeliunas
Topological order in some single particle cold atom systems can now be measured directly, instead of relying on proxies such as the quantized Hall conductance as is usually the case in conventional materials. This new measurement technique complements the
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