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Physics

Condensed matter

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Displaying 951 - 975 of 1237

Graphene-metal interconnect: an atomistic simulation

August 11, 2011
Author(s)
Alexander Y. Smolyanitsky, Vinod K. Tewary
We develop a set of computationally efficient and accurate interatomic interactions for an atomistic simulation of the properties of graphene on nickel surface. The approach is based on the modified embedded atom method (MEAM) for the C-C and Ni-Ni

Controlling Formation of Atomic Step Morphology on Micro-patterned Si (100)

August 9, 2011
Author(s)
Kai Li, Pradeep Namboodiri, Sumanth B. Chikkamaranahalli, Gheorghe Stan, Ravikiran Attota, Joseph Fu, Richard M. Silver
Micro scale features are fabricated on Si (100) surfaces using lithographic techniques and then thermally processed in an ultra high vacuum (UHV) environment. Samples are flash heated at 1200 °C and further annealed at 1050 °C for 18 hours. The surface

Damping phenomena in Co 90 Fe 10 /Ni multilayers and alloys

July 6, 2011
Author(s)
Justin M. Shaw, Hans T. Nembach, Thomas J. Silva
We used perpendicular ferromagnetic resonance to measure the damping parameter in Co 90Fe 10/Ni multilayers over a wide range of layer thicknesses. The magnetic anisotropy within this range varied from in-pane to out-of-plane. We measured (Co 90Fe 10) xNi

Strongly quadrature-dependent noise in superconducting microresonators measured at the vacuum-noise limit

June 9, 2011
Author(s)
Jiansong Gao, Kent D. Irwin, Gene C. Hilton, John A. Mates, Daniel R. Schmidt, Leila R. Vale, Konrad W. Lehnert, Francois Mallet, Jonas Zmuidzinas
We report noise measurement of superconducting micro-resonators with a Josephson parametric amplifier. These resonators show significant amount of frequency noise caused by surface two-level systems. However, in the dissipation quadrature, no excess noise

Method for determining the irreversible strain limit of Nb 3 Sn wires

June 6, 2011
Author(s)
Loren F. Goodrich, Najib Cheggour, Xifeng Lu, Jolene D. Splett, Theodore C. Stauffer, Bernard J. Filla
We have defined a rigorous and reliable method for determining the irreversible strain limit of Nb 3Sn wires. The critical current (I c) is measured as a function of applied longitudinal strain (ε), I c(ε), at one magnetic field and a temperature of 4.0 K

HIGHLY CHARGED ION INTERACTIONS WITH THIN INSULATING FILMS

June 1, 2011
Author(s)
Joshua M. Pomeroy, Russell E. Lake, C E. Sosolik
The electrical conductance of magnetic tunnel junction (MTJ) devices whose ultra-thin aluminum oxide tunnel barrier was irradiated by highly charged ions (HCIs) increases linearly with the fluence of HCIs, while retaining a current-voltage relationship

An optical lattice of flux

April 25, 2011
Author(s)
Ian B. Spielman
A suitable optical lattice for cold atoms could produce a large effective magnetic field in which the atoms would realize analogs to quantum Hall states.

Chiral Rashba Spin Textures in Ultra-Cold Fermi Gases

April 21, 2011
Author(s)
Ian B. Spielman, Jay Sau, Rajdeep Sensarma, Stephen Powell, Sankar Das Sarma
Spin-orbit coupling is an important ingredient in many recently discovered phenomena such as the spin-Hall effect and topological insulators. Of particular interest is topological superconductivity, with its potential application in topological quantum

Short-Range Ordering in the Modified Honeycomb Lattice Compound SrHo 2 O 4

April 17, 2011
Author(s)
S Ghosh, H. D. Zhou, L. Balicas, Jason S. Gardner, Yiming Qiu, C. R. Wiebe
The low temperature behaviour of single crystalline SrHo 2O 4 has been characterized by DC mag- netic susceptibility, heat capacity, and neutron scattering experiments. Our results show that despite the lack of magnetic long-ranged ordering in the presence

A Route to Quantum Magnetism

April 13, 2011
Author(s)
Ian B. Spielman
The trend in using ultracold atoms as simulators of condensed-matter and many-body phenomena is gaining momentum. These systems can now be used to simulate quantum magnetism.

Superflow in a Toroidal Bose-Einstein Condensate: An Atom Circuit with a Tunable Weak Link

March 28, 2011
Author(s)
Kevin C. Wright, Anand Ramanathan, Sergio R. Muniz, Wendell Hill, Kristian Helmerson, William D. Phillips, Gretchen K. Campbell, Christopher Lobb
We have created a long-lived (40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier creates a tunable weak link in the condensate circuit, which can affect the current around the loop

Optics contamination studies in support of high-throughput EUV lithography tools

March 25, 2011
Author(s)
Shannon B. Hill, Fardina Asikin, Lee J. Richter, Steven E. Grantham, Charles S. Tarrio, Thomas B. Lucatorto, Sergiy Yulin, Mark Schurmann, Viatcheslav Nesterenko, Torsten Feigl
We report on optics contamination rates induced by exposure to broad-bandwidth, high-intensity EUV radiation peaked near 8 nm in a new beamline at the NIST synchrotron. The peak intensity of 50 mW/mm2 allows extension of previous investigations of

Perspective on Probing Metallic Ferromagnetism with Electrons

March 21, 2011
Author(s)
Daniel T. Pierce
This article presents a brief review of some of the many insights gained about metallic ferromagnetism using spin-polarized electrons as probes. Aspects of metallic ferromagnetism discussed include spin-dependent electronic structure, spin-dependent mean

Bethe-Salpeter Equation Calculations of Core Excitation Spectra

March 4, 2011
Author(s)
Eric L. Shirley, Vinson T. John, John J. Rehr, Joshua J. Kas
We present a hybrid approach for GW/Bethe-Salpeter Equation (BSE) calculations of core excitation spectra, including x-ray absorption (XAS), electron energy loss spectra (EELS), and nonresonant inelastic x-ray scattering (NRIXS). The method is based on ab

Two Level System Loss in Superconducting Microwave Resonators

January 13, 2011
Author(s)
David P. Pappas, Michael R. Vissers, David S. Wisbey, Jeffrey S. Kline, Jiansong Gao
High quality factor, i.e. low loss, resonators are important for quantum information storage and addressing. In this work we study the resonance frequency and loss in superconducting coplanar waveguide resonators as a function of temperature and power. We

Evidence that the reversible strain effect on critical current density and flux pinning in Bi2Sr2Ca2Cu3Ox tapes is caused entirely by the pressure dependence of the critical temperature

December 23, 2010
Author(s)
Daniel C. van der Laan, J. F. Douglas, Cameron C. Clickner, Theodore C. Stauffer, Loren F. Goodrich, Hans J. van Eck
It is well known that the critical temperature of cuprate- and iron-based high-temperature superconductors changes with pressure. YBa 2Cu 3O 7-δ coated conductors, as well as Bi 2Sr 2CaCu 2O x and Bi 2Sr 2Ca 2Cu 3O x tapes and wires, show a clear

Engineering Time-Reversal Invariant Topological Insulators With Ultra-Cold Atoms

December 16, 2010
Author(s)
Ian B. Spielman, Nathan Goldman, Indubala I. Satija, Predrag Nikolic, Alejandro Bermudez, Miguel A. Martin-Delgado, Maciej Lewenstein
Topological insulators are a broad class of unconventional states that respect all symmetries of the system, but have non-trivial transport and topological properties which cannot be defined locally. Until recently, all known realizations of these phases

Modeling of Self-Heating Mechanism in the Design of Superconducting Limiters

December 10, 2010
Author(s)
Eduard Rocas, Juan C. Collado Gomez, Jordi Mateu, Nathan D. Orloff, James C. Booth
This work proposes a modeling method to simulate how temperature rise, due to power dissipation, affects the performance of a HTS limiter. The spatial temperature rise distribution across and along a HTS transmission line is determined by heat generation

Low loss superconducting titanium nitride coplanar waveguide resonators

December 9, 2010
Author(s)
Michael Vissers, Jiansong Gao, David S. Wisbey, David P. Pappas, C. C. Tsuei, A. D. Corcoles, Matthias Steffen
Thin films of TiN were sputter-deposited onto Si and sapphire wafers with and without SiN buffer layers. The films were fabricated into RF coplanar waveguide resonators, and internal quality factor measurements were taken at millikelvin temperatures in

Time-division SQUID multiplexers with reduced sensitivity to external magnetic fields

November 29, 2010
Author(s)
Greg Stiehl, Hsiao-Mei Cho, Gene C. Hilton, Kent D. Irwin, John A. Mates, Carl D. Reintsema, Barry L. Zink
We have developed time-division SQUID multiplexers to read out large arrays of transition-edge sensor (TES) detectors. These multiplexers are used in many applications that require exquisite control of systematic error. One important application is the

Electron Dynamics of Crystalline 4-He at High Pressures

October 29, 2010
Author(s)
Eric L. Shirley, H. K. Mao, Yang Ding, Peter Eng, Yong Q. Cai, Paul Chow, Yuming Xiao, Jinfu Shu, Russell J. Hemley, Chichang Kao, Wendy L. Mao
At high pressures, helium crystallizes as a unique insulator with the widest known electronic band gap. However, in the vicinity of the band gap and above, electronic excitations have been previously inaccessible to direct measurements. Using an optimized
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