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Physics

Condensed matter

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Displaying 751 - 775 of 1261

High-resolution valence and core excitation spectra of solid C60 via first-principles calculations and experiment

March 8, 2017
Author(s)
Eric L. Shirley, Keith Gilmore, Josh J. Kas, John J. Rehr, Fernando D. Vila, Frederic Fossard, Gilles Hug
We present calculated optical and carbon 1s near-edge spectra of crystalline and molecular C60 and those measured with high-resolution electron energy-loss spectroscopy. The near-edge calculations are carried out using three different methods: solution of

Sodium Layer Chiral Distribution and Spin Structure of Na 2 Ni 2 TeO 6 with a Ni Honeycomb Lattice

March 8, 2017
Author(s)
Sunil K. Karna, Yang Zhao, R. Sankar, M. Avdeev, P. C. Tseng, C. W. Wang, G. J. Shu, K. Matan, G. Y. Guo, F. C. Chou
The crystal structure of P2-type Na 2Ni 2TeO 6 is best described as layers that are composed of Te-centered edge-sharing NiO 6 octahedra in honeycomb lattice with intercalated Na ions in the van der Waals (vdW) gaps. Although the crystal symmetry has been

Accurate X-Ray Spectral Predictions: An Advanced Self-Consistent-Field Approach Inspired by Many-Body Perturbation Theory

March 2, 2017
Author(s)
Yufeng Liang, John Vinson, Chaitanya D. Pemmaraju, Walter Drisdell, Eric L. Shirley, David Prendergast
The self-consistent-field method and the many-body approach are two cornerstones for obtaining electronic excitations from first- principles. Using the two distinct theories, we study the O 1s core excitations that have become increasingly important for

Observation of optomechanical buckling phase transitions

March 1, 2017
Author(s)
Jacob M. Taylor, John R. Lawall, Haitan Xu, Utku Kemiktarak, Jingyun Fan, Stephen Ragole
Correlated phases of matter provide long-term stability for systems as diverse as solids, magnets, and potential exotic quantum materials. Mechanical systems, such as relays and buckling transition spring switches can yield similar stability by exploiting

Predicting low-temperature free energy landscapes with flat-histogram Monte Carlo methods

February 21, 2017
Author(s)
Nathan Mahynski, Marco A. Blanco Medina, Jeffrey R. Errington, Vincent K. Shen
We present a method of predicting the free energy landscape of fluids at low temperatures from flat-histogram grand canonical Monte Carlo simulations performed at higher ones. We illustrate our approach for both pure and multicomponent systems using two

Ba 8 CoNb 6 O 24 : A Spin-1/2 Triangular-Lattice Heisenberg Antiferromagnet in the Two-Dimensional Limit

February 17, 2017
Author(s)
R. Rawl, L. Ge, H. Agrawal, Y. Kamiya, C. R. Dela Cruz, Nicholas Butch, X. F. Sun, M. Lee, E. S. Choi, J. Oitmaa, C. D. Batista, M. Mourigal, H. D. Zhou, J. Ma
The quasi-two-dimensional perovskite Ba 8CoNb 6O 24 comprises equilateral effective spin-1/2 Co 2+ triangular layers separated by six nonmagnetic Nb 5+ layers. Susceptibility, specific heat and neutron scattering measurements combined with high-temperature

Field Programmable Josephson Amplifier for non-reciprocal microwave signal processing

February 17, 2017
Author(s)
Florent Q. Lecocq, Leonardo Ranzani, Gabriel A. Peterson, Katarina Cicak, Raymond W. Simmonds, John D. Teufel, Jose A. Aumentado
We report on the design and implementation of a Field Programmable Josephson Amplifier (FPJA) - a compact and lossless superconducting circuit that can be programmed in-situ by a set of microwave drives to perform reciprocal and non-reciprocal frequency

Partial breakdown of quantum thermalization in a Hubbard-like model

February 17, 2017
Author(s)
James R. Garrison, Ryan Mishmash, Matthew P. Fisher
We study the possible breakdown of quantum thermalization in a model of itinerant electrons on a one-dimensional chain without disorder, with both spin and charge degrees of freedom. The eigenstates of this model exhibit peculiar properties in the

Ultrafast time-resolved x-ray absorption spectroscopy of ferrioxalate photolysis with a laser plasma x-ray source and microcalorimeter array

February 17, 2017
Author(s)
Galen C. O'Neil, Joel N. Ullom, Luis Miaja Avila, Young Il Joe, Joseph W. Fowler, Carl D. Reintsema, Daniel S. Swetz, Kevin L. Silverman, Daniel R. Schmidt, Bruce D. Ravel, Gene C. Hilton, William B. Doriese, Bradley K. Alpert, Ralph Jimenez
Using a table-top apparatus based upon a laser plasma x-ray source and an array of cryogenic microcalorimeter x-ray detectors, we have measured the transient x-ray absorption spectrum during the ferrioxalate photoreduction reaction. We observe the Fe K

Unified scaling law for flux pinning in practical superconductors: Part 3. Extrapolations from minimum datasets and applications of the extrapolative scaling expression

February 16, 2017
Author(s)
John (Jack) W. Ekin, Najib Cheggour, Loren F. Goodrich, Jolene D. Splett
The accuracy of present fitting equations to interpolate and extrapolate full Ic(B,T,ε) datasets is evaluated and compared with the extrapolative scaling expression (ESE) derived in Part 2. Accuracy is analyzed in terms of RMS error and fractional

Enabling photoemission electron microscopy in liquids via graphene-capped microchannel arrays

February 8, 2017
Author(s)
Hongxuan Guo, Evgheni Strelcov, Alexander Yulaev, Jian Wang, Narayana Appathurai, Stephen Urquhart, John Vinson, Subin Sahu, Michael P. Zwolak, Andrei Kolmakov
Photoelectron emission microscopy (PEEM) is a powerful tool to spectroscopically access dynamic surface processes at the nanoscale but is traditionally limited to ultra-high or moderate vacuum conditions. Here, we develop a novel graphene-capped

Ultrafast modulation of x-ray absorption by coherent phonon excitations

February 1, 2017
Author(s)
Eric L. Shirley, Jannick Weisshaupt, Michael Woerner, Marc J. Vrakking, Thomas Elsaesser, Andreas Borgschulte
X-ray absorption in solids promotes an electron from an atomic core level to the conduction band states, and near-edge spectra structure gives insight into local atomic geometry and chemical bonding effects. Based on a novel implementation of femtosecond x

Compact 2.2 K Cooling System for Superconducting Nanowire Single Photon Detectors

January 25, 2017
Author(s)
Vincent Y. Kotsubo, Ray Radebaugh, Sae Woo Nam, Joel N. Ullom, Brandon L. Wilson, Paul Hendershott, Micheal Bonczyski
We are developing a compact, low power, closed cycle cooling system for Superconducting Nanowire Single Photon Detectors. The base temperature of the present prototype, which uses a helium-4 Joule-Thomson stage, is 2.2 K with over 1.2 mW of cooling. This

Measurements of trapped-ion heating rates with exchangeable surfaces in close proximity

January 15, 2017
Author(s)
Dustin A. Hite, Kyle S. McKay, Shlomi Salman Kotler, Dietrich G. Leibfried, David J. Wineland, David P. Pappas
Electric-field noise from the surfaces of ion-trap electrodes couples to the ion’s charge causing heating of the ion’s motional modes. This heating limits the fidelity of quantum gates implemented in quantum information processing experiments. The exact

Advances in RRAM technology: identifying and mitigating roadblocks

January 13, 2017
Author(s)
Dmitry Veksler, Gennadi Bersuker
The filament-based RRAM has demonstrated superior scalability, endurance, low power operation, retention, and operating speed. A challenge navigating trade-offs between high density, low switching power, and stability can be addressed by capitalizing on

Tricritical Point of the f-Electron Antiferromagnet USb 2 Driven by High Magnetic Fields

January 12, 2017
Author(s)
Ryan L. Stillwell, I Lin NMN Liu, N. Harrison, M. Jaime, J. R. Jeffries, Nicholas Butch
In pulsed magnetic fields up to 65T and at temperatures below the Neel transition, our magnetization and magnetostriction measurements reveal a field-induced metamagnetic-like transition that is suggestive of an antiferromagnetic to polarized paramagnetic

Gapped Excitation in Dense Kondo Lattice CePtZn

January 10, 2017
Author(s)
Leland Weldon Harriger, Steven M.T. Disseler, J. Gunasekera, Jose A. Rodriguez, J. Pixley, P. Manfrinetti, S. K. Dhar, D. K. Singh
We report on neutron υSR scattering studies of dense Kondo lattice CePtZn. The system develops long range incommensurate magnetic order as the temperature is reduced below T N = 1.75 K. Interesting, a Q-indpenedent characteristic and its persistence to

Extrapolative Scaling Expression: A Fitting Equation for Extrapolating Full Ic(B,T,e) Data Matrixes from Limited Data

January 4, 2017
Author(s)
John (Jack) W. Ekin, Najib Cheggour, Loren F. Goodrich, Jolene D. Splett, Bernardo Bordini, David Richter, Luca Bottura
Scaling analysis of several thousand Nb3Sn critical-current (Ic) measurements is used to derive the extrapolative scaling expression (ESE), a global fitting equation that can quickly and accurately extrapolate (or interpolate) limited datasets to obtain

Tailoring Exchange Couplings in Magnetic Topological Insulator/Antiferromagnet Heterostructures

January 1, 2017
Author(s)
Qing Lin He, Xufeng Kou, Alexander Grutter, Gen Yin, Lei Pan, Xiaoyu Che, Yuxiang Liu, Tianxiao Nie, Bin Zhang, Steven M.T. Disseler, Brian Kirby, William D. Ratcliff, Qiming Shao, Koichi Murata, Xiaodan Zhu, Guoqiang Yu, Yabin Fan, Mohammad Montazeri, Xiaodong Han, Julie Borchers, Kang L. Wang
Magnetic topological insulators such as Cr-doped (Bi,Sb) 2Te 3 provide a platform for the realization of versatile time-reversal symmetry-breaking physics. By constructing heterostructures with the unique Neel order in an antiferromagnetic CrSb and the

Stoner vs. Heisenberg: Ultrafast exchange reduction and magnon generation during laser-induced demagnetization

December 28, 2016
Author(s)
Thomas J. Silva, Hans T. Nembach, Justin M. Shaw, Emrah Turgut, Dmitriy Zusin, Dominik Legut, Karel Carva, Ronny Knut, Cong Chen, Zhensheng Tao, Stefan Mathias, Martin Aeschlimann, Peter Oppeneer, Henry Kapteyn, Margaret Murnane, Patrik Grychtol
Understanding how the electronic band structure of a ferromagnetic material is modified during laser-induced demagnetization on femtosecond timescales has been a long-standing question in condensed matter physics. Here, we use ultrafast high harmonics to
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