Physics Commons^™

Afci Quarterly Input – Unlv October 1 Through December 31, 2005, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

High-Temperature Calcium Vapor Cell For Spectroscopy On The 4s2 1s0-4s4p 3p1 Intercombination Line, Christopher J. Erickson, Brian Neyenhuis, Dallin S. Durfee

Faculty Publications

We have demonstrated a high-temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual-chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high-temperature vacuum valves and glass-to-metal seals. We have observed over 50% absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the broadening resulted in higher signal-to-noise ratios by allowing us to probe the atoms with intensities much greater than the 0.2µW/cm2 saturation intensity of the unbroadened transition. The techniques presented in this …

Nonmetal Ordering In Tic1-Xnx: Ground-State Structure And The Effects Of Finite Temperature, Gus L. W. Hart, Brian Kolb

Faculty Publications

The TiC1-xNx system has long been prized in industry because of its desirable thermodynamic and hardness characteristics. Previous studies have not produced comprehensive results describing the ordering tendencies of TiC1-xNx at any temperature. We apply the mixed-basis cluster expansion and Monte Carlo methods to the problem and find a fascinating array of ground-state structures occurring at precise nitrogen-concentration intervals of ∆x=1/16 and related to each other by simple (201) quasisuperlattice motifs. Thermodynamic Monte Carlo results indicate that the critical ordering temperatures at all concentrations are well below room temperature. short-range ordering develops at T ≈ 800 K and exhibits the …

Magnetic And Spectroscopic Characteristics Of Znmno System, Aswini K. Pradhan, D. Hunter, Kai Zhang, J.B. Dadson, S. Mohanty, T.M. Williams, K. Lord, R.R. Rakimhov, U.N. Roy, Y. Cui, A. Burger, Jun Zhang, David J. Sellmyer

David Sellmyer Publications

We report on the observation of room-temperature ferromagnetism in epitaxial (Zn,Mn)O films grown by a pulsed-laser deposition technique using high-density targets. The X-ray, microscopic, spectroscopic and magnetic properties of target material containing 6 at.% of Mn and films were compared. The target shows the presence of large clusters exhibiting paramagnetic behavior. However, ferromagnetic properties were observed in (Zn,Mn)O films grown at a substrate temperature of 500 °C and with an oxygen partial pressure of 1 mTorr. Although, crystalline quality of the film improves with increasing substrate temperature, the ferromagnetism becomes weaker.

An Event-Based Approach To Validating Solar Wind Speed Predictions: High-Speed Enhancements In The Wang-Sheeley-Arge Model, M. J. Owens, C. N. Arge, Harlan E. Spence, A. Pembroke

Physics & Astronomy

[1] One of the primary goals of the Center for Integrated Space Weather Modeling (CISM) effort is to assess and improve prediction of the solar wind conditions in near-Earth space, arising from both quasi-steady and transient structures. We compare 8 years of L1 in situ observations to predictions of the solar wind speed made by the Wang-Sheeley-Arge (WSA) empirical model. The mean-square error (MSE) between the observed and model predictions is used to reach a number of useful conclusions: there is no systematic lag in the WSA predictions, the MSE is found to be highest at solar minimum and lowest …

Spin-Photovoltaic Effect In Quantum Wires Due To Intersubband Transitions, Arkady Fedorov, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

We consider the current induced in a quantum wire by external electromagnetic radiation. The photocurrent is caused by the interplay of spin-orbit interaction (Rashba and Dresselhaus terms) and an external in-plane magnetic field. We calculate this current using a Wigner functions approach, taking into account radiation-induced transitions between transverse subbands. The magnitude and the direction of the current depends on the Dresselhaus and Rashba constants, strength of magnetic field, radiation frequency, and intensity. The current can be controlled by changing some of these parameters.

Laser-Controlled Local Magnetic Field With Semiconductor Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi

Faculty Publications

We analyze theoretically the dynamics of N electrons localized in a narrow semiconductor quantum ring under a train of phase-locked infrared laser pulses. The pulse sequence is designed to control the total angular momentum of the electrons. The quantum ring can be put in states characterized by strong currents. The local magnetic field created by these currents can be used for a selective quantum control of single spins in semiconductor systems. The current generation in quantum rings with finite width is also studied.

Rescattering Effects In The Multiphoton Regime, M. V. Frolov, A. V. Flegel, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

LETTER TO THE EDITOR

The plateau features that characterize the low-frequency spectra of fundamental strong-field processes such as harmonic generation, above-threshold ionization and laser-assisted electron-atom scattering are shown to exist also for photon energies E_γ of the order of the energy |E₀| of a bound electron. The existence of these rescattering effects in such a high-frequency (and thus nontunnelling) regime is supported by accurate quantum analyses of intense Ti-Sapphire laser interactions with halogen negative ions, for which E_γ ≈ 0.5|E0|.

Ultracold Neutral Plasma Expansion In Two Dimensions, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson

Faculty Publications

An isothermal model of ultracold neutral plasma expansion is extended to systems without spherical symmetry. It is used to interpret new fluorescence measurements on ultracold neutral calcium plasmas. For a self-similar expansion, the fluid equations are solved both analytically and numerically. The density and velocity solutions are used to predict fluorescence signals induced by a laser beam weakly focused into the plasma. Despite the simplicity of the model, predicted fluorescence signals reproduce major features of the experimental data

Structural Studies On A Mitochondrial Glyoxalase Ii, Gishanthi P. K. Marasinghe, Ian M. Sander, Brian Bennett, Gopal R. Periyannan, Ke-Wu Yang, Christopher A. Makaroff, Michael W. Crowder

Physics Faculty Research and Publications

Glyoxalase 2 is a β-lactamase fold-containing enzyme that appears to be involved with cellular chemical detoxification. Although the cytoplasmic isozyme has been characterized from several organisms, essentially nothing is known about the mitochondrial proteins. As a first step in understanding the structure and function of mitochondrial glyoxalase 2 enzymes, a mitochondrial isozyme (GLX2-5) from Arabidopsis thaliana was cloned, overexpressed, purified, and characterized using metal analyses, EPR and ¹H NMR spectroscopies, and x-ray crystallography. The recombinant enzyme was shown to bind 1.04 ± 0.15 eq of iron and 1.31 ± 0.05 eq of Zn(II) and to exhibit k_cat and …

Fluid And Kinetic Structure Of Magnetic Merging In The Swarthmore Spheromak Experiment, W. H. Matthaeus, C. D. Cothran, Matthew Joseph Landreman , '03, Michael R. Brown

Physics & Astronomy Faculty Works

Measurement of the in-plane Lorentz force and the out-of-plane magnetic field associated with the Hall electric field near the reconnection zone in the Swarthmore Spheromak Experiment (SSX) confirms expectations, based on simulation, theory and spacecraft data, that the quadrupolar out-of-plane magnetic field is a signature of collisionless effects in magnetic reconnection with a weak guide field.

Dynamical Control Of Qubit Coherence: Random Versus Deterministic Schemes, Lea F. Santos, Lorenza Viola

Dartmouth Scholarship

We reexamine the problem of switching off unwanted phase evolution and decoherence in a single two-state quantum system in the light of recent results on random dynamical decoupling methods [L. Viola and E. Knill, Phys. Rev. Lett. 94, 060502 (2005)]. A systematic comparison with standard cyclic decoupling is effected for a variety of dynamical regimes, including the case of both semiclassical and fully quantum decoherence models. In particular, exact analytical expressions are derived for randomized control of decoherence from a bosonic environment. We investigate quantitatively control protocols based on purely deterministic, purely random, as well as hybrid design, and …

Extreme Sensitivity Of Differential Momentum Transfer Cross Sections To Target Atom Initial Conditions, Ronald E. Olson, J. Fiol

Physics Faculty Research & Creative Works

Heavy-particle cross sections differential in the momentum transferred to the target are investigated using the classical trajectory Monte Carlo method. with the 3.6  MeV/u Au53++He system as a test case, it is shown that these cross sections are extremely sensitive to the initial target temperature. In particular, when thermal motion is varied for one of the target's initial momentum components between 0 and 25 K the absolute cross sections vary by orders of magnitude and, in addition, their relative shapes undergo major changes. We find that by setting one of the target's transverse momenta to a temperature of 16 K, …

Physics Department News, December 2005, College Of Arts And Sciences

Physics Newsletter

Contents from Volume 4, Issue 1:

• A Note from the Editor
• From the Chair
• What’s New at the University
• Faculty Highlights
• Staff Highlights
• ICPEAC 2009
• Year of Physics 2005
• PhysTEC
• Alumni News
• Student News
• Annual Student Awards
• Recent Graduates
• Department Roster
• Feedback/Update Reply For

Nonrelativistic Qed Approach To The Lamb Shift, Ulrich D. Jentschura, Andrzej Czarnecki, Krzysztof Pachucki

Physics Faculty Research & Creative Works

We calculate the one- and two-loop corrections of order α(Zα)⁶ and α²(Zα)⁶, respectively, to the Lamb shift in hydrogenlike systems using the formalism of nonrelativistic quantum electrodynamics. We obtain general results valid for all hydrogenic states with nonvanishing orbital angular momentum and for the normalized difference of S states. These results involve the expectation value of local effective operators and relativistic corrections to Bethe logarithms. The one-loop correction is in agreement with previous calculations for the particular cases of S, P, and D states. The two-loop correction in the order α²(Zα)⁶ includes …

Mutual Ionization In 200-Kev H⁻+ He Collisions, T. Ferger, Daniel Fischer, Michael Schulz, R. Moshammer, A. B. Voitkiv, B. Najjari, J. Ullrich

Physics Faculty Research & Creative Works

We studied mutual ionization in 200-keV H-⁺He collisions in a kinematically complete experiment by measuring the fully momentum-analyzed recoil ions and both active electrons in coincidence. Comparison of the data to our calculations, based on various theoretical models, show that mutual ionization proceeds predominantly through the interaction between both electrons. The post-collision interaction between the outgoing ejected electrons as well as higher order processes involving the interaction between the core of both collision partners are also important.

Soft-Gluon Corrections To Hard-Scattering Cross Sections Through Nnnlo, Nikolaos Kidonakis

Faculty and Research Publications

I present a systematic approach to calculating soft-gluon corrections through next-to-next-to-nextto-leading order for arbitrary hard-scattering cross sections. Using a unified approach, master formulas are derived for processes with both simple and complex color flows. Applications and numerical results are given for some processes of interest, including charged Higgs production and top quark production in the Standard Model and beyond.

Lattice Quantum Algorithm For The Schrodinger Wave Equation In 2+1 Dimensions With A Demonstration By Modeling Soliton Instabilities, Jeffrey Yepez, George Vahala, Linda L. Vahala

Electrical & Computer Engineering Faculty Publications

A lattice-based quantum algorithm is presented to model the non-linear Schrödinger-like equations in 2 + 1 dimensions. In this lattice-based model, using only 2 qubits per node, a sequence of unitary collide (qubit-qubit interaction) and stream (qubit translation) operators locally evolve a discrete field of probability amplitudes that in the long-wavelength limit accurately approximates a non-relativistic scalar wave function. The collision operator locally entangles pairs of qubits followed by a streaming operator that spreads the entanglement throughout the two dimensional lattice. The quantum algorithmic scheme employs a non-linear potential that is proportional to the moduli square of the wave function. …

Search For Lepton-Flavor Violation At Hera, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini

Faculty Publications

A search for lepton-flavor-violating interactions ep → μX and ep → τX has been performed with the ZEUS detector using the entire HERA I data sample, corresponding to an integrated luminosity of 130 pb-1. The data were taken at center-of-mass energies, √s, of 300 and 318 GeV. No evidence of lepton-flavor violation was found, and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below √s, limits were set on λeq1 √β ℓq, where λeq1 is the coupling of the LQ to an electron and a first-generation quark q1, and βℓq is the branching ratio …

Ferroelectric Polymer Langmuir–Blodgett Films For Nonvolatile Memory Applications, Stephen Ducharme, Timothy J. Reece, Christina M. Othon, R. K. Rannow

Department of Physics and Astronomy: Faculty Publications

We review the potential for integrating ferroelectric polymer Langmuir–Blodgett (LB) films with semiconductor technology to produce nonvolatile ferroelectric random-access memory (NV-FRAM or NV-FeRAM) and data-storage devices. The prototype material is a copolymer consisting of 70% vinylidene fluoride (VDF) and 30% trifluoroethylene (TrFE), or P(VDF-TrFE 70:30). Recent work with LB films and more conventional solventformed films shows that the VDF copolymers are promising materials for nonvolatile memory applications. The prototype device is themetal–ferroelectric–insulator–semiconductor (MFIS) capacitance memory. Field-effect transistor (FET)-based devices are also discussed. The LB films afford devices with low-voltage operation, but there are two important technical hurdles that must be …

Focused-Laser Interferometric Position Sensor, Stephen J. Friedman, Brett E. Barwick, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

We describe a simple method to measure the position shifts of an object with a range of tens of micrometers using a focused-laser (FL) interferometric position sensor. In this article we examine the effects of mechanical vibration on FL and Michelson interferometers. We tested both interferometers using vibration amplitudes ranging from 0 to 20 μm. Our FL interferometer has a resolution much better than the diffraction grating periodicities of 10 and 14 μm used in our experiments. A FL interferometer provides improved mechanical stability at the expense of spatial resolution. Our experimental results show that Michelson interferometers cannot be used …

Klein Paradox With Spin-Resolved Electrons And Positrons, P Krekora, Q Su, Rainer Grobe

Faculty publications – Physics

Using numerical solutions to relativistic quantum field theory with space-time resolution, we illustrate how an incoming electron wave packet with a definite spin scatters off a supercritical potential step. We show that the production rate is reduced of only those electrons that have the same spin as the incoming electron is reduced. This spin-resolved result further clarifies the importance of the Pauli-exclusion principle for the Klein paradox.

Investigation Of The Probe-Sample Interaction In The Ultrasonic/Shear-Force Microscope: The Phononic Friction Mechanism, Xiquan Cui, Andres H. La Rosa

Physics Faculty Publications and Presentations

The dissipative and conservative interactions between a sharp probe and a flat Si sample in the ultrasonic/shear-force microscope are investigated. It is shown that, when working in the ambient condition, there are two distinct probe-sample interaction regions: the pure dissipative interaction region in the relatively far probe-sample distance, and the highly correlated dissipative and conservative interaction region in the close probe-sample distance. The ultrasonic data suggest that the phonon generation is a dissipative channel for the probe-sample interaction in the shear force microscope. A shaking potential model is proposed to explain the phononic friction mechanism

Multivalued Logic, Neutrosophy And Schrodinger Equation, Florentin Smarandache, Victor Christianto

Branch Mathematics and Statistics Faculty and Staff Publications

This book was intended to discuss some paradoxes in Quantum Mechanics from the viewpoint of Multi-Valued-logic pioneered by Lukasiewicz, and a recent concept Neutrosophic Logic. Essentially, this new concept offers new insights on the idea of ‘identity’, which too often it has been accepted as given. Neutrosophy itself was developed in attempt to generalize Fuzzy-Logic introduced by L. Zadeh. While some aspects of theoretical foundations of logic are discussed, this book is not intended solely for pure mathematicians, but instead for physicists in the hope that some of ideas presented herein will be found useful. The book is motivated by …

Fractal Dimensions In Perceptual Color Space: A Comparison Study Using Jackson Pollock’S Art, Jonas R. Mureika

Physics Faculty Works

The fractal dimensions of color-specific paint patterns in various Jackson Pollock paintings are calculated using a filtering process that models perceptual response to color differences (L*a*b* color space). The advantage of the L*a*b* space filtering method over traditional red-green-blue (RGB) spaces is that the former is a perceptually uniform (metric) space, leading to a more consistent definition of “perceptually different” colors. It is determined that the RGB filtering method underestimates the perceived fractal dimension of lighter-colored patterns but not of darker ones, if the same selection criteria is applied to each. Implications of the findings to Fechner’s “principle of …

Dynamics Of A Nanomechanical Resonator Coupled To A Superconducting Single-Electron Transistor, M. P. Blencowe, J. Imbers, A. D. Armour

Dartmouth Scholarship

We present an analysis of the dynamics of a nanomechanical resonator coupled to a superconducting single-electron transistor (SSET) in the vicinity of Josephson quasi-particle (JQP) and double Josephson quasi-particle (DJQP) resonances. For weak coupling and wide separation of dynamical timescales, we find that for either superconducting resonances the dynamics of the resonator are given by a Fokker–Planck equation, i.e. the SSET behaves effectively as an equilibrium heat bath, characterized by an effective temperature, which also damps the resonator and renormalizes its frequency. Depending on the gate and drain–source voltage bias points with respect to the superconducting resonance, the SSET can …

Fluorescence Measurements Of Expanding Strongly Coupled Neutral Plasmas, E. A. Cummings, J. E. Daily, Dallin S. Durfee, Scott D. Bergeson

Faculty Publications

We report new detailed density profile measurements in expanding strongly coupled neutral calcium plasmas. Using laser-induced fluorescence techniques, we determine plasma densities in the range of 10^5 to 10^9 cm^-3 with a time resolution limit as small as 7 ns. Strong coupling in the plasma ions is inferred directly from the fluorescence signals. Evidence for strong coupling at late times is presented, confirming a recent theoretical result.

Percolation Quantum Phase Transitions In Diluted Magnets, Thomas Vojta, Jörg Schmalian

Physics Faculty Research & Creative Works

We show that the interplay of geometric criticality and quantum fluctuations leads to a novel universality class for the percolation quantum phase transition in diluted magnets. All critical exponents involving dynamical correlations are different from the classical percolation values, but in two dimensions they can nonetheless be determined exactly. We develop a complete scaling theory of this transition, and we relate it to recent experiments in La2Cu1-p(Zn,Mg)pO4. Our results are also relevant for disordered interacting boson systems.

Reversible Hysteresis Loop Tuning, Andreas Berger, Christian Binek, D. T. Margulies, A. Moser, E. E. Fullerton

Christian Binek Publications

We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching fi eld distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The nonoverlapping switching fi eld distribution allows the measurement of magnetization reversal in the SL at low fi elds while keeping the magnetization state of the HL unperturbed. Applying an appropriate high fi eld or high fi eld sequence changes the magnetic …

Ferroelectric Switch For Spin Injection, Mikhail Y. Zhuravlev, Sitaram Jaswal, Evgeny Y. Tsymbal, Renat F. Sabirianov

Physics Faculty Publications

A method for the switching of the spin polarization of the electric current injected into a semiconductor is proposed, based on injecting spins from a diluted magnetic semiconductor through a ferroelectric tunnel barrier. We show that the reversal of the electric polarization of the ferroelectric results in a sizable change in the spin polarization of the injected current, thereby providing a two-state electrical control of this spintronic device. We also predict a possibility of switching of tunneling magnetoresistance in magnetic tunnel junctions with a ferroelectric barrier and coexistence of tunneling magnetoresistance and giant electroresistance effects in these multiferroic tunnel junctions.