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University of Nebraska - Lincoln

2011

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Articles 61 - 89 of 89

Full-Text Articles in Physics

Search For Avectorlike Quarkwith Charge 2/3 In T + Z Events From Pp Collisions At √S = 7 Tev, S. Chatrchyan, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, T. Kelly, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2011

Search For Avectorlike Quarkwith Charge 2/3 In T + Z Events From Pp Collisions At √S = 7 Tev, S. Chatrchyan, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, T. Kelly, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search for pair-produced heavy vectorlike charge-2/3 quarks, T, in pp collisions at a center-of-mass energy of 7 TeV, is performed with the CMS detector at the LHC. Events consistent with the flavorchanging- neutral-current decay of a T quark to a top quark and a Z boson are selected by requiring two leptons from the Z-boson decay, as well as an additional isolated charged lepton. In a data sample corresponding to an integrated luminosity of 1.14 fb-1, the number of observed events is found to be consistent with the standard model background prediction. Assuming a branching …

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Wy Production And Limits On Anomalous Wwy Couplings In Pp̅ Collisions √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 2011

Wy Production And Limits On Anomalous Wwy Couplings In Pp̅ Collisions √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 measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→ lv) + y production in ey and µy final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp̅ → Wy + X → lvy + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW[1] couplings for data …

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Ultrafast Rempi In Benzene And The Monohalobenzenes Without The Focal Volume Effect, Timothy D. Scarborough, James Strohaber, David B. Foote, Collin J. Mcacy, Cornelis J. Uiterwaal Jan 2011

Ultrafast Rempi In Benzene And The Monohalobenzenes Without The Focal Volume Effect, Timothy D. Scarborough, James Strohaber, David B. Foote, Collin J. Mcacy, Cornelis J. Uiterwaal

C.J.G.J. Uiterwaal Publications

We report on the photoionization and photofragmentation of benzene (C6H6) and of the monohalobenzenes C6H5–X (X = F, Cl, Br, I) under intense-field, single-molecule conditions. We focus 50-fs, 804-nm pulses from a Ti:sapphire laser source, and record ion mass spectra as a function of intensity in the range ~1013 W/cm2 to ~1015 W/cm2. We count ions that were created in the central, most intense part of the focal area; ions from other regions are rejected. For all targets, stable parent ions (C6H5X+) are …

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Metastability Of Free Cobalt And Iron Clusters: A Possible Precursor To Bulk Ferromagnetism, Xiaoshan Xu, Shuangye Yin, Ramiro Moro, Anthony Liang, John Bowlan, Walt A. De Heer Jan 2011

Metastability Of Free Cobalt And Iron Clusters: A Possible Precursor To Bulk Ferromagnetism, Xiaoshan Xu, Shuangye Yin, Ramiro Moro, Anthony Liang, John Bowlan, Walt A. De Heer

Xiaoshan Xu Papers

Homonuclear cobalt and iron clusters CoN and FeN measured in a cryogenic molecular beam exist in two states with distinct magnetic moments (μ), polarizabilities, and ionization potentials, indicating distinct valences. The μ is approximately quantized: μN ~ 2NμB in the ground states and μN* ~ NμB in the excited states for Co; μN ~ 3N μB and μN * ~ NμB for Fe. At a large size, the average μ of the two states converges to the bulk value with diminishing ionization potential differences. …

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Electron And Hole Traps In Ag-Doped Lithium Tetraborate (Li2b4o7) Crystals, A. T. Brant, B. E. Kananan, M. K. Murari, J. Mcclory, J. C. Petrosky, V. T. Adamiv, Ya. V. Burak, Peter A. Dowben, L. E. Halliburton Jan 2011

Electron And Hole Traps In Ag-Doped Lithium Tetraborate (Li2b4o7) Crystals, A. T. Brant, B. E. Kananan, M. K. Murari, J. Mcclory, J. C. Petrosky, V. T. Adamiv, Ya. V. Burak, Peter A. Dowben, L. E. Halliburton

Peter Dowben Publications

Electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and thermoluminescence (TL) are used to characterize the primary electron and hole trapping centers in a lithium tetraborate (Li2B4O7) crystal doped with Ag+. Three defects, two holelike and one electronlike, are observed after exposure at room temperature to 60 kV x-rays. The as-grown crystal contains both interstitial Ag+ ions and Ag+ ions substituting for Liþ ions. During the irradiation, substitutional Ag+ ions (4d10) trap holes and two distinct Ag2+ centers (4d9) are formed. These Ag2+ …

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Colossal Negative Magnetoresistance In Dilute Fluorinated Graphene, X. Hong, S. -H. Cheng, C. Herding, J. Zhu Jan 2011

Colossal Negative Magnetoresistance In Dilute Fluorinated Graphene, X. Hong, S. -H. Cheng, C. Herding, J. Zhu

Xia Hong Publications

Adatoms offer an effective route to modify and engineer the properties of graphene. In this work, we create dilute fluorinated graphene using a clean, controlled, and reversible approach. At low carrier densities, the system is strongly localized and exhibits an unexpected, colossal negative magnetoresistance. The zero-field resistance is reduced by a factor of 40 at the highest field of 9 T and shows no sign of saturation. Unusual staircaselike field dependence is observed below 5 K. The magnetoresistance is highly anisotropic. These observations cannot be explained by existing theories, but likely require adatom-induced magnetism and/or a metal-insulator transition driven by …

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Resonant Photoemission Of Rare Earth Doped Gan Thin Films, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben Jan 2011

Resonant Photoemission Of Rare Earth Doped Gan Thin Films, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben

Peter Dowben Publications

The 4d → 4f Fano resonances for various rare earth doped GaN thin films (RE = Gd, Er, Yb) were investigated using synchrotron photoemission spectroscopy. The resonant photoemission Fano profiles show that the major Gd and Er rare earth 4f weight is at about 5–6 eV below the valence band maximum, similar to the 4f weights in the valence band of many other rare earth doped semiconductors. For Yb, there is very little resonant enhancement of the valence band of Yb doped GaN, consistent with a largely 4f14 occupancy.

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Schottky Barrier Formation At The Au To Rare Earth Doped Gan Thin Film Interface, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben Jan 2011

Schottky Barrier Formation At The Au To Rare Earth Doped Gan Thin Film Interface, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben

Peter Dowben Publications

The Schottky barriers formed at the interface between gold and various rare earth doped GaN thin films (RE = Yb, Er, Gd) were investigated in situ using synchrotron photoemission spectroscopy. The resultant Schottky barrier heights were measured as 1.68 ± 0.1 eV (Yb:GaN), 1.64 ± 0.1 eV (Er:GaN), and 1.33 ± 0.1 eV (Gd:GaN). We find compelling evidence that thin layers of gold do not wet and uniformly cover the GaN surface, even with rare earth doping of the GaN. Furthermore, the trend of the Schottky barrier heights follows the trend of the rare earth metal work function.

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Aligned And Exchange-Coupled Fept-Based Films, Yi Liu, Thomas A. George, Ralph Skomski, David J. Sellmyer Jan 2011

Aligned And Exchange-Coupled Fept-Based Films, Yi Liu, Thomas A. George, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

Two-phase nanostructures of hard L10-ordered FePt and soft iron-rich fcc Fe-Pt are investigated experimentally and by model calculations. The Fe-Pt thin films were produced by epitaxial co-sputtering onto MgO and have a thickness of about 10 nm. They form two-phase dots that cover a large fraction of the surface but are separated from each other. X-ray diffraction and TEM show that the c-axis of the phase FePt is aligned in the direction normal to the film plane. The experimental and theoretical hysteresis loops indicate archetypical exchange coupling, and excellent magnetic properties are obtained. The largest values of …

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Dissociative Electron Attachment And Vibrational Excitation Of Cf3cl: Effect Of Two Vibrational Modes Revisited, Michal Tarana, Karel Houfek, Jiri Horacek, Ilya I. Fabrikant Jan 2011

Dissociative Electron Attachment And Vibrational Excitation Of Cf3cl: Effect Of Two Vibrational Modes Revisited, Michal Tarana, Karel Houfek, Jiri Horacek, Ilya I. Fabrikant

Ilya Fabrikant Publications

We present a study of dissociative electron attachment and vibrational excitation processes in electron collisions with the CF3Cl molecule. The calculations are based on the two-dimensional nuclear dynamics including the C-Cl symmetric stretch coordinate and the CF3 symmetric deformation (umbrella) coordinate. The complex potential energy surfaces are calculated using the ab initio R-matrix method. The results for dissociative attachment and vibrational excitation of the umbrella mode agree quite well with experiment whereas the cross section for excitation of the C-Cl symmetric stretch vibrations is about a factor-of-three too low in comparison with experimental data.

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Length Scales Of Interactions In Magnetic, Dielectric, And Mechanical Nanocomposites, Ralph Skomski, Balamurugan Balamurugan, Eva Schubert, Axel Enders, David J. Sellmyer Jan 2011

Length Scales Of Interactions In Magnetic, Dielectric, And Mechanical Nanocomposites, Ralph Skomski, Balamurugan Balamurugan, Eva Schubert, Axel Enders, David J. Sellmyer

Axel Enders Publications

It is investigated how figures of merits of nanocomposites are affected by structural and interaction length scales, Aside from macroscopic effects without characteristic lengths scales and atomic-scale quantum-mechanical interactions there are nanoscale interactions that reflect a competition between different energy contributions. We consider three systems, namely dielectric media, carbon-black reinforced rubbers and magnetic composites. In all cases, it is relatively easy to determine effective materials constants, which do not involve specific length scales. Nucleation and breakdown phenomena tend to occur on a nanoscale and yield a logarithmic dependence of figures of merit on the macroscopic system size. Essential system-specific differences …

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Detecting An Extended Light Source Through A Lens, E. T. Litaker, J. R. Machacek, Timothy J. Gay Jan 2011

Detecting An Extended Light Source Through A Lens, E. T. Litaker, J. R. Machacek, Timothy J. Gay

Timothy J. Gay Publications

We present a Monte Carlo simulation of a cylindrical luminescent volume and a typical lens–detector system. The results of this simulation yield a graphically simple picture of the regions within the cylindrical volume from which this system detects light. Because the cylindrical volume permits large angles of incidence, we use a modification of the thin-lens approximation for ray tracing. We compare simulation results with concepts from imaging optics, and comment on implications for experimental design.

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Production Of Excited Atomic Hydrogen And Deuterium From H2, Hd And D2 Photodissociation, J R. Machacek, V M. Andrianarijaona, J. E. Furst, A L D Kilcoyne, A L Landers, E T Litaker, K W Mclaughlin, Timothy J. Gay Jan 2011

Production Of Excited Atomic Hydrogen And Deuterium From H2, Hd And D2 Photodissociation, J R. Machacek, V M. Andrianarijaona, J. E. Furst, A L D Kilcoyne, A L Landers, E T Litaker, K W Mclaughlin, Timothy J. Gay

Timothy J. Gay Publications

We have measured the production of Lyman α and Balmer α fluorescence from atomic H and D for the photodissociation of H2, HD and D2 by linearly-polarized photons with energies between 22 and 64 eV. We discuss systematic uncertainties associated with our data, and compare our results with previous experimental results and ab initio calculations of the dissociation process. We comment on the discrepancies.

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Measurement Of Electron Beam Polarization From Unstrained Bulk Gaas Via Two Photon Photoemission, J L Mccarter, Timothy J. Gay, J Hansknecht, M Poelker, M L Stutzman Jan 2011

Measurement Of Electron Beam Polarization From Unstrained Bulk Gaas Via Two Photon Photoemission, J L Mccarter, Timothy J. Gay, J Hansknecht, M Poelker, M L Stutzman

Timothy J. Gay Publications

This paper describes measurements of the beam polarization and quantum efficiency for photo-emission using two-photon excitation from unstrained bulk GaAs illuminated with pulsed, high intensity 1560nm laser light. Quantum efficiency is linearly proportional to 1560nm peak laser intensity, which was varied in three independent ways, indicating that the emitted electrons are promoted from the valence to the conduction band via two-photon absorption. Beam polarization was measured using a microMott polarimeter, with a value of 16.8(4)% polarization at 1560nm, which is roughly half the measured value of 33.4(8)% using 778 nm light.

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Quantum Description And Properties Of Electrons Emitted From Pulsed Nanotip Electron Sources, Pavel Lougovski, Herman Batelaan Jan 2011

Quantum Description And Properties Of Electrons Emitted From Pulsed Nanotip Electron Sources, Pavel Lougovski, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

We present a quantum calculation of the electron degeneracy for electron sources. We explore quantum interference of electrons in the temporal and spatial domain and demonstrate how it can be utilized to characterize a pulsed electron source. We estimate effects of Coulomb repulsion on two-electron interference and show that currently available nano tip pulsed electron sources operate in the regime where the quantum nature of electrons can be made dominant.

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In Memoriam Robert Katz (1917–2011), Michael P. R. Waligorski, Francis A. Cucinotta Jan 2011

In Memoriam Robert Katz (1917–2011), Michael P. R. Waligorski, Francis A. Cucinotta

Department of Physics and Astronomy: Faculty Publications

Dr. Robert (Bob) Katz, emeritus professor of physics at the University of Nebraska, author of the Katz Model, a deceptively simple but profound parametric model of the action of charged particles on physical and biological systems, died peacefully at his home at Lincoln, NE, on March 12, 2011, after a brief illness. Bob, born in New York City in 1917, and his sister Gladys, were of immigrant Russian Jewish descent. Their parents owned a delicatessen in the Bronx, not far from the Yankee Stadium, where, as Bob recalled, Babe Ruth stopped by for hot dogs, a huge man driving a …

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Magnetometry And Transport Data Complement Polarized Neutron Reflectometry In Magnetic Depth Profiling, Yi Wang, Xi He, Tathagata Mukherjee, Mary Lee Fitzsimmons, Sarbeswar Sahoo, Christian Binek Jan 2011

Magnetometry And Transport Data Complement Polarized Neutron Reflectometry In Magnetic Depth Profiling, Yi Wang, Xi He, Tathagata Mukherjee, Mary Lee Fitzsimmons, Sarbeswar Sahoo, Christian Binek

Christian Binek Publications

Exchange coupled magnetic hard layer/soft layer thin films show a variety of complex magnetization reversal mechanisms depending on the hierarchy of interaction strengths within and between the films. Magnetization reversal can include uniform rotation, soft layer biasing, as well as exchange spring behavior. We investigate the magnetization reversal of a CoPt/Permalloy/Ta/Permalloy heterostructure. Here, Stoner-Wohlfarth-type uniform magnetization rotation of the virtually free Permalloy layer and exchange spring behavior of the strongly pinned Permalloy layer are found in the same sample. We investigate the complex magnetization reversal by polarized neutron reflectometry, magnetometry, and magneto-transport. The synergy of combining these experimental methods together …

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Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3, R. G.P. Mcquaid, L. J. Mcgilly, Pankaj Sharma, Alexei Gruverman, J. M. Gregg Jan 2011

Mesoscale Flux-Closure Domain Formation In Single-Crystal Batio3, R. G.P. Mcquaid, L. J. Mcgilly, Pankaj Sharma, Alexei Gruverman, J. M. Gregg

Alexei Gruverman Publications

Over 60 years ago, Charles Kittel predicted that quadrant domains should spontaneously form in small ferromagnetic platelets. He expected that the direction of magnetization within each quadrant should lie parallel to the platelet surface, minimizing demagnetizing fields, and that magnetic moments should be configured into an overall closed loop, or flux-closure arrangement. Although now a ubiquitous observation in ferromagnets, obvious flux-closure patterns have been somewhat elusive in ferroelectric materials. This is despite the analogous behaviour between these two ferroic subgroups and the recent prediction of dipole closure states by atomistic simulations research. Here we show Piezoresponse Force Microscopy images of …

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Tailoring A Two-Dimensional Electron Gas At The Laalo3 ∕ Srtio3 (001) Interface By Epitaxial Strain, C. W. Bark, D. A. Felker, Yong Wang, H. W. Jang, C. M. Folkman, J. W. Park, S. H. Baek, H. Zhou, D. D. Fong, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, C. B. Eom Jan 2011

Tailoring A Two-Dimensional Electron Gas At The Laalo3 ∕ Srtio3 (001) Interface By Epitaxial Strain, C. W. Bark, D. A. Felker, Yong Wang, H. W. Jang, C. M. Folkman, J. W. Park, S. H. Baek, H. Zhou, D. D. Fong, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, C. B. Eom

Evgeny Tsymbal Publications

Recently a metallic state was discovered at the interface between insulating oxides, most notably LaAlO3 and SrTiO3. Properties of this two-dimensional electron gas (2DEG) have attracted significant interest due to its potential applications in nanoelectronics. Control over this carrier density and mobility of the 2DEG is essential for applications of these unique systems, and may be achieved by epitaxial strain. However, despite the rich nature of strain effects on oxide materials properties, such as ferroelectricity, magnetism, and superconductivity, the relationship between the strain and electrical properties of the 2DEG at the LaAlO3∕SrTiO3 heterointerface remains …

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A Giant Tunneling Electroresistance Effect Driven By Electrically Controlled Spin Valve At A Complex Oxide Interface, John D. Burton, Evgeny Y. Tsymbal Jan 2011

A Giant Tunneling Electroresistance Effect Driven By Electrically Controlled Spin Valve At A Complex Oxide Interface, John D. Burton, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

A giant tunneling electroresistance effect may be achieved in a ferroelectric tunnel junction by exploiting the magnetoelectric effect at the interface between the ferroelectric barrier and a magnetic La1-xSrxMnO3 electrode. Using first-principles density-functional theory we demonstrate that a few magnetic monolayers of La1-xSrxMnO3 near the interface act, in response to ferroelectric polarization reversal, as an atomic-scale spin valve by filtering spin-dependent current. This produces more than an order of magnitude change in conductance, and thus constitutes a giant resistive switching effect.

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Is The Magnetic Anisotropy Proportional To The Orbital Moment?, Ralph Skomski, Arti Kashyap, Axel Enders Jan 2011

Is The Magnetic Anisotropy Proportional To The Orbital Moment?, Ralph Skomski, Arti Kashyap, Axel Enders

Axel Enders Publications

The relation between orbital moment and magnetic anisotropy is investigated by model calculations, which show that only a part of the spin-orbit coupling contributes to the anisotropy. A large part of the anisotropy energy, about 50% for iron series elements and nearly 100% for rare-earths, is stored in the nonrelativistic part of the Hamiltonian. A feature important for x-ray magnetic circular dichroism is that the orbital moment of heavy atoms rotates with the spin moment, whereas in light atoms, the orbital moment is recreated in each different direction. In the discussion, we consider three examples of current interest in different …

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Anisotropy Of Zigzag Chains Of Palladium, P. K. Sahota, Ralph A. Skomski, Axel Enders, David J. Sellmyer, Arti Kashyap Jan 2011

Anisotropy Of Zigzag Chains Of Palladium, P. K. Sahota, Ralph A. Skomski, Axel Enders, David J. Sellmyer, Arti Kashyap

Axel Enders Publications

Ab initio calculations of the biaxial anisotropy of infinite Pd zigzag chains are presented. The simulations were performed with the Vienna Ab-Initio Simulation Package, using a tetragonal unit cell with a supercell approach where the atoms are repeated along the z-direction. The anisotropy is determined from the energies along the three principal directions [001], [100], and [010]. The second-order anisotropy constants K1 and K'1 were extracted by fitting the calculated energy values to the phenomenological energy. The easiest magnetization direction is along the wire axis, whereas the hardest direction is perpendicular to the plane of the …

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Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman Jan 2011

Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman

Stephen Ducharme Publications

We report orientational imaging of the polarization distribution in nanostructured ferroelectric copolymer of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) and collagen fibrils using vertical and lateral modes of piezoresponse force microscopy (PFM). In PVDF-TrFE, detection of azimuthal variations in the lateral PFM signal is attributed to the alignment of the molecular chains along different directions. Local switching in PVDF-TrFE is shown to proceed via 120° or 180° rotation of dipoles around the molecular chain, depending upon the strength of the applied electric field. Analysis of the vertical and lateral PFM signals in collagen reveals polar anisotropy of the electromechanical properties along the axes …

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Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman Jan 2011

Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman

Stephen Ducharme Publications

We report orientational imaging of the polarization distribution in nanostructured ferroelectric copolymer of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) and collagen fibrils using vertical and lateral modes of piezoresponse force microscopy (PFM). In PVDF-TrFE, detection of azimuthal variations in the lateral PFM signal is attributed to the alignment of the molecular chains along different directions. Local switching in PVDF-TrFE is shown to proceed via 120 degrees or 180 degrees rotation of dipoles around the molecular chain, depending upon the strength of the applied electric field. Analysis of the vertical and lateral PFM signals in collagen reveals polar anisotropy of the electromechanical properties along …

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Decay Of A Negative Molecular Ion In A Constant Electric Field, S. V. Borzunov, N. L. Manakov, Anthony F. Starace, M. V. Frolov Jan 2011

Decay Of A Negative Molecular Ion In A Constant Electric Field, S. V. Borzunov, N. L. Manakov, Anthony F. Starace, M. V. Frolov

Anthony F. Starace Publications

The problem of the shift and broadening of the electron energy levels in the field of two 3D short-range potentials (e.g., the model of a negative molecular ion) by a constant electric field F is considered. The interaction of an electron with attraction centers is taken into account in the effective range approximation. We analyze the cases when both centers maintain weakly bound s states and when the electron state in the field of one of the centers is a p state. Exact numerical results for the shift and the width of the energy levels of a quasi-molecule as functions …

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Large Magnetoelectric Effect In Ferroelectric/Piezomagnetic Heterostructures, Pavel Lukashev, Kirill D. Belashchenko, Renat F. Sabirianov Jan 2011

Large Magnetoelectric Effect In Ferroelectric/Piezomagnetic Heterostructures, Pavel Lukashev, Kirill D. Belashchenko, Renat F. Sabirianov

Department of Physics and Astronomy: Faculty Publications

We present results of the first-principles calculations on the large magnetoelectric effect in ferroelectric/ piezomagnetic multilayers. We consider thin-film layered heterostructures of typical ferroelectrics, such as PbTiO3, with piezomagnetic (PzM) Mn-based antiperovskites, such as Mn3GaN. The atomic displacements induced by the FE polarization as well as mechanical stress at the interface break the triangular magnetic symmetry of the PzM phase producing net magnetization in the system. The induced magnetization can be controlled by changing the direction of polarization in the ferroelectric phase. Our calculations show that reversal of the polarization results in change of the net magnetization in …

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Effective Mass Of Electrons And Holes In Bilayer Graphene: Electron-Hole Asymmetry And Electron-Electron Interaction, K. Zou, X. Hong, J. Zhu Jan 2011

Effective Mass Of Electrons And Holes In Bilayer Graphene: Electron-Hole Asymmetry And Electron-Electron Interaction, K. Zou, X. Hong, J. Zhu

Department of Physics and Astronomy: Faculty Publications

Precision measurements of the effective mass m* in high-quality bilayer graphene using the temperature dependence of the Shubnikov–de Haas oscillations are reported. In the density range 0.7 × 1012 < n < 4.1 × 1012 cm−2, both the hole mass m*h and the electron mass m*e increase with increasing density, demonstrating the hyperbolic nature of the bands. The hole mass m*h is approximately 20–30% larger than the electron mass m*e . Tight-binding calculations provide a good description of the electron-hole asymmetry and yield an accurate measure of the interlayer hopping parameter v4 = …

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Experimental Observation Of Time-Delays Associated With Electric Matteucci–Pozzi Phase Shifts, Shawn A. Hilbert, Adam Caprez, Herman Batelaan Jan 2011

Experimental Observation Of Time-Delays Associated With Electric Matteucci–Pozzi Phase Shifts, Shawn A. Hilbert, Adam Caprez, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

In 1985, Matteucci and Pozzi (1985 Phys. Rev. Lett. 54 2469) demonstrated the presence of a quantum mechanical phase shift for electrons passing a pair of oppositely charged biprism wires. For this experimental arrangement no forces deflect the electrons. Consequently, the result was reported as a non-local type-2 Aharonov–Bohm effect. Boyer (2002 Found. Phys. 32 41–50; 1987 Nuovo Cimento B 100 685–701) showed theoretically that the Matteucci–Pozzi effect could be associated with a time delay caused by a classical force. We present experimental data that confirm the presence of a time delay. This result is in contrast to the situation …

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Transverse Quantum Stern–Gerlach Magnets For Electrons, Scot Mcgregor, Roger Bach, Herman Batelaan Jan 2011

Transverse Quantum Stern–Gerlach Magnets For Electrons, Scot Mcgregor, Roger Bach, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

In the Stern–Gerlach experiment, silver atoms were separated according to their spin state (Gerlach and Stern 1922 Z. Phys. 9 353–355). This experiment demonstrates the quantization of spin and relies on the classical description of motion. However, so far, no design has led to a functional Stern–Gerlach magnet for free electrons. Bohr and Pauli showed in the 1930 Solvay conference that Stern–Gerlach magnets for electrons cannot work, at least if the design is based on classical trajectories (Pauli W 1932 Proc. of the 6th Solvay Conf. 2 (1930) (Brussels: Gauthier-Villars) pp 183–86, 217–20, 275–80; Pauli W 1964 Collected Scientific Papers …

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