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University of Nebraska - Lincoln

2012

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Articles 61 - 90 of 96

Full-Text Articles in Physics

Ferroelectric Control Of Magnetocrystalline Anisotropy At Cobalt/Poly(Vinylidene Fluoride) Interfaces, Pavel Lukashev, Tula R. Paudel, Juan M. López-Encarnación, Shireen Adenwalla, Evgeny Y. Tsymbal, Julian P. Velev Jan 2012

Ferroelectric Control Of Magnetocrystalline Anisotropy At Cobalt/Poly(Vinylidene Fluoride) Interfaces, Pavel Lukashev, Tula R. Paudel, Juan M. López-Encarnación, Shireen Adenwalla, Evgeny Y. Tsymbal, Julian P. Velev

Shireen Adenwalla Papers

Electric field control of magnetization is one of the promising avenues for achieving high-density energy-efficient magnetic data storage. Ferroelectric materials can be especially useful for that purpose as a source of very large switchable electric fields when interfaced with a ferromagnet. Organic ferroelectrics, such as poly(vinylidene fluoride) (PVDF), have an additional advantage of being weakly bonded to the ferromagnet, thus minimizing undesirable effects such as interface chemical modification and/or strain coupling. In this work we use first-principles density functional calculations of Co/PVDF heterostructures to demonstrate the effect of ferroelectric polarization of PVDF on the interface magnetocrystalline anisotropy ...


Evidence For Spin Correlation In Tt̅ Production, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow Jan 2012

Evidence For Spin Correlation In Tt̅ Production, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

We present a measurement of the ratio of events with correlated t and spins to the total number of tt̅ events. This ratio f is evaluated using a matrix-element-based approach in 729 tt̅ candidate events with a single lepton (electron or muon) and at least four jets. The analyzed pp̅ collisions data correspond to an integrated luminosity of 5.3 fb-1 and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy √s = 1.96 TeV. Combining this result with a recent measurement of f in dileptonic final states, we find ...


Measurement Of The Λb Cross Section And The Λb To Λb Ratio With J/Ψλ Decays In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, Helena Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Measurement Of The Λb Cross Section And The Λb To Λb Ratio With J/Ψλ Decays In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, Helena Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

The Λb differential production cross section and the cross section ratio σ(Λ̅b )/σ(Λb) are measured as functions of transverse momentum pΛbT and rapidity |yΛb | in pp collisions at √ s = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Λb decays reconstructed in the exclusive final state J/ψΛ, with the subsequent decays J/ψ →μ+μ and Λ→pπ, using a data sample corresponding to an integrated luminosity of 1.9 fb−1. The product σ(Λb) × B(Λb →J ...


Search For Signatures Of Extra Dimensions In The Diphoton Mass Spectrum At The Large Hadron Collider, S. Chatrchyan, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory R. Snow Jan 2012

Search For Signatures Of Extra Dimensions In The Diphoton Mass Spectrum At The Large Hadron Collider, S. Chatrchyan, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory R. Snow

Kenneth Bloom Publications

A search for signatures of extra spatial dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at √s = 7 TeV corresponding to an integrated luminosity of 2.2 fb-1. In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3–3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most ...


Search For Charge-Asymmetric Production Of W' Bosons In Tt + Jet Events From Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Charge-Asymmetric Production Of W' Bosons In Tt + Jet Events From Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search is presented for charge-asymmetric production of a W' boson that has been proposed to accommodate the forward–backward asymmetry observed in the production of top–antitop quark pairs at the Tevatron. The new heavy W' boson would be produced in association with a top quark and would decay into top and down quarks. The data correspond to an integrated luminosity of 5.0 fb−1 in pp collisions at a center-of-mass energy of 7 TeV, recorded by the CMS detector at the LHC. No significant excess above the standard model expectations is observed, and, from a combination of ...


Search For Neutral Higgs Bosons Decaying To Tau Pairs In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Neutral Higgs Bosons Decaying To Tau Pairs In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search for neutral Higgs bosons decaying to tau pairs at a center-of-mass energy of 7 TeV is performed using a dataset corresponding to an integrated luminosity of 4.6 fb−1 recorded by the CMS experiment at the LHC. The search is sensitive to both the standard model Higgs boson and to the neutral Higgs bosons predicted by the minimal super symmetric extension of the standard model (MSSM). No excess of events is observed in the tau-pair invariant-mass spectrum. For a standard model Higgs boson in the mass range of 110–145 GeV upper limits at 95% confidence level ...


Inclusive And Differential Measurements Of The Tt̅ Charge Asymmetry In Proton–Proton Collisions At √S= 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Inclusive And Differential Measurements Of The Tt̅ Charge Asymmetry In Proton–Proton Collisions At √S= 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

The tt̅ charge asymmetry is measured in events containing a charged lepton (electron or muon) and at least four jets, one of which is identified as originating from b-quark hadronization. The analyzed data set corresponds to an integrated luminosity of 5.0 fb−1 collected with the CMS detector at the LHC. An inclusive and three differential measurements of the tt̅ charge asymmetry as a function of rapidity, transverse momentum, and invariant mass of the tt̅ system are presented. The measured inclusive tt̅ charge asymmetry is AC = 0.004 ± 0.010 (stat.) ± 0.011 (syst.). This result and the ...


Search For Heavy, Top-Like Quark Pair Production In The Dilepton Final State In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Heavy, Top-Like Quark Pair Production In The Dilepton Final State In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

The results of a search for pair production of a heavy, top-like quark, t', in the decay mode t't̅' → bW+ b̅W → b +νb̅ν̅ are presented. The search is performed with a data sample corresponding to an integrated luminosity of 5.0 fb−1 in pp collisions at a center-of-mass energy of 7 TeV, collected by the CMS experiment at the LHC. The observed number of events agrees with the expectation from standard model processes, and no evidence of t't̅' production is found. Upper limits on the production cross section as a function of t ...


Search For High-Mass Resonances Decaying Into Τ -Lepton Pairs In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For High-Mass Resonances Decaying Into Τ -Lepton Pairs In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search for high-mass resonances decaying into τ+τ is performed using a data sample of pp collisions at √s = 7 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 4.9 fb−1. The number of observed events is in agreement with the standard model prediction. An upper limit on the product of the resonance cross section and branching fraction into τ -lepton pairs is calculated as a function of the resonance mass. Using the sequential standard model resonance Z'SSM and the superstring-inspired E6 model with resonance ...


Study Of W Boson Production In Pbpb And Pp Collisions At √Snn = 2.76 Tev, Ekaterina Avdeeva, Kenneth A. Bloom, S. S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Study Of W Boson Production In Pbpb And Pp Collisions At √Snn = 2.76 Tev, Ekaterina Avdeeva, Kenneth A. Bloom, S. S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A measurement is presented of W-boson production in PbPb collisions carried out at a nucleon–nucleon (NN) centre-of-mass energy √sNN of 2.76 TeV at the LHC using the CMS detector. In data corresponding to an integrated luminosity of 7.3 μb−1, the number of W → μνμ decays is extracted in the region of muon pseudorapidity |ημ| < 2.1 and transverse momentum pμT > 25 GeV/c. Yields of muons found per unit of pseudorapidity correspond to (159 ± 10(stat.) ± 12(syst.)) × 10−8 W+ and (154 ± 10(stat.) ± 12(syst.)) × 10−8 W bosons per minimum-bias PbPb collision. The dependence ...


Search For The Standard Model Higgs Boson Decaying To Bottom Quarks In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For The Standard Model Higgs Boson Decaying To Bottom Quarks In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search for the standard model Higgs boson (H) decaying to bb̅ when produced in association with weak vector bosons (V) is reported for the following modes: W(μν)H, W(eν)H, Z(μμ)H, Z(ee)H and Z(νν)H. The search is performed in a data sample corresponding to an integrated luminosity of 4.7 fb−1, recorded by the CMS detector in proton–proton collisions at the LHC with a center-of-mass energy of 7 TeV. No significant excess of events above the expectation from background is observed. Upper limits on the V H production cross ...


Measurement Of The Inclusive Jet Cross Section In Pp̅ Collisions At √S= 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow, P. Svoisky, M. Takahashi, M. Voutilainen Jan 2012

Measurement Of The Inclusive Jet Cross Section In Pp̅ Collisions At √S= 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow, P. Svoisky, M. Takahashi, M. Voutilainen

Kenneth Bloom Publications

We present a measurement of the inclusive jet cross section using the Run II cone algorithm and data collected by the D0 experiment in pp̅ collisions at a center-of-mass energy √s= 1.96 TeV, corresponding to an integrated luminosity of 0.70 fb-1. The jet energy calibration and the method used to extract the inclusive jet cross section are described.We discuss the main uncertainties, which are dominated by the jet energy scale uncertainty. The results cover jet transverse momenta from 50 GeV to 600 GeV with jet rapidities in the range -2.4 to 2.4 and are ...


Search For Physics Beyond The Standard Model In Events With A Z Boson, Jets, And Missing Transverse Energy In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Physics Beyond The Standard Model In Events With A Z Boson, Jets, And Missing Transverse Energy In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search is presented for physics beyond the standard model (BSM) in events with a Z boson, jets, and missing transverse energy (EmissT ). This signature is motivated by BSM physics scenarios, including supersymmetry. The study is performed using a sample of proton–proton collision data collected at √s = 7 TeV with the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.98 fb−1. The contributions from the dominant standard model backgrounds are estimated from data using two complementary strategies, the jet-Z balance technique and a method based on modeling EmissT with data ...


Structure And Magnetic Properties Of Co-W Clusters Produced By Inert Gas Condensation, Farhad Reza Golkar-Fard, Matthew J. Kramer, Y. Zhang, R. W. Mccallum, Ralph Skomski, David J. Sellmyer, Jeffrey E. Shield Jan 2012

Structure And Magnetic Properties Of Co-W Clusters Produced By Inert Gas Condensation, Farhad Reza Golkar-Fard, Matthew J. Kramer, Y. Zhang, R. W. Mccallum, Ralph Skomski, David J. Sellmyer, Jeffrey E. Shield

David Sellmyer Publications

In this article, inert-gas condensation was used to synthesize Co-W clusters. The formation, structure, and magnetic properties of the clusters were investigated. Sub-10-nm clusters were obtained, and the structures and average sizes were strongly dependent on sputtering power. At low sputtering powers, the clusters were predominantly amorphous, while, at high sputtering power, the clusters were crystalline. X ray diffraction and transmission electron microscopy revealed clusters with hcp structure at high sputtering power. The magnetic properties were dependent on the sputtering power and temperature, with the highest coercivity of 810 Oe at 10 K for high sputtering power.


Search For A Narrow Tt̅ Resonance In Pp̅ Collisions At √S= 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow Jan 2012

Search For A Narrow Tt̅ Resonance In Pp̅ Collisions At √S= 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

We report a search for a narrow tt̅ resonance that decays into a lepton + jets final state based on an integrated luminosity of 5.3 fb-1 of proton-antiproton collisions at √s= 1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the production cross section of such a resonance multiplied by its branching fraction to tt̅. We exclude a leptophobic topcolor Z! at the 95% confidence level for masses below 835 GeV (940 GeV) if its width is 1.2% (3%) of its mass. We also exclude color octet vector bosons ...


Spin And Elastic Contributions To Isothermal Entropy Change, Tathagata Mukherjee, Ralph Skomski, Steven A. Michalski, David J. Sellmyer, Christian Binek Jan 2012

Spin And Elastic Contributions To Isothermal Entropy Change, Tathagata Mukherjee, Ralph Skomski, Steven A. Michalski, David J. Sellmyer, Christian Binek

David Sellmyer Publications

Statistical considerations of ensembles of localized magnetic moments reveal an upper bound of the isothermal entropy change when only the magnetic degrees of freedom are considered. In this case, the maximum molar isothermal entropy change is determined by the spin multiplicity and is equal to Rln(2J+1), where J is the angular momentum of an individual atom. However, in materials with giant magnetocaloric effect, the isothermal field-induced entropy change goes beyond the spin-multiplicity limit due to field-activated elastic degrees of freedom. Recently, we investigated a model of pairs of exchange-coupled Ising spins with variable real-space positions. We showed ...


Aligned And Exchange-Coupled L10 (Fe,Co)Pt-Based Magnetic Films, Yi Liu, Thomas A. George, Ralph Skomski, David J. Sellmyer Jan 2012

Aligned And Exchange-Coupled L10 (Fe,Co)Pt-Based Magnetic Films, Yi Liu, Thomas A. George, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

Films of aligned L10-structure (Fe,Co)Pt with fcc Fe(Co,Pt) are synthesized by co-sputtering Fe, Co, and Pt on an (001) MgO substrate with in situ heating at 830 degrees C. The nanostructures and magnetic properties of the films are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID). The compositions of the samples (Fe,Co)xPt1-x are designed to maintain an atomic Fe: Co ratio of 65: 35 while increasing the Fe,Co content in each successive sample. In samples with low Fe and Co concentration, the ...


Isothermal Entropy Changes In Nanocomposite Co:Ni67Cu33, Steven A. Michalski, Ralph Skomski, Xingzhong Li, Damien Le Roy, Tathagata Mukherjee, Christian Binek, David J. Sellmyer Jan 2012

Isothermal Entropy Changes In Nanocomposite Co:Ni67Cu33, Steven A. Michalski, Ralph Skomski, Xingzhong Li, Damien Le Roy, Tathagata Mukherjee, Christian Binek, David J. Sellmyer

David Sellmyer Publications

The temperature-dependent magnetic properties of artificial rare-earth, free-magnetic nanostructures are investigated for magnetic cooling. We consider two-phase nanocomposites, where 2 nm nanoclusters of cobalt are embedded in a Ni67Cu33 matrix. Several composite films were produced by cluster deposition. The average Co nanocluster size can be tuned by varying the deposition conditions. Isothermalmagnetization curves weremeasured at various temperatures 150K


Orientation Of Doubly Excited States In N2, John E. Furst, Timothy J. Gay, Joshua Machacek, David Kilkoyne, Kenneth W. Mclaughlin Jan 2012

Orientation Of Doubly Excited States In N2, John E. Furst, Timothy J. Gay, Joshua Machacek, David Kilkoyne, Kenneth W. Mclaughlin

Timothy J. Gay Publications

We have measured the total fluorescent intensity and circular polarization of light emitted in 3p 4Po → 3s4P transitions of excited neutral nitrogen atoms created by the photofragmentation of the N2 molecule with circularly polarized light having energies between 21 and 26 eV. The intensity measurements show the effect of predissociation of the N2 Rydberg series R(C) 1Σ+u states by non-Rydberg doubly excited resonances (NRDERs), while nonzero values of circular polarization allow us to unambiguously identify the presence of a directly excited NRDER with 1Πu symmetry in this ...


Understanding The Effect Of Ferroelectric Polarization On Power Conversion Efficiency Of Organic Photovoltaic Devices, Yongbo Yuan, Pankaj Sharma, Zhengguo Xiao, Shashi Poddar, Alexei Gruverman, Stephen Ducharme, Jinsong Huang Jan 2012

Understanding The Effect Of Ferroelectric Polarization On Power Conversion Efficiency Of Organic Photovoltaic Devices, Yongbo Yuan, Pankaj Sharma, Zhengguo Xiao, Shashi Poddar, Alexei Gruverman, Stephen Ducharme, Jinsong Huang

Stephen Ducharme Publications

It is demonstrated that the power conversion efficiency (PCE) of organic photovoltaic devices can be increased by inserting an ultrathin film of a ferroelectric co-polymer, poly(vinylidenefluoridetrifluoroethylene) (P(VDF-TrFE)), at the metal–organic interface, due to an enhancement of the charge extraction efficiency. Specifically, the effect of P(VDF-TrFE) crystallinity on its function in ferroelectric organic photovoltaic (FE-OPV) devices has been studied by several methods. Highly crystalline and amorphous P(VDF-TrFE) films have been prepared by the Langmuir–Blodgett method and spincoating from acetone solution, respectively. The polymer solar cell devices with a crystalline P(VDFTrFE) interfacial layer at the ...


Perpendicular Magnetization In Coo (111) Layers Induced By Exchange Interaction With Ferromagnetic Co And Ni60cu40 Nanoclusters, Damien Le Roy, R. Morel, A. Brenac, S. Pouget, L. Notin Jan 2012

Perpendicular Magnetization In Coo (111) Layers Induced By Exchange Interaction With Ferromagnetic Co And Ni60cu40 Nanoclusters, Damien Le Roy, R. Morel, A. Brenac, S. Pouget, L. Notin

Faculty Publications, Department of Physics and Astronomy

The magnetization reversal of ferromagnetic nanoparticles coupled by exchange with a CoO (111) thin film has been studied. The interfacial exchange interaction triggers the appearance of an out-of-plane magnetization in the CoO (111) film. Co and Ni60Cu40 particles were chosen, as they present an order of magnitude difference in the saturation magnetization and Curie temperatures that surround the Ne´el temperature of CoO. In both cases, the exchange coupling leads to an increase of the coercive field, up to 200% in Co particles, and small exchange bias of 100 Oe when the external magnetic field is applied ...


Tailoring Magnetocrystalline Anisotropy Of Fept By External Strain, Pavel Lukashev, Nathan Horrell, Renat F. Sabirianov Jan 2012

Tailoring Magnetocrystalline Anisotropy Of Fept By External Strain, Pavel Lukashev, Nathan Horrell, Renat F. Sabirianov

Faculty Publications, Department of Physics and Astronomy

We propose using strain assisted reduction in anisotropy of FePt to control magnetization reversal in the writing on the magnetic storage devices. Our first-principles calculations show 21% decrease of the magnetocrystalline anisotropy energy (MAE) with application of 1.5% tensile biaxial strain. The reduction of MAE is primarily due to the change of the c/a ratio and to some extent due to the increase in volume. We propose building bilayer (or heterostructure) of FePt and piezoelectric film. This system is expected to allow the control of anisotropy constant by applying electric field to the system. Finally, we discuss the ...


Controlled Double-Slit Electron Diffraction, Roger Bach, Damian Pope, Sy-Hwang Liou, Herman Batelaan Jan 2012

Controlled Double-Slit Electron Diffraction, Roger Bach, Damian Pope, Sy-Hwang Liou, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

Double-slit diffraction is a corner stone of quantum mechanics. It illustrates key features of quantum mechanics: interference and the particle-wave duality of matter. In 1965, Richard Feynman presented a thought experiment to show these features. Here we demonstrate the full realization of his famous thought experiment. By placing a movable mask in front of a double-slit to control the transmission through the individual slits, probability distributions for single- and double-slit arrangements were observed. Also, by recording single electron detection events diffracting through a double-slit, a diffraction pattern was built up from individual events.


On The Relation Between The Feynman Paradox And The Aharonov–Bohm Effects, Scot Mcgregor, Ryan Hotovy, Adam Caprez, Herman Batelaan Jan 2012

On The Relation Between The Feynman Paradox And The Aharonov–Bohm Effects, Scot Mcgregor, Ryan Hotovy, Adam Caprez, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

The magnetic Aharonov–Bohm (A–B) effect occurs when a point charge interacts with a line of magnetic flux, while its reciprocal, the Aharonov–Casher (A–C) effect, occurs when a magnetic moment interacts with a line of charge. For the two interacting parts of these physical systems, the equations of motion are discussed in this paper. The generally accepted claim is that both parts of these systems do not accelerate, while Boyer has claimed that both parts of these systems do accelerate. Using the Euler–Lagrange equations we predict that in the case of unconstrained motion, only one part ...


Dynamics Underlying The Gaussian Distribution Of The Classical Harmonic Oscillator In Zero-Point Radiation, Wayne Cheng-Wei Huang, Herman Batelaan Jan 2012

Dynamics Underlying The Gaussian Distribution Of The Classical Harmonic Oscillator In Zero-Point Radiation, Wayne Cheng-Wei Huang, Herman Batelaan

Faculty Publications, Department of Physics and Astronomy

No abstract provided.


Dispersion Compensation For Attosecond Electron Pulses, Peter Hansen, Cory Baumgarten, Herman Batelaan, Martin Centurion Jan 2012

Dispersion Compensation For Attosecond Electron Pulses, Peter Hansen, Cory Baumgarten, Herman Batelaan, Martin Centurion

Martin Centurion Publications

We propose a device to compensate for the dispersion of attosecond electron pulses. The device uses only static electric and magnetic fields and therefore does not require synchronization to the pulsed electron source. Analogous to the well-known optical dispersion compensator, an electron dispersion compensator separates paths by energy in space. Magnetic fields are used as the dispersing element, while a Wien filter is used for compensation of the electron arrival times. We analyze a device with a size of centimeters, which can be applied to ultrafast electron diffraction and microscopy, and fundamental studies.


Imaging Of Isolated Molecules With Ultrafast Electron Pulses, Christopher J. Hensley, Jie Yang, Martin Centurion Jan 2012

Imaging Of Isolated Molecules With Ultrafast Electron Pulses, Christopher J. Hensley, Jie Yang, Martin Centurion

Martin Centurion Publications

Imaging isolated molecules in three dimensions with atomic resolution is important for elucidating complex molecular structures and intermediate states in molecular dynamics. This goal has so far remained elusive due to the random orientation of molecules in the gas phase. We show that threedimensional structural information can be retrieved from multiple electron diffraction patterns of aligned molecules. The molecules are aligned impulsively with a femtosecond laser pulse and probed with a femtosecond electron pulse two picoseconds later, when the degree of alignment reaches a maximum.


Updated Results From The Rice Experiment And Future Prospects For Ultra-High Energy Neutrino Detection At The South Pole, Ilya Kravchenko, S. Hussain, D. Seckel, Dave Z. Besson, E. Fensholt, John P. Ralston, J. Taylor, Kenneth L. Ratzlaff, R. Young Jan 2012

Updated Results From The Rice Experiment And Future Prospects For Ultra-High Energy Neutrino Detection At The South Pole, Ilya Kravchenko, S. Hussain, D. Seckel, Dave Z. Besson, E. Fensholt, John P. Ralston, J. Taylor, Kenneth L. Ratzlaff, R. Young

Faculty Publications, Department of Physics and Astronomy

The RICE experiment seeks observation of ultra-high energy (UHE; Ev > 1017 eV) neutrinos interacting in Antarctic ice, by measurement of the radio frequency (RF) Cherenkov radiation resulting from the collision of a neutrino with an ice molecule. RICE was initiated in 1999 as a first-generation prototype for an eventual, large-scale in-ice UHE neutrino detector. Herein, we present updated limits on the diffuse UHE neutrino flux, based on 12 years of data taken between 1999 and 2010. We find no convincing neutrino candidates, resulting in 95% confidence-level model-dependent limits on the flux E2v dϕ/ dEv < 0.5 X 10-6 ...


Measurement Of The Ultrafast Temporal Response Of A Plasmonic Antenna, Maria Becker, Wayne Cheng-Wei Huang, Herman Batelaan, Elizabeth J. Smythe, Federico Capasso Jan 2012

Measurement Of The Ultrafast Temporal Response Of A Plasmonic Antenna, Maria Becker, Wayne Cheng-Wei Huang, Herman Batelaan, Elizabeth J. Smythe, Federico Capasso

Faculty Publications, Department of Physics and Astronomy

We report a measurement on the temporal response of a plasmonic antenna at the femtosecond time scale. The antenna consists of a square array of nanometer-size gold rods. We find that the far-field dispersion of light reflected from the plasmonic antenna is less than that of a 1.2 mm thick glass slide. Assuming a simple oscillating dipole model this implies that the near-field of the antenna may be used as an electron switch that responds faster than 20 f s. Alternatively, ultrafast electron diffraction may be used to investigate the near-field dynamics of the plasmonic antenna.


Effect Of Gadolinium Doping On The Electronic Band Structure Of Europium Oxide, Juan Colon Santana, Joonhee Michael An, Ning Wu, Kirill D. Belashchenko, Xianjie Wang, Pan Liu, Jinke Tang, Yaroslav B. Losovyj, I. N. Yakovkin, Peter A. Dowben Jan 2012

Effect Of Gadolinium Doping On The Electronic Band Structure Of Europium Oxide, Juan Colon Santana, Joonhee Michael An, Ning Wu, Kirill D. Belashchenko, Xianjie Wang, Pan Liu, Jinke Tang, Yaroslav B. Losovyj, I. N. Yakovkin, Peter A. Dowben

Peter Dowben Publications

High quality films of EuO and Eu0.96Gd0.04O were grown on p-type Si(100) via pulsed laser deposition. X-raydiffraction results show that the addition of Gd changes the growth texture from [001] to [111]. Angular-resolved photoemission spectroscopy reveals electron pockets around the X points in Gd-doped EuO, indicating that the band gap in EuO is indirect. Combined photoemission and inverse photoemission measurements showan apparent transition from n-type to p-type behavior, which is likely due to band bending near the polar (111) surface.