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Physics

Condensed matter

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Displaying 826 - 850 of 1253

Optical Control of Spin-Valley-Orbital States of Group-V Donors in Silicon

November 11, 2015
Author(s)
Michael Gullans, Jacob M. Taylor
We show how to to achieve spin-selective excitation of the valley-orbit states of group-V donors (P, As, Sb, Bi) in silicon using optical fields. We consider two approaches based on exploiting resonant, far-infrared (IR) transitions of the neutral donor or

Injection Locking of a Semiconductor Double Quantum Dot Micromaser

November 2, 2015
Author(s)
Michael Gullans, Y.-Y. Liu, J. Stehlik, Jacob M. Taylor, Jason Petta
The semiconductor double quantum dot (DQD) micromaser generates photons through single electron tunneling events. Charge noise couples to the DQD energy levels, resulting in a maser linewidth that is 100 times larger than the Schawlow-Townes prediction. We

Efficient Quantum State Transfer in an Engineered Chain of Quantum Bits

September 15, 2015
Author(s)
Emanuel Knill, Michael Vissers, David P. Pappas, Martin Sandberg
Here we present a method of performing quantum state transfer in a chain of superconducting quantum bits. Our protocol is based on the engineerability of the energy levels of superconducting quantum systems. This, together with the tunability of the

Large-scale core-level Bethe-Salpeter equation calculations

August 31, 2015
Author(s)
Keith Gilmore, John Vinson, Eric L. Shirley, David Prendergast, Chaitanya D. Pemmaraju, Josh J. Kas, John J. Rehr, Fernando D. Vila
We present an efficient implementation of the Bethe-Salpeter equation (BSE) method for obtaining core-level spectra including x-ray absorption (XAS), x-ray emission (XES), and both resonant and non-resonant inelastic x-ray scattering spectra (N/RIXS)

Frequency-tunable Superconducting Resonators via Nonlinear Kinetic Inductance

August 13, 2015
Author(s)
Michael Vissers, Johannes Hubmayr, Jiansong Gao, Martin Sandberg, Saptarshi Chaudhuri, Clint Bockstiegel
We have designed, fabricated and tested a frequency-tunable high-Q superconducting resonator made from niobium titanium nitride film. The frequency tunability is achieved by injecting a DC current through a special current-directing circuit into the

Physical implementation of coherently-coupled oscillator networks

August 13, 2015
Author(s)
Matthew R. Pufall, William H. Rippard, Gyorgy Csaba, Wolfgang Porod, George Bourianoff, Dmitri Nikonov
We present a combined experimental and simulation study of the physical implementation of coherently coupled oscillator networks composed of spin-torque oscillators (STOs). Based on published works and on our recent experiments, we review the behavior of

Macroscopic Subkelvin Refrigerator Employing Superconducting Tunnel Junctions

August 10, 2015
Author(s)
Xiaohang NMN Zhang, Peter J. Lowell, Brandon L. Wilson, Galen C. O'Neil, Joel N. Ullom
In this paper, we demonstrate a general-purpose macroscopic refrigerator based on the transport of hot electrons through superconducting tunnel junctions. Our refrigerator is intended to provide access to temperatures below those accessible using pumped

Quasiparticle recombination in hotspots in superconducting current-carrying nanowires

August 6, 2015
Author(s)
Alex Kozorezov, Colin Lambert, Francesco Marsili, Martin Stevens, Varun Verma, Jeffrey A. Stern, Rob Horansky, Shellee D. Dyer, Shannon Duff, David P. Pappas, Adriana Lita, Matthew D. Shaw, Richard Mirin, Sae Woo Nam
We describe a kinetic model of recombination of nonequilibrium quasiparticles generated by single photon absorption in superconducting current-carrying nanowires. The model is developed to interpret two-photon detection experiments in which a single photon

Thermal Conductance Engineering for High-Speed TES Microcalorimeters

July 22, 2015
Author(s)
James P. Hays-Wehle, Daniel R. Schmidt, Joel N. Ullom, Daniel S. Swetz
Many current and future applications for superconducting transition-edge sensor (TESmicrocalorimeters require significantly faster pulse-response than is currently available. X-ray spectroscopy experiments at next-generation synchrotron light sources need

Controlling the electronic structure of graphene using surface-adsorbate interactions

July 21, 2015
Author(s)
Piotr Matyba, Adra V. Carr, Cong Chen, David L. Miller, Thomas Orlando, Stefan Mathias, Mark W. Keller, Henry C. Kapteyn, Margaret M. Murnane
Hybridization of atomic orbitals in graphene on Ni(111) opens up a large energy gap of ≈2.8 eV between nonhybridized states at the K point. Here we use alkali-metal adsorbate to reduce and even eliminate this energy gap, and also identify a new mechanism

Suppression of Spin Pumping between Ni80Fe20 and Cu by a Graphene Interlayer

June 7, 2015
Author(s)
William J. Gannett, Mark W. Keller, Hans Nembach, Thomas J. Silva, Ann Chiaramonti Debay
Abstract We compare ferromagnetic resonance measurements of Py (Ni80Fe20) films sputtered onto Cu(111) with and without a graphene (Gr) interlayer grown by chemical vapor deposition before Py deposition. We find the expected damping enhancement from spin

Tunable Spin Qubit Coupling Mediated by a Multi-Electron Quantum Dot

June 4, 2015
Author(s)
Vanita Srinivasa, Haitan Xu, Jacob M. Taylor
We present an approach for entangling electron spin qubits localized on spatially separated impurity atoms or quantum dots via a multi-electron, two-level quantum dot. The effective exchange interaction mediated by the dot can be understood as the simplest

Density-Functional Theory Investigation of Oxidative Corrosion on the UO2(111) Surface

May 14, 2015
Author(s)
Anne M. Chaka, Gloria A. Oxford, Joanne E. Stubbs, Peter J. Eng, John R. Bargar, Thomas P. Trainor
Corrosion and weathering of uranium dioxide (UO2) is a serious concern in a broad range of technological and environmental systems. Oxidation of UO2 can destroy the integrity of nuclear fuel rods, as well as result in the bioavailability of uranium in

Phonon Assisted Gain in a Semiconductor Quantum Dot Maser

May 13, 2015
Author(s)
Michael Gullans, Yinyiu Liu, George Stehlik, Jason Petta, Jacob M. Taylor
We develop a microscopic model for the recently demonstrated double quantum dot (DQD) maser. In characterizing the gain of this device we find that, in addition to the direct stimulated emission of photons, there is a large contribution from transitions

Computational Study of Trimer Self-Assembly and Fluid Phase Behavior

April 24, 2015
Author(s)
Harold W. Hatch, Vincent K. Shen, Jeetain Mittal
The fluid phase diagram of trimer particles composed of one central attractive bead and two repulsive beads was determined as a function of simple geometric parameters using flat-histogram Monte Carlo methods. A variety of self-assembled structures were

Nanoscale Spin Valve Josephson Junction Devices

April 14, 2015
Author(s)
Burm Baek, William H. Rippard, Matthew R. Pufall, Samuel P. Benz, Stephen E. Russek, Horst Rogalla, Paul D. Dresselhaus
Traditionally, superconductivity and magnetism have had a mutually exclusive relationship. However, the physics of superconductor-ferromagnet hybrid structures turned out to be far from being simply destructive, which has led to the hope of a new breed of

Nearly-linear light cones in long-range interacting quantum systems

April 13, 2015
Author(s)
Michael S. Foss-Feig, Zhexuan Gong, Charles W. Clark, Alexey V. Gorshkov
In non-relativistic quantum theories with short-range Hamiltonians, a velocity $v$ can be chosen such that the influence of any local perturbation is approximately confined to within a distance $r$ until a time $t \sim r/v$, thereby defining a linear light

Model colloid system for interfacial sorption kinetics

March 24, 2015
Author(s)
Paul NMN Salipante, Steven D Hudson
Adsorption kinetics of nanometer scale molecules, such as proteins at interfaces, is usually determined through measurements of surface coverage. Their small size limits the ability to directly observe individual molecule behavior. Hence, the effect of

Local Strain Exerted on Nb 3 Sn Filaments in an ITER Strand

March 13, 2015
Author(s)
Kozo Osamura, Shutaro Machiya, Stefanus Harjo, Tatsushi Nakamoto, Najib Cheggour, Arend Nijhuis
As part of an international project to benchmark facilities for measuring the strain dependence of critical current in ITER Nb 3Sn strands, direct measurement of local strain exerted on Nb 3Sn filaments was attempted at cryogenic temperature by means of
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