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Physics

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Displaying 826 - 850 of 1261

Field Effects of Current Crowding at Metal-MoS2 Contacts

March 10, 2016
Author(s)
Hui H. Yuan, Guangjun Cheng, Sheng Yu, Angela R. Hight Walker, Curt A. Richter, Qiliang Li
Gate assisted contact-end Kelvin test structures and gate assisted 4-probe structures have been designed and fabricated to measure the field effects of current crowding at the source/drain contacts of top-gate MoS2 field effect transistors. The transistors

The Structural Origin of Electron Injection Enhancements with Fulleropyrrolidine Interlayers

February 25, 2016
Author(s)
Lee J. Richter, Hyunbok Lee, Christopher McNeil, Eliot Gann, Lars Thomsen, S. Park, J. Jeong, Z. A. Page, Egle Puodziukynaite, Todd Emrick, Alejandro Briseno, John C. Stephenson, Dean M. DeLongchamp
Market demand for ubiquitous, increased functionality products at low cost (the internet of things) is spurring development in additive, solution processing of electronic devices. Performance in thin-film functional devices, be they transistors, diodes, or

Spintronics: Chiral damping

February 24, 2016
Author(s)
Kyoung-Whan Kim, Hyun-Woo Lee
Many objects in nature prefer to spiral in one particular direction to the other. A nanostructured magnetic system with strong spin-orbit coupling now shows that the energy loss is also chiral.

Morphological origins of polarization-induced scattering anisotropy from organic thin films

January 14, 2016
Author(s)
Eliot Gann, Brian A. Collins, Maolong Tang, John R. Tumbleston, Subhrangsu Mukherjee, Harald W. Ade
Anisotropic scattering patterns have been observed from organic thin films that are isotropic on the scale of the probe in polarized resonant X-ray scattering experiments. The symmetry is broken by local correlations between molecular orientation and

Edge-state Transport in Graphene p-n Junctions in the Quantum Hall Regime

December 7, 2015
Author(s)
Nikolai Klimov, Son T. Le, Jun Yan, Pratik Agnihotri, Everett Comfort, Ji Ung Lee, David B. Newell, Curt A. Richter
We experimentally investigate charge carrier transport in a graphene p-n junction device by using independent p-type and n-type electrostatic gating which allow full characterization of the junction interface in the quantum Hall regime covering a wide

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
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