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Physics

Condensed matter

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Displaying 926 - 950 of 1261

A high resolution gamma-ray spectrometer based on superconducting microcalorimeters

September 28, 2012
Author(s)
Douglas A. Bennett, Robert D. Horansky, Daniel R. Schmidt, Andrew Hoover, Ryan Winkler, Bradley K. Alpert, James A. Beall, William B. Doriese, Joseph W. Fowler, Gene C. Hilton, Kent D. Irwin, Nathan J. Hoteling, Vincent Y. Kotsubo, John A. Mates, Galen C. O'Neil, Michael W. Rabin, Carl D. Reintsema, Francis J. Schima, Daniel S. Swetz, Leila R. Vale, Joel N. Ullom
Improvements in superconductor device fabrication, detector hybridization techniques, and superconducting quantum interference device readout have made square-centimeter-sized arrays of gammaray microcalorimeters, based on transition-edge sensors (TESs)

Characterization and In-situ Monitoring of Sub-stoichiometric Adjustable TC Titanium Nitride Growth

September 21, 2012
Author(s)
Michael R. Vissers, Jiansong Gao, Jeffrey S. Kline, Martin O. Sandberg, Martin P. Weides, David S. Wisbey, David P. Pappas
The structural and electrical properties of Ti-N films deposited by reactive sputtering depend on their growth parameters, in particular the Ar:N2 gas ratio. We show that the nitrogen percentage changes the crystallographic phase of the film progressively

Anomalous Friction in Suspended Graphene

September 20, 2012
Author(s)
Alexander Y. Smolyanitsky, Jason P. Killgore
Since the discovery of the Amonton's law and with support of modern tribological models, friction between surfaces of three-dimensional materials is known to generally increase when the surfaces are in closer contact. Here, using molecular dynamics

Spin Dynamics in the Time and Frequency Domain

September 15, 2012
Author(s)
Thomas J. Silva
The current status of experimental approaches to analyze the spin wave dynamics in ferromagnetic nanoscale structures is reviewed. Recent developments in frequency- and field swept spectroscopy to determine the resonant response of nanoscale ferromagnets

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

September 13, 2012
Author(s)
Markus Kindermann, Bruno Uchoa, David L. Miller
In this article, we derive an effective theory of graphene on a hexagonal boron nitride (h-BN) substrate. We show that the h-BN substrate generically opens a spectral gap in graphene despite the lattice mismatch. The origin of that gap is particularly

Ultrafast manetization enhancement in metallic multilayers driven by superdiffusive spin current

September 4, 2012
Author(s)
Thomas J. Silva, Justin M. Shaw, Hans T. Nembach, Dennis Rudolf, Chan La-O-Vorakiat, Marco Battiato, Roman Adam, Emrah Turgut, Stefan Mathias, Margaret M. Murnane, Henry C. Kapteyn, Claus M. Schneider
Uncovering the physical mechanisms that govern ultrafast charge and spin dynamics is crucial for understanding correlated matter as well as the fundamental limits of ultrafast spin-based electronics. Spin dynamics in magnetic materials can be driven by

Etch induced microwave losses in titanium nitride superconducting resonators

June 25, 2012
Author(s)
Martin O. Sandberg, Jeffrey S. Kline, Martin P. Weides, David S. Wisbey, David P. Pappas
We have investigated the correlation between the microwave loss and patterning method for coplanar waveguide titanium nitride resonators fabricated on silicon wafers. Three different methods were investigated: fluorine- and chlorine-based reactive ion

Propagation and control of nano-scale, magnetic droplet solitons

June 11, 2012
Author(s)
Thomas J. Silva, Mark Hoefer, Matteo Sommacal
The propagation and controlled manipulation of strongly nonlinear, two-dimensional solitonic states in a thin, anisotropic ferromagnet is theoretically demonstrated. It has been recently proposed that spin polarized currents in a nanocontact device could

Real-time measurements of plasma photoresist modifications: The role of plasma vacuum ultraviolet radiation and ions

May 23, 2012
Author(s)
Weilnboeck Florian, Nirav Kumar, Gottlieb Oehrlein, Ting-Ying Chung, D Graves, Mingqi Li, Eric A. Hudson, Eric Benck
Plasma-induced roughness development of photoresist (PR) can be due to synergistic interactions of surface modifications introduced by ions, bulk material modifications by ultraviolet (UV)/vacuum ultraviolet (VUV) radiation, and increased temperature

A two-fluid model for the transition shape in transition-edge sensors

May 1, 2012
Author(s)
Douglas A. Bennett, Daniel S. Swetz, Robert D. Horansky, Daniel R. Schmidt, Joel N. Ullom
Superconducting microcalorimeters based on transition-edge sensors (TESs) are being successfully used in applications ranging from optical photon counting to gamma-ray and alpha particle spectroscopy. Practical instruments often require a complex

Quantum interference between two single photons of different microwave frequencies

April 20, 2012
Author(s)
Francois E. Nguyen, Eva A. Zakka-Bajjani, Jose A. Aumentado, Raymond W. Simmonds
Quantum interference is an important tool for fields such as lithography, metrology and quantum processing. Two identical optical photons (photons with the same wavelength and polarization) simultaneously sent through the two input ports of a semi

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
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