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1

Quantum recoil and Bohm diffusion  

SciTech Connect

It is argued that the inclusion of the Bohm potential in quantum fluid equations is equivalent to inclusion of a nonrelativistic form of the quantum recoil in plasma kinetic theory. The Bohm term is incorrect when applied to waves with phase speed greater than the speed of light.

Melrose, D. B.; Mushtaq, A. [School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia)

2009-09-15

2

Dispersion in a thermal plasma including arbitrary degeneracy and quantum recoil  

SciTech Connect

The longitudinal response function for a thermal electron gas is calculated including two quantum effects exactly, degeneracy, and the quantum recoil. The Fermi-Dirac distribution is expanded in powers of a parameter that is small in the nondegenerate limit and the response function is evaluated in terms of the conventional plasma dispersion function to arbitrary order in this parameter. The infinite sum is performed in terms of polylogarithms in the long-wavelength and quasistatic limits, giving results that apply for arbitrary degeneracy. The results are applied to the dispersion relations for Langmuir waves and to screening, reproducing known results in the nondegenerate and completely degenerate limits, and generalizing them to arbitrary degeneracy.

Melrose, D. B. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Mushtaq, A. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Theoretical Plasma Physics Division, PINSTECH, Nilore, 44000 Islamabad (Pakistan)

2010-11-15

3

Recoil effects in valence band photoemission of organic solids.  

PubMed

Recoil effects in valence band X-ray photoelectron spectroscopy (XPS) are studied for both abb-trifluorostyrene and styrene molecular crystal systems. The gradual changes of XPS spectra excited by several photon energies are theoretically investigated within the tight-binding approximation and harmonic approximation of lattice vibrations and have been explained in terms of not only atomic mass but also atomic orbital (AO) population. The recoil effect of valence band photoemission strongly depends on the population and partial photoionization cross section (PICS) of AOs as well as the masses of composite atoms. In abb-trifluorostyrene F 2p dominant bands show the recoil shift close to free F atom recoil shift, and C 2s dominant bands show that to free C atom recoil shift, whereas the mixed bands of C and F give rise to the peak asymmetries due to their different recoil shifts. For these systems, hydrogen contribution is negligibly small which is in contrast to our previous results for the crystals composed of small organic molecules. We also discuss some potential uses of the recoil shifts for these systems. PMID:23441983

Shang, Ming-Hui; Fujikawa, Takashi; Ueno, Nobuo

2013-03-18

4

Quantum effects on the dispersion of ion acoustic waves  

SciTech Connect

The longitudinal response function for an isotropic, nonrelativistic, thermal plasma with the quantum recoil included exactly is used to generalize the dispersion relation for ion acoustic waves and the absorption coefficient for Landau damping to include the quantum recoil. The results are compared to recent treatment of the dispersion relation derived using a fluid theory with the quantum effects included through the Bohm potential.

Mushtaq, A. [School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia); Theoretical Plasma Physics Division, PINSTECH, Nilore, 44000 Islamabad (Pakistan); Melrose, D. B. [School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia)

2009-10-15

5

The effect of recoil on edge singularities  

NASA Astrophysics Data System (ADS)

A transient local perturbation gives rise to infrared edge singularities. These singularities are shown to disappear if the scatterer is free to diffuse to infinity, as long as the dimension exceeds 1. When d = 1, or in the présence of localisation when d > 1, the characteristic exponents are reduced by recoil, by a factor that involves an angular average over the Fermi surface. Une perturbation locale transitoire induit une singularité de seuil infrarouge. Cette singularité disparaît si la perturbation peut diffuser à l'infini et si d > 1. Si d = 1, ou en présence de localisation si d > 1, les exposants caractéristiques sont réduits par le recul. Le facteur de réduction fait intervenir une moyenne angulaire sur la surface de Fermi.

Nozières, P.

1994-09-01

6

Quantum fluctuations and entanglement in the collective atomic recoil laser using a Bose-Einstein condensate  

SciTech Connect

We present a quantum description of the interaction between a Bose-Einstein condensate and a single-mode quantized radiation field in the presence of a strong far-off-resonant pump laser. In the linear regime, the atomic medium is described approximately by two momentum states coupled to the radiation mode. We calculate the evolution of the operators in the Heisenberg picture and their expectation values, such as average and variance of the occupation numbers, atom-atom and atom-field correlations, and two-mode squeezing parameters. Then, we disentangle the evolution operator and obtain the exact evolution of the state vector in the linear regime. This allows us to demostrate that the system can be atom-atom or atom-field thermally entangled. We define the quasiclassical and the quantum recoil limits, for which explicit expressions of the average population numbers are obtained.

Piovella, N.; Cola, M.; Bonifacio, R. [Dipartimento di Fisica, Universita Degli Studi di Milano, INFN and INFM, Via Celoria 16, Milan I-20133 (Italy)

2003-01-01

7

Collective atomic recoil lasing including friction and diffusion effects  

SciTech Connect

We extend the collective atomic recoil lasing (CARL) model including the effects of friction and diffusion forces acting on the atoms due to the presence of optical molasses fields. The results from this model are consistent with those from a recent experiment by Kruse et al. [ Phys. Rev. Lett. 91, 183601 (2003) ]. In particular, we obtain a threshold condition above which collective backscattering occurs. Using a nonlinear analysis we show that the backscattered field and the bunching evolve to a steady state, in contrast to the nonstationary behavior of the standard CARL model. For a proper choice of the parameters, this steady state can be superfluorescent.

Robb, G.R.M. [Department of Physics, University of Strathclyde, Glasgow, G4 0NG, Scotland (United Kingdom); Piovella, N.; Ferraro, A.; Bonifacio, R. [Dipartimento di Fisica, Universita Degli Studi di Milano and INFM, Via Celoria 16, I-20133 Milan (Italy); Courteille, Ph.W.; Zimmermann, C. [Physikalisches Institut, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2004-04-01

8

Recoil effects in multiphoton electron-positron pair creation  

SciTech Connect

Triply differential probability rates for electron-positron pair creation in laser-nucleus collisions, calculated within the S-matrix approach, are investigated as functions of the nuclear recoil. Pronounced enhancements of differential probability rates of multiphoton pair production are found for a nonzero momentum transfer from the colliding nucleus. The corresponding rates show a very dramatic dependence on the polarization of the laser field impinging on the nucleus; only for a linearly polarized light are the multiphoton rates for electron-positron pair production considerably large. We focus therefore on this case. Our numerical results for different geometries of the reaction particles demonstrate that, for the linearly polarized laser field of an infinite extent (which is a good approximation for femtosecond laser pulses), the pair creation is far more efficient if the nucleus is detected in the direction of the laser-field propagation. The corresponding angular distributions of the created particles show that the high-energy pairs are predominantly produced in the plane spanned by the polarization vector and the laser-field propagation direction, while the low-energy pairs are rather spread around the latter of the two directions. The enhancement of differential probability rates at each energy sector, defined by the four-momentum conservation relation, is observed with varying the energy of the produced particles. The total probability rates of pair production are also evaluated and compared with the corresponding results for the case when one disregards the recoil effect. A tremendous enhancement of the total probability rates of the electron-positron pair creation is observed if one takes into account the nuclear recoil.

Krajewska, K.; Kaminski, J. Z. [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Hoza 69, PL-00-681 Warszawa (Poland)

2010-07-15

9

Direct Measurement of Recoil Effects on Ar-Ar Standards  

NASA Astrophysics Data System (ADS)

Advances in the precision possible with the Ar-Ar method using new techniques and equipment have led to considerable effort to improve the accuracy of the calibration of interlaboratory standards. However, ultimately the accuracy of the method relies on the measurement of 40Ar*/39ArK ratios on primary standards that have been calibrated with the K-Ar method and, in turn, on secondary standards that are calibrated against primary standards. It is usually assumed that an Ar-Ar total gas age is equivalent to a K-Ar age, but this assumes that there is zero loss of Ar due to recoil. Instead, traditional Ar-Ar total gas ages are in fact Ar retention ages [1] and not, strictly speaking, comparable to K-Ar ages. There have been efforts to estimate the importance of this effect on standards along with prescriptions for minimizing recoil effects [2,3], but these studies have relied on indirect evidence for 39Ar recoil. We report direct measurements of 39Ar recoil for a set of primary and secondary standards using the vacuum encapsulation techniques of [1] and show that significant adjustments to ages assigned to some standards may be needed. The fraction f of 39Ar lost due to recoil for primary standards MMhb-1 hornblende and GA-1550 biotite are 0.00367 and 0.00314 respectively. It is possible to modify the assumed K-Ar ages of these standards so that when using their measured Ar retention 40Ar*/39ArK ratios, one obtains a correct K-Ar age for an unknown, assuming that the unknown sample has zero loss of 39Ar due to recoil. Assuming a primary K-Ar age for MMhb-1 of 520.4 Ma, the modified age would be 522.1 Ma and assuming a primary K-Ar age for GA-1550 of 98.79 Ma [4] yields a modified effective age of 99.09 Ma. Measured f values for secondary standards FCT-3 biotite, FCT-2 sanidine and TCR-2 sanidine are 0.00932, 0.00182 and 0.00039 respectively. Using an R value for FCT-3 biotite relative to MMhb-1 [5], the K-Ar age for this standard would be 27.83 Ma and using R values for FCT and TC sanidines [4] against GA-1550, their K-Ar ages would be 28.06 Ma and 28.41 Ma respectively. For retrospective recalculation purposes, the effective Ar-Ar age of these samples that should yield correct K-Ar ages for unknowns with zero recoil loss would be 28.09 Ma, 28.11 Ma and 28.42 Ma for FCT-3 biotite, FCT-2 sanidine and TCR-2 sanidine respectively. The measured f for FCT-3 appears to explain the R value of it relative to FCT sanidine of 1.0086 found by [8]. From the low T portion of the Ar release spectra of the biotite and amphibole standards, it is clear that the dominant recoil artifact affecting Ar release is the re-implantation mechanism seen in clay samples [1,6,7] and not the loss of 39Ar at the surface of the grain. The geometry of neighboring grains during irradiation and internal defects may predominate in controlling recoil loss. [1] Dong et al., 1995, Science, 267, 355-359. [2] Paine et al., 2006, Geochim.Cosmochim. Acta, 70, 1507-1517. [3] Jourdan et al., 2007, Geochim. Cosmochim. Acta, 71, 2791-2808 [4] Renne et al., 1998, Chem. Geol., 145 117-152. [5] Hall & Farrell, 1995, Earth Planet. Sci. Lett., 133, 327-338. [6] Hall et al., 1997, Earth Planet. Sci. Lett., 148, 287-298. [7] Hall et al., 2000, Econ. Geol., 95, 1739-1752. [8] Di Vincenzo & Roman Skála, 2009, Geochim. Cosmochim. Acta, 73, 493-513.

Hall, C. M.

2011-12-01

10

Reactive and inelastic hydrogen + deuterium collisions: Classical recoil, quantum interference, and the tug-of-war mechanism  

NASA Astrophysics Data System (ADS)

Differential cross sections (DCSs) are presented for reactive and inelastic H + D2 collisions over a wide range of collision energies and product quantum states. A mixture of HBr and D2 is expanded into a vacuum chamber; a laser photolyzes HBr to initiate the collision process. Three-dimensional ion imaging is employed to detect HD/D2 products that have been quantum state selected by resonance enhanced multiphoton ionization. The construction of the imaging instrument and a novel application of two-color Doppler-free ionization are described. Reactively scattered HD(v' = 1, j') products are mostly back scattered, and the DCS contains a single peak; the dependence of the DCS on the collision energy over the range 1.48 ? Ecoll ? 1.94 eV is very weak. This behavior is consistent with the direct recoil mechanism that is known to be dominant. For HD( v' = 1, j' = 1, 2) at collision energies Ecoll ? 1.72 eV, a bimodal feature is observed, which may be caused by indirect scattering from the conical intersection. For HD( v' = 3, j = 0), there are three major peaks whose widths and centers vary rapidly with the collision energy. Recent quantum mechanical (QM) calculations attributed this behavior to the interference between nearside and farside pathways. New and existing QM calculations accurately reproduce the measured DCSs for reactive scattering; the experiments presented here corroborate the theoretical predictions to a much higher level of detail compared with previous measurements. Inelastically scattered D2(v' = 1-4, j') products are mostly forward scattered. This observation is contrary to the commonly accepted wisdom that collisions capable of transferring a large amount of energy into vibration occur at low impact parameters and are back scattered. We compare our results with quasi-classical trajectory calculations and suggest that the forward scattering can be explained by a tug-of-war mechanism in which attractive forces dominate the inelastic scattering process. Many inelastic trajectories recross the reaction barrier, and we find evidence of quantum interference effects for D2(v' = 3, j' ? 2) that may be related to those observed for the HD( v' = 3, j' = 0) reactive channel.

Goldberg, Noah Tribe

11

Quantum effects in electron beam pumped GaAs  

NASA Astrophysics Data System (ADS)

Propagation of waves in nano-sized GaAs semiconductor induced by electron beam are investigated. A dispersion relation is derived by using quantum hydrodynamics equations including the electrons and holes quantum recoil effects, exchange-correlation potentials, and degenerate pressures. It is found that the propagating modes are instable and strongly depend on the electron beam parameters, as well as the quantum recoil effects and degenerate pressures. The instability region shrinks with the increase of the semiconductor number density. The instability arises because of the energetic electron beam produces electron-hole pairs, which do not keep in phase with the electrostatic potential arising from the pair plasma.

Yahia, M. E.; Azzouz, I. M.; Moslem, W. M.

2013-08-01

12

EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: Recoil momentum at a solid surface during developed laser ablation  

NASA Astrophysics Data System (ADS)

The recoil momentum from a laser light pulse in the intensity range 105-107 W/cm2 is experimentally investigated for dielectric and metallic targets as a function of the pressure of the surrounding medium and angle of illumination. An equation with empirical coefficients is obtained for the recoil momentum of illuminated targets. Effects of the screening properties of the erosion jet and the back pressure on the recoil momentum are analyzed as the external pressure is varied.

Kuznetsov, L. I.

1993-12-01

13

Cosmogenic production rates and recoil loss effects in micrometeorites and interplanetary dust particles  

NASA Astrophysics Data System (ADS)

We present a purely physical model to determine cosmogenic production rates for noble gases and radionuclides in micrometeorites (MMs) and interplanetary dust particles (IDPs) by solar cosmic-rays (SCR) and galactic cosmic-rays (GCR) fully considering recoil loss effects. Our model is based on various nuclear model codes to calculate recoil cross sections, recoil ranges, and finally the percentages of the cosmogenic nuclides that are lost as a function of grain size, chemical composition of the grain, and the spectral distribution of the projectiles. The main advantage of our new model compared with earlier approaches is that we consider the entire SCR particle spectrum up to 240 MeV and not only single energy points. Recoil losses for GCR-produced nuclides are assumed to be equal to recoil losses for SCR-produced nuclides. Combining the model predictions with Poynting-Robertson orbital lifetimes, we calculate cosmic-ray exposure ages for recently studied MMs, cosmic spherules, and IDPs. The ages for MMs and the cosmic-spherule are in the range <2.2-233 Ma, which corresponds, according to the Poynting-Robertson drag, to orbital distances in the range 4.0-34 AU. For two IDPs, we determine exposure ages of longer than 900 Ma, which corresponds to orbital distances larger than 150 AU. The orbital distance in the range 4-6 AU for one MM and the cosmic spherule indicate an origin either in the asteroid belt or release from comets coming either from the Kuiper Belt or the Oort Cloud. Three of the studied MMs have orbital distances in the range 23-34 AU, clearly indicating a cometary origin, either from short-period comets from the Kuiper Belt or from the Oort Cloud. The two IDPs have orbital distances of more than 150 AU, indicating an origin from Oort Cloud comets.

Trappitsch, Reto; Leya, Ingo

2013-02-01

14

Quantum Effects  

NSDL National Science Digital Library

Quantum theory is an extremely advanced and complicated model. However, some aspects are accessible and useful for building an appreciation and understanding of the novel properties exhibited by matter at the nanoscale. In this chapter, the authors presen

Krajcik, Joseph S.; Sutherland, Leeann M.; Stevens, Shawn Y.

2009-10-14

15

The effects of multiple and plural scattering on Heavy Ion Elastic Recoil Detection Analysis  

SciTech Connect

An increasing number of groups use Heavy Ion Elastic Recoil Detection Analysis (HIERDA) to study a wide range of problems in materials science, however there is no accurate and reliable methodology for the analysis of HIERDA spectra. Major impediments are the effects of multiple and plural scattering which are very significant, even for quite thin ({approx}100 nm) layers of very heavy elements. To examine the effects of multiple scattering, a fast FORTRAN version of TRIM has been adapted to simulate the spectrum of backscattered and recoiled ions reaching the detector. The results of the simulations will be compared with experimental measurements on well characterized samples of thin Au layers on Si performed using ToF-E HIERDA at the Lucas Heights Laboratories of the Australian Nuclear Science and Technology Organization.

Johnston, P. N.; Bubb, I. F.; El Bouanani, M.; Cohen, D. D.; Dytlewski, N. [Department of Applied Physics, Royal Melbourne Institute of Technology, GPO Box 2476V, Melbourne 3001 (Australia); Australian Nuclear Science and Technology Organisation, PMB 1, Menai 2234 (Australia)

1999-06-10

16

Relativistic calculations of the nuclear recoil effect in highly charged Li-like ions  

NASA Astrophysics Data System (ADS)

Relativistic theory of the nuclear recoil effect in highly charged Li-like ions is considered within the Breit approximation. The normal mass shift (NMS) and the relativistic NMS (RNMS) are calculated by perturbation theory to zeroth and first orders in the parameter 1/Z. The calculations are performed using the dual kinetic balance method with the basis functions constructed from B-splines. The results of the calculations are compared with the theoretical values obtained by other methods.

Zubova, N. A.; Shabaev, V. M.; Tupitsyn, I. I.; Plunien, G.

2013-09-01

17

The alpha-recoil effects of uranium in the Oklo reactor  

Microsoft Academic Search

A series of acid-leaching experiments have been carried out on a sample of uranium ore from reactor zone number 10 of the Oklo mines in Gabon. Anomalously high U-234\\/U-238 ratios were observed accompanied by modestly increased U-235\\/U-238 ratios in uranium fractions. These results, which can be interpreted as being due to the alpha-recoil effects of U-238 and Pu-239, provide a

Z. Z. Sheng; P. K. Kuroda

1984-01-01

18

Radiation to atom quantum mapping by collective recoil in a Bose-Einstein condensate  

NASA Astrophysics Data System (ADS)

We propose a scheme to realize radiation to atom continuous variable quantum mapping, i.e., to teleport the quantum state of a single mode radiation field onto the collective state of atoms with a given momentum out of a Bose-Einstein condensate. The atoms-radiation entanglement needed for the teleportation protocol is established through the interaction of a single mode with the condensate in the presence of a strong far off-resonant pump laser, whereas the coherent atomic displacement is obtained by the same interaction with the radiation in a classical coherent field.

Paris, Matteo G. A.; Cola, Mary; Piovella, Nicola; Bonifacio, Rodolfo

2003-11-01

19

EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: Recoil momentum at a solid surface during developed laser ablation  

Microsoft Academic Search

The recoil momentum from a laser light pulse in the intensity range 105-107 W\\/cm2 is experimentally investigated for dielectric and metallic targets as a function of the pressure of the surrounding medium and angle of illumination. An equation with empirical coefficients is obtained for the recoil momentum of illuminated targets. Effects of the screening properties of the erosion jet and

L. I. Kuznetsov

1993-01-01

20

Isotopic Disequilibrium of Uranium: Alpha-Recoil Damage and Preferential Solution Effects  

Microsoft Academic Search

Preferential loss of uranium-234 relative to uranium-238 from rocks into solutions has long been attributed to recoiling alpha-emitting nuclei. Direct evidence has been obtained for two mechanisms, first, recoil ejection from grains, and now release by natural etching of alpha-recoil tracks. The observations have implications for radon emanation and for the storage of alpha-emitting radioactive waste.

Robert L. Fleischer

1980-01-01

21

Isotopic disequilibrium of uranium: alpha-recoil damage and preferential solution effects  

Microsoft Academic Search

Preferential loss of uranium-234 relative to uranium-238 from rocks into solutions has long been attributed to recoiling alpha-emitting nuclei. Direct evidence has been obtained for two mechanisms, first, recoil ejection from grains, and now release by natural etching of alpha-recoil tracks. The observations have implications for radon emanation and for the storage of alpha-emitting radioactive waste.

R. L. FLEISCHER

1980-01-01

22

Chemical effects of 56 Mn-recoils in mixed crystals of potassium permanganate with perchlorates  

Microsoft Academic Search

The chemical effects of56Mn-recoils following neutron capture produced in mixed crystals \\/KMnO4–LiClO4, KMnO4–NaClO4 and KMnO4–KClO4\\/ have been investigated. A linear increase of initial retention with the mol fraction of perchlorate was observed which is tentatively ascribed to the tendency to form species having structures similar to that of the host matrix. The ultimate chemical fate of the manganese atom also

S. P. Mishra; J. Singh

1986-01-01

23

Relativistic nuclear recoil, electron correlation and QED effects in highly charged Ar ions  

NASA Astrophysics Data System (ADS)

We have performed extensive theoretical studies on the 1s^22s^22p^2P3/2 -- ^2P1/2 M1 transition in Ar^13+ ions. Accurate radiative lifetimes are sensitive to QED corrections like the electron anomalous magnetic moment and to relativistic electron correlation effects. The lifetime of the P3/2 metastable state was determined to be 9.573(4)(5) ms (stat)(syst) [1] using the Heidelberg electron beam ion trap. Theoretical predictions cluster around a value that is significantly shorter than this high-precision experimental result. This discrepancy is presently unexplained. The wavelengths of the above transition in Ar^13+ and the 1s^22s2p ^3P1 -- ^3P2 M1 transition in Ar^14+ were compared for the isotopes ^36Ar and ^40Ar [2]. The observed mass shift has confirmed the relativistic theory of nuclear recoil effects in many-body systems. Our calculations, based on the fully relativistic recoil operator, are in excellent agreement with the measured results. [1] A. Lapierre, U.D. Jentschura, J.R. Crespo L'opez-Urrutia et al., Phys. Rev. Lett. 95, 183001 (2005); [2] R. Soria Orts, Z. Harman, J.R. Crespo L'opez-Urrutia et al., Phys. Rev. Lett. 97, 103002 (2006)

Harman, Z.; Soria Orts, R.; Lapierre, A.; Crespo Lopez-Urrutia, J. R.; Artemyev, A. N.; Tupitsyn, I. I.; Jentschura, U. D.; Keitel, C. H.; Tawara, H.; Ullrich, J.; Shabaev, V. M.; Volotka, A. V.

2007-06-01

24

Recoil effect of the ice hockey stick during a slap shot.  

PubMed

The purpose of this study was to examine the "recoil" effect of the ice hockey stick shaft during a stationary slap shot. Nine male adult subjects (four elite and five recreational) were tested. Their performances were evaluated by simultaneously recording stick movement and internal bending from high-speed digital video (1,000 Hz) and puck acceleration from a triaxial accelerometer positioned inside the puck. In addition, an electrical circuit measured blade-puck contact time. Data were analyzed with a one-way MANOVA for several dependent variables, including final puck velocity, puck acceleration, maximum stick shaft bending (angle and distance deflection), stick shaft angular velocities, blade-puck contact time, and corresponding time events. The results indicate the following. First, blade-puck contact time was greater for the elite than for recreational players (38 +/- 9 ms and 27 +/- 5 ms); however, measures for puck acceleration were essentially the same (63.8 g +/- 9.9 and 61.8 g +/- 19.5). Two, the elite players were able to generate greater puck velocities (120 +/- 18 km/h and 80.3 +/- 11.6 km/h). Three, the recoil timing was found to be reater for elite players (59.8% of blade-puck contact). PMID:17215552

Villaseñor, A; Turcotte, R A; Pearsall, D J

2006-08-01

25

Alpha-recoil damage and solution effects in minerals: uranium isotopic disequilibrium and radon release  

Microsoft Academic Search

Preferential loss relative to 238 U of 234 U from rocks into solutions has long been attributed to recoiling alpha-emitting nuclei. Using fission-track activation direct evidence has been obtained for two mechanisms: 1. (1) recoil ejection from grains. 2. (2) release by natural etching of alpha-recoil tracks. Tests of the second mechanism have been done using 239 PuO 2 sources

Robert L. Fleischer

1982-01-01

26

Quantum Spin Hall Effect  

Microsoft Academic Search

The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin

B. Andrei Bernevig; Shou-Cheng Zhang

2010-01-01

27

Quantum Spin Hall Effect  

Microsoft Academic Search

The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. The existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic

B. Andrei Bernevig; Shou-Cheng Zhang

2006-01-01

28

Final state effects in quantum fluids  

SciTech Connect

The extraction of momentum distributions from high energy scattering experiment depends on the validity of the impulse approximation (IA) which has been extensively discussed in the workshop overview. The IA assumes that in the scattering process the kinetic energy imparted to a recoiling particle is large compared to the potential energy due to neighboring particles. While this may be true for x-ray Compton scattering from electronic systems, it is less true for quasielastic electron-nucleus scattering, and it is invalid for deep inelastic neutron scattering (DINS) from quantum fluids and solids such as helium. In the latter case, the interatomic potential has a steeply repulsive core which is never negligible compared to the kinetic energies which can be imparted in feasible neutron scattering experiments. The corrections to the IA due to interactions of the recoiling atom with neighboring atoms are termed ''final state effects'' (FSE). This paper presents the theory of FSE for the case of deep inelastic neutron scattering from /sup 4/He quantum fluids. The lessons should also be applicable to momentum distribution experiments in many other systems. 28 refs., 12 figs.

Silver, R.N.

1989-01-01

29

alpha-Actin: disposition, quantities, and estimated effects on lung recoil and compliance.  

PubMed

We have investigated the basis and implications of pneumoconstriction by measuring disposition and quantities of alpha-smooth muscle actin in rat and guinea pig lungs and modeling its effects on lung recoil and compliance. A robust marker of contractility, alpha-smooth muscle actin appears in smooth muscle or myofibroblast-like cells in pleura, airways, blood vessels, and alveolar ductal tissues. In each site, we measured its transected area by immunofluorescent staining and frequency-modulated scanning confocal microscopy. We incorporated these data in a model of the parenchyma consisting of an extensive elastic network with embedded contractile structures. We conclude that contraction at any one of these sites alone can decrease parenchymal compliance by 20-30% during tidal breathing. This is due mostly to the stiffness of activated contractile elements undergoing passive cycling; constant muscle tension would have little effect. The magnitude of the effect corresponds with known responses of the lung to hypocapnia, consistent with a homeostatic function in which gas exchange is defended by redistributing ventilation away from overventilated units. PMID:11408464

Oldmixon, E H; Carlsson, K; Kuhn, C; Butler, J P; Hoppin, F G

2001-07-01

30

Effect of recoiled O on damage regrowth and electrical properties of through-oxide implanted Si  

SciTech Connect

High dose (4 to 7.5 x 10/sup 15/ cm/sup -2/) As implantations into p-type (100) Si have been carried out through a screen-oxide of thicknesses less than or equal to 775A and without screen oxide. The effect of recoiled O on damage annealing and electrical properties of the implanted layers has been investigated using a combination of the following techniques: TEM, RBS/MeV He/sup +/ channeling, SIMS and Hall measurements in conjunction with chemical stripping and sheet resistivity measurements. The TEM results show that there is a dramatically different annealing behavior of the implantation damage for the through oxide implants (Case I) as compared to implants into bare silicon (Case II). Comparison of the structural defect profiles with O distributions obtained by SIMS demonstrated that retardation in the secondary damage growth in Case I can be directly related with the presence of O. Weak-beam TEM showed that a high density of fine defect clusters (less than or equal to 50A) were present both in Case I and Case II. The electrical profiles showed only 30% of the total As to be electrically active. The structural and electrical results have been explained by a model that entails As-O, Si-O and As-As complex formation and their interaction with the dislocations.

Sadana, D.K.; Wu, N.R.; Washburn, J.; Current, M.; Morgan, A.; Reed, D.; Maenpaa, M.

1982-10-01

31

Treatment for the recoil effects of the multi-step heavy-ion nucleon transfers with the orthogonalized coupled-reaction-channel theory.  

National Technical Information Service (NTIS)

We have investigated recoil effects in heavy-ion reactions for the nucleon transfers, and the validity of the spatially local approximation for the non- local transfer interaction defined by the orthogonalized coupled-reaction-channel (OCRC) theory. This ...

S. Misono B. Imanishi

1997-01-01

32

Theory of alpha recoil effects on radon release and isotopic disequilibrium  

Microsoft Academic Search

Using the present understanding of the mechanisms of release from rocks and soils of recoiling products of alpha emission, physical predictions can be made of the fraction of these nuclei that are directly freed and the fraction that can subsequently be freed by the action of water. The fractions depend on the size and nature of the grains in which

Robert L. Fleischer

1983-01-01

33

Effects of post-Newtonian spin alignment on the distribution of black-hole recoils  

NASA Astrophysics Data System (ADS)

Recent numerical relativity simulations have shown that the final black hole produced in a binary merger can recoil with a velocity as large as 5000km/s. Because of enhanced gravitational-wave emission in the so-called “hang-up” configurations, this maximum recoil occurs when the black-hole spins are partially aligned with the orbital angular momentum. We revisit our previous statistical analysis of post-Newtonian evolutions of black-hole binaries in the light of these new findings. We demonstrate that despite these new configurations with enhanced recoil velocities, spin alignment during the post-Newtonian stage of the inspiral will still significantly suppress (or enhance) kick magnitudes when the initial spin of the more massive black hole is more (or less) closely aligned with the orbital angular momentum than that of the smaller hole. We present a preliminary study of how this post-Newtonian spin alignment affects the ejection probabilities of supermassive black holes from their host galaxies with astrophysically motivated mass ratio and initial spin distributions. We find that spin alignment suppresses (enhances) ejection probabilities by ˜40% (20%) for an observationally motivated mass-dependent galactic escape velocity, and by an even greater amount for a constant escape velocity of 1000km/s. Kick suppression is thus at least a factor two more efficient than enhancement.

Berti, Emanuele; Kesden, Michael; Sperhake, Ulrich

2012-06-01

34

Potential effects of alpha-recoil on uranium-series dating of calcrete  

USGS Publications Warehouse

Evaluation of paleosol ages in the vicinity of Yucca Mountain, Nevada, at the time the site of a proposed high-level nuclear waste repository, is important for fault-displacement hazard assessment. Uranium-series isotope data were obtained for surface and subsurface calcrete samples from trenches and boreholes in Midway Valley, Nevada, adjacent to Yucca Mountain. 230Th/U ages of 33 surface samples range from 1.3 to 423 thousand years (ka) and the back-calculated 234U/238U initial activity ratios (AR) are relatively constant with a mean value of 1.54 ± 0.15 (1?), which is consistent with the closed-system behavior. Subsurface calcrete samples are too old to be dated by the 230Th/U method. U-Pb data for post-pedogenic botryoidal opal from a subsurface calcrete sample show that these subsurface calcrete samples are older than ~ 1.65 million years (Ma), old enough to have attained secular equilibrium had their U-Th systems remained closed. However, subsurface calcrete samples show U-series disequilibrium indicating open-system behavior of 238U daughter isotopes, in contrast with the surface calcrete, where open-system behavior is not evident. Data for 21 subsurface calcrete samples yielded calculable 234U/238U model ages ranging from 130 to 1875 ka (assuming an initial AR of 1.54 ± 0.15, the mean value calculated for the surface calcrete samples). A simple model describing continuous ?-recoil loss predicts that the 234U/238U and 230Th/238U ARs reach steady-state values ~ 2 Ma after calcrete formation. Potential effects of open-system behavior on 230Th/U ages and initial 234U/238U ARs for younger surface calcrete were estimated using data for old subsurface calcrete samples with the 234U loss and assuming that the total time of water-rock interaction is the only difference between these soils. The difference between the conventional closed-system and open-system ages may exceed errors of the calculated conventional ages for samples older than ~ 250 ka, but is negligible for younger soils.

Neymark, L. A.

2011-01-01

35

Recoil and Equilibrator Systems.  

National Technical Information Service (NTIS)

The pamphlet provides a general guide for the testing of recoil and equilibrator systems. Described are the arrival, prefiring, firing, post-firing and road tests to which the hydropneumatic and hydrospring recoil systems, and pneumatic, hydropneumatic an...

1966-01-01

36

Quantum Zeno effect of general quantum operations  

NASA Astrophysics Data System (ADS)

In this paper, we show that the quantum Zeno effect can occur for generalized quantum measurements or operations. As a consequence of frequently performing nonselective measurements (or trace-preserving completely positive maps), the evolution of a certain measurement-invariant state is governed by an effective Hamiltonian defined by the measurement (or map) and the free-evolution Hamiltonian. For selective measurements, the state may change randomly with time according to measurement outcomes, but some physical quantities (operators) still evolve according to the effective Hamiltonian.

Li, Ying; Herrera-Martí, David A.; Kwek, Leong Chuan

2013-10-01

37

Quantum effects in channeling radiation  

Microsoft Academic Search

The quantum effects on the total radiation intensity in channeling have been considered. It is shown that the problem can be considered in the frame of the magnetic bremsstrahlung limit. In the region where quantum effects are weak, the general formulae have been obtained for quantum corrections to the total intensity of the channeling radiation. While in diamond and silicon

V. N. Baier; V. M. Katkov; V. M. Strakhovenko

1992-01-01

38

Dilatation Effect of ''Quantum Clocks''.  

National Technical Information Service (NTIS)

The relativistic dilatation effect of the life-time of unstable microparticles combined with quantum symmetry of their description results in the ''quantum-dilatation'' dilemma. It is due to the classical character of the relativity theory which here reve...

Z. Chylinski

1981-01-01

39

Quantum effects in biology  

Microsoft Academic Search

The idea that quantum-mechanical phenomena can play nontrivial roles in biology has fascinated researchers for a century. Here we review some examples of such effects, including light-harvesting in photosynthesis, vision, electron- and proton-tunneling, olfactory sensing, and magnetoreception. We examine how experimental tests have aided this field in recent years and discuss the importance of developing new experimental probes for future

Graham R. Fleming; Gregory D. Scholes; Yuan-Chung Cheng

2011-01-01

40

Quantum Zeno effect: Quantum shuffling and Markovianity  

NASA Astrophysics Data System (ADS)

The behavior displayed by a quantum system when it is perturbed by a series of von Neumann measurements along time is analyzed. Because of the similarity between this general process with giving a deck of playing cards a shuffle, here it is referred to as quantum shuffling, showing that the quantum Zeno and anti-Zeno effects emerge naturally as two time limits. Within this framework, a connection between the gradual transition from anti-Zeno to Zeno behavior and the appearance of an underlying Markovian dynamics is found. Accordingly, although a priori it might result counterintuitive, the quantum Zeno effect corresponds to a dynamical regime where any trace of knowledge on how the unperturbed system should evolve initially is wiped out (very rapid shuffling). This would explain why the system apparently does not evolve or decay for a relatively long time, although it eventually undergoes an exponential decay. By means of a simple working model, conditions characterizing the shuffling dynamics have been determined, which can be of help to understand and to devise quantum control mechanisms in a number of processes from the atomic, molecular and optical physics.

Sanz, A. S.; Sanz-Sanz, C.; González-Lezana, T.; Roncero, O.; Miret-Artés, S.

2012-04-01

41

Quantum effects in Coulomb blockade  

Microsoft Academic Search

We review the quantum interference effects in a system of interacting electrons confined to a quantum dot. The review starts with a description of an isolated quantum dot. We discuss the random matrix theory (RMT) of the one-electron states in the dot, present the universal form of the interaction Hamiltonian compatible with the RMT, and derive the leading corrections to

I. L. Aleiner; P. W. Brouwer; L. I. Glazman

2002-01-01

42

The Quantum Spin Hall Effect  

Microsoft Academic Search

Most quantum states of condensed matter are classified by the symmetries they break. For example, crystalline solids break translational symmetry, and ferromagnets break rotational symmetry. By contrast, topological states of matter evade traditional symmetry-breaking classification schemes, and they signal the existence of a fundamentally different organizational principle of quantum matter. The integer and fractional quantum Hall effects were the first

Joseph Maciejko; Taylor L. Hughes; Shou-Cheng Zhang

2011-01-01

43

Quantum Computing With Quasiparticles of the Fractional Quantum Hall Effect.  

National Technical Information Service (NTIS)

The focus of this project was the theoretical study of quantum computation based on controlled transfer of individual quasiparticles in systems of quantum antidots in the regime of the Fractional Quantum Hall Effect (FQHE). The work addressed the basic is...

D. Averin

2001-01-01

44

Quantum effects in accelerator physics.  

National Technical Information Service (NTIS)

Quantum effects for electrons in a storage ring are discussed, in particular the polarization effect due to spin flip synchrotron radiation. The electrons are treated as a simple quantum mechnical two-level system coupled to the orbital motion and the rad...

J. M. Leinaas

1991-01-01

45

Effective equations for the quantum pendulum from momentous quantum mechanics  

SciTech Connect

In this work we study the quantum pendulum within the framework of momentous quantum mechanics. This description replaces the Schroedinger equation for the quantum evolution of the system with an infinite set of classical equations for expectation values of configuration variables, and quantum dispersions. We solve numerically the effective equations up to the second order, and describe its evolution.

Hernandez, Hector H.; Chacon-Acosta, Guillermo [Universidad Autonoma de Chihuahua, Facultad de Ingenieria, Nuevo Campus Universitario, Chihuahua 31125 (Mexico); Departamento de Matematicas Aplicadas y Sistemas, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40, Mexico D. F. 01120 (Mexico)

2012-08-24

46

Quantum resonant effects in the delta-kicked rotor revisited  

NASA Astrophysics Data System (ADS)

We review the theoretical model and experimental realization of the atom optics ?-kicked rotor (AOKR), a paradigm of classical and quantum chaos. We have performed a number of experiments with an all-optical Bose-Einstein condensate (BEC) in a periodic standing wave potential in an AOKR system. We discuss results of the investigation of the phenomena of quantum resonances in the AOKR. An interesting feature of the momentum distribution of the atoms obtained as a result of short pulses of light, is the variance of the momentum distribution or the kinetic energy ? p 2?/2 m in units of the recoil energy E rec = ? ? rec . The energy of the system is examined as a function of pulse period for a range of kicks that allow the observation of quantum resonances. In particular we study the behavior of these resonances for a large number of kicks. Higher order quantum resonant effects corresponding to the fractional Talbot time of (1/4) T T and (1/5) T T for five and ten kicks have been observed. Moreover, we describe the effect of the initial momentum of the atoms on quantum resonances in the AOKR.

Ullah, A.; Ruddell, S. K.; Currivan, J. A.; Hoogerland, M. D.

2012-12-01

47

The Quantum Spin Hall Effect  

Microsoft Academic Search

We show that the intrinsic spin orbit interaction in a single plane of graphene converts the ideal two dimensional semi metallic groundstate of graphene into a quantum spin Hall (QSH) state [1]. This novel electronic phase shares many similarities with the quantum Hall effect. It has a bulk excitation gap, but supports the transport of spin and charge in gapless

Charles Kane

2006-01-01

48

Macroscopic quantum effects in Josephson systems  

Microsoft Academic Search

Macroscopic quantum effects in Josephson systems have attracted great interest in the scientific community both for the physics involved and in view of applications. We present data on macroscopic quantum tunneling on Josephson junctions. Actually the most fascinating topic is the observation of macroscopic quantum coherence in rf-SQUID. This effect also has implications for quantum computing, because a quantum two-state

Valentina Corato; Emanuela Esposito; Carmine Granata; Antonia Monaco; Berardo Ruggiero; Maurizio Russo; Leo Stodolsky; Paolo Silvestrini

2001-01-01

49

Quantum Wipe Effect  

NASA Astrophysics Data System (ADS)

We consider a model of a spin system under the influence of decoherence such that a system coupled with a dissipating environmental system consisting of either spins or bosonic modes. The dissipation of an environment is governed by a certain probability with which an environmental system localized around a principal system dissipates into a larger bath and a thermal environmental system instead migrates into the place. A certain threshold on the probability is found in the growth of decoherence in a principal system. A larger as well as a smaller dissipation probability than the threshold results in smaller decoherence. This finding is utilized to elucidate a spin relaxation theory of a magnetic resonance spectrometer. In particular, a seamless description of transverse relaxation and motional narrowing is possible. We also numerically evaluate the dynamics of coherence useful for quantum information processing. The bang-bang control and anti-Zeno effect in entanglement and the Oppenheim-Horodecki nonclassical correlation are investigated in the model of spin-boson coupling.

Saitoh, Akira; Rahimi, Robabeh; Nakahara, Mikio

2010-11-01

50

Josephson effect and quantum fluctuations  

NASA Astrophysics Data System (ADS)

Phase fluctuations destroy the DC Josephson effect and replace the supercurrent at zero voltage by a peak at small but finite voltages. We study the effect of quantum fluctuations of the phase at zero temperature by accounting for a finite junction capacitance and an environmental resistance. The Josephson peak is expressed analytically by two complementary expansions. This result establishes the connection between the regimes of classical phase diffusion, Coulomb blockade and macroscopic quantum tunneling.

Ingold, G.-L.; Grabert, H.

2000-07-01

51

Quantum Parrondo game based on a quantum ratchet effect  

NASA Astrophysics Data System (ADS)

A Parrondo game is a counterintuitive game where two losing games can be combined to form a winning game. We construct a quantum version of a Parrondo game based on a quantum ratchet effect for a delta-kicked model, which can be realized in optical lattices. A game set is presented and a quantum anti-Parrondo game is also investigated.

Chen, Lei; Li, Chuan-Feng; Gong, Ming; Guo, Guang-Can

2010-10-01

52

Transport of Radioactive Material by Alpha Recoil  

SciTech Connect

The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and results of a number of the studies.

Icenhour, A.S.

2005-05-19

53

Transport of Radioactive Material by Alpha Recoil  

Microsoft Academic Search

The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and

A. S. Icenhour

2005-01-01

54

The quantum spin Hall effect  

Microsoft Academic Search

In a two-dimensional system the quantum spin Hall effect (QSHE) state is characterized by an insulating bulk and two counter-propagating helical edge states. These edge channels are protected by time reversal symmetry and spin currents propagate without dissipation. It was shown that HgTe-based quantum well structures are the most suitable candidates for its experimental realization. Here, the experimental requirements are

Hartmut Buhmann

2011-01-01

55

Quantum Spin Hall Effect  

Microsoft Academic Search

Search for topologically non-trivial states of matter has become a prime goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the edge states give rise to the quantum spin

Shoucheng Zhang

2008-01-01

56

What is an Essentially Quantum Mechanical Effect?  

Microsoft Academic Search

Abstract When asking whether consciousness is an “essentially quantum effect”, one must first lay down criteria for considering an effect ,quantum ,mechanical. After a brief survey ,of the ,interpretations of quantum theory, three such sufficient criteria are proposed and examined: wave-particle duality (or collapse), entanglement (“non-locality”), and quantum condensation (involving “identical” particles). A fourth criteria could involve the use of

Osvaldo Pessoa Jr

57

Boost, recoil, and Wigner rotation effects on no-pair analyses of proton elastic scattering  

NASA Astrophysics Data System (ADS)

The relativistic ``no-pair'' potential for elastic proton scattering is shown to reduce to a conventional t? form using optimal factorization of the optical potential and the impulse approximation. The nucleon-nucleon t matrix is needed in the Breit frame and it may be obtained by boosting the NN c.m. frame t matrix. It is shown that the general form of the boost involves a Moller factor, Wigner rotation operators acting on spins, and a Lorentz boost of momentum arguments. The reduction to t? form clarifies how the no-pair analysis differs from conventional Watson or Kerman, McManus, and Thaler (KMT) analyses which usually omit Wigner rotation effects and use a Galilean boost of momentum arguments of the t matrix instead of a Lorentz boost. Recent calculations in momentum space have found rather minor off-shell effects based on the no-pair analysis but other calculations have reported substantial effects based on the KMT formalism. Off-shell effects owing to the momentum dependence of the NN t matrix are found to be considerably smaller than the difference between published no-pair and KMT calculations. It is shown that technical differences, predominantly caused by use of a Galilean boost and inaccurate Coulomb corrections, are capable of explaining the disparate results at least at 200 MeV. Wigner rotations are found to cause negligible differences in proton scattering observables at 200 and 500 MeV. KMT calculations based on a Lorentz boost and accurate Coulomb corrections in momentum space yield rather minor off-shell effects owing to the momentum dependence of the NN t matrix in essential agreement with the no-pair analysis.

Tjon, J. A.; Wallace, S. J.

1991-09-01

58

Recoil by Auger electrons: Theory and application  

SciTech Connect

General equations accounting for the molecular dynamics induced by the recoil of a fast Auger electron are presented. The implications of the degree of localization of the molecular orbitals of diatomic molecules involved in the Auger decay are analyzed. It is shown that the direct and exchange terms of the Auger transition matrix element may give rise to opposite signs and hence to opposite directions of the recoil momenta transferred to the nuclear vibrational motion. Consequently, these terms have a different impact on the recoil-induced nuclear dynamics in the final Auger decay state. The developed theory is applied to study the influence of the recoil on the interatomic Coulombic decay (ICD) following the K-LL Auger decay of the Ne dimer. Our calculations illustrate a significant effect of the recoil of nuclei on the computed wave packets propagating on the potential energy curve populated by the Auger decay. The corresponding final states of the Auger process decay further by ICD. We show that the recoil momentum imparted onto the nuclei modifies the computed ICD spectra considerably.

Demekhin, Ph. V. [Institut fuer Physik, Experimental-Physik IV, Universitaet Kassel, Heinrich-Plett-Str. 40, Kassel D-34132 (Germany); Scheit, S. [Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902 (Japan); Cederbaum, L. S. [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, Heidelberg D-69120 (Germany)

2009-10-28

59

Comparison of quantum confinement effects between quantum wires and dots  

SciTech Connect

Dimensionality is an important factor to govern the electronic structures of semiconductor nanocrystals. The quantum confinement energies in one-dimensional quantum wires and zero-dimensional quantum dots are quite different. Using large-scale first-principles calculations, we systematically study the electronic structures of semiconductor (including group IV, III-V, and II-VI) surface-passivated quantum wires and dots. The band-gap energies of quantum wires and dots have the same scaling with diameter for a given material. The ratio of band-gap-increases between quantum wires and dots is material-dependent, and slightly deviates from 0.586 predicted by effective-mass approximation. Highly linear polarization of photoluminescence in quantum wires is found. The degree of polarization decreases with the increasing temperature and size.

Li, Jingbo; Wang, Lin-Wang

2004-03-30

60

Wave kinetics of relativistic quantum plasmas  

SciTech Connect

A quantum kinetic equation, valid for relativistic unmagnetized plasmas, is derived here. This equation describes the evolution of a quantum quasi-distribution, which is the Wigner function for relativistic spinless charged particles in a plasma, and it is exactly equivalent to a Klein-Gordon equation. Our quantum kinetic equation reduces to the Vlasov equation in the classical limit, where the Wigner function is replaced by a classical distribution function. An approximate form of the quantum kinetic equation is also derived, which includes first order quantum corrections. This is applied to electron plasma waves, for which a new dispersion relation is obtained. It is shown that quantum recoil effects contribute to the electron Landau damping with a third order derivative term. The case of high frequency electromagnetic waves is also considered. Its dispersion relation is shown to be insensitive to quantum recoil effects for equilibrium plasma distributions.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2011-06-15

61

Efimov effect in quantum magnets  

NASA Astrophysics Data System (ADS)

Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly. Because of its universality and peculiarity, the Efimov effect has been the subject of extensive research in chemical, atomic, nuclear and particle physics for decades. Here we employ an anisotropic Heisenberg model to show that collective excitations in quantum magnets (magnons) also exhibit the Efimov effect. We locate anisotropy-induced two-magnon resonances, compute binding energies of three magnons and find that they fit into the universal scaling law. We propose several approaches to experimentally realize the Efimov effect in quantum magnets, where the emergent Efimov states of magnons can be observed with commonly used spectroscopic measurements. Our study thus opens up new avenues for universal few-body physics in condensed matter systems.

Nishida, Yusuke; Kato, Yasuyuki; Batista, Cristian D.

2013-02-01

62

3D Quantum Gravity and Effective Noncommutative Quantum Field Theory  

SciTech Connect

We show that the effective dynamics of matter fields coupled to 3D quantum gravity is described after integration over the gravitational degrees of freedom by a braided noncommutative quantum field theory symmetric under a {kappa} deformation of the Poincare group.

Freidel, Laurent; Livine, Etera R. [Perimeter Institute, 31 Caroline Street, North Waterloo, Ontario N2L 2Y5, Canada, and Laboratoire de Physique, ENS Lyon, CNRS UMR 5672, 46 Allee d'Italie, 69364 Lyon Cedex 07 (France)

2006-06-09

63

Biological Effect of Lead-212 Localized in the Nucleus of Mammalian Cells: Role of Recoil Energy in the Radiotoxicity of Internal Alpha-Particle Emitters1  

PubMed Central

The radiochemical dipyrrolidinedithiocarbamato-212Pb(II) [212Pb(PDC)2] is synthesized and its effects on colony formation in cultured Chinese hamster V79 cells are investigated. The cellular uptake, biological retention, subcellular distribution and cytotoxicity of the radiocompound are determined. The 212Pb is taken up quickly by the cells, reaching saturation levels in 1.25 h. When the cells are washed, the intracellular activity is retained with a biological half-life of 11.6 h. Gamma-ray spectroscopy indicates that the 212Pb daughters (212Bi, 212Po and 208Tl) are in secular equilibrium within the cell. About 72% of the cellular activity localizes in the cell nucleus, of which 35% is bound specifically to nuclear DNA. The mean cellular uptake required to achieve 37% survival is 0.35 mBq of 212Pb per cell, which delivers a dose of 1.0 Gy to the cell nucleus when the recoil energy of 212Bi and 212Po decays is ignored and 1.7 Gy when recoil is included. The corresponding RBE values compared to acute external 137Cs ? rays at 37% survival are 4.0 and 2.3, respectively. The chemical Pb(PDC)2 is not chemotoxic at the concentrations used in this study. Because the ?-particle emitter 212Pb decays to the ?-particle-emitting daughters 212Bi and 212Po, these studies provide information on the biological effects of ?-particle decays that occur in the cell nucleus. Our earlier studies with cells of the same cell line using 210Po (emits 5.3 MeV ? particle) localized predominantly in the cytoplasm resulted in an RBE of 6. These earlier results for 210Po, along with the present results for 212Pb, suggest that the recoil energy associated with the 212Bi and 212Po daughter nuclei plays little or no role in imparting biological damage to critical targets in the cell nucleus.

Azure, Michael T.; Archer, Ronald D.; Sastry, Kandula S. R.; Rao, Dandamudi V.; Howell, Roger W.

2012-01-01

64

Nuclear quantum effects in water  

Microsoft Academic Search

In this work, a path integral Car-Parrinello molecular dynamics ootnotetextCPMD V3.11 Copyright IBM Corp 1990-2006, Copyright MPI fuer Festkoerperforschung Stuttgart 1997-2001. simulation of liquid water is performed. It is found that the inclusion of nuclear quantum effects systematically improves the agreement of first-principles simulations of liquid water with experiment. In addition, the proton momentum distribution is computed utilizing a recently

Joseph A. Morrone; Roberto Car

2008-01-01

65

Fractionalized quantum spin Hall effect  

Microsoft Academic Search

Effects of electron correlations on a two-dimensional quantum spin Hall (QSH) system are studied. We examine possible phases of a generalized Hubbard model on a bilayer honeycomb lattice with a spin-orbit coupling and short-range electron-electron repulsions at half filling, based on the slave-rotor mean-field theory. Besides the conventional QSH phase and a broken-symmetry insulating phase, we find a third phase,

Michael W. Young; Sung-Sik Lee; Catherine Kallin

2008-01-01

66

Exclusive rare B{yields}K* vertical bar{sup +} vertical bar{sup -} decays at low recoil: Controlling the long-distance effects  

SciTech Connect

We present a model-independent description of the exclusive rare decays B{yields}K*e{sup +}e{sup -} in the low recoil region (large lepton invariant mass q{sup 2}{approx}m{sub b}{sup 2}). In this region the long-distance effects from quark loops can be computed with the help of an operator product expansion in 1/Q, with Q={l_brace}m{sub b},{radical}(q{sup 2}){r_brace}. Nonperturbative effects up to and including terms suppressed by {lambda}/Q and m{sub c}{sup 2}/m{sub b}{sup 2} relative to the short-distance amplitude can be included in a model-independent way. Based on these results, we propose an improved method for determining the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V{sub ub} vertical bar from a combination of rare and semileptonic B and D decays near the zero recoil point. The residual theoretical uncertainty from long-distance effects in this vertical bar V{sub ub} vertical bar determination comes from terms in the operator product expansion of order {alpha}{sub s}(Q){lambda}/m{sub b}, {alpha}{sub s}{sup 2}(Q), m{sub c}{sup 4}/m{sub b}{sup 4}, and duality violations, and is estimated to be below 10%.

Grinstein, Benjamin [Department of Physics, UCSD, 9500 Gilman Drive, La Jolla, California 92093 (United States); Pirjol, Dan [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2004-12-01

67

Proposed structure for large quantum interference effects  

Microsoft Academic Search

A semiconductor structure exhibiting large (near 100 percent) quantum interference effects is proposed. The structure can be fabricated by means of conventional etching and regrowth techniques and has potential applications as a quantum interference transistor requiring very low gate voltages (about 1 mV or less). The physical structure of the semiconductor consists of two parallel GaAs quantum wells separated by

S. Datta; M. R. Melloch; S. Bandyopadhyay; M. S. Lundstrom

1986-01-01

68

The quantum spin Hall effect  

NASA Astrophysics Data System (ADS)

In a two-dimensional system the quantum spin Hall effect (QSHE) state is characterized by an insulating bulk and two counter-propagating helical edge states. These edge channels are protected by time reversal symmetry and spin currents propagate without dissipation. It was shown that HgTe-based quantum well structures are the most suitable candidates for its experimental realization. Here, the experimental requirements are discussed which lead to the observation of quantized edge channel transport which is one of the main signatures of the QSHE. Experiments will be presented which demonstrate the stability of the quantized conductance and its nonlocal character. Furthermore, evidence for the spin polarization of the QSHE edge channels is shown in an all-electrical measurement which demonstrates the potential of the QSHE for spin injection and detection applications in spintronics.

Buhmann, Hartmut

2011-05-01

69

Modeling maximum astrophysical gravitational recoil velocities  

SciTech Connect

We measure the recoil velocity as a function of spin for equal-mass, highly spinning black-hole binaries, with spins in the orbital plane, equal in magnitude, and opposite in direction. We confirm that the leading-order effect is linear in the spin and the cosine of angle between the spin direction and the infall direction at the merger. We find higher-order corrections that are proportional to the odd powers in both the spin and cosine of this angle. Taking these corrections into account, we predict that the maximum recoil will be 3680{+-}130 km s{sup -1}.

Lousto, Carlos O.; Zlochower, Yosef [Center for Computational Relativity and Gravitation, School of Mathematical Sciences, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, New York 14623 (United States)

2011-01-15

70

Thermoelectromechanical effects in quantum dots  

NASA Astrophysics Data System (ADS)

Electromechanical effects are important in semiconductor nanostructures as most of the semiconductors are piezoelectric in nature. These nanostructures find applications in electronic and optoelectronic devices where they may face challenges for thermal management. Low dimensional semiconductor nanostructures, such as quantum dots (QD) and nanowires, are the nanostructures where such challenges must be particularly carefully addressed. In this contribution we report a study on thermoelectromechanical effects in QDs. For the first time a coupled model of thermoelectroelasticity has been applied to the analysis of quantum dots and the influence of thermoelectromechanical effects on bandstructures of low dimensional nanostructures has been quantified. Finite element solutions are obtained for different thermal loadings and their effects on the electromechanical properties and bandstructure of QDs are presented. Our model accounts for a practically important range of internal and external thermoelectromechanical loadings. Results are obtained for typical QD systems based on GaN/AlN and CdSe/CdS (as representatives of III-V and II-VI group semiconductors, respectively), with cylindrical and truncated conical geometries. The wetting layer effect on electromechanical quantities is also accounted for. The energy bandstructure calculations for various thermal loadings are performed. Electromechanical fields are observed to be more sensitive to thermal loadings in GaN/AlN QDs as compared to CdSe/CdS QDs. The results are discussed in the context of the effect of thermal loadings on the performance of QD-based nanosystems.

Patil, Sunil R.; Melnik, Roderick V. N.

2009-03-01

71

Gravitational recoil from accretion-aligned black-hole binaries  

NASA Astrophysics Data System (ADS)

We explore the newly discovered “hangup-kick” effect, which greatly amplifies the recoil for configurations with partial spin-/orbital angular momentum alignment, by studying a set of 48 new simulations of equal-mass, spinning black-hole binaries. We propose a phenomenological model for the recoil that takes this new effect into account and then use this model, in conjunction with statistical distributions for the spin magnitude and orientations, based on accretion simulations, to find the probabilities for observing recoils of several thousand kms-1. In addition, we provide initial parameters, eccentricities, radiated linear and angular momentum, precession rates and remnant mass, spin, and recoils for all 48 configurations. Our results indicate that surveys exploring peculiar (redshifted or blueshifted) differential line-of-sight velocities should observe at least one case above 2000kms-1 out of 4000 merged galaxies. On the other hand, the probability that a remnant black hole recoils in any direction at a velocity exceeding the ˜2000kms-1 escape velocity of large elliptical galaxies is 0.03%. Probabilities of recoils exceeding the escape velocity quickly rise to 5% for galaxies with escape velocities of 1000kms-1 and nearly 20% for galaxies with escape velocities of 500kms-1. In addition the direction of these large recoils is strongly peaked toward the angular momentum axis, with very low probabilities of recoils exceeding 350kms-1 for angles larger than 45° with respect to the orbital angular momentum axis.

Lousto, Carlos O.; Zlochower, Yosef; Dotti, Massimo; Volonteri, Marta

2012-04-01

72

Effect of the recoil pressure induced by evaporation on motion of powder particles in the light field during laser cladding  

NASA Astrophysics Data System (ADS)

A model is proposed, which takes into account acceleration of powder particles by a force induced by recoil of material vapors from the irradiated region of the particle surface. Results of a numerical analysis of heat and mass transfer in the case of motion of individual stainless steel powder particles in a gas flow and in a light field of laser radiation under conditions of laser cladding are presented. Acceleration of particles is found to depend on their diameter, carrier gas velocity, powder material properties, laser radiation power, and degree of attenuation of the power density in the laser beam in the direction of its action on the substrate. The calculated results are compared with experimental data on light-propulsion acceleration of individual particles (of aluminum, aluminum oxide, and graphite) under the action of pulsed laser radiation.

Kovaleva, I. O.; Kovalev, O. B.

2012-01-01

73

Tunable quantum spin Hall effect in double quantum wells  

Microsoft Academic Search

The field of topological insulators (TIs) is rapidly growing. Concerning possible applications, the search for materials showing a TI phase that is easily controllable is a key issue. The quantum spin Hall effect, characterized by a single pair of helical edge modes protected by time-reversal symmetry, has so far been demonstrated only in HgTe-based quantum wells (QWs) with an inverted

Paolo Michetti; Jan C. Budich; Patrik Recher

2011-01-01

74

Recoil-reducing shooting rest  

US Patent & Trademark Office Database

A shooting rest supports a firearm and reduces recoil energy of the firearm. The shooting rest has a rear support and a front support for supporting the firearm and a frame connecting the rear support and the front support. The frame supports at least one weight to reduce the amount of recoil energy felt by a shooter.

Cauley; Dennis (Boonville, MO); Morrow; Tim (Jefferson City, MO)

2011-09-06

75

The quantum effects of electromagnetic fluxes  

Microsoft Academic Search

This paper is a review of the problem of the observable action of enclosed electromagnetic fluxes on the quantum-mechanical state of charged particles, known as the Aharonov-Bohm effect. The authors first describe the quantum effects of the fluxes in the quasiclassical approximation, and discuss their relation with basic quantum-mechanical principles. Then they examine the influence of modeling assumptions on the

S. Olariu; I. Iovitzu Popescu

1985-01-01

76

The Effect of Dopant Dose Loss during Annealing on Heavily Doped Surface Layers Obtained by Recoil Implantation of Antimony in Silicon  

NASA Astrophysics Data System (ADS)

The aim of our investigation is focused on studying the effect of dopant dose loss during annealing treatments on heavily doped surface layers, obtained by recoil implantation of antimony in silicon. We are interested particularly by the increase of sheet resistance consequently to the shallow junctions obtained at the surface of substrate and the contribution of the dopant dose loss phenomenon following the high concentration of impurities at the surface. In this work, we report some quantitative data concerning the dopant loss at the surface of silicon implanted and its dependence with annealing treatments. Electrical measurements associated with Rutherford backscattering (RBS) technical analysis showed interesting values of sheet resistance compared with classical ion implantation and despite dopant dose loss phenomenon.

Mesli, M. N.; Benbahi, B.; Bouafia, H.; Belmekki, M.; Abidri, B.; Hiadsi, S.

2013-08-01

77

Directional recoil rates for WIMP direct detection  

SciTech Connect

New techniques for the laboratory direct detection of dark matter weakly interacting massive particles (WIMPs) are sensitive to the recoil direction of the struck nuclei. We compute and compare the directional recoil rates dR/dcos{theta} (where {theta} is the angle measured from a reference direction in the sky) for several WIMP velocity distributions including the standard dark halo and anisotropic models such as Sikivie's late-infall halo model and logarithmic-ellipsoidal models. Since some detectors may be unable to distinguish the beginning of the recoil track from its end (lack of head-tail discrimination), we introduce a folded directional recoil rate dR/d|cos{theta}|, where |cos{theta}| does not distinguish the head from the tail of the track. We compute the CS{sub 2} and CF{sub 4} exposures required to distinguish a signal from an isotropic background noise, and find that dR/d|cos{theta}| is effective for the standard dark halo and some but not all anisotropic models.

Alenazi, Moqbil S.; Gondolo, Paolo [Department of Physics, University of Utah, 115 S 1400 E Rm 201, Salt Lake City, Utah 84112-0830 (United States)

2008-02-15

78

Real measurements and the quantum Zeno effect  

NASA Astrophysics Data System (ADS)

In 1977, Mishra and Sudarshan [J. Math. Phys. 18, 756 (1977)] showed that an unstable particle would never be found decayed while it was continuously observed. They called this effect the quantum Zeno effect (or paradox). Later it was realized that the frequent measurements could also accelerate the decay (quantum anti-Zeno effect). In this paper, we investigate the quantum Zeno effect using the definite model of the measurement. We take into account the finite duration and the finite accuracy of the measurement. A general equation for the jump probability during the measurement is derived. We find that the measurements can cause inhibition (quantum Zeno effect) or acceleration (quantum anti-Zeno effect) of the evolution, depending on the strength of the interaction with the measuring device and on the properties of the system. However, the evolution cannot be fully stopped.

Ruseckas, Julius; Kaulakys, B.

2001-06-01

79

Stimulated Brillouin scattering in semiconductors: Quantum effects  

NASA Astrophysics Data System (ADS)

Present work is an attempt to find the influence of quantum effects on the Stimulated Brillouin Scattering in semiconductor plasmas using quantum hydrodynamic model. Third-order Brillouin susceptibility arising due to induced nonlinear current density in an n-type semiconductor crystal has been determined using coupled mode analysis. Effect of Bohm potential on the Brillouin gain coefficient is studied through the quantum corrections in classical hydrodynamic equations. It is found that the Bohm potential in the electron dynamics enhances the Brillouin gain. Reduction in the threshold pump intensity of the said process has been realized as a consequence of inclusion of quantum correction term.

Vanshpal, Ravi; Dubey, Swati; Ghosh, S.

2013-06-01

80

Quantum Effects in a Rotating Spacetime  

Microsoft Academic Search

The behavior of a arbitrary coupled quantum scalar field is studied in the background of the Gödel spacetime. Closed forms are derived for the effective action and the vacuum expectation value of quadratic field fluctuations by using zeta-function regularization. Based on these results, we argue that causality violation presented in this spacetime cannot be removed by quantum effects.

Eugen Radu; Dumitru Astefanesei; A. Dolgov

2002-01-01

81

Quantum fluctuations in XUV free electron lasers  

Microsoft Academic Search

We have studied the applicability of classical theory to describe the operation of XUV free electron lasers. Both electron recoil effects and photon shot noise effects are considered. It is found that, for reasonable designs, the classical theory is a good approximation to the quantum mechanical theory.

Stephen Benson; John M. J. Madey

1984-01-01

82

INTERACTION OF LASER RADIATION WITH MATTER: Effect of a target size on the recoil momentum upon laser irradiation of absorbing materials  

NASA Astrophysics Data System (ADS)

The dependence of a recoil momentum on the radius of a target irradiated by a single-pulse Nd3+:YAG laser (?=1.064 ?m, ?=20 ns, E<=300 mJ) in the air is studied. The recoil momentum decreases three-fold with increasing the relative target radius from 0.3 to 5 and tends to saturation for r>3. The calculation of the recoil momentum on the basis of the Euler and Navier—Stokes equations gave understated values for r>1, which lowered to negative values. The reasons for the qualitative discrepancy between the experimental and calculated data is discussed.

Chumakou, A. N.; Petrenko, A. M.; Bosak, N. A.

2004-10-01

83

Effective scenario of loop quantum cosmology.  

PubMed

Semiclassical states in isotropic loop quantum cosmology are employed to show that the improved dynamics has the correct classical limit. The effective Hamiltonian for the quantum cosmological model with a massless scalar field is thus obtained, which incorporates also the next to leading order quantum corrections. The possibility that the higher order correction terms may lead to significant departure from the leading order effective scenario is revealed. If the semiclassicality of the model is maintained in the large scale limit, there are great possibilities for a k=0 Friedmann expanding universe to undergo a collapse in the future due to the quantum gravity effect. Thus the quantum bounce and collapse may contribute a cyclic universe in the new scenario. PMID:19257499

Ding, You; Ma, Yongge; Yang, Jinsong

2009-02-05

84

Band mixing effects on quantum well gain  

Microsoft Academic Search

The band structure and the optical matrix elements of a quantum well are studied by the kp perturbation method within the envelope function approximation. The quantum well gain spectra calculated by the kp method and the k-selection rules clearly show the effects of band mixing both in shape and in peak magnitude. The results differ considerably from those based on

Sel Colak; R. Eppenga; Martin F. H. Schuurmans

1987-01-01

85

Graphene and the Quantum Spin Hall Effect  

Microsoft Academic Search

We show that the intrinsic spin orbit interaction in a single plane of graphene converts the ideal two dimensional semi metallic groundstate of graphene into a quantum spin Hall (QSH) state. This novel electronic phase shares many similarities with the quantum Hall effect. It has a bulk excitation gap, but supports the transport of spin and charge in gapless \\

C. L. Kane

2007-01-01

86

Further insight into gravitational recoil  

SciTech Connect

We test the accuracy of our recently proposed empirical formula to model the recoil velocity imparted to the merger remnant of spinning, unequal-mass black-hole binaries. We study three families of black-hole binary configurations, all with mass ratio q=3/8 (to nearly maximize the unequal-mass contribution to the kick) and spins aligned (or counter-aligned) with the orbital angular momentum, two with spin configurations chosen to minimize the spin-induced tangential and radial accelerations of the trajectories, respectively, and a third family where the trajectories are significantly altered by spin-orbit coupling. We find good agreement between the measured and predicted recoil velocities for the first two families, and reasonable agreement for the third. We also reexamine our original generic binary configuration that led to the discovery of extremely large spin-driven recoil velocities and inspired our empirical formula, and find rough agreement between the predicted and measured recoil speeds.

Lousto, Carlos O.; Zlochower, Yosef [Center for Computational Relativity and Gravitation, School of Mathematical Sciences, Rochester Institute of Technology, 78 Lomb Memorial Drive, Rochester, New York 14623 (United States)

2008-02-15

87

Quantum effects in optomechanical systems  

Microsoft Academic Search

The search for experimental demonstrations of the quantum behavior of macroscopic mechanical resonators is a fastly growing field of investigation and recent results suggest that the generation of quantum states of resonators with a mass at the microgram scale is within reach. In this chapter we give an overview of two important topics within this research field: cooling to the

C. Genes; A. Mari; D. Vitali; P. Tombesi

2009-01-01

88

Nuclear quantum effects in water  

NASA Astrophysics Data System (ADS)

In this work, a path integral Car-Parrinello molecular dynamicsootnotetextCPMD V3.11 Copyright IBM Corp 1990-2006, Copyright MPI fuer Festkoerperforschung Stuttgart 1997-2001. simulation of liquid water is performed. It is found that the inclusion of nuclear quantum effects systematically improves the agreement of first-principles simulations of liquid water with experiment. In addition, the proton momentum distribution is computed utilizing a recently developed ``open'' path integral molecular dynamics methodologyootnotetextJ.A. Morrone, V. Srinivasan, D. Sebastiani, R. Car J. Chem. Phys. 126 234504 (2007).. It is shown that these results, which are consistent with our computations of the liquid structure, are in good agreement with neutron Compton scattering dataootnotetextG.F. Reiter, J.C. Li, J. Mayers, T. Abdul-Redah, P. Platzman Braz. J. Phys. 34 142 (2004).. The remaining discrepancies between experiment and the present results are indicative of some degree of over-binding in the hydrogen bond network, likely engendered by the use of semi-local approximations to density functional theory in order to describe the electronic structure.

Morrone, Joseph; Car, Roberto

2008-03-01

89

Recoil Based Fuel Breeding Fuel Structure  

SciTech Connect

Nuclear transmutation reactions are based on the absorption of a smaller particle as neutron, proton, deuteron, alpha, etc. The resulting compound nucleus gets out of its initial lattice mainly by taking the recoil, also with help from its sudden change in chemical properties. The recoil implantation is used in correlation with thin and ultra thin materials mainly for producing radiopharmaceuticals and ultra-thin layer radioactive tracers. In nuclear reactors, the use of nano-particulate pellets could facilitate the recoil implantation for breeding, transmutation and partitioning purposes. Using enriched {sup 238}U or {sup 232}Th leads to {sup 239}Pu and {sup 233}U production while using other actinides as {sup 240}Pu, {sup 241}Am etc. leads to actinide burning. When such a lattice is immersed into a radiation resistant fluid (water, methanol, etc.), the recoiled product is transferred into the flowing fluid and removed from the hot area using a concentrator/purifier, preventing the occurrence of secondary transmutation reactions. The simulation of nuclear collision and energy transfer shows that the impacted nucleus recoils in the interstitial space creating a defect or lives small lattices. The defect diffuses, and if no recombination occurs it stops at the lattices boundaries. The nano-grains are coated in thin layer to get a hydrophilic shell to be washed by the collection liquid the particle is immersed in. The efficiency of collection depends on particle magnitude and nuclear reaction channel parameters. For {sup 239}Pu the direct recoil extraction rate is about 70% for {sup 238}UO{sub 2} grains of 5 nm diameters and is brought up to 95% by diffusion due to {sup 239}Neptunium incompatibility with Uranium dioxide lattice. Particles of 5 nm are hard to produce so a structure using particles of 100 nm have been tested. The particles were obtained by plasma sputtering in oxygen atmosphere. A novel effect as nano-cluster radiation damage robustness and cluster amplified defects rejection will be discussed. The advantage of the method and device is its ability of producing small amount of isotopic materials easy to separate, using the nuclear reactors, with higher yield than the accelerator based methods and requiring less chemistry. (author)

Popa-Simil, Liviu [R and D, LAVM LLC., Los Alamos, NM, 87544 (United States)

2008-07-01

90

Effective constraints for relativistic quantum systems  

NASA Astrophysics Data System (ADS)

Determining the physical Hilbert space is often considered the most difficult but crucial part of completing the quantization of a constrained system. In such a situation it can be more economical to use effective constraint methods, which are extended here to relativistic systems as they arise for instance in quantum cosmology. By sidestepping explicit constructions of states, such tools allow one to arrive much more feasibly at results for physical observables at least in semiclassical regimes. Several questions discussed recently regarding effective equations and state properties in quantum cosmology, including the spreading of states and quantum backreaction, are addressed by the examples studied here.

Bojowald, Martin; Tsobanjan, Artur

2009-12-01

91

Effective constraints for relativistic quantum systems  

SciTech Connect

Determining the physical Hilbert space is often considered the most difficult but crucial part of completing the quantization of a constrained system. In such a situation it can be more economical to use effective constraint methods, which are extended here to relativistic systems as they arise for instance in quantum cosmology. By sidestepping explicit constructions of states, such tools allow one to arrive much more feasibly at results for physical observables at least in semiclassical regimes. Several questions discussed recently regarding effective equations and state properties in quantum cosmology, including the spreading of states and quantum backreaction, are addressed by the examples studied here.

Bojowald, Martin; Tsobanjan, Artur [Institute for Gravitation and the Cosmos, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States)

2009-12-15

92

Noise induced quantum effects in photosynthetic complexes  

NASA Astrophysics Data System (ADS)

Recent progress in coherent multidimensional optical spectroscopy revealed effects of quantum coherence coupled to population leading to population oscillations as evidence of quantum transport. Their description requires reevaluation of the currently used methods and approximations. We identify couplings between coherences and populations as the noise-induced cross-terms in the master equation generated via Agarwal-Fano interference that have been shown earlier to enhance the quantum yield in a photocell. We investigated a broad range of typical parameter regimes, which may be applied to a variety of photosynthetic complexes. We demonstrate that quantum coherence may be induced in photosynthetic complexes under natural conditions of incoherent light from the sun. This demonstrates that a photosynthetic reaction center may be viewed as a biological quantum heat engine that transforms high-energy thermal photon radiation into low entropy electron flux.

Dorfman, Konstantin; Voronine, Dmitri; Mukamel, Shaul; Scully, Marlan

2012-02-01

93

Discrimination of recoil backgrounds in scintillating calorimeters  

NASA Astrophysics Data System (ADS)

The alpha decay of 210Po is a dangerous background to rare event searches. Here, we describe observations related to this alpha decay in the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST). We find that lead nuclei show a scintillation light yield in our CaWO crystals of 0.0142±0.0013 relative to electrons of the same energy. We describe a way to discriminate this source of nuclear recoil background by means of a scintillating foil, and demonstrate its effectiveness. This leads to an observable difference in the pulse shape of the light detector, which can be used to tag these events. Differences in pulse shape of the phonon detector between lead and electron recoils are also extracted, opening the window to future additional background suppression techniques based on pulse shape discrimination in such experiments.

Lang, R. F.; Angloher, G.; Bauer, M.; Bavykina, I.; Bento, A.; Brown, A.; Bucci, C.; Ciemniak, C.; Coppi, C.; Deuter, G.; von Feilitzsch, F.; Hauff, D.; Henry, S.; Huff, P.; Imber, J.; Ingleby, S.; Isaila, C.; Jochum, J.; Kiefer, M.; Kimmerle, M.; Kraus, H.; Lanfranchi, J.-C.; Malek, M.; McGowan, R.; Mikhailik, V. B.; Pantic, E.; Petricca, F.; Pfister, S.; Potzel, W.; Pröbst, F.; Roth, S.; Rottler, K.; Sailer, C.; Schäffner, K.; Schmaler, J.; Scholl, S.; Seidel, W.; Stodolsky, L.; Tolhurst, A. J. B.; Usherov, I.; Westphal, W.

2010-02-01

94

RELATIVISTIC SUPPRESSION OF BLACK HOLE RECOILS  

SciTech Connect

Numerical-relativity simulations indicate that the black hole produced in a binary merger can recoil with a velocity up to v {sub max} {approx_equal} 4000 km s{sup -1} with respect to the center of mass of the initial binary. This challenges the paradigm that most galaxies form through hierarchical mergers, yet retain supermassive black holes (SBHs) at their centers despite having escape velocities much less than v {sub max}. Interaction with a circumbinary disk can align the binary black hole spins with their orbital angular momentum, reducing the recoil velocity of the final black hole produced in the subsequent merger. However, the effectiveness of this alignment depends on highly uncertain accretion flows near the binary black holes. In this paper, we show that if the spin S {sub 1} of the more massive binary black hole is even partially aligned with the orbital angular momentum L, relativistic spin precession on sub-parsec scales can align the binary black hole spins with each other. This alignment significantly reduces the recoil velocity even in the absence of gas. For example, if the angle between S {sub 1} and L at large separations is 10{sup 0} while the second spin S {sub 2} is isotropically distributed, the spin alignment discussed in this paper reduces the median recoil from 864 km s{sup -1} to 273 km s{sup -1} for maximally spinning black holes with a mass ratio of 9/11. This reduction will greatly increase the fraction of galaxies retaining their SBHs.

Kesden, Michael; Sperhake, Ulrich; Berti, Emanuele [California Institute of Technology, MC 350-17, 1216 E. California Blvd., Pasadena, CA 91125 (United States)

2010-06-01

95

Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells  

Microsoft Academic Search

We show that the Quantum Spin Hall Effect, a state of matter with topological properties distinct from conventional insulators, can be realized in HgTe\\/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the electronic state changes from a normal to an ``inverted'' type at a critical thickness dc. We show that this transition is a topological quantum

Shou-Cheng Zhang; B. Andrei Bernevig; Taylor Hughes

2007-01-01

96

Continuous and Pulsed Quantum Zeno Effect  

Microsoft Academic Search

The quantum Zeno effect is the suppression of transitions between quantum states by frequent measurement. Oscillation between two ground hyperfine states of a magnetically trapped ^87Rb Bose-Einstein condensate, externally driven at a transition rate phiR, was substantially suppressed by destructively measuring one of the levels with resonant optical scattering. While an ideal continuous measurement will stop the transition, any real

Erik W. Streed; Jongchul Mun; Micah Boyd; Gretchen K. Campbell; Patrick Medley; Wolfgang Ketterle

2006-01-01

97

Recoiling Supermassive Black Holes in Spin-flip Radio Galaxies  

NASA Astrophysics Data System (ADS)

Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q >~ 0.3 with a minimum possible value q min ~= 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s-1 in the direction within an angle <~ 40° relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to "dust-poor" active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

Liu, F. K.; Wang, Dong; Chen, Xian

2012-02-01

98

Recoil-induced subradiance in an ultracold atomic gas  

SciTech Connect

Subradiance, i.e., the cooperative inhibition of spontaneous emission by destructive interatomic interference, can be realized in a cold atomic sample confined in a ring cavity and lightened by a two-frequency laser. The atoms, scattering the photons of the two laser fields into the cavity mode, recoil and change their momentum. Under proper conditions the atomic initial momentum state and the first two momentum recoil states form a three-level degenerate cascade. A stationary subradiant state is obtained after the scattered photons have left the cavity, leaving the atoms in a coherent superposition of the three collective momentum states. Both a semiclassical description of the process and the quantum subradiant state with its Wigner function are given. Antibunching, quantum correlations, and entanglement between the atomic modes of the subradiant state are demonstrated.

Cola, M. M.; Bigerni, D.; Piovella, N. [Dipartimento di Fisica, Universita degli Studi di Milano and INFN Sezione di Milano, Via Celoria 16, Milano I-20133 (Italy)

2009-05-15

99

The recoiling of liquid droplets upon collision with solid surfaces  

NASA Astrophysics Data System (ADS)

Although the spreading behavior of liquid droplets impacting on solid surfaces has been extensively studied, the mechanism of recoiling which takes place after the droplet reaches its maximum spread diameter has not yet been fully understood. This paper reports the study of the recoiling behavior of different liquid droplets (water, ink, and silicone oil) on different solid surfaces (polycarbonate and silicon oxide). The droplet dynamics are experimentally studied using a high speed video system. Analytical methods using the variational principle, which were originated by Kendall and Rohsenow (MIT Technical Report 85694-100, 1978) and Bechtel et al. [IBM J. Res. Dev. 25, 963 (1981)], are modified to account for wetting and viscous effects. In our model, an empirically determined dissipation factor is used to estimate the viscous friction. It is shown that the model closely predicts the experimental results obtained for the varying dynamic impact conditions and wetting characteristics. This study shows that droplets recoil fast and vigorously when the Ohnesorge number decreases or the Weber number increases. Droplets with a large equilibrium contact angle are also found to recoil faster. Here the Ohnesorge number scales the resisting force to the recoiling motion, and is shown to play the most important role in characterizing the recoiling motion.

Kim, H.-Y.; Chun, J.-H.

2001-03-01

100

Possible observational effects of loop quantum cosmology  

NASA Astrophysics Data System (ADS)

In this paper, we consider realistic model of inflation embedded in the framework of loop quantum cosmology. Phase of inflation is preceded here by the phase of a quantum bounce. We show how parameters of inflation depend on the initial conditions established in the contracting, prebounce phase. Our investigations indicate that phase of the bounce easily sets proper initial conditions for the inflation. Subsequently, we study observational effects that might arise due to the quantum gravitational modifications. We perform preliminary observational constraints for the Barbero-Immirzi parameter ?, critical density ?c, and parameter ?. In the next step, we study effects on power spectrum of perturbations. We calculate spectrum of perturbations from the bounce and from the joined bounce+inflation phase. Based on these studies, we indicate a possible way to relate quantum cosmological models with the astronomical observations. Using the Sachs-Wolfe approximation, we calculate the spectrum of the superhorizontal CMB anisotropies. We show that quantum cosmological effects can, in the natural way, explain suppression of the low CMB multipoles. We show that fine-tuning is not required here, and the model is consistent with observations. We also analyze other possible probes of the quantum cosmologies and discuss perspectives of their implementation.

Mielczarek, Jakub

2010-03-01

101

Quantum spin Hall effect in 2D topological insulators  

Microsoft Academic Search

The original motivation of great interest to topological insulators was the hope to observe the quantum spin Hall effect. Therefore if a material is in the topological insulator state they frequently call it the quantum spin Hall state. However, despite impressive experimental results confirming the existence of the quantum spin Hall state, the quantum spin Hall effect has not yet

E. B. Sonin

2011-01-01

102

Operator quantum Zeno effect: protecting quantum information with noisy two-qubit interactions.  

PubMed

The time evolution of some quantum states can be slowed down or even stopped under frequent measurements. This is the usual quantum Zeno effect. Here, we report an operator quantum Zeno effect, in which the evolution of some physical observables is slowed down through measurements even though the quantum state changes randomly with time. Based on the operator quantum Zeno effect, we show how we can protect quantum information from decoherence with two-qubit measurements, realizable with noisy two-qubit interactions. PMID:23521242

Wang, Shu-Chao; Li, Ying; Wang, Xiang-Bin; Kwek, Leong Chuan

2013-03-08

103

Recoil Separators for Nuclear Astrophysics  

NASA Astrophysics Data System (ADS)

Hydrogen and helium capture reactions are important in many astrophysical environments. Measurements in inverse kinematics using recoil separators have demonstrated a particularly sensitive technique for studying low-yield capture reactions.(M. S. Smith, C. E. Rolfs, and C. A. Barnes, Nucl. Instrum. Meth. Phys. Res. A306) (1991) 233. This approach allows a low background rate to be achieved with a high detection efficiency (about 50%) for the particles of interest using a device with only modest acceptance. Recoil separators using a variety of ion-optic configurations have been installed at numerous accelerator facilities in the past decade and have been used to measure, for example, alpha capture reactions using stable beams(D. Rogalla et al.), Eur. Phys. J. 6 (1999) 471. and proton capture reactions using radioactive ion beams.(S. Bishop et al.), Phys. Rev. Lett. 90 (2003) 162501. Measurements in inverse kinematics are the only viable means for studying reactions on short-lived nuclei that are crucial for understanding stellar explosions, and a recoil separator optimized for the measurement of capture reactions with radioactive ion beams figures prominently into the design of the low energy experimental area at the Rare Isotope Accelerator (RIA). The operational requirements for such a device will be outlined, and recoil separator designs and characteristics will be presented.

Blackmon, J. C.

2004-10-01

104

Rubber band recoil in fluids  

Microsoft Academic Search

The recoil of a stretched rubber band is a familiar phenomenon which does not last for more than a millisecond. When an initially stretched rubber band is released at one end, a front leaving behind it stress-free elastic material propagates towards the clamped end. Its rebound results in a compression front propagating backwards, which triggers an elastic instability referred to

Romain Vermorel

2005-01-01

105

Quantum Effect in Enhanced Nuclear Magnets  

Microsoft Academic Search

Effective nuclear Hamiltonian is derived by using the canonical transformation to study enhanced nuclear magnets. The system described by it is the Heisenberg model reflecting the symmetry of the crystal field states. The exchange interaction and pseudo-quadrupole energy turn anisotropic for non-cubic crystals. In various cases this makes the magnetization incommutable with the Hamiltonian and brings quantum effect. The system

Hiroumi Ishii; Shingo Aoyama

1991-01-01

106

The spin Hall effect in quantum wires  

Microsoft Academic Search

Numerical simulations are used to study the nature of the spin Hall effect in semiconductor quantum wires. The strength of the spin Hall effect is first examined as a function of spin-orbit coupling strength, electron density, and wire width, and is found to exhibit a non-monotonic dependence on these parameters. This behavior is explained by a dispersion relation characterized by

Aron William Cummings

2009-01-01

107

The Compton effect: Transition to quantum mechanics  

NASA Astrophysics Data System (ADS)

The discovery of the Compton effect at the end of 1922 was a decisive event in the transition to the new quantum mechanics of 1925-1926 because it stimulated physicists to examine anew the fundamental problem of the interaction between radiation and matter. I first discuss Albert Einstein's light-quantum hypothesis of 1905 and why physicists greeted it with extreme skepticism, despite Robert A. Millikan's confirmation of Einstein's equation of the photoelectric effect in 1915. I then follow in some detail the experimental and theoretical research program that Arthur Holly Compton pursued between 1916 and 1922 at the University of Minnesota, the Westinghouse Lamp Company, the Cavendish Laboratory, and Washington University that culminated in his discovery of the Compton effect. Surprisingly, Compton was not influenced directly by Einstein's light-quantum hypothesis, in contrast to Peter Debye and H.A. Kramers, who discovered the quantum theory of scattering independently. I close by discussing the most significant response to that discovery, the Bohr-Kramers-Slater theory of 1924, its experimental refutation, and its influence on the emerging new quantum mechanics.

Stuewer, R. H.

2000-11-01

108

The quantum Hall's effect: A quantum electrodynamic phenomenon  

NASA Astrophysics Data System (ADS)

We have applied Maxwell's equations to study the physics of quantum Hall's effect. The electromagnetic properties of this system are obtained. The Hall's voltage, VH = 2??2ns/em, where ns is the electron number density, for a 2-dimensional system, and h = 2?? is the Planck's constant, is found to coincide with the voltage drop across the quantum capacitor. Consideration of the cyclotronic motion of electrons is found to give rise to Hall's resistance. Ohmic resistances in the horizontal and vertical directions have been found to exist before equilibrium state is reached. At a fundamental level, the Hall's effect is found to be equivalent to a resonant LCR circuit with LH = 2? m/e2ns and CH = me2/2??2ns satisfying the resonance condition with resonant frequency equal to the inverse of the scattering (relaxation) time, ?s. The Hall's resistance is found to be . The Hall's resistance may be connected with the impedance that the electron wave experiences when it propagates in the 2-dimensional gas.

I. Arbab, A.

2012-12-01

109

Effective constraints of loop quantum gravity  

SciTech Connect

Within a perturbative cosmological regime of loop quantum gravity corrections to effective constraints are computed. This takes into account all inhomogeneous degrees of freedom relevant for scalar metric modes around flat space and results in explicit expressions for modified coefficients and of higher order terms. It also illustrates the role of different scales determining the relative magnitude of corrections. Our results demonstrate that loop quantum gravity has the correct classical limit, at least in its sector of cosmological perturbations around flat space, in the sense of perturbative effective theory.

Bojowald, Martin; Kagan, Mikhail; Hernandez, Hector H.; Skirzewski, Aureliano [Institute for Gravitational Physics and Geometry, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States); Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, D-14476 Potsdam (Germany)

2007-03-15

110

Effective noise channels for encoded quantum systems  

NASA Astrophysics Data System (ADS)

We investigate effective noise channels for encoded quantum systems with and without active error correction. Noise acting on physical qubits forming a logical qubit is thereby described as a logical noise channel acting on the logical qubits, which leads to a significant decrease of the effective system dimension. This provides us with a powerful tool to study entanglement features of encoded quantum systems. We demonstrate this framework by calculating lower bounds on the lifetime of distillable entanglement and the negativity for encoded multipartite qubit states with different encodings. At the same time, this approach leads to a simple understanding of the functioning of (concatenated) error correction codes.

Kesting, Frederik; Fröwis, Florian; Dür, Wolfgang

2013-10-01

111

Spectral Effects in Quantum Teleportation  

SciTech Connect

We use a multimode description of polarization-encoded qubits to analyze the quantum teleportation protocol. Specifically, we investigate how the teleportation fidelity depends on the spectral correlations inherent to polarization-entangled photons generated by type-II spontaneous parametric down conversion. We find that the maximal obtainable fidelity depends on the spectral entanglement carried by the joint probability amplitude, a result which we quantify for the case of a joint spectrum approximated by a correlated Gaussian function. We contrast these results with a similar analysis of the visibility obtained in a polarization-correlation experiment.

Humble, Travis S [ORNL; Grice, Warren P [ORNL

2007-01-01

112

Spectral effects in quantum teleportation  

SciTech Connect

We use a multimode description of polarization-encoded qubits to analyze the quantum teleportation protocol. Specifically, we investigate how the teleportation fidelity depends on the spectral correlations inherent to polarization-entangled photons generated by type-II spontaneous parametric down conversion. We find that the maximal obtainable fidelity depends on the spectral entanglement carried by the joint probability amplitude, a result which we quantify for the case of a joint spectrum approximated by a correlated Gaussian function. We contrast these results with a similar analysis of the visibility obtained in a polarization-correlation experiment.

Humble, Travis S.; Grice, Warren P. [Center for Engineering Science Advanced Research, Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6016 (United States)

2007-02-15

113

Effect of temperature and recoil-energy spectra on irradiation-induced amorphization in Ca{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2}  

SciTech Connect

Single crystals of Ca{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2} have been irradiated with different ions/energies in an in situ study of the effects of temperature and recoil-energy spectra on irradiation-induced amorphization. The dose for complete amorphization increases with temperature in two stages. The low-temperature stage (below 250 K) has an activation energy of 0.01 {plus_minus} 0.003 eV and is believed to be associated with simultaneous close-pair recombination. The high-temperature stage (above 250 K) has an activation energy of 0.13 {plus_minus} 0.02 eV and may be associated with irradiation-enhanced defect mobility. The critical temperature for amorphization increases from {approximately}360 K for 0.8 MeV Ne{sup +} to {approximately}710 K for 1.5 MeV Kr{sup +}. At 15 K, the amorphization dose is {approximately}0.36 dpa and is independent of recoil-energy spectra. The amorphization dose increases more rapidly with temperature for Ne{sup +} due to the larger fraction of mobile defects produced by the low energy recoils. The temperature dependence is similar for 1.0 MeV Ar{sup +}, 1.5 MeV Kr{sup +}, and 1.5 MeV Xe{sup +}.

Weber, W.J. [Pacific Northwest Lab., Richland, WA (United States); Wang, L.M. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences

1993-09-01

114

Room-Temperature Quantum Hall Effect in Graphene  

Microsoft Academic Search

The quantum Hall effect (QHE), one example of a quantum phenomenon that occurs on a truly macroscopic scale, has attracted intense interest since its discovery in 1980 and has helped elucidate many important aspects of quantum physics. It has also led to the establishment of a new metrological standard, the resistance quantum. Disappointingly, however, the QHE has been observed only

K. S. Novoselov; Philip Kim; Zhigang Jiang; Horst Stormer; Yuanbo Zhang; Sergey Morozov; G. S. Boebinger; P. Kim; A. K. Geim

2007-01-01

115

Quantum-effect and single-electron devices  

Microsoft Academic Search

In this paper, we review the current status of nanoelectronic devices based on quantum effects such as quantization of motion and interference, and those based on single electron charging phenomena in ultrasmall structures. In the first part, we discuss wave-behavior in quantum semiconductor structures, and several device structures based on quantum waveguide behavior such as stub tuners, Y-branches, and quantum

Stephen M. Goodnick; Jonathan Bird

2003-01-01

116

Loop quantum gravity as an effective theory  

NASA Astrophysics Data System (ADS)

As a canonical and generally covariant gauge theory, loop quantum gravity requires special techniques to derive effective actions or equations. If the proper constructions are taken into account, the theory, in spite of considerable ambiguities at the dynamical level, allows for a meaningful phenomenology to be developed, by which it becomes falsifiable. The traditional problems plaguing canonical quantum-gravity theories, such as the anomaly issue or the problem of time, can be overcome or are irrelevant at the effective level, resulting in consistent means of physical evaluations. This contribution presents aspects of canonical equations and related notions of (deformed) space-time structures and discusses implications in loop quantum gravity, such as signature change at high density from holonomy corrections, and falsifiability thanks to inversetriad corrections.

Bojowald, Martin

2012-09-01

117

Median recoil direction as a WIMP directional detection signal  

SciTech Connect

Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP 'smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of {approx}2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

Green, Anne M. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Morgan, Ben [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2010-03-15

118

Unconventional Integer Quantum Hall Effect in Graphene  

Microsoft Academic Search

Monolayer graphite films, or graphene, have quasiparticle excitations that\\u000acan be described by 2+1 dimensional Dirac theory. We demonstrate that this\\u000aproduces an unconventional form of the quantized Hall conductivity $\\\\sigma_{xy}\\u000a= - (2 e^2\\/h)(2n+1)$ with $n=0,1,...$, that notably distinguishes graphene from\\u000aother materials where the integer quantum Hall effect was observed. This\\u000aunconventional quantization is caused by the quantum

V. P. Gusynin; S. G. Sharapov

2005-01-01

119

Intermixing effect on asymmetric quantum well  

NASA Astrophysics Data System (ADS)

Ion implantation enhanced intermixing of quantum well has become an important technology in device fabrication and material modification. We report the intermixing effect in a single asymmetric coupled quantum well (GaAs/AlGaAs) at different ion implantation dose by photoluminescence. More than 80meV of blue shift of the interband transition was observed before rapid thermal annealing process. It indicates that the intermixing has almost finished during the implantation process. A diffusion length of 1nm is obtained by the theoretical analysis.

Chen, Guibin; Li, Zhifeng; Miao, Zhongli; Chen, Xiaoshuang; Lu, Wei

2002-12-01

120

Quantum interference effects in semiconductors: a bibliography  

Microsoft Academic Search

The bibliography has been compiled as an introduction and study guide to this field. The papers listed describe the extensive theoretical and experimental results that have been obtained on quantum interference effects and discuss possible application areas. Works of a fundamental nature concerning phenomena that are basic to all semiconductor behavior have not been included. Articles on the properties and

THOMAS K. GAYLORD; ELIAS N. GLYTSIS; G. N. Henderson; K. P. Martin; D. B. Walker; D. W. Wilson; K. F. Brennan

1991-01-01

121

Quantum size effects in simple colored glass  

Microsoft Academic Search

Finite size effects have been observed at low temperatures for electrons confined to semiconductor microcrystallites embedded in a simple borosilicate glass. Luminescence data reveal large electronic energy shifts relative to bulk energy levels which can be used to calculate the confinement energy of the localized electrons. This system provides an attractive alternative to quantum well heterostructures, permitting direct optical studies

J. Warnock; D. D. Awschalom

1985-01-01

122

Effective equilibrium theory of nonequilibrium quantum transport  

NASA Astrophysics Data System (ADS)

The theoretical description of strongly correlated quantum systems out of equilibrium presents several challenges and a number of open questions persist. Here, we focus on nonlinear electronic transport through an interacting quantum dot maintained at finite bias using a concept introduced by Hershfield [S. Hershfield, Phys. Rev. Lett. 70 2134 (1993)] whereby one can express such nonequilibrium quantum impurity models in terms of the system's Lippmann-Schwinger operators. These scattering operators allow one to reformulate the nonequilibrium problem as an effective equilibrium problem associated with a modified Hamiltonian. In this paper, we provide a pedagogical analysis of the core concepts of the effective equilibrium theory. First, we demonstrate the equivalence between observables computed using the Schwinger-Keldysh framework and the effective equilibrium approach, and relate Green's functions in the two theoretical frameworks. Second, we expound some applications of this method in the context of interacting quantum impurity models. We introduce a novel framework to treat effects of interactions perturbatively while capturing the entire dependence on the bias voltage. For the sake of concreteness, we employ the Anderson model as a prototype for this scheme. Working at the particle-hole symmetric point, we investigate the fate of the Abrikosov-Suhl resonance as a function of bias voltage and magnetic field.

Dutt, Prasenjit; Koch, Jens; Han, Jong; Le Hur, Karyn

2011-12-01

123

Quantum Spin Hall Effect in Graphene  

Microsoft Academic Search

We study the effects of spin orbit interactions on the low energy electronic structure of a single plane of graphene. We find that in an experimentally accessible low temperature regime the symmetry allowed spin orbit potential converts graphene from an ideal two-dimensional semimetallic state to a quantum spin Hall insulator. This novel electronic state of matter is gapped in the

C. L. Kane; E. J. Mele

2005-01-01

124

Noncommutative Description of Quantum Spin Hall Effect  

Microsoft Academic Search

We propose an approach based on a generalized quantum mechanics to deal with the basic features of the intrinsic spin Hall effect. This can be done by considering two decoupled harmonic oscillators on the noncommutative plane and evaluating the spin Hall conductivity. Focusing on the high frequency regime, we obtain a diagonalized Hamiltonian. After getting the corresponding spectrum, we show

Ahmed Jellal; Rachid Houca

2006-01-01

125

Quantum effects in biological electron transfer.  

PubMed

Over recent decades, quantum effects such as coherent electronic energy transfers, electron and hydrogen tunneling have been uncovered in biological processes. In this Perspective, we highlight some of the main conceptual and methodological tools employed in the field to investigate electron tunneling in proteins, with a particular emphasis on the methodologies we are currently developing. In particular, we describe our recent contributions to the development of a mixed quantum-classical framework aimed at describing physical systems lying at the border between the quantum and semi-classical worlds. We present original results obtained by combining our approach with constrained Density Functional Theory calculations. Moving to coarser levels of description, we summarize our latest findings on electron transfer between two redox proteins, thereby showing the stabilization of inter-protein, water-mediated, electron-transfer pathways. PMID:22434318

de la Lande, Aurélien; Babcock, Nathan S; Rezá?, Jan; Lévy, Bernard; Sanders, Barry C; Salahub, Dennis R

2012-03-20

126

Quantum synchronization effects in intrinsic Josephson junctions  

NASA Astrophysics Data System (ADS)

We investigate quantum dynamics of the superconducting phase in intrinsic Josephson junctions of layered high-Tc superconductors motivated by a recent experimental observation for the switching rate enhancement in the low temperature quantum regime. We pay attention to only the capacitive coupling between neighboring junctions and perform large-scale simulations for the Schrödinger equation derived from the Hamiltonian considering the capacitive coupling alone. The simulation focuses on an issue whether the switching of a junction induces those of the other junctions or not. The results reveal that the superconducting phase dynamics show synchronous behavior with increasing the quantum character, e.g., decreasing the junction plane area and effectively the temperature. This is qualitatively consistent with the experimental result.

Machida, M.; Kano, T.; Yamada, S.; Okumura, M.; Imamura, T.; Koyama, T.

2008-04-01

127

Matrix effective theories of the fractional quantum Hall effect  

Microsoft Academic Search

The present understanding of nonperturbative ground states in the fractional quantum Hall effect is based on effective theories of the Jain 'composite fermion' excitations. We review the approach based on matrix variables, i.e. D0 branes, originally introduced by Susskind and Polychronakos. We show that the Maxwell-Chern-Simons matrix gauge theory provides a matrix generalization of the quantum Hall effect, where the

Andrea Cappelli; Ivan D. Rodriguez

2009-01-01

128

Stochasticity effects in quantum radiation reaction.  

PubMed

When an ultrarelativistic electron beam collides with a sufficiently intense laser pulse, radiation-reaction effects can strongly alter the beam dynamics. In the realm of classical electrodynamics, radiation reaction has a beneficial effect on the electron beam as it tends to reduce its energy spread. Here we show that when quantum effects become important, radiation reaction induces the opposite effect; i.e., the energy distribution of the electron beam spreads out after interacting with the laser pulse. We identify the physical origin of this opposite tendency in the intrinsic stochasticity of photon emission, which becomes substantial in the quantum regime. Our numerical simulations indicate that the predicted effects of the stochasticity can be measured already with presently available lasers and electron accelerators. PMID:23952410

Neitz, N; Di Piazza, A

2013-08-02

129

Quantum Mechanical Effects in Gravitational Collapse  

NASA Astrophysics Data System (ADS)

In this thesis we investigate quantum mechanical effects to various aspects of gravitational collapse. These quantum mechanical effects are implemented in the context of the Functional Schrödinger formalism. The Functional Schrödinger formalism allows us to investigate the time-dependent evolutions of the quantum mechanical effects, which is beyond the scope of the usual methods used to investigate the quantum mechanical corrections of gravitational collapse. Utilizing the time-dependent nature of the Functional Schrödinger formalism, we study the quantization of a spherically symmetric domain wall from the view point of an asymptotic and infalling observer, in the absence of radiation. To build a more realistic picture, we then study the time-dependent nature of the induced radiation during the collapse using a semi-classical approach. Using the domain wall and the induced radiation, we then study the time-dependent evolution of the entropy of the domain wall. Finally we make some remarks about the possible inclusion of backreaction into the system.

Greenwood, Eric

2010-01-01

130

Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells  

Microsoft Academic Search

We show that the quantum spin Hall (QSH) effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluride-cadmium telluride semiconductor quantum wells. When the thickness of the quantum well is varied, the electronic state changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We show

Bernevig

2010-01-01

131

Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells  

Microsoft Academic Search

We show that the Quantum Spin Hall Effect, a state of matter with topological\\u000aproperties distinct from conventional insulators, can be realized in HgTe\\/CdTe\\u000asemiconductor quantum wells. By varying the thickness of the quantum well, the\\u000aelectronic state changes from a normal to an \\

B. Andrei Bernevig; Taylor L. Hughes; Shou-Cheng Zhang

2006-01-01

132

Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells  

Microsoft Academic Search

We show that the quantum spin Hall (QSH) effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluride cadmium telluride semiconductor quantum wells. When the thickness of the quantum well is varied, the electronic state changes from a normal to an ``inverted'' type at a critical thickness dc. We show

B. Andrei Bernevig; Taylor L. Hughes; Shou-Cheng Zhang

2006-01-01

133

Quantum Anomalous Hall Effect with Higher Plateaus  

NASA Astrophysics Data System (ADS)

The quantum anomalous Hall (QAH) effect in magnetic topological insulators is driven by the combination of spontaneous magnetic moments and spin-orbit coupling. Its recent experimental discovery raises the question if higher plateaus can also be realized. Here, we present a general theory for a QAH effect with higher Chern numbers and show by first-principles calculations that a thin film magnetic topological insulator of Cr-doped Bi2(Se,Te)3 is a candidate for the C=2 QAH insulator. Remarkably, whereas a higher magnetic field leads to lower Hall conductance plateaus in the integer quantum Hall effect, a higher magnetic moment leads to higher Hall conductance plateaus in the QAH effect.

Wang, Jing; Lian, Biao; Zhang, Haijun; Xu, Yong; Zhang, Shou-Cheng

2013-09-01

134

Quantum anomalous Hall effect with higher plateaus.  

PubMed

The quantum anomalous Hall (QAH) effect in magnetic topological insulators is driven by the combination of spontaneous magnetic moments and spin-orbit coupling. Its recent experimental discovery raises the question if higher plateaus can also be realized. Here, we present a general theory for a QAH effect with higher Chern numbers and show by first-principles calculations that a thin film magnetic topological insulator of Cr-doped Bi_{2}(Se,Te)_{3} is a candidate for the C=2 QAH insulator. Remarkably, whereas a higher magnetic field leads to lower Hall conductance plateaus in the integer quantum Hall effect, a higher magnetic moment leads to higher Hall conductance plateaus in the QAH effect. PMID:24116800

Wang, Jing; Lian, Biao; Zhang, Haijun; Xu, Yong; Zhang, Shou-Cheng

2013-09-24

135

Quantum size effects in simple colored glass  

NASA Astrophysics Data System (ADS)

Finite size effects have been observed at low temperatures for electrons confined to semiconductor microcrystallites embedded in a simple borosilicate glass. Luminescence data reveal large electronic energy shifts relative to bulk energy levels which can be used to calculate the confinement energy of the localized electrons. This system provides an attractive alternative to quantum well heterostructures, permitting direct optical studies of electron-confinement effects over a wide range of temperatures.

Warnock, J.; Awschalom, D. D.

1985-10-01

136

Rayleigh scattering from a trapped bose condensate and the corresponding recoil atom velocity distribution  

SciTech Connect

An approach has been developed that allows the Rayleigh scattering cross section to be calculated with allowance for the quantum character of motion of the center of mass of the trapped scattering particles. The shape of the line of light scattering from a Bose condensate in a parabolic trap has been studied. A shift of the scattering line center is equal to the recoil shift, while the line width depends on the chemical potential of the Bose gas and on the relaxation time of the velocity of the above-condensate recoil particles. A velocity distribution function in the beam of recoil atoms formed in the course of induced Rayleigh scattering is determined. It is shown that, under the typical experimental conditions, the characteristic width {delta}v/v of the recoil velocity distribution in this beam is on the order of 10{sup -3} at a velocity v on the order of several centimeters per second.

Alekseev, V. A. [Russian Academy of Sciences, Lebedev Institute of Physics (Russian Federation)], E-mail: valeks@sci.lebedev.ru

2007-03-15

137

Enhancing the sensitivity of recoil-beta tagging  

NASA Astrophysics Data System (ADS)

Tagging with ?-particles at the focal plane of a recoil separator has been shown to be an effective technique for the study of exotic proton-rich nuclei. This article describes three new pieces of apparatus used to greatly improve the sensitivity of the recoil-beta tagging technique. These include a highly-pixelated double-sided silicon strip detector, a plastic phoswich detector for discriminating high-energy ?-particles, and a charged-particle veto box. The performance of these new detectors is described and characterised, and the resulting improvements are discussed.

Henderson, J.; Ruotsalainen, P.; Jenkins, D. G.; Scholey, C.; Auranen, K.; Davies, P. J.; Grahn, T.; Greenlees, P. T.; Henry, T. W.; Herzá?, A.; Jakobsson, U.; Joshi, P.; Julin, R.; Juutinen, S.; Konki, J.; Leino, M.; Lotay, G.; Nichols, A. J.; Obertelli, A.; Pakarinen, J.; Partanen, J.; Peura, P.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Sorri, J.; Stolze, S.; Uusitalo, J.; Wadsworth, R.

2013-04-01

138

Quantum Spin Hall Effect in Inverted Type II Semiconductors  

Microsoft Academic Search

The quantum spin Hall (QSH) state is a topologically non-trivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells. In this work we predict a similar effect arising in Type-II semiconductor quantum

Chaoxing Liu; Taylor L. Hughes; Xiao-Liang Qi; Kang Wang; Shou-Cheng Zhang

2010-01-01

139

Quantum gravity effects in the Kerr spacetime  

NASA Astrophysics Data System (ADS)

We analyze the impact of the leading quantum gravity effects on the properties of black holes with nonzero angular momentum by performing a suitable renormalization group improvement of the classical Kerr metric within quantum Einstein gravity. In particular, we explore the structure of the horizons, the ergosphere, and the static limit surfaces as well as the phase space available for the Penrose process. The positivity properties of the effective vacuum energy-momentum tensor are also discussed and the “dressing” of the black hole’s mass and angular momentum are investigated by computing the corresponding Komar integrals. The pertinent Smarr formula turns out to retain its classical form. As for their thermodynamical properties, a modified first law of black-hole thermodynamics is found to be satisfied by the improved black holes (to second order in the angular momentum); the corresponding Bekenstein-Hawking temperature is not proportional to the surface gravity.

Reuter, M.; Tuiran, E.

2011-02-01

140

Quantum renormalization of the spin Hall effect.  

PubMed

By quantum Monte Carlo simulation of a realistic multiorbital Anderson impurity model, we study the spin-orbit interaction (SOI) of an Fe impurity in Au host metal. We show, for the first time, that the SOI is strongly renormalized by the quantum spin fluctuation. Based on this mechanism, we can explain why the gigantic spin Hall effect in Au with Fe impurities was observed in recent experiments, while it is not visible in the anomalous Hall effect. In addition, we show that the SOI is strongly renormalized by the Coulomb correlation U. Based on this picture, we can explain past discrepancies in the calculated orbital angular momenta for an Fe impurity in an Au host. PMID:20868117

Gu, Bo; Gan, Jing-Yu; Bulut, Nejat; Ziman, Timothy; Guo, Guang-Yu; Nagaosa, Naoto; Maekawa, Sadamichi

2010-08-18

141

Nuclear quantum effects on molecular magnetic properties  

Microsoft Academic Search

We have proposed the computational method to analyze the nuclear quantum effect on the molecular magnetic properties and applied to some small molecules. Our method is based on the multi-component molecular orbital (MC_MO) procedure with the gauge-including atomic orbital (GIAO) and continuous set of gauge transformation (CSGT) methods. The absolute magnetic shielding constants and the magnetic susceptibility are evaluated by

Yukiumi Kita; Masanori Tachikawa

2009-01-01

142

Quantum Spin Hall Effect in Graphene  

Microsoft Academic Search

We study the effects of spin orbit interactions on the low energy electronic\\u000astructure of a single plane of graphene. We find that in an experimentally\\u000aaccessible low temperature regime the symmetry allowed spin orbit potential\\u000aconverts graphene from an ideal two dimensional semimetallic state to a quantum\\u000aspin Hall insulator. This novel electronic state of matter is gapped in

C. L. Kane; E. J. Mele

2005-01-01

143

Quantum Size Effect on Adatom Surface Diffusion  

Microsoft Academic Search

Using scanning tunneling microscopy, we demonstrate that the nucleation density of Fe islands on the surface of nanoscale Pb films oscillates with the film thickness, providing a direct manifestation of the quantum size effect on surface diffusion. The Fe adatom diffusion barriers were derived to be 204±5 and 187±5meV on a 21 and 26 monolayer (ML) Pb film, respectively, by

Li-Ying Ma; Lin Tang; Ze-Lei Guan; Ke He; Kang An; Xu-Cun Ma; Jin-Feng Jia; Qi-Kun Xue; Y. Han; Steve Huang; Feng Liu

2006-01-01

144

Magnetic field and quantum screening effects on the occurrence time advance in quantum magnetoplasmas  

SciTech Connect

The magnetic field and quantum screening effects on the occurrence scattering time advance for the electron-ion collision are investigated in quantum magnetoplasmas. The result shows that the occurrence scattering time advance decreases with an increase of the magnetic-field strength. It is also found that the occurrence time advance decreases with increasing projectile energy and increases with increasing scattering angle. In addition, the occurrence time advance decreases with an increase of the quantum effect, i.e., Fermi wavelength.

Ki, Dae-Han; Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

2011-07-15

145

Oscillatory quantum screening effects on the positronium (Ps) formation in quantum plasmas  

SciTech Connect

The oscillatory quantum screening effects on the positronium formation by the positron are investigated in quantum plasmas. It is found that the oscillatory screening effects suppress the positronium formation radius as well as the positronium formation cross section. It is also found that the positronium formation radius decreases with increasing quantum wave number. It is found that the peak position of the differential cross section is receded from the projectile with decreasing quantum wave number. In addition, the oscillatory screening effects on the positronium formation cross section are found to be decreased with an increase of the collision energy.

Kim, Chang-Geun [National Center for Standard Reference Data, Korea Research Institute of Standards and Science, Doryong-Dong, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

2011-11-07

146

Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells  

SciTech Connect

We show that the quantum spin Hall (QSH) effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluride-cadmium telluride semiconductor quantum wells. When the thickness of the quantum well is varied, the electronic state changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We show that this transition is a topological quantum phase transition between a conventional insulating phase and a phase exhibiting the QSH effect with a single pair of helical edge states. We also discuss methods for experimental detection of the QSH effect.

Bernevig, A.

2010-03-02

147

Non-linear quantum effects on electron transfer reactions  

Microsoft Academic Search

To study nuclear quantum effects on electron transfer reactions, the non-adiabatic rate constant is expanded in terms of Planck's constant. The expansion to the second order reproduces well the quantum correction in the activation free energy for a quantum Monte Carlo simulation of water. In addition, the spin-boson model is discussed using the expansion. The validity of the rate constant

A. Yoshimori

1997-01-01

148

Approximate inclusion of quantum effects in transition path sampling  

Microsoft Academic Search

We propose a method for incorporating nuclear quantum effects in transition path sampling studies of systems that consist of a few degrees of freedom that must be treated quantum mechanically, while the rest are classical-like. We used the normal mode centroid method to describe the quantum subsystem, which is a method that is not CPU intensive but still reasonably accurate.

Dimitri Antoniou; Steven D. Schwartz

2009-01-01

149

Coherent and collective quantum optical effects in mesoscopic systems  

Microsoft Academic Search

A review of coherent and collective quantum optical effects like superradiance and coherent population trapping in mesoscopic systems is presented. Various new physical realizations of these phenomena are discussed, with a focus on their role for electronic transport and quantum dissipation in coupled nano-scale systems like quantum dots. A number of theoretical tools such as Master equations, polaron transformations, correlation

Tobias Brandes

2005-01-01

150

Quantum and Collective Effects in Information Processing and Communication.  

National Technical Information Service (NTIS)

The original aim of this MURI was to combine an experimental effort to develop tools to manipulate quantum coherence in the solid state. based on metallic wires, quantum point contacts, and the quantum Hall effect, with theoretical efforts aimed at unders...

C. M. Marcus

1999-01-01

151

Quantum interference effects in linear and nonlinear optics  

Microsoft Academic Search

In this thesis, the effects of quantum interference on the linear and nonlinear optical properties of various media are investigated. The first part deals with the implementation of the well- known induced transparency in semiconductor structures. Quantum interference is realized by coherent resonant tunneling between collective intersubband resonances. The first observation of destructive quantum interference of such transitions in the

Holger Schmidt

1999-01-01

152

Interaction effects in coupled quantum dots.  

NASA Astrophysics Data System (ADS)

We study a linear array of coupled semiconductor quantum dots (``artificial molecules'') using an extended Hubbard Hamiltonian approach to account for the effects of intradot and interdot Coulomb interactions, as well as interdot tunneling. We obtain the electron addition spectrum from direct diagonalizations (C. A. Stafford and S. Das Sarma, Phys. Rev. Lett. 72), 3590 (1994) for identical double and triple quantum dots explaining qualitatively the splitting of the conductance peaks observed in recent experiments on these systems. We note that, depending on the number of particles in the system, the interdot Coulomb interaction gives rise to an interesting asymmetry in the conduction spectrum and is also responsible for splitting of the peaks even for weak coupling. We also consider dots of different sizes (``heteronuclear molecules'') and calculate the relevant many-body overlaps that enter in the calculation of the current in the nonlinear regime, to make contact with transport spectroscopy experiments.

Ramirez, F.; Cota, E.; Ulloa, S. E.

1996-03-01

153

Engineering of perturbation effects in onion-like heteronanocrystal quantum dot–quantum well  

NASA Astrophysics Data System (ADS)

In this article, the perturbation influences on optical characterization of quantum dot and quantum dot–quantum well (modified quantum dot) heteronanocrystal is investigated. The original aim of this article is to investigate the quantum dot–quantum well heteronanocrystal advantages and disadvantages, when used as a functionalized particle in biomedical applications. Therefore, all of the critical features of quantum dots are fundamentally studied and their influences on optical properties are simulated. For the first time, the perturbation effects on optical characteristics are observed in the quantum dot–quantum well heteronanocrystals by 8-band K.P theory. The impact of perturbation on optical features such as photoluminescence and shifting of wavelength is studied. The photoluminescence and operation wavelength of quantum dots play a vital role in biomedical applications, where their absorption and emission in biological assays are altered by shifting of wavelength. Furthermore, in biomedical applications, by tuning the emission wavelengths of the quantum dot into far-red and near-infrared ranges, non-invasive in-vivo imaging techniques have been easily developed. In this wavelength window, tissue absorption, scattering and auto-fluorescence intensities have minimum quantities; thus fixing or minimizing of wavelength shifting can be regarded as an important goal which is investigated in this work.

SalmanOgli, A.; Rostami, R.

2013-10-01

154

Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions  

SciTech Connect

Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a starlike geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S{sub 1/2}{yields}5P{sub 3/2}{yields}6S{sub 1/2}{yields}nP in Rb atoms have shown that, compared to the one- and two-photon laser excitation, this approach provides much narrower linewidth and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

Ryabtsev, I. I.; Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A. [A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Prospekt Lavrentyeva 13, 630090 Novosibirsk (Russian Federation)

2011-11-15

155

Recoil corrections in the hydrogen isoelectronic sequence  

SciTech Connect

A version of the Bethe-Salpeter equation appropriate for calculating recoil corrections in highly charged hydrogenlike ions is presented. The nucleus is treated as a scalar particle of charge Z, and the electron treated relativistically. The known recoil corrections of order m{sup 2}/M(Z{alpha}){sup 4} are derived in both this formalism and in NRQED.

Adkins, G. S.; Sapirstein, J. [Department of Physics, Franklin and Marshall College, Lancaster, Pennsylvania 17604 (United States); Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

2006-03-15

156

Photon Recoil Momentum in Dispersive Media  

Microsoft Academic Search

We have measured a systematic shift of the photon recoil momentum due to the index of refraction of a dilute gas of atoms. The recoil frequency was measured with a two pulse light grating interferometer using near resonant laser light. By measuring the resulting frequency as a function of the laser detuning, we found a distinctive dispersive shape for phirec

Gretchen K. Campbell; Aaron E. Leanhardt; Jongchul Mun; Micah Boyd; Erik W. Streed; Wolfgang Ketterle; David E. Pritchard

2005-01-01

157

In-Plane Magnetization-Induced Quantum Anomalous Hall Effect  

NASA Astrophysics Data System (ADS)

The quantum Hall effect can only be induced by an out-of-plane magnetic field for two-dimensional electron gases, and similarly, the quantum anomalous Hall effect has also usually been considered for systems with only out-of-plane magnetization. In the present work, we predict that the quantum anomalous Hall effect can be induced by in-plane magnetization that is not accompanied by any out-of-plane magnetic field. Two realistic two-dimensional systems, Bi2Te3 thin film with magnetic doping and HgMnTe quantum wells with shear strains, are presented and the general condition for the in-plane magnetization-induced quantum anomalous Hall effect is discussed based on the symmetry analysis. Nonetheless, an experimental setup is proposed to confirm this effect, the observation of which will pave the way to search for the quantum anomalous Hall effect in a wider range of materials.

Liu, Xin; Hsu, Hsiu-Chuan; Liu, Chao-Xing

2013-08-01

158

Recoil Experiments Using a Compressed Air Cannon  

NASA Astrophysics Data System (ADS)

Ping-Pong vacuum cannons, potato guns, and compressed air cannons are popular and dramatic demonstrations for lecture and lab.1-3 Students enjoy them for the spectacle, but they can also be used effectively to teach physics. Recently we have used a student-built compressed air cannon as a laboratory activity to investigate impulse, conservation of momentum, and kinematics. It is possible to use the cannon, along with the output from an electronic force plate, as the basis for many other experiments in the laboratory. In this paper, we will discuss the recoil experiment done by our students in the lab and also mention a few other possibilities that this apparatus could be used for.

Taylor, Brett

2006-12-01

159

The compound factor of the 10B(n,alpha)7Li reaction from borocaptate sodium and the relative biological effectiveness of recoil protons for induction of brain damage in boron neutron capture therapy.  

PubMed

To make clinical trials of boron neutron capture therapy safe for patients, it is necessary to know the relative biological effectiveness (RBE) of the radiation components and the compound factor of the boron carrier to be used. Here a method is derived to determine the RBE of recoil protons and the compound factor of compounds from in vivo experiments with different concentrations of boron. The method uses a simultaneous fit of both these parameters to all experimental data. This method is applied to the studies of tolerance of healthy tissue in dogs at the High Flux Reactor in Petten, The Netherlands. The RBE for the recoil protons generated by the neutrons present in the epithermal neutron beam [together with the RBE of the protons from the 14N(n,p)14C reaction] for induction of severe neurological symptoms was found to be 3.93+/-0.43 (95% confidence limits 3.06-4.79), and 2.33+/-0.14 (2.04-2.61) for induction of changes detectable by magnetic resonance imaging. The compound factor for Na2B12H11SH in brain tissue, using severe neurological symptoms as end point, was determined to be 0.37+/-0.06 (95% confidence limits 0.24-0.50). For changes detectable by magnetic resonance imaging, the value was found to be 0.65+/-0.04 (0.58-0.73). PMID:9525503

Gabel, D; Philipp, K H; Wheeler, F J; Huiskamp, R

1998-04-01

160

The Collective Atomic Recoil Laser  

SciTech Connect

An ensemble of periodically ordered atoms coherently scatters the light of an incident laser beam. The scattered and the incident light may interfere and give rise to a light intensity modulation and thus to optical dipole forces which, in turn, emphasize the atomic ordering. This positive feedback is at the origin of the collective atomic recoil laser (CARL). We demonstrate this dynamics using ultracold atoms confined by dipole forces in a unidirectionally pumped far red-detuned high-finesse optical ring cavity. Under the influence of an additional dissipative force exerted by an optical molasses the atoms, starting from an unordered distribution, spontaneously form a density grating moving at constant velocity. Additionally, steady state lasing is observed in the reverse direction if the pump laser power exceeds a certain threshold. We compare the dynamics of the atomic trajectories to the behavior of globally coupled oscillators, which exhibit phase transitions from incoherent to coherent states if the coupling strength exceeds a critical value.

Courteille, Ph.W.; Cube, C. avon; Deh, B.; Kruse, D.; Ludewig, A.; Slama, S.; Zimmermann, C. [Physikalisches Institut, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2005-05-05

161

Rubber band recoil in fluids  

NASA Astrophysics Data System (ADS)

The recoil of a stretched rubber band is a familiar phenomenon which does not last for more than a millisecond. When an initially stretched rubber band is released at one end, a front leaving behind it stress-free elastic material propagates towards the clamped end. Its rebound results in a compression front propagating backwards, which triggers an elastic instability referred to as dynamic buckling. High speed movies reveal that the fluid environment affects both the propagation of axial stress waves along the elastic band and the buckling development itself. Our analysis quantifies the impact of a fluid environment on both the rubber motion and on the buckling wavelength selection, in agreement with the experimental findings.

Vermorel, Romain

2005-11-01

162

Quantum Spin-Hall Effect in a Quantum Wire  

Microsoft Academic Search

In this paper, we show that spatially displaced helical states that transport electrons with opposite spins in opposite directions are formed in a harmonic quantum wire due to the spin-orbit (SO) coupling induced by lateral confinement. These states give rise to a transverse spin imbalance in response to the longitudinal charge current as well as a transverse charge imbalance in

Kiminori Hattori

2010-01-01

163

Effect of noise on quantum teleportation  

SciTech Connect

The effect of noise on quantum teleportation of a spin-(1/2) state using an entangled pair is studied. We calculate the time evolution of the density matrix of the three involved particles due to their coupling with the environmental degrees of freedom. We evaluate the fidelity of transmission as a function of time under a variety of conditions and compare the fidelities obtained for different entangled states. We find that for a generic coupling to environment, use of the singlet state for the entangled pair yields the highest fidelity in noisy conditions.

Kumar, Deepak; Pandey, P. N. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110057, (India); ASRD College, Delhi University, Dhaulakuan, New Delhi, (India)

2003-07-01

164

Quantum Hall effect in narrow Coulomb channels  

NASA Astrophysics Data System (ADS)

Proposed is a scenario for the development of magnetic-field-induced electron states (MESs) in finite charged systems. These states arise due to incomplete screening of external electrostatic fields governing the electron density distribution and therefore exist within a certain static skin layer of width ? along the edge of a two-dimensional (2D) charged system (either classical or degenerate). In the magnetic field normal to the 2D system the electrons in the skin layer are dragged along the MES orbits by the Lorentz force in both classical and degenerate 2D systems. Details of the ? scenario for MESs in the narrow-channel quantum Hall effect problem are reported.

Nazin, S.; Shikin, V.

2011-10-01

165

Non-Markovian effect on the quantum discord  

SciTech Connect

We study the non-Markovian effect on the dynamics of the quantum discord by exactly solving a model consisting of two independent qubits subject to two zero-temperature non-Markovian reservoirs, respectively. Considering the two qubits initially prepared in Bell-like or extended Werner-like states, we show that there is no occurrence of the sudden death, but only instantaneous disappearance of the quantum discord at some time points, in comparison to the entanglement sudden death in the same range of the parameters of interest. This implies that the quantum discord is more useful than the entanglement to describe the quantum correlation involved in quantum systems.

Wang Bo; Xu Zhenyu [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Chen Zeqian; Feng Mang [Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China)

2010-01-15

166

Approximate inclusion of quantum effects in transition path sampling  

PubMed Central

We propose a method for incorporating nuclear quantum effects in transition path sampling studies of systems that consist of a few degrees of freedom that must be treated quantum mechanically, while the rest are classical-like. We used the normal mode centroid method to describe the quantum subsystem, which is a method that is not CPU intensive but still reasonably accurate. We applied this mixed centroid?classical transition path sampling method to a model system that has nontrivial quantum behavior, and showed that it can capture the correct quantum dynamical features.

Antoniou, Dimitri; Schwartz, Steven D.

2009-01-01

167

Quantum spring from the Casimir effect  

NASA Astrophysics Data System (ADS)

The Casimir effect arises not only in the presence of material boundaries but also in space with nontrivial topology. In this Letter, we choose a topology of the flat (D+1)-dimensional spacetime, which causes the helix boundary condition for a Hermitian massless scalar field. Especially, Casimir effect for a massless scalar field on the helix boundary condition is investigated in two and three dimensions by using the zeta function techniques. The Casimir force parallel to the axis of the helix behaves very much like the force on a spring that obeys the Hooke's law when the ratio r of the pitch to the circumference of the helix is small, but in this case, the force comes from a quantum effect, so we would like to call it quantum spring. When r is large, this force behaves like the Newton's law of universal gravitation in the leading order. On the other hand, the force perpendicular to the axis decreases monotonously with the increasing of the ratio r. Both forces are attractive and their behaviors are the same in two and three dimensions.

Feng, Chao-Jun; Li, Xin-Zhou

2010-07-01

168

Final state effects in inclusive quasielastic electron scattering from nuclei: Clues from quantum fluids  

SciTech Connect

The impulse approximation (IA) predicts that momentum distributions, n/sub k/, in many-body systems should be measurable by inclusive quasielastic scattering at high energy and momentum (w,Q) transfer. The observations that the cross section appears to satisfy ''Y-scaling'' (i.e., is a function not of both w and Q of a single variable, Y) is usually taken as a signature of the IA. In nuclear physics, inelastic electron scattering at GeV energies should reveal the high momentum components of the nuclear wave function. In quantum fluids, neutron scattering at hundreds of MeV energies should measure the Bose condensate in superfluid /sup 4/He and the Fermi surface discontinuity and depletion of the Fermi sea in /sup 3/He. In molecular and condensed matter systems, X-ray Compton scattering at keV energies reveals electronic n/sub k/. Such experiments test many-body wave functions calculated by methods such as Green Function and Path Integral Monte Carlo, and Fermi Hypernetted Chain. However, an outstanding issue has been the corrections to the IA due to the scattering of the recoiling particle from neighboring particles, which are termed ''final state effects'' (FSE). The FSE should be especially important in nuclei and quantum fluids where the potentials have steeply repulsive cores. While there have been a variety of theories proposed for FSE, until now none has been adequately tested by experiment. Recently, the ''hard core perturbation theory'' (HCPT) for FSE in quantum fluids by Silver has been successfully compared to new neutron scattering measurements on /sup 4/He by P. E. Sokol and colleagues. In this paper, we shall discuss the lessons of this success for the extraction of n/sub k/ in nuclei by inclusive ''quasielastic electron-nucleus scattering'' (QENS). 19 refs., 12 figs.

Silver, R.N.; Clark, J.W.

1988-01-01

169

Quantum Hall effect in (cadmium flouride)-based nanostructures  

SciTech Connect

Shubnikov-de Haas oscillations and a ladder of quantum steps in the Hall resistance were observed in a p-CdF{sub 2} quantum well confined by {delta}-like barriers for CdB{sub x}F{sub 2-x} on the surface of n-CdF{sub 2}. Due to the small effective mass of two-dimensional holes, observation of the quantum Hall effect became possible at room temperature.

Bagraev, N. T., E-mail: Bagraev@mail.ioffe.ru; Gimbitskaya, O. N.; Klyachkin, L. E.; Malyarenko, A. M.; Shelykh, I. A. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Ryskin, A. I.; Shcheulin, A. S. [St. Petersburg State University of Information Technologies, Mechanics, and Optics (Russian Federation)

2009-01-15

170

Quantum Spin Hall Effect in Inverted Type-II Semiconductors  

Microsoft Academic Search

The quantum spin Hall (QSH) state is a topologically nontrivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells and in this Letter we predict a similar effect arising in Type-II semiconductor

Chaoxing Liu; Taylor L. Hughes; Xiao-Liang Qi; Kang Wang; Shou-Cheng Zhang

2008-01-01

171

Fractional quantum Hall effect in optical lattices  

SciTech Connect

We analyze a recently proposed method to create fractional quantum Hall (FQH) states of atoms confined in optical lattices [A. Soerensen et al., Phys. Rev. Lett. 94, 086803 (2005)]. Extending the previous work, we investigate conditions under which the FQH effect can be achieved for bosons on a lattice with an effective magnetic field and finite on-site interaction. Furthermore, we characterize the ground state in such systems by calculating Chern numbers which can provide direct signatures of topological order and explore regimes where the characterization in terms of wave-function overlap fails. We also discuss various issues which are relevant for the practical realization of such FQH states with ultracold atoms in an optical lattice, including the presence of a long-range dipole interaction which can improve the energy gap and stabilize the ground state. We also investigate a detection technique based on Bragg spectroscopy to probe these systems in an experimental realization.

Hafezi, M.; Demler, E.; Lukin, M. D. [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States); Soerensen, A. S. [QUANTOP, Danish National Research Foundation Centre of Quantum Optics, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen O (Denmark)

2007-08-15

172

Quantum Spin Hall Effect in a Triple-Well Quantum Dot System  

Microsoft Academic Search

A scheme for generating a quantum spin Hall effect for an ensemble of electrons trapped in a triple-well quantum dot system\\u000a is proposed. Light-induced effective spin-dependent gauge potential and gauge filed are both given in a real Gaussian pulses\\u000a space. In our scheme, the spin Hall effect can be demonstrated by electronic population without spin-orbit coupled interaction\\u000a in the absence

Ping Dong; Zhuo-Liang Cao

2011-01-01

173

Anomalous nuclear quantum effects in ice  

NASA Astrophysics Data System (ADS)

The lattice parameters of light (H2O) and heavy (D2O) Ih ice at 10 K differ by 0.09%.[1] The larger lattice constant is that of the heavier isotope. This isotope shift with anomalous sign is linked to the zero point point energy of phonons in ice. To determine the origin of this anomaly, we use ab initio density functional theory to compute the free energy of ice within the quasiharmonic approximation. As expected, the frozen lattice constant at T = 0 K is smaller than the quantum lattice constant, independent of the isotopic substitution. We find that, the heavy isotope D gives more zero point expansion than H, whereas the heavy isotope ^18O gives normal zero point expansion, i.e smaller than ^16O. Relative to the the classical result, the net effect of quantum nuclei (H and O) on volume has the conventional (positive) sign at T = 0 but it becomes negative above 70 K, indicating that it may be also relevant for liquid water. These results are not reproduced by state of art polarizable empirical potentials.[2] [1] B. K. R"ottger et. al., Acta Cryst. B 50, 644-648 (1994). [2] C. P. Herrero and R. Ram'irez, J. Chem. Phys. 134, 094510 (2011).

Pamuk, Betül; Soler, Jose M.; Allen, Philip B.; Fernández-Serra, Marivi

2012-02-01

174

Nuclear Quantum Effects and Enzyme Dynamics in Dihydrofolate Reductase Catalysis  

Microsoft Academic Search

Mixed quantum\\/classical molecular dynamics simulations of the hydride transfer reaction catalyzed by dihydrofolate reductase are presented. The nuclear quantum effects such as zero point energy and hydrogen tunneling, as well as the motion of the entire solvated enzyme, are included during the generation of the free energy profiles and the real-time dynamical trajectories. The calculated deuterium kinetic isotope effect agrees

Pratul K. Agarwal; Salomon R. Billeter; Sharon Hammes-Schiffer

2002-01-01

175

Quantum effects and the excess proton in water  

Microsoft Academic Search

The influence of nuclear quantum effects on the excess proton in water is examined through quantum dynamical computer simulations. Results are presented for the isotope effects on both the proton exchange process and the infrared absorption spectrum. A critical assessment of the accuracy of density-functional-theory-based molecular dynamics simulation methods for addressing this problem is also given.

Marc Pavese; Sanjay Chawla; Dongsheng Lu; John Lobaugh; Gregory A. Voth

1997-01-01

176

Spin polarized quantum pump effect in zigzag graphene nanoribbons  

Microsoft Academic Search

The spin polarized adiabatic quantum pump effect in zigzag graphene nanoribbons has been numerically analyzed. Since the ground state of such a ribbon is antiferromagnetic (the opposite spin electrons are located on the opposite edges of the ribbon), the spin currents can be generated in this system with the help of the quantum pump effect when symmetry between the opposite

E. S. Grichuk; E. A. Manykin

2011-01-01

177

Thermal effect in quantum-dot cellular automata  

Microsoft Academic Search

We present a theoretical study of thermal effect in quantum-dot cellular automata (QCA). A quantum statistical model has been introduced to obtain the thermal average of polarization of a QCA cell. We have studied the thermal effect on an inverter, a majority gate and planar arrays of different sizes. The theoretical analysis has been approximated for a two-state model where

I. Sturzu; J. L. Kanuchok; M. Khatun; P. D. Tougaw

2005-01-01

178

Destruction of the fractional quantum Hall effect by disorder  

SciTech Connect

It is suggested that Hall steps in the fractional quantum Hall effect are physically similar to those in the ordinary quantum Hall effect. This proposition leads to a simple scaling diagram containing a new type of fixed point, which is identified with the destruction of the fractional states by disorder. 15 refs., 3 figs.

Laughlin, R.B.

1985-07-01

179

Exercising of Recoil Mechanisms and Equilibrators.  

National Technical Information Service (NTIS)

This bulletin provides instructions and guidance on methods of exercising all types of recoil mechanisms and equilibrators, mounted on weapons or unmounted, on weapons not fired for prolonged periods, in the field, in storage, or at a manufacturer or over...

1996-01-01

180

Ion scattering and recoiling from liquid surfaces  

Microsoft Academic Search

We have shown that ion beams can be used to probe the surface composition and molecular orientation of liquid surfaces. Time-of-flight analysis of the kinetic energy of scattered inert gas ions and recoil atoms ejected from the surface reveals the identity of atoms in the topmost atomic surface layer of the liquid. In this report we describe the first scattering\\/recoil

Michael Tassotto; Thomas J. Gannon; Philip R. Watson

1997-01-01

181

On quantum effects in a theory of biological evolution.  

PubMed

We construct a descriptive toy model that considers quantum effects on biological evolution starting from Chaitin's classical framework. There are smart evolution scenarios in which a quantum world is as favorable as classical worlds for evolution to take place. However, in more natural scenarios, the rate of evolution depends on the degree of entanglement present in quantum organisms with respect to classical organisms. If the entanglement is maximal, classical evolution turns out to be more favorable. PMID:22413059

Martin-Delgado, M A

2012-03-12

182

Quantum random walk: Effect of quenching  

NASA Astrophysics Data System (ADS)

We study the effect of quenching on a discrete quantum random walk by removing a detector placed at a position xD abruptly at time tR from its path. The results show that this may lead to an enhancement of the occurrence probability at xD provided the time of removal tR

Goswami, Sanchari; Sen, Parongama

2012-08-01

183

The effective field theory treatment of quantum gravity  

SciTech Connect

This is a pedagogical introduction to the treatment of quantum general relativity as an effective field theory. It starts with an overview of the methods of effective field theory and includes an explicit example. Quantum general relativity matches this framework and I discuss gravitational examples as well as the limits of the effective field theory. I also discuss the insights from effective field theory on the gravitational effects on running couplings in the perturbative regime.

Donoghue, John F. [Department of Physics, University of Massachusetts, Amherst, MA 01003 (United States)

2012-09-24

184

Parametric instabilities in quantum plasmas with electron exchange—correlation effects  

NASA Astrophysics Data System (ADS)

Parametric instabilities induced by the nonlinear interaction between high frequency quantum Langmuir waves and low frequency quantum ion-acoustic waves in quantum plasmas with the electron exchange—correlation effects are presented. By using the quantum hydrodynamic equations with the electron exchange—correlation correction, we obtain an effective quantum Zaharov model, which is then used to derive the modified dispersion relations and the growth rates of the decay and four-wave instabilities. The influences of the electron exchange—correlation effects and the quantum effects on the existence of quantum Langmuir waves and the parametric instabilities are discussed in detail. It is shown that the electron exchange—correlation effects and quantum effects are strongly coupled. The quantum Langmuir wave can propagate in quantum plasmas only when the electron exchange—correlation effects and the quantum effects satisfy a certain condition. The electron exchange—correlation effects tend to enhance the parametric instabilities, while quantum effects suppress the instabilities.

He, Cai-Xia; Xue, Ju-Kui

2013-02-01

185

Quantum teleportation of nonclassical wave packets: An effective multimode theory  

SciTech Connect

We develop a simple and efficient theoretical model to understand the quantum properties of broadband continuous variable quantum teleportation. We show that, if stated properly, the problem of multimode teleportation can be simplified to teleportation of a single effective mode that describes the input state temporal characteristic. Using that model, we show how the finite bandwidth of squeezing and external noise in the classical channel affect the output teleported quantum field. We choose an approach that is especially relevant for the case of non-Gaussian nonclassical quantum states and we finally back-test our model with recent experimental results.

Benichi, Hugo; Takeda, Shuntaro; Lee, Noriyuki; Furusawa, Akira [Department of Applied Physics, University of Tokyo, Tokyo (Japan)

2011-07-15

186

Quantum corrections to conductivity under conditions of the integer quantum Hall effect  

SciTech Connect

Quantum corrections to the conductivity of a two-dimensional electron gas under conditions of the integer quantum Hall effect have been studied. It is shown that violation of the one-parameter scaling under conditions of quantizing magnetic fields, {omega}{sub c}{tau} Much-Greater-Than 1, occurs at a level of the perturbation theory. The results of diagrammatic calculation of the quantum correction are in agreement with the numerical dependences of the peaks in the longitudinal conductivity on the effective size of the sample, in contrast to earlier calculations based on the unitary nonlinear {sigma}-model. Due to this, consideration of Landau quantization represents a criterion for correct description of the quantum Hall effect.

Greshnov, A. A., E-mail: a_greshnov@hotmail.com [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2012-06-15

187

Quenching and channeling of nuclear recoils in NaI(Tl): Implications for dark-matter searches  

NASA Astrophysics Data System (ADS)

A new experimental evaluation of the quenching factor for nuclear recoils in NaI[Tl] is described. Systematics affecting previous measurements are addressed by careful characterization of the emission spectrum of the neutron source, use of a small scintillator coupled to an ultra-bialkali high-quantum-efficiency photomultiplier, and evaluation of nonlinearities in the electron recoil response via Compton scattering. A trend towards a rapidly diminishing quenching factor with decreasing sodium recoil energy is revealed. Additionally, no evidence for crystal lattice channeling of low-energy recoiling ions is found in a scintillator of known crystallographic orientation. A discussion on how these findings affect dark matter searches employing NaI[Tl] (e.g., DAMA/LIBRA) is offered.

Collar, J. I.

2013-09-01

188

Oscillatory quantum screening effects on the transition bremsstrahlung radiation in quantum plasmas  

SciTech Connect

The oscillatory screening effects on the transition bremsstrahlung radiation due to the polarization interaction between the electron and shielding cloud are investigated in dense quantum plasmas. The impact-parameter analysis with the modified Debye-Hueckel potential is applied to obtain the bremsstrahlung radiation cross section as a function of the quantum wave number, impact parameter, photon energy, and projectile energy. The results show that the oscillatory quantum screening effect strongly suppresses the transition bremsstrahlung radiation spectrum in dense quantum plasmas. It is also found that the oscillatory quantum screening effect is more significant near the maximum peak of the bremsstrahlung radiation cross section. In addition, the maximum peak of the bremsstrahlung radiation cross section is getting close to the center of the shielding cloud as increasing quantum wave number. It is interesting to note that the range of the bremsstrahlung photon energy would be broadened with an increase of the oscillatory screening effect. It is also found that the oscillatory screening effects on the transition bremsstrahlung spectrum decreases with increasing projectile energy.

Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791, South Korea and Department of Electrical and Computer Engineering, MC 0407, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0407 (United States)

2011-06-15

189

Quantum Logic Operations Using Single Photons and the Zeno Effect  

Microsoft Academic Search

We show that the quantum Zeno effect can be used to implement several quantum logic gates for photonic qubits, including a gate that is similar to the square-root of SWAP operation. The operation of these devices depends on the fact that photons can behave as if they were non-interacting fermions instead of bosons in the presence of a strong Zeno

J. D. Franson; B. C. Jacobs; T. B. Pittman

2004-01-01

190

Nuclear Quantum Vibrational Effects in Shock Hugoniot Temperatures  

Microsoft Academic Search

We present a straightforward method for the inclusion of quantum nuclear vibrational effects in molecular dynamics calculations of shock Hugoniot temperatures. Using a Griineisen equation of state and a quasi-harmonic approximation to the vibrational energies, we derive a simple, post-processing method for calculation of the quantum corrected Hugoniot temperatures. We have used our technique on ab initio simulations of shock

Nir Goldman; Evan J. Reed; Laurence E. Fried

2009-01-01

191

Quantum effects in solid hydrogen at ultra-high pressure  

Microsoft Academic Search

We present ab initio path integral simulations of solid hydrogen in the pressure range from about 150 to 700 GPa at 50 K. Comparisons of the fully quantum-mechanical simulations with analogous ones with classical protons allow us to assess the nuclear quantum effects on the structure. Taking into account the zero-point motion in the framework of the (quasi-) harmonic approximation

S. Biermann; D. Hohl; D. Marx

1998-01-01

192

NUCLEAR QUANTUM VIBRATIONAL EFFECTS IN SHOCK HUGONIOT TEMPERATURES  

Microsoft Academic Search

We present a straightforward method for the inclusion of quantum nuclear vibrational effects in molecular dynamics calculations of shock Hugoniot temperatures. Using a Griineisen equation of state and a quasi-harmonic approximation to the vibrational energies, we derive a simple, post-processing method for calculation of the quantum corrected Hugoniot temperatures. We have used our technique on ab initio simulations of shock

Nir Goldman; Evan J. Reed; Laurence E. Fried

2009-01-01

193

Kinetic modelling of quantum effects in laser-beam interaction  

Microsoft Academic Search

We present the results of kinetic modelling of quantum effects in laser-beam interaction. In the developed numerical model, electron-positron pair production by hard photons, hard photon emission and the electromagnetic fields generated by the created charged particles are taken into account. Interaction of a relativistic electron beam with a strong laser pulse is analyzed. It is shown that the quantum

E. N. Nerush; I. Yu. Kostyukov

2011-01-01

194

Kinetic modelling of quantum effects in laser–beam interaction  

Microsoft Academic Search

We present the results of kinetic modelling of quantum effects in laser–beam interaction. In the developed numerical model, electron–positron pair production by hard photons, hard photon emission and the electromagnetic fields generated by the created charged particles are taken into account. Interaction of a relativistic electron beam with a strong laser pulse is analyzed. It is shown that the quantum

Evgeny Nerush; Igor Kostyukov

2011-01-01

195

Effects of Confining Geometry on Ballistic Transport in Quantum Wires  

Microsoft Academic Search

The effects of confining geometry are investigated on ballistic transport in quasi-one-dimensional quantum wires. The coupled channel type method is used in order to calculate the conductance of the quantum wires as a function of the Fermi energy. It is shown that oscillations existing in the conductance of the wire with a confining potential of `step wise' type geometry disappear

Hideaki Kasai; Kunihiro Mitsutake; Ayao Okiji

1991-01-01

196

A recoil resilient lumen support, design, fabrication and mechanical evaluation  

NASA Astrophysics Data System (ADS)

Stents are artificial implants that provide scaffolding to a cavity inside the body. This paper presents a new luminal device for reducing the mechanical failure of stents due to recoil, which is one of the most important issues in stenting. This device, which we call a recoil-resilient ring (RRR), is utilized standalone or potentially integrated with existing stents to address the problem of recoil. The proposed structure aims to minimize the need for high-pressure overexpansion that can induce intra-luminal trauma and excess growth of vascular tissue causing later restenosis. The RRR is an overlapped open ring with asymmetrical sawtooth structures that are intermeshed. These teeth can slide on top of each other, while the ring is radially expanded, but interlock step-by-step so as to keep the final expanded state against compressional forces that normally cause recoil. The RRRs thus deliver balloon expandability and, when integrated with a stent, bring both radial rigidity and longitudinal flexibility to the stent. The design of the RRR is investigated through finite element analysis (FEA), and then the devices are fabricated using micro-electro-discharge machining of 200-µm-thick Nitinol sheet. The standalone RRR is balloon expandable in vitro by 5-7 Atm in pressure, which is well within the recommended in vivo pressure ranges for stenting procedures. FEA compression tests indicate 13× less reduction of the cross-sectional area of the RRR compared with a typical stainless steel stent. These results also show perfect elastic recovery of the RRR after removal of the pressure compared to the remaining plastic deformations of the stainless steel stent. On the other hand, experimental loading tests show that the fabricated RRRs have 2.8× radial stiffness compared to a two-column section of a commercial stent while exhibiting comparable elastic recovery. Furthermore, testing of in vitro expansion in a mock artery tube shows around 2.9% recoil, approximately 5-11× smaller than the recoil reported for commercial stents. These experimental results demonstrate the effectiveness of the device design for the targeted luminal support and stenting applications.

Mehdizadeh, Arash; Ali, Mohamed Sultan Mohamed; Takahata, Kenichi; Al-Sarawi, Said; Abbott, Derek

2013-06-01

197

On recoil-energy-dependent defect accumulation in pure copper Part II. Theoretical treatment  

Microsoft Academic Search

Over the years, an enormous amount of experimental results have been reported on damage accumulation (e.g. void swelling) in metals and alloys irradiated under vastly different recoil energy conditions. Unfortunately, however, very little is known either experimentally or theoretically about the effect of recoil energy on damage accumulation. Recently, dedicated irradiation experiments using 2.5 MeV electrons, 3.0 MeV protons and

S. I. Golubov; B. N. Singh; H. Trinkaus

2001-01-01

198

Quantum Zeno effect rationalizes the phonon bottleneck in semiconductor quantum dots.  

PubMed

Quantum confinement can dramatically slow down electron-phonon relaxation in nanoclusters. Known as the phonon bottleneck, the effect remains elusive. Using a state-of-the-art time-domain ab initio approach, we model the observed bottleneck in CdSe quantum dots and show that it occurs under quantum Zeno conditions. Decoherence in the electronic subsystem, induced by elastic electron-phonon scattering, should be significantly faster than inelastic scattering. Achieved with multiphonon relaxation, the phonon bottleneck is broken by Auger processes and structural defects, rationalizing experimental difficulties. PMID:23683182

Kilina, Svetlana V; Neukirch, Amanda J; Habenicht, Bradley F; Kilin, Dmitri S; Prezhdo, Oleg V

2013-05-02

199

Chapter 2 Quantum Effects in Optomechanical Systems  

Microsoft Academic Search

The search for experimental demonstration of the quantum behavior of macroscopic mechanical resonators is a fast growing field of investigation and recent results suggest that the generation of quantum states of resonators with a mass at the microgram scale is within reach. In this chapter we give an overview of two important topics within this research field: cooling to the

C. Genes; A. Mari; D. Vitali; P. Tombesi

2009-01-01

200

Quantum effects in ion implanted devices  

Microsoft Academic Search

Fabrication of nanoscale devices that exploit the rules of quantum mechanics to process information presents formidable technical challenges because of the need to control quantum states at the level of individual atoms, electrons or photons. We have used ion implantation to fabricate devices on the scale of 10nm that have allowed the development and test of nanocircuitry for the control

D. N. Jamieson; V. Chan; F. E. Hudson; S. E. Andresen; C. Yang; T. Hopf; S. M. Hearne; C. I. Pakes; S. Prawer; E. Gauja; A. S. Dzurak; R. G. Clark

2006-01-01

201

Recoil-ion and electron momentum spectroscopy: reaction-microscopes  

NASA Astrophysics Data System (ADS)

Recoil-ion and electron momentum spectroscopy is a rapidly developing technique that allows one to measure the vector momenta of several ions and electrons resulting from atomic or molecular fragmentation. In a unique combination, large solid angles close to 4pi and superior momentum resolutions around a few per cent of an atomic unit (a.u.) are typically reached in state-of-the art machines, so-called reaction-microscopes. Evolving from recoil-ion and cold target recoil-ion momentum spectroscopy (COLTRIMS), reaction-microscopes—the `bubble chambers of atomic physics'—mark the decisive step forward to investigate many-particle quantum-dynamics occurring when atomic and molecular systems or even surfaces and solids are exposed to time-dependent external electromagnetic fields. This paper concentrates on just these latest technical developments and on at least four new classes of fragmentation experiments that have emerged within about the last five years. First, multi-dimensional images in momentum space brought unprecedented information on the dynamics of single-photon induced fragmentation of fixed-in-space molecules and on their structure. Second, a break-through in the investigation of high-intensity short-pulse laser induced fragmentation of atoms and molecules has been achieved by using reaction-microscopes. Third, for electron and ion-impact, the investigation of two-electron reactions has matured to a state such that the first fully differential cross sections (FDCSs) are reported. Fourth, comprehensive sets of FDCSs for single ionization of atoms by ion-impact, the most basic atomic fragmentation reaction, brought new insight, a couple of surprises and unexpected challenges to theory at keV to GeV collision energies. In addition, a brief summary on the kinematics is provided at the beginning. Finally, the rich future potential of the method is briefly envisaged.

Ullrich, J.; Moshammer, R.; Dorn, A.; Dörner, R.; Schmidt, L. Ph H.; Schmidt-Böcking, H.

2003-09-01

202

Quantum Spin Hall Effect in Inverted Type II Semiconductors  

SciTech Connect

The quantum spin Hall (QSH) state is a topologically non-trivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells. In this work we predict a similar effect arising in Type-II semiconductor quantum wells made from InAs/GaSb/AlSb. Because of a rare band alignment the quantum well band structure exhibits an 'inverted' phase similar to CdTe/HgTe quantum wells, which is a QSH state when the Fermi level lies inside the gap. Due to the asymmetric structure of this quantum well, the effects of inversion symmetry breaking and inter-layer charge transfer are essential. By standard self-consistent calculations, we show that the QSH state persists when these corrections are included, and a quantum phase transition between the normal insulator and the QSH phase can be electrically tuned by the gate voltage.

Liu, Chaoxing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Hughes, Taylor L.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Wang, Kang; /UCLA; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-03-19

203

Anatomy of the binary black hole recoil: A multipolar analysis  

SciTech Connect

We present a multipolar analysis of the gravitational recoil computed in recent numerical simulations of binary black hole coalescence, for both unequal masses and nonzero, nonprecessing spins. We show that multipole moments up to and including l=4 are sufficient to accurately reproduce the final recoil velocity (within {approx_equal}2%) and that only a few dominant modes contribute significantly to it (within {approx_equal}5%). We describe how the relative amplitudes, and more importantly, the relative phases, of these few modes control the way in which the recoil builds up throughout the inspiral, merger, and ringdown phases. We also find that the numerical results can be reproduced by an 'effective Newtonian' formula for the multipole moments obtained by replacing the radial separation in the Newtonian formulas with an effective radius computed from the numerical data. Beyond the merger, the numerical results are reproduced by a superposition of three Kerr quasinormal modes. Analytic formulas, obtained by expressing the multipole moments in terms of the fundamental quasinormal modes of a Kerr black hole, are able to explain the onset and amount of 'antikick' for each of the simulations. Lastly, we apply this multipolar analysis to help explain the remarkable difference between the amplitudes of planar and nonplanar kicks for equal-mass spinning black holes.

Schnittman, Jeremy D.; Buonanno, Alessandra [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Meter, James R. van [Gravitational Astrophysics Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland 20771 (United States); Center for Space Science and Technology, University of Maryland Baltimore County, Physics Department, 1000 Hilltop Circle, Baltimore, Maryland 21250 (United States); Baker, John G.; Centrella, Joan; Kelly, Bernard J. [Gravitational Astrophysics Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland 20771 (United States); Boggs, William D.; McWilliams, Sean T. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

2008-02-15

204

Quantum spin Hall effect in inverted InAs\\/GaSb quantum wells  

Microsoft Academic Search

We review the recent experimental progress towards observing quantum spin Hall effect in inverted InAs\\/GaSb quantum wells (QWs). Low temperature transport measurements in the hybridization gap show bulk conductivity of a non-trivial origin, while the length and width dependence of conductance in this regime show strong evidence for the existence of helical edge modes proposed by Liu et al. [Phys.

Ivan Knez; Rui-Rui Du

2011-01-01

205

Towards Quantum Spin Hall Effect in InAs\\/GaSb Quantum Wells  

Microsoft Academic Search

Recently, it has been proposed that inverted InAs\\/GaSb composite quantum wells (CQWs) should exhibit the Quantum Spin Hall Effect (QSHE), characterized by the energy gap in the bulk and gapless edge modes which are protected from backscattering by time reversal symmetry. We have successfully fabricated a double-gated device on high-quality MBE-grown InAs\\/GaAs CQWs in the inverted regime, in which we

Ivan Knez; Rui-Rui Du; Gerrard Sullivan

2011-01-01

206

Quantum effects in large molecule collisional energy transfer?  

NASA Astrophysics Data System (ADS)

Recently, Gilbert and Zare proposed that dynamical quantum effects might explain the poor performance of classical trajectory calculations in simulating the vibrational deactivation of excited azulene by the lighter noble gases. They proposed an experimental test: a comparison of 3He and 4He deactivation of azulene. In this Letter, the collisional deactivation of benzene, toluene and toluene-d8 by 3He and 4He has been investigated by infrared fluorescence to assess the importance of dynamical quantum effects. The results show that the proposed dynamical quantum effect is not important for these systems over the range of vibrational energies from ?8000 to ?35000 cm-1.

Toselli, Beatriz M.; Barker, John R.

1990-11-01

207

Geometry of the fractional quantum Hall effect  

NASA Astrophysics Data System (ADS)

Unlike the integer effect, the incompressible electron fluid that exhibits the fractional effect is not invariant under ``area-preserving diffeomorphisms'' of the guiding-center degrees of freedom. Instead (F. D. M. Haldane, Phys. Rev. Lett. 108, 116801 (2011)), it has a shear modulus that characterizes the energy cost of distortions of the correlation hole around the electrons, and a ``guiding-center metric tensor'' that exhibits quantum zero-point fluctuations around a preferred shape. In a simple (one-component) fluid, electronic charge-density fluctuations relative to the background set by the magnetic flux density are given by ?? = (e^*/2?)s K, where e^* is the elementary fractional charge, s is an integer or half-integer ``guiding-center spin'' that is topologically quantized by the Gauss-Bonnet theorem, and K is the local Gaussian curvature of the guiding-center metric. These results provide a simple explanation of the seminal 1985 results of Girvin, MacDonald and Platzman on the FQH structure factor and collective mode, which remained unexplained in previous proposed narrative explanations of FQH incompressibility (Ginzburg-Landau Chern-Simons theory, composite fermions, and non-commutative Chern-Simons field theory).

Haldane, F. D. M.

2012-02-01

208

Investigation on modeling and controability of a magnetorheological gun recoil damper  

NASA Astrophysics Data System (ADS)

Magnetorheological (MR) fluid as a new smart material has done well in the vibration and impact control engineering fields because of its good electromechanical coupling characteristics, preferable dynamic performance and higher sensitivity. And success of MRF has been apparent in many engineering applied fields, such as semi-active suspension, civil engineering, etc. So far, little research has been done about MR damper applied into the weapon system. Its primary purpose of this study is to identify its dynamic performance and controability of the artillery recoil mechanism equipped with MR damper. Firstly, based on the traditional artillery recoil mechanism, a recoil dynamic model is developed in order to obtain an ideal rule between recoil force and its stroke. Then, its effects of recoil resistance on the stability and firing accuracy of artillery are explored. Because MR gun recoil damper under high impact load shows a typical nonlinear character and there exists a shear-thinning phenomenon, to establish an accurate dynamic model has been a seeking aim of its design and application for MR damper under high impact load. Secondly, in this paper, considering its actual bearing load, an inertia factor was introduced to Herschel-Bulkley model, and some factor's effect on damping force are simulated and analyzed by using numerical simulation, including its dynamic performance under different flow coefficients and input currents. Finally, both of tests with the fixed current and different On-Off control algorithms have been done to confirm its controability of MR gun recoil damper under high impact load. Experimental results show its dynamic performances of the large-scale single-ended MR gun recoil damper can be changed by altering the applied currents and it has a good controllability.

Hu, Hongsheng; Wang, Juan; Wang, Jiong; Qian, Suxiang; Li, Yancheng

2009-07-01

209

New mechanism of recoil fractionation of uranium isotopes  

SciTech Connect

A number of extremely high /sup 234/U//sup 238/U activity ratios (up to 410 +/- 16) were observed in the uranium-poor acid-residues (and their chemical and physical separates) of various uranium ores from different locations on the world. For interpreting this kind of enrichment of /sup 234/U, a new mechanism of uranium isotopic fraction, referred to as poor-rich mechanism, was presented, which says that in a uranium-bearing system consisting of two phases, the uranium-poor phase becomes enriched in /sup 234/U and the uranium-rich phase depleted in /sup 234/U due to the ejection of recoil /sup 234/U atoms across the interface of the two phases; the recoil /sup 234/U atoms are then re-fixed firmly in new crystalline lattices due to self-annealing effect of recoil tracks; and when the two phases are separated by selective dissolution or other manners, enrichment of /sup 234/U in the uranium-poor phase (and depletion in the uranium-rich phase probably) will be observed. A set of mathematical equations expressing the new mechanism were derived. The recipes for extracting uranium fractions with high /sup 234/U//sup 238/U activity ratios from uranium ores were described. A complete classification of the factors responsible for uranium isotopic fractionation was presented. The direct ejection mechanism, preferential solution mechanism and poor-rich mechanism are three major mechanisms causing the uranium isotopic fractionation in nature. The range of recoil /sup 234/U atoms in uranium ore and the neutron fluence and conversion factor of Oklo natural reactor were estimated from the experimental data.

Sheng, Z.

1987-01-01

210

Improved measurement of atomic recoil frequency using atom interferometry  

NASA Astrophysics Data System (ADS)

We have recently used a single state time domain atom interferometer to make a measurement of atomic recoil frequency in cold ^85 Rb atoms precise to 2.5 ppm. The interferometer involves excitation by off-resonant standing wave pulses applied at t=0 and t=T. The pulses diffract and recombine a superposition of momentum states corresponding to the same internal state. This results in a population grating ``echo'' in the vicinity of t=2T. The grating was detected using an off resonant readout pulse. This pulse results in a backscattered signal detected using a heterodyne technique. Our measurement of the recoil frequency is in excellent agreement with the value of the recoil frequency obtained from previous measurements of the transition wavelength, atomic mass, and Planck's constant. We present improved measurements using PMT detection, reducing the effect of magnetic field gradients, and increasing the spatial extent of our interferometry beams. We also investigate the role of collisions between hot and cold ^85 Rb atoms on the lifetime of our echo signal and discuss the precision that can be achieved using an atomic fountain.

Beattie, Scott

2005-05-01

211

Quantum mechanical effects on the shock Hugoniot.  

National Technical Information Service (NTIS)

Calculations of the locus of shock Hugoniot states of aluminum, using two equations of state that either omit or include a quantum mechanical treatment for the material's electronic excitations, will be presented. The difference between the loci will be a...

B. I. Bennett D. A. Liberman

1991-01-01

212

Quantum size effects in ?-Pu (110) films  

NASA Astrophysics Data System (ADS)

First-principles full-potential linearized-augmented-plane-wave (FP-LAPW) calculations have been carried out for ?-Pu (110) films up to seven layers. The layers have been studied at the non-spin-polarized-no-spin-orbit coupling (NSP-NSO), non-spin-polarized-spin-orbit coupling (NSP-SO), spin-polarized-no-spin-orbit coupling (SP-NSO), spin-polarized-spin-orbit coupling (SP-SO), antiferromagnetic-no-spin-orbit coupling (AFM-NSO), and antiferromagnetic-spin-orbit-coupling (AFM-SO) levels of theory. The ground state of ?-Pu (110) films is found to be at the AFM-SO level of theory and the surface energy is found to rapidly converge. The semi-infinite surface energy for ?-Pu (110) films is predicted to be 1.41 J/m2, while the magnetic moments show an oscillating behavior, gradually approaching the bulk value of zero with increase in the number of layers. Work functions indicate a strong quantum size effect up to and including seven layers. The work function of the seven-layer ?-Pu (110) film at the ground state is found to be 2.99 eV.

Gong, H.; Ray, A. K.

2005-12-01

213

Random matrices, fractional statistics, and the quantum Hall effect  

SciTech Connect

The fractional-statistics Laughlin picture of the quantum Hall effect is reformulated as a random-matrix problem. This reformulation connects two large sets of results, and should lead to simplifications for both analytical and numerical studies.

Callaway, D.J.E. (Department of Physics, The Rockefeller University, 1230 York Avenue, New York, New York 10021-6399 (US))

1991-04-01

214

Electronic states and curved surface effect of silicon quantum dots  

NASA Astrophysics Data System (ADS)

The calculation results show that the bonding energy and electronic states of silicon quantum dots (Si QDs) are different on various curved surfaces (CS), for example, a Si-O-Si bridge bond on curved surface provides the localized levels in band gap and its bonding energy is shallower than that on facet. Curved surface breaks symmetrical shape of silicon quantum dots on which some bonds can produce localized electronic states in band gap. The red-shifting of photoluminescence spectra on smaller silicon quantum dots can be explained by CS effect. In CS effect, surface curvature is determined by the shape of Si QDs or silicon nanostructures, which is independent of their sizes. The CS effect has the interesting fundamental physical properties in nanophysics as that of quantum confinement effect.

Huang, Wei-Qi; Huang, Zhong-Mei; Cheng, Han-Qiong; Miao, Xin-Jian; Shu, Qin; Liu, Shi-Rong; Qin, Chao-Jian

2012-10-01

215

Spin blockade of quantum cellular automata effects in a few electron triple quantum dot  

NASA Astrophysics Data System (ADS)

It has been previously demonstrated, employing charge detection techniques, that quantum cellular automata (QCA) processes exist in the vicinity of quadruple degeneracy points in both ring and serial arrangements of lateral triple quantum dots. The effect is primarily an electrostatic one. In this paper, we report on transport measurements through a triple dot potential and study experimentally the interplay between these QCA phenomena and the Pauli (spin) blockade effect. We demonstrate experimentally that the interaction between these processes leads to a higher order and indirect form of spin blockade in which the QCA effect itself is blockaded.

Gaudreau, L.; Sachrajda, A. S.; Studenikin, S. A.; Zawadzki, P.; Kam, A.

2008-03-01

216

Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells  

SciTech Connect

Spin Hall effect can be induced both by the extrinsic impurity scattering and by the intrinsic spin-orbit coupling in the electronic structure. The HgTe/CdTe quantum well has a quantum phase transition where the electronic structure changes from normal to inverted. We show that the intrinsic spin Hall effect of the conduction band vanishes on the normal side, while it is finite on the inverted side. This difference gives a direct mechanism to experimentally distinguish the intrinsic spin Hall effect from the extrinsic one.

Yang, Wen; Chang, Kai; /Beijing, Inst. Semiconductors; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-03-19

217

Elastic recoil detection analysis for large recoil angles (LA-ERDA)  

NASA Astrophysics Data System (ADS)

In this paper, elastic recoil detection (ERD) measurements at recoil angle of 60° using ion-induced electron emission (IEE) for particle identification are presented. In our IEE system for particle identification, recoiled target atoms and scattered projectiles penetrate a set of thin carbon foils before their energy is analyzed in a solid state detector. Particle identification is based on the fact that the total number of electrons emitted from the foils depends on the particle nuclear charge. This method is characterized by its low minimum detectable energy, which stimulated us to study ERDA at 60°. Due to collision kinematics and due to the angular dependence of the scattering cross-sections, it is expected that the sensitivity can be significantly improved. In this work, the detection efficiency of the IEE particle identification system for H recoils at energies below 1 MeV was determined. LA-ERDA measurements were performed with 4He and 12C projectiles using two different types of samples with a well-known amount and depth distribution of H atoms near the surface. Sample 1 consisted of a 50 ?g/cm2 melamine layer evaporated on a flat Si substrate, sample 2 was a Si wafer with implanted H. Sensitivity and depth resolution were measured using LA-ERDA with a recoil angle of 60° and ERDA with recoil angles of 30° and 45°. The results for different recoil geometries and projectiles are discussed and compared with theoretical predictions.

Bogdanovi?, I.; Steinbauer, E.; Benka, O.

2000-09-01

218

Nuclear Quantum Vibrational Effects in Shock Hugoniot Temperatures  

Microsoft Academic Search

We present a straightforward technique for the inclusion of nuclear quantum vibrational effects in molecular dynamics (MD) calculations of shock Hugoniot temperatures. Although ab initio MD simulations accurately reproduce the high pressure-density equation of state for many materials, they have been shown to under-predict experimental Hugoniot temperatures by 20-30%, partially due to the exclusion of nuclear quantum effects in standard

Nir Goldman; Evan J. Reed; Laurence E. Fried

2009-01-01

219

Quantum effects and color transparency in charmonium photoproduction on nuclei  

Microsoft Academic Search

We develop a rigorous quantum-mechanical treatment of color transparency effects in diffractive photoproduction of {ital {bar c}c} pairs on nuclei. The evolution of the {ital {bar c}c} wave function during propagation through a nucleus is more a considerable distortion of its form than a trivial attenuation. One of the manifestations of the quantum effects is a nuclear antishadowing of the

Boris Kopeliovich; Bronislav Zakharov

1991-01-01

220

Quantum effects and color transparency in charmonium photoproduction on nuclei  

Microsoft Academic Search

We develop a rigorous quantum-mechanical treatment of color transparency effects in diffractive photoproduction of c¯c pairs on nuclei. The evolution of the c¯c wave function during propagation through a nucleus is more a considerable distortion of its form than a trivial attenuation. One of the manifestations of the quantum effects is a nuclear antishadowing of the psi' yield, i.e., transparency

Boris Z. Kopeliovich; Bronislav G. Zakharov

1991-01-01

221

Quantum effects in diffractive photoproduction of charmonia on nuclei  

Microsoft Academic Search

We develop a quantum-mechanical treatment of color transparency effects in diffractive photoproduction of cc-pairs on nuclei, using the path-integral method. The evolution of the cc wave function during propagation through a nucleus is rather a considerable distortion of its form, than a trivial attenuation. One of the manifestations of the quantum effects is a nuclear antishadowing of Psi' yield, i.e.

Boris Kopeliovich; Bronislav Zakharov

1992-01-01

222

Spin polarized quantum pump effect in zigzag graphene nanoribbons  

Microsoft Academic Search

The spin polarized adiabatic quantum pump effect in zigzag graphene nanoribbons has been numerically analyzed. Since the ground\\u000a state of such a ribbon is antiferromagnetic (the opposite spin electrons are located on the opposite edges of the ribbon),\\u000a the spin currents can be generated in this system with the help of the quantum pump effect when symmetry between the opposite

E. S. Grichuk; E. A. Manykin

2011-01-01

223

Nuclear quantum effects in electronically adiabatic quantum time correlation functions: Application to the absorption spectrum of a hydrated electron  

Microsoft Academic Search

A general formalism for introducing nuclear quantum effects in the expression of the quantum time correlation function of an operator in a multilevel electronic system is presented in the adiabatic limit. The final formula includes the nuclear quantum time correlation functions of the operator matrix elements, of the energy gap, and their cross terms. These quantities can be inferred and

La´szlo´ Turi; György Hantal; Peter J. Rossky; Daniel Borgis

2009-01-01

224

Effect of localization in quantum wells and quantum wires on heavy-light hole mixing and acceptor binding energy  

SciTech Connect

The variational method taking into account the complex valence band structure is used to study the effect of localization in quantum wells and quantum wires on the acceptor binding energy. Trial functions that make possible tracing of the transition from the bulk material to narrow quantum wells and quantum wires of small radius are constructed. The possibility of the appearance of an unsteadily varying dependence of the acceptor binding energy on the characteristic dimension of the system is shown.

Semina, M. A., E-mail: msemina@gmail.com; Suris, R. A. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-07-15

225

Essay: Quantum Field Theory Is Not Merely Quantum Mechanics Applied to Low Energy Effective Degrees of Freedom  

Microsoft Academic Search

It is commonly assumed that quantum field theory arises by applying ordinary quantum mechanics to the low energy effective degrees of freedom of a more fundamental theory defined at ultra-high-energy\\/short-wavelength scales. We shall argue here that, even for free quantum fields, there are holistic aspects of quantum field theory that cannot be properly understood in this manner. Specifically, the “subtractions”

Stefan Hollands; Robert M. Wald

2004-01-01

226

Recoil-proton polarization in high-energy deuteron photodisintegration with circularly polarized photons.  

PubMed

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance. PMID:17501566

Jiang, X; Arrington, J; Benmokhtar, F; Camsonne, A; Chen, J P; Choi, S; Chudakov, E; Cusanno, F; Deur, A; Dutta, D; Garibaldi, F; Gaskell, D; Gayou, O; Gilman, R; Glashauser, C; Hamilton, D; Hansen, O; Higinbotham, D W; Holt, R J; de Jager, C W; Jones, M K; Kaufman, L J; Kinney, E R; Kramer, K; Lagamba, L; de Leo, R; Lerose, J; Lhuillier, D; Lindgren, R; Liyanage, N; McCormick, K; Meziani, Z-E; Michaels, R; Moffit, B; Monaghan, P; Nanda, S; Paschke, K D; Perdrisat, C F; Punjabi, V; Qattan, I A; Ransome, R D; Reimer, P E; Reitz, B; Saha, A; Schulte, E C; Sheyor, R; Slifer, K; Solvignon, P; Sulkosky, V; Urciuoli, G M; Voutier, E; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Zhu, L

2007-05-01

227

Recoil-proton polarization in high-energy deuteron photodisintegration with circularly plarized photons.  

SciTech Connect

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

Jiang, X.; Arrington, J.; Benmokhtar, F.; Camsonne, A.; Chen, J. P.; Holt, R. J.; Qattan, I. A.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Physics; Rutgers Univ.; Univ. Blaise Pascal; Thomas Jefferson National Accelerator Facility

2007-05-01

228

Effects of symmetry breaking in finite quantum systems  

NASA Astrophysics Data System (ADS)

The review considers the peculiarities of symmetry breaking and symmetry transformations and the related physical effects in finite quantum systems. Some types of symmetry in finite systems can be broken only asymptotically. However, with a sufficiently large number of particles, crossover transitions become sharp, so that symmetry breaking happens similarly to that in macroscopic systems. This concerns, in particular, global gauge symmetry breaking, related to Bose-Einstein condensation and superconductivity, or isotropy breaking, related to the generation of quantum vortices, and the stratification in multicomponent mixtures. A special type of symmetry transformation, characteristic only for finite systems, is the change of shape symmetry. These phenomena are illustrated by the examples of several typical mesoscopic systems, such as trapped atoms, quantum dots, atomic nuclei, and metallic grains. The specific features of the review are: (i) the emphasis on the peculiarities of the symmetry breaking in finite mesoscopic systems; (ii) the analysis of common properties of physically different finite quantum systems; (iii) the manifestations of symmetry breaking in the spectra of collective excitations in finite quantum systems. The analysis of these features allows for the better understanding of the intimate relation between the type of symmetry and other physical properties of quantum systems. This also makes it possible to predict new effects by employing the analogies between finite quantum systems of different physical nature.

Birman, J. L.; Nazmitdinov, R. G.; Yukalov, V. I.

2013-05-01

229

Quantum-confined Stark effect measurements in Ge/SiGe quantum-well structures.  

PubMed

We investigate the room-temperature quantum-confined Stark effect in Ge/SiGe multiple quantum wells (MQWs) grown by low-energy plasma-enhanced chemical vapor deposition. The active region is embedded in a p-i-n diode, and absorption spectra at different reverse bias voltages are obtained from optical transmission, photocurrent, and differential transmission measurements. The measurements provide accurate values of the fraction of light absorbed per well of the Ge/SiGe MQWs. Both Stark shift and reduction of exciton absorption peak are observed. Differential transmission indicates that there is no thermal contribution to these effects. PMID:20808367

Chaisakul, Papichaya; Marris-Morini, Delphine; Isella, Giovanni; Chrastina, Daniel; Le Roux, Xavier; Gatti, Eleonora; Edmond, Samson; Osmond, Johann; Cassan, Eric; Vivien, Laurent

2010-09-01

230

Quantum Spin Hall Effect in HgTe in a Magnetic Field  

Microsoft Academic Search

Recently, the quantum spin Hall effect has been proposed in HgTe quantum wells. It has been shown that this system exhibits the quantum spin Hall effect and the Hamiltonian is analogous to two copies of the quantum anomalous Hall effect. Here we examine the features of this system in a strong magnetic field. We use an analytic transfer matrix formalism

Taylor Hughes; Andrei Bernevig; Shou-Cheng Zhang

2007-01-01

231

Complex dynamics of the integer quantum Hall effect  

SciTech Connect

We investigate both classical and quantum potential scattering in two dimensions in a magnetic field, with applications to the integer quantum Hall effect. Classical scattering is complex, due in one case to the approach of scattering states to an infinite number of bound states. We show that bound states are generic, and occur for all but extremely smooth scattering potentials ({vert bar}{rvec {gradient}}{vert bar} {yields} 0). Quantum scattering follows the classical behavior rather closely, exhibiting sharp resonances rather than classical bound states. Extended scatterers provide an explanation for the breakdown of the QHE at a comparatively small Hall voltage. 16 refs., 14 figs.

Trugman, S.A. (Los Alamos National Lab., NM (USA)); Nicopoulos, V.N. (Los Alamos National Lab., NM (USA) Florida Univ., Gainesville, FL (USA). Dept. of Physics)

1991-01-01

232

The etching of alpha-recoil tracks in phlogopite  

Microsoft Academic Search

This work uses three phlogopite samples to investigate the etching behavior of alpha-recoil tracks (?-recoil tracks), which is a key problem in dating procedures. At the initial stage of the etching process, the number of alpha-recoil tracks increased linearly with etching time, then the linearity was interrupted due to the overlapping of alpha-recoil tracks. The slope of the etching line

Wanming Yuan; Shaokai Gao; Jinquan Dong; Zenkuan Bao; Xiuming Jia

2008-01-01

233

Quantum dissipative effects in moving mirrors: A functional approach  

SciTech Connect

We use a functional approach to study various aspects of the quantum effective dynamics of moving, planar, dispersive mirrors, coupled to scalar or Dirac fields, in different numbers of dimensions. We first compute the Euclidean effective action, and use it to derive the imaginary part of the 'in-out' effective action. We also obtain, for the case of the real scalar field in 1+1 dimensions, the Schwinger-Keldysh effective action and a semiclassical Langevin equation that describes the motion of the mirror including noise and dissipative effects due to its coupling to the quantum fields.

Fosco, C. D. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, R8402AGP Bariloche (Argentina); Lombardo, F. C.; Mazzitelli, F. D. [Departamento de Fisica Juan Jose Giambiagi, FCEyN Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)

2007-10-15

234

Proton recoil scintillator neutron rem meter  

DOEpatents

A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

Olsher, Richard H. (Los Alamos, NM); Seagraves, David T. (Los Alamos, NM)

2003-01-01

235

Recoiling Massive Black Holes in Galaxy Mergers  

NASA Astrophysics Data System (ADS)

The asymmetric emission of gravitational waves produced during the coalescence of a massive black hole (MBH) binary imparts a velocity "kick" to the system that can displace the hole from the center of its host. I will discuss the trajectories and observability of MBHs recoiling in gas-rich galaxy merger remnants using high-resolution hydrodynamical simulations.

Madau, Piero

2012-05-01

236

Implantation of Radioactive Atoms by alpha Recoil.  

National Technical Information Service (NTIS)

The penetration depths of exp 224 Ra recoils in a polycrystalline target (Au) were measured, for parallel and isotropic implantation beams. Also measured were the penetration depths of exp 212 Pb from a exp 224 Ra source. The peeling technique of Whitton ...

S. Abrashkin

1976-01-01

237

Quantum instanton evaluation of the kinetic isotope effects  

NASA Astrophysics Data System (ADS)

The quantum instanton approximation is used to compute kinetic isotope effects for intramolecular hydrogen transfer in cis-1,3-pentadiene. Due to the importance of skeleton motions, this system with 13 atoms is a simple prototype for hydrogen transfer in enzymatic reactions. The calculation is carried out using thermodynamic integration with respect to the mass of the isotopes and a path integral Monte Carlo evaluation of relevant thermodynamic quantities. Efficient ``virial'' estimators are derived for the logarithmic derivatives of the partition function and the delta-delta correlation functions. These estimators require significantly fewer Monte Carlo samples since their statistical error does not increase with the number of discrete time slices in the path integral. The calculation treats all 39 degrees of freedom quantum-mechanically and uses an empirical valence bond potential based on a modified general AMBER force field. The importance of quantum effects due to the skeleton motion is demonstrated by comparison with a mixed quantum-classical calculation.

Vanicek, Jiri; Miller, William H.

2007-03-01

238

Quantum Backreaction (casimir) Effect Without Infinities: Algebraic Analysis  

NASA Astrophysics Data System (ADS)

Casimir effect, in most general terms, is the backreaction of a quantum system responding to an adiabatic change of external conditions. This backreaction is expected to be quantitatively measured by a change in the expectation value of a certain energy observable of the system. However, for this concept to be applicable, the system has to retain its identity in the process. Most prevailing tendencies in the analysis of the effect seem to ignore this question. In general, a quantum theory is defined by an algebra of observables, whose representations by operators in a Hilbert space define concrete physical systems described by the theory. A quantum system retains its identity if both the algebra as well as its representation do not change. We discuss the resulting restrictions for admissible models of changing external conditions. These ideas are applied to quantum field models. No infinities arise, if the algebraic demands are respected.

Herdegen, Andrzej

2012-07-01

239

Enhancing quantum effects via periodic modulations in optomechanical systems  

NASA Astrophysics Data System (ADS)

Parametrically modulated optomechanical systems have been recently proposed as a simple and efficient setting for the quantum control of a micromechanical oscillator: relevant possibilities include the generation of squeezing in the oscillator position (or momentum) and the enhancement of entanglement between mechanical and radiation modes. In this paper we further investigate this modulation regime, considering an optomechanical system with one or more parameters being modulated over time. We first apply a sinusoidal modulation of the mechanical frequency and characterize the optimal regime in which the visibility of purely quantum effects is maximal. We then introduce a second modulation on the input laser intensity and analyze the interplay between the two. We find that an interference pattern shows up, so that different choices of the relative phase between the two modulations can either enhance or cancel the desired quantum effects, opening new possibilities for optimal quantum control strategies.

Farace, Alessandro; Giovannetti, Vittorio

2012-07-01

240

Thermal effects on photon-induced quantum transport in a single quantum dot.  

PubMed

We theoretically investigate laser induced quantum transport in a single quantum dot attached to electrical contacts. Our approach, based on a nonequilibrium Green function technique, allows us to include thermal effects on the photon-induced quantum transport and excitonic dynamics, enabling the study of non-Markovian effects. By solving a set of coupled integrodifferential equations, involving correlation and propagator functions, we obtain the photocurrent and the dot occupation as a function of time. Two distinct sources of decoherence, namely, incoherent tunneling and thermal fluctuations, are observed in the Rabi oscillations. As temperature increases, a thermally activated Pauli blockade results in a suppression of these oscillations. Additionally, the interplay between photon and thermally induced electron populations results in a switch of the current sign as time evolves and its stationary value can be maximized by tuning the laser intensity. PMID:23462318

Assunção, M O; de Oliveira, E J R; Villas-Bôas, J M; Souza, F M

2013-03-05

241

Quantum Logic Operations Using Single Photons and the Zeno Effect  

Microsoft Academic Search

We show that the quantum Zeno effect can be used to implement several quantum\\u000alogic gates for photonic qubits, including a gate that is similar to the\\u000asquare-root of SWAP operation. The operation of these devices depends on the\\u000afact that photons can behave as if they were non-interacting fermions instead\\u000aof bosons in the presence of a strong Zeno

J. D. Franson; B. C. Jacobs; T. B. Pittman

2004-01-01

242

Loss of coherence and memory effects in quantum dynamics  

Microsoft Academic Search

The last years have witnessed fast growing developments in the use of quantum mechanics in technology-oriented and information-related fields, especially in metrology, in the developments of nano-devices and in understanding highly efficient transport processes. The consequent theoretical and experimental outcomes are now driving new experimental tests of quantum mechanical effects with unprecedented accuracies that carry with themselves the concrete possibility

Fabio Benatti; Roberto Floreanini; Greg Scholes

2012-01-01

243

Disorder-effects in reduced dimensional and quantum electronics  

NASA Astrophysics Data System (ADS)

We present data and review results on displacement damage effects in reduced-dimensional and quantum-electronic systems such as resonant tunneling diodes, resonant interband tunneling diodes, low-temperature and high-temperature superconductors, high electron mobility transistors, and multiquantum well infrared detectors. Quantum mechanics and/or reduced dimension give these systems unique responses to radiation damage, including special sensitivities and immunities. Radiation damage mechanisms are discussed, and radiation-tolerance is compared to conventional devices. .

Weaver, B. D.; Magno, R.; Jackson, E. M.; Wilkins, R.; Shojah-Ardalan, S.; Seabaugh, A. C.; Brar, B.; Manasreh, M. O.; Berhane, Y.

2001-02-01

244

Phonon spectroscopy of the fractional quantum Hall effect  

Microsoft Academic Search

The low-lying bulk excitations of two-dimensional electron systems subject to a strong perpendicular magnetic field have been studied using phonon absorption. Results reported earlier lead to the conclusion that the magnetoroton minimum energy in the fractional quantum Hall effect can be measured by phonon absorption. Recent time-resolved measurements have demonstrated fundamental differences in phonon absorption between fractional quantum Hall states,

J. E. Digby; U. Zeitler; C. J. Mellor; A. J. Kent; K. A. Benedict; M. Henini; C. T. Foxon; J. J. Harris

1996-01-01

245

Theory of Non-Adiabatic Optical Effects in Quantum Dots  

Microsoft Academic Search

Quantum dots continue to be an area of intense scientific activity, because they have a number of advantages as the `building blocks' for advanced semiconductor devices with three-dimensional band-structure engineering. Considerable effort is being devoted to the investigation of effects due to the exciton-phonon interaction on the optical properties of quantum dots. Our theory of photoluminescence and Raman scattering in

J. T. Devreese

2002-01-01

246

Manipulating the Kondo Resonance through Quantum Size Effects  

Microsoft Academic Search

Manipulating the Kondo effect by quantum confinement has been achieved by placing magnetic molecules on silicon-supported nanostructures. The Kondo resonance of individual manganese phthalocyanine (MnPc) molecules adsorbed on the top of Pb islands was studied by scanning tunneling spectroscopy. Oscillating Kondo temperatures as a function of film thickness were observed and attributed to the formation of the thickness-dependent quantum-well states

Ying-Shuang Fu; Shuai-Hua Ji; Xi Chen; Xu-Cun Ma; Rui Wu; Chen-Chen Wang; Wen-Hui Duan; Xiao-Hui Qiu; Bo Sun; Ping Zhang; Jin-Feng Jia; Qi-Kun Xue

2007-01-01

247

A gun recoil system employing a magnetorheological fluid damper  

Microsoft Academic Search

This research aims to design and control a full scale gun recoil buffering system which works under real firing impact loading conditions. A conventional gun recoil absorber is replaced with a controllable magnetorheological (MR) fluid damper. Through dynamic analysis of the gun recoil system, a theoretical model for optimal design and control of the MR fluid damper for impact loadings

Z C Li; J Wang

2012-01-01

248

Alpha-Recoil Tracks in Mica: Registration Efficiency  

Microsoft Academic Search

Recoils from alpha-particle decay of naturally occurring radioactive nuclides have energies between 70 and 169 kiloelectron volts. It is shown that these alpha recoils register tracks in mica, observable as etch pits, with an efficiency of about 80 percent. When the recoil energy is degraded to 40 kiloelectron volts the efficiency drops to 50 percent. But, since the decay of

Seymour Katcoff

1969-01-01

249

Quantum brownian particle and memory effects.  

National Technical Information Service (NTIS)

The Quantum Brownian particle, immersed in a heat bath, is described by a statistical operator whose evolution is ruled by a Generalized Master Equation (GME). The heat bath degrees of freedom are considered to be either white noise or coloured noise corr...

J. R. Britani S. S. Mizrahi B. M. Pimentel

1991-01-01

250

The \\\\mathbb{Z}_{2} network model for the quantum spin Hall effect: two-dimensional Dirac fermions, topological quantum numbers and corner multifractality  

Microsoft Academic Search

The quantum spin Hall effect shares many similarities (and some important differences) with the quantum Hall effect for electric charge. As with the quantum (electric charge) Hall effect, there exists a correspondence between bulk and boundary physics that allows one to characterize the quantum spin Hall effect in diverse and complementary ways. In this paper, we derive from the network

Shinsei Ryu; Christopher Mudry; Hideaki Obuse; Akira Furusaki

2010-01-01

251

Disclosing hidden information in the quantum Zeno effect: Pulsed measurement of the quantum time of arrival  

NASA Astrophysics Data System (ADS)

Repeated measurements of a quantum particle to check its presence in a region of space was proposed long ago [G. R. Allcock, Ann. Phys. 53, 286 (1969)] as a natural way to determine the distribution of times of arrival at the orthogonal subspace, but the method was discarded because of the quantum Zeno effect: in the limit of very frequent measurements the wave function is reflected and remains in the original subspace. We show that by normalizing the small bits of arriving (removed) norm, an ideal time distribution emerges in correspondence with a classical local-kinetic-energy distribution.

Echanobe, J.; Del Campo, A.; Muga, J. G.

2008-03-01

252

Quantum Statistical Calculations for Thermal Effect in Quantum-Dot Cellular Automata (QCA)1  

Microsoft Academic Search

A theoretical study of thermal effect in QCA is presented. Quantum statistical analysis for average polarization of each cell is done. A computational model has been developed to find all the possible configurations of polarizations in an array of cells. All cells are in one of the two possible eigenstates corresponding to the total Hamiltonian. Here, only the locked states

Mahfuza Khatun; Ioan Sturzu; Jonathan Kanuchok; Douglas Tougaw

2003-01-01

253

Quantum Zeno Effect Induced by Quantum Measurement of Momentum of Atomic Mass Center  

Microsoft Academic Search

In this article, we obtained the factorization form of the evolution operator corresponding to the Hamiltonian which describes the interaction of a two-level atom with one propagating mode in an optical ring cavity and the exact solution is followed. A new scheme for realizing quantum Zeno effect is proposed by measuring the atomic momentum (external state) frequently to freeze the

Xiaoguang Wang

1995-01-01

254

Quantum phase transition and underscreened Kondo effect in electron transport through parallel double quantum dots.  

PubMed

We investigate electronic transport through a parallel double quantum dot (DQD) system with strong on-site Coulomb interaction and capacitive interdot coupling. By applying the numerical renormalization group (NRG) method, the ground state of the system and the transmission probability at zero temperature have been obtained. For a system of quantum dots with degenerate energy levels and small interdot tunnel coupling, the spin correlations between the DQDs is ferromagnetic and the ground state of the system is a spin-1 triplet state. The linear conductance will reach the unitary limit (2e(2)/h) due to the underscreened Kondo effect at low temperature. As the interdot tunnel coupling increases, there is a quantum phase transition from ferromagnetic to antiferromagnetic spin correlation in DQDs and the linear conductance is strongly suppressed. PMID:21694008

Ding, Guo-Hui; Ye, Fei; Dong, Bing

2009-10-23

255

Quantum Zeno and anti-Zeno effects on quantum and classical correlations  

SciTech Connect

In this paper we study the possibility of modifying the dynamics of both quantum correlations, such as entanglement and discord, and classical correlations of an open bipartite system by means of the quantum Zeno effect. We consider two qubits coupled to a common boson reservoir at zero temperature. This model describes, for example, two atoms interacting with a quantized mode of a lossy cavity. We show that when the frequencies of the two atoms are symmetrically detuned from that of the cavity mode, oscillations between the Zeno and anti-Zeno regimes occur. We also calculate analytically the time evolution of both classical correlations and quantum discord, and we compare the Zeno dynamics of entanglement with the Zeno dynamics of classical correlations and discord.

Francica, F.; Plastina, F. [Dipartimento di Fisica, Universita della Calabria, I-87036 Arcavacata di Rende (Italy); INFN-Gruppo Collegato di Cosenza, Cosenza (Italy); Maniscalco, S. [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FIN-20014 Turun yliopisto (Finland)

2010-11-15

256

Colloidal quantum dot photovoltaics: the effect of polydispersity.  

PubMed

The size-effect tunability of colloidal quantum dots enables facile engineering of the bandgap at the time of nanoparticle synthesis. The dependence of effective bandgap on nanoparticle size also presents a challenge if the size dispersion, hence bandgap variability, is not well-controlled within a given quantum dot solid. The impact of this polydispersity is well-studied in luminescent devices as well as in unipolar electronic transport; however, the requirements on monodispersity have yet to be quantified in photovoltaics. Here we carry out a series of combined experimental and model-based studies aimed at clarifying, and quantifying, the importance of quantum dot monodispersity in photovoltaics. We successfully predict, using a simple model, the dependence of both open-circuit voltage and photoluminescence behavior on the density of small-bandgap (large-diameter) quantum dot inclusions. The model requires inclusion of trap states to explain the experimental data quantitatively. We then explore using this same experimentally tested model the implications of a broadened quantum dot population on device performance. We report that present-day colloidal quantum dot photovoltaic devices with typical inhomogeneous linewidths of 100-150 meV are dominated by surface traps, and it is for this reason that they see marginal benefit from reduction in polydispersity. Upon eliminating surface traps, achieving inhomogeneous broadening of 50 meV or less will lead to device performance that sees very little deleterious impact from polydispersity. PMID:22257205

Zhitomirsky, David; Kramer, Illan J; Labelle, André J; Fischer, Armin; Debnath, Ratan; Pan, Jun; Bakr, Osman M; Sargent, Edward H

2012-01-24

257

A quantitative account of quantum effects in liquid water  

SciTech Connect

We report quantum statistical mechanical simulations of liquid water with the TTM2.1-F flexible, polarizable interaction potential for water. The potential is the first representation of the molecular interaction that reproduces the converged Born-Oppenheimer potential energy surface obtained from systematically improvable electronic structure analysis of binding energies of water clusters. Proper quantum statistical simulation of properties allows for a quantitative account of the magnitude of quantum effects in liquid water. We report path integral quantum dynamical simulations of total length of 600 ps with a 0.05 fs time step for a periodic system of 256 molecules. The representation of the quantum effects was achieved using up to 32 replicas per atom. These allow for a quantitative description of the broadening of the radial distribution functions and the corresponding energy shifts in the heat of vaporization. Our best estimate for the enthalpy of the liquid from the results of the quantum simulations is in the range 10.4 ? 10.6 kcal/mol, in agreement with the experimental value of 10.51 kcal/mol. 1Battelle operates PNNL for the USDOE

Fanourgakis, Georgios S.; Schenter, Gregory K.; Xantheas, Sotiris S.

2006-10-14

258

Quantum dissipative Brownian motion and the Casimir effect  

NASA Astrophysics Data System (ADS)

We explore an analogy between the thermodynamics of a free dissipative quantum particle in one dimension and that of an electromagnetic field between two mirrors of finite conductivity. While a free particle isolated from its environment will effectively be in the high-temperature limit for any nonvanishing temperature, a finite coupling to the environment leads to quantum effects ensuring the correct low-temperature behavior. Even then, it is found that under appropriate circumstances the entropy can be a nonmonotonic function of the temperature. Such a scenario with its specific dependence on the ratio of temperature and damping constant also appears for the transverse electric mode in the Casimir effect. The limits of vanishing dissipation for the quantum particle and of infinite conductivity of the mirrors in the Casimir effect both turn out to be noncontinuous.

Ingold, Gert-Ludwig; Lambrecht, Astrid; Reynaud, Serge

2009-10-01

259

Quantum dissipative Brownian motion and the Casimir effect.  

PubMed

We explore an analogy between the thermodynamics of a free dissipative quantum particle in one dimension and that of an electromagnetic field between two mirrors of finite conductivity. While a free particle isolated from its environment will effectively be in the high-temperature limit for any nonvanishing temperature, a finite coupling to the environment leads to quantum effects ensuring the correct low-temperature behavior. Even then, it is found that under appropriate circumstances the entropy can be a nonmonotonic function of the temperature. Such a scenario with its specific dependence on the ratio of temperature and damping constant also appears for the transverse electric mode in the Casimir effect. The limits of vanishing dissipation for the quantum particle and of infinite conductivity of the mirrors in the Casimir effect both turn out to be noncontinuous. PMID:19905279

Ingold, Gert-Ludwig; Lambrecht, Astrid; Reynaud, Serge

2009-10-08

260

Quantum Effect Induced Reverse Kinetic Molecular Sieving in Microporous Materials  

NASA Astrophysics Data System (ADS)

We report kinetic molecular sieving of hydrogen and deuterium in zeolite rho at low temperatures, using atomistic molecular dynamics simulations incorporating quantum effects via the Feynman-Hibbs approach. We find that diffusivities of confined molecules decrease when quantum effects are considered, in contrast with bulk fluids which show an increase. Indeed, at low temperatures, a reverse kinetic sieving effect is demonstrated in which the heavier isotope, deuterium, diffuses faster than hydrogen. At 65 K, the flux selectivity is as high as 46, indicating a good potential for isotope separation.

Kumar, A. V. Anil; Bhatia, Suresh K.

2005-12-01

261

Alpha-recoil atoms of plutonium in the environment  

Microsoft Academic Search

The -recoil effect of239Pu has been observed in environmental samples and theN\\u000a\\u000a5\\u000aP\\u000a\\/N5 ratio in these samples has been calculated. This ratio in atmospheric samples is in the range between 10–5 and 10–4 (atom\\/atom). For other contemporary terrestrial samples it is in the range between 10–7 and 10–6 (atom\\/atom), while that of uranium mineral is about 10–10 (atom\\/atom).

I. O. Essien

1994-01-01

262

A causal look into the quantum Talbot effect.  

PubMed

A well-known phenomenon in both optics and quantum mechanics is the so-called Talbot effect. This near field interference effect arises when infinitely periodic diffracting structures or gratings are illuminated by highly coherent light or particle beams. Typical diffraction patterns known as quantum carpets are then observed. Here the authors provide an insightful picture of this nonlocal phenomenon as well as its classical limit in terms of Bohmian mechanics, also showing the causal reasons and conditions that explain its appearance. As an illustration, theoretical results obtained from diffraction of thermal He atoms by both N-slit arrays and weak corrugated surfaces are analyzed and discussed. Moreover, the authors also explain in terms of what they call the Talbot-Beeby effect how realistic interaction potentials induce shifts and distortions in the corresponding quantum carpets. PMID:17600403

Sanz, A S; Miret-Artés, S

2007-06-21

263

Focus on quantum effects and noise in biomolecules  

NASA Astrophysics Data System (ADS)

The role of quantum mechanics in biological organisms has been a fundamental question of twentieth-century biology. It is only now, however, with modern experimental techniques, that it is possible to observe quantum mechanical effects in bio-molecular complexes directly. Indeed, recent experiments have provided evidence that quantum effects such as wave-like motion of excitonic energy flow, delocalization and entanglement can be seen even in complex and noisy biological environments (Engel et al 2007 Nature 446 782; Collini et al 2010 Nature 463 644; Panitchayangkoon et al 2010 Proc. Natl Acad. Sci. USA 107 12766). Motivated by these observations, theoretical work has highlighted the importance of an interplay between environmental noise and quantum coherence in such systems (Mohseni et al 2008 J. Chem. Phys. 129 174106; Plenio and Huelga 2008 New J. Phys. 10 113019; Olaya-Castro et al 2008 Phys. Rev. B 78 085115; Rebentrost et al 2009 New J. Phys. 11 033003; Caruso et al 2009 J. Chem. Phys. 131 105106; Ishizaki and Fleming 2009 J. Chem. Phys. 130 234111). All of this has led to a surge of interest in the exploration of quantum effects in biological systems in order to understand the possible relevance of non-trivial quantum features and to establish a potential link between quantum coherence and biological function. These studies include not only exciton transfer across light harvesting complexes, but also the avian compass (Ritz et al 2000 Biophys. J. 78 707), and the olfactory system (Turin 1996 Chem. Sens. 21 773; Chin et al 2010 New J. Phys. 12 065002). These examples show that the full understanding of the dynamics at bio-molecular length (10 Å) and timescales (sub picosecond) in noisy biological systems can uncover novel phenomena and concepts and hence present a fertile ground for truly multidisciplinary research.

Fleming, G. R.; Huelga, S. F.; Plenio, M. B.

2011-11-01

264

``Interaction--free'' interaction: entangling evolution via quantum Zeno effect  

Microsoft Academic Search

The effect of entangling evolution induced by frequently repeated quantum measurement is presented. The interesting possibility of conditional freezing the system in maximally entangled state out of Zeno effect regime is also revealed. The illustration of the phenomena in terms of dynamical version of ``interaction free'' measurement is presented. Some general conclusions are provided.

Pawel Horodecki

1998-01-01

265

Three Dimensional Quantum Simulation of Multigate Nanowire Field Effect Transistors  

Microsoft Academic Search

Detailed numerical methods for the three dimensional quantum simulation of the multi- gate nanowire field effect transistors in the ballistic transport regime are presented in this work. The device has been modeled based on the effective mass theory and the non-equilibrium Green's function formalism, and its simulation consists of solutions of the three dimensional Poisson's equation, two dimensional Schrodinger equations

Mincheol Shina

266

Subband anticrossing and the spin Hall effect in quantum wires  

Microsoft Academic Search

We report on numerical simulations of the intrinsic spin Hall effect in semiconductor quantum wires as a function of the Rashba spin–orbit coupling strength, the electron density, and the width of the wire. We find that the strength of the spin Hall effect does not depend monotonically on these parameters, but instead exhibits a local maximum. This behavior is explained

A W Cummings; R Akis; D K Ferry

2009-01-01

267

Anisotropic intrinsic spin Hall effect in quantum wires  

Microsoft Academic Search

We use numerical simulations to investigate the spin Hall effect in quantum wires in the presence of both Rashba and Dresselhaus spin–orbit coupling. We find that the intrinsic spin Hall effect is highly anisotropic with respect to the orientation of the wire, and that the nature of this anisotropy depends strongly on the electron density and the relative strengths of

A W Cummings; R Akis; D K Ferry

2011-01-01

268

Fractional quantum Hall effect in AlAs quantum wells: Role of valley degree of freedom  

NASA Astrophysics Data System (ADS)

When interacting two-dimensional electrons are placed in a large perpendicular magnetic field, to minimize their energy, they capture an even number of flux quanta and create new particles called composite fermions (CFs). These complex electron-flux-bound states offer an elegant explanation for the fractional quantum Hall effect. Thanks to the flux attachment, the effective field vanishes at half-filled Landau levels (?= 1/2 and 3/2) and CFs exhibit Fermi-liquid-like properties, similar to their zero-field electron counterparts. Here, we study a two-dimensional electron system in AlAs quantum wells where the electrons occupy two conduction band valleys with anisotropic Fermi contours and strain-tunable occupation. We address a fundamental question whether the anisotropy of the electron effective mass and Fermi surface is transferred to the CFs formed around filling factors ?= 1/2 and 3/2. Similar to their electron counter parts, CFs also exhibit anisotropic transport, suggesting an anisotropy of CF effective mass and Fermi surface. We also study quantum Hall ferromagnetism for fractional quantum Hall states formed at ?= 1/3 and 5/3 as a function of valley splitting. Within the framework of the CF theory, electronic fractional filling factors ?= 1/3 and 5/3 are equivalent to the integer filling factor p= 1 of CFs. Reminiscent of the quantum Hall ferromagnetism observed at ?= 1, we report persistent fractional quantum Hall states at filling factors ?= 1/3 and 5/3 when the two valleys are degenerate. However, the comparison of the energy gaps measured at ?= 1/3 and 5/3 to the available theory developed for single-valley, two-spin systems reveals that the gaps and their rates of rise with strain are much smaller than predicted.[4pt] [1] ``Transference of Transport Anisotropy to Composite Fermions,'' T. Gokmen, M. Padmanabhan, and M. Shayegan, Nature Physics 6, 621-624 (2010).[4pt] [2] `Ferromagnetic Fractional Quantum Hall States in a Valley-Degenerate Two-Dimensional Electron System,'' M. Padmanabhan, T. Gokmen, and M. Shayegan, Phys. Rev. Lett. 104, 016805 (2010).

Gokmen, Tayfun

2013-03-01

269

Fractional quantum Hall effect in a quantum point contact at filling fraction 5/2  

NASA Astrophysics Data System (ADS)

Recent theories suggest that the quasiparticles that populate certain quantum Hall states should exhibit exotic braiding statistics that could be used to build topological quantum gates. Confined systems that support such states at a filling fraction ?=5/2 are of particular interest for testing these predictions. Here, we report transport measurements of just such a system, which consists of a quantum point contact (QPC) in a two-dimensional GaAs/AlGaAs electron gas that itself exhibits a well-developed fractional quantum Hall effect at a bulk filling fraction ?bulk=5/2. We observe plateau-like features at an effective filling fraction of ?QPC=5/2 for lithographic contact widths of 1.2?m and 0.8?m, but not 0.5?m. Transport near ?QPC=5/2 in the QPCs is consistent with a picture of chiral Luttinger-liquid edge states with inter-edge tunnelling, suggesting that an incompressible state at ?QPC=5/2 forms in this confined geometry.

Miller, Jeffrey B.; Radu, Iuliana P.; Zumbühl, Dominik M.; Levenson-Falk, Eli M.; Kastner, Marc A.; Marcus, Charles M.; Pfeiffer, Loren N.; West, Ken W.

2007-08-01

270

Cavity cooling below the recoil limit.  

PubMed

Conventional laser cooling relies on repeated electronic excitations by near-resonant light, which constrains its area of application to a selected number of atomic species prepared at moderate particle densities. Optical cavities with sufficiently large Purcell factors allow for laser cooling schemes, avoiding these limitations. Here, we report on an atom-cavity system, combining a Purcell factor above 40 with a cavity bandwidth below the recoil frequency associated with the kinetic energy transfer in a single photon scattering event. This lets us access a yet-unexplored regime of atom-cavity interactions, in which the atomic motion can be manipulated by targeted dissipation with sub-recoil resolution. We demonstrate cavity-induced heating of a Bose-Einstein condensate and subsequent cooling at particle densities and temperatures incompatible with conventional laser cooling. PMID:22767925

Wolke, Matthias; Klinner, Julian; Keßler, Hans; Hemmerich, Andreas

2012-07-01

271

Dynamical quantum Hall effect in the parameter space  

PubMed Central

Geometric phases in quantum mechanics play an extraordinary role in broadening our understanding of fundamental significance of geometry in nature. One of the best known examples is the Berry phase [M.V. Berry (1984), Proc. Royal. Soc. London A, 392:45], which naturally emerges in quantum adiabatic evolution. So far the applicability and measurements of the Berry phase were mostly limited to systems of weakly interacting quasi-particles, where interference experiments are feasible. Here we show how one can go beyond this limitation and observe the Berry curvature, and hence the Berry phase, in generic systems as a nonadiabatic response of physical observables to the rate of change of an external parameter. These results can be interpreted as a dynamical quantum Hall effect in a parameter space. The conventional quantum Hall effect is a particular example of the general relation if one views the electric field as a rate of change of the vector potential. We illustrate our findings by analyzing the response of interacting spin chains to a rotating magnetic field. We observe the quantization of this response, which we term the rotational quantum Hall effect.

Gritsev, V.; Polkovnikov, A.

2012-01-01

272

Quantum circuit analog of the dynamical Casimir effect  

NASA Astrophysics Data System (ADS)

We investigate a quantum-circuit analog of the dynamical Casimir effect discussed in cavity quantum electrodynamics (QED). A double superconducting quantum interference device (SQUID), consisting of a superconducting loop interrupted by a dc-SQUID, is regarded as a harmonic oscillator with a time-dependent frequency imitating the nonadiabatic boundaries in a cavity QED. Squeezing occurs due to parametric processes inherent in the system. We reformulate squeezing based on the Bogoliubov transformation between eigenstates at different times and derive the analytic formula for quantum-state evolutions of the system. The squeezing parameter clearly reveals the relationship between squeezing and nonadiabatic nature of the system. Thus, the squeezing parameter serves as a measure for the dynamical Casimir effect. We demonstrate squeezing for two types of frequency modulation and propose a method for measuring squeezing by using a circuit QED technique under coherent oscillations between an artificial atom and an LC circuit in the presence of dissipation. These observations suggest that a quantum circuit with a Josephson junction is a promising candidate for detecting the dynamical Casimir effect.

Fujii, Toshiyuki; Matsuo, Shigemasa; Hatakenaka, Noriyuki; Kurihara, Susumu; Zeilinger, Anton

2011-11-01

273

Dynamical quantum Hall effect in the parameter space.  

PubMed

Geometric phases in quantum mechanics play an extraordinary role in broadening our understanding of fundamental significance of geometry in nature. One of the best known examples is the Berry phase [M.V. Berry (1984), Proc. Royal. Soc. London A, 392:45], which naturally emerges in quantum adiabatic evolution. So far the applicability and measurements of the Berry phase were mostly limited to systems of weakly interacting quasi-particles, where interference experiments are feasible. Here we show how one can go beyond this limitation and observe the Berry curvature, and hence the Berry phase, in generic systems as a nonadiabatic response of physical observables to the rate of change of an external parameter. These results can be interpreted as a dynamical quantum Hall effect in a parameter space. The conventional quantum Hall effect is a particular example of the general relation if one views the electric field as a rate of change of the vector potential. We illustrate our findings by analyzing the response of interacting spin chains to a rotating magnetic field. We observe the quantization of this response, which we term the rotational quantum Hall effect. PMID:22493228

Gritsev, V; Polkovnikov, A

2012-04-09

274

Experiments with recoil ions and other considerations  

SciTech Connect

Some opportunities in collisions physics with slow, multiply charged ions are addressed. A distinction between inner and outer shell collisions is drawn. The applicability of recoil ion sources to outer shell collision systems is discussed, with emphasis on the quality of the beam desired. An example of an inner shell collision is discussed, and the usefulness of not pushing the collision energy too low is pointed out. 13 refs., 14 figs.

Cocke, C.L.

1987-01-01

275

Quantum effects in unimolecular reaction dynamics  

SciTech Connect

This work is primarily concerned with the development of models for the quantum dynamics of unimolecular isomerization and photodissociation reactions. We apply the rigorous quantum methodology of a Discrete Variable Representation (DVR) with Absorbing Boundary Conditions (ABC) to these models in an attempt to explain some very surprising results from a series of experiments on vibrationally excited ketene. Within the framework of these models, we are able to identify the experimental signatures of tunneling and dynamical resonances in the energy dependence of the rate of ketene isomerization. Additionally, we investigate the step-like features in the energy dependence of the rate of dissociation of triplet ketene to form {sup 3}B{sub 1} CH{sub 2} + {sup 1}{sigma}{sup +} CO that have been observed experimentally. These calculations provide a link between ab initio calculations of the potential energy surfaces and the experimentally observed dynamics on these surfaces. Additionally, we develop an approximate model for the partitioning of energy in the products of photodissociation reactions of large molecules with appreciable barriers to recombination. In simple bond cleavage reactions like CH{sub 3}COCl {yields} CH{sub 3}CO + Cl, the model does considerably better than other impulsive and statistical models in predicting the energy distribution in the products. We also investigate ways of correcting classical mechanics to include the important quantum mechanical aspects of zero-point energy. The method we investigate is found to introduce a number of undesirable dynamical artifacts including a reduction in the above-threshold rates for simple reactions, and a strong mixing of the chaotic and regular energy domains for some model problems. We conclude by discussing some of the directions for future research in the field of theoretical chemical dynamics.

Gezelter, J.D.

1995-12-01

276

The enhanced Stark effects of coupled quantum wells and their application to tunable IR photodetectors  

Microsoft Academic Search

A tunable asymmetric coupled quantum well far-infrared photodetector is proposed. The basic asymmetric coupled quantum wells are composed of two quantum wells separated by a thin barrier. In this way, the electron in each well interacts strongly with other electrons to achieve a large Stark tuning effect. The eigenenergies and the wave functions of the quantum-well structures are solved by

Yimin Huang; Chenhsin Lien; Tan-Fu Lei

1993-01-01

277

The enhanced Stark effects of coupled quantum wells and their application to tunable IR photodetectors  

Microsoft Academic Search

A tunable asymmetric coupled quantum well far-infrared photodetector is proposed in this paper. The basic asymmetric coupled quantum wells are composed of two quantum wells separated by a thin barrier. In this way, the electron in each well interacts strongly with other electrons to achieve a large Stark tuning effect. The eigenenergies and the wave functions of the quantum-well structures

Yimin Huang; Chenhsin Lien; Tan-Fu Lei

1993-01-01

278

Effects of reservoir squeezing on quantum systems and work extraction.  

PubMed

We establish a quantum Otto engine cycle in which the working substance contacts with squeezed reservoirs during the two quantum isochoric processes. We consider two working substances: (1) a qubit and (2) two coupled qubits. Due to the effects of squeezing, the working substance can be heated to a higher effective temperature, which leads to many interesting features different from the ordinary ones, such as (1) for the qubit as working substance, if we choose the squeezed parameters properly, the positive work can be exported even when T(H) quantum fuel is more efficient than the classical one. PMID:23214736

Huang, X L; Wang, Tao; Yi, X X

2012-11-05

279

Entangling photons via the double quantum Zeno effect  

SciTech Connect

We propose a scheme for entangling two photons via the quantum Zeno effect, which describes the inhibition of quantum evolution by frequent measurements and is based on the difference between summing amplitudes and probabilities. For a given error probability P{sub error}, our scheme requires that the one-photon loss rate {xi}{sub 1{gamma}} and the two-photon absorption rate {xi}{sub 2{gamma}} in some medium satisfy {xi}{sub 1{gamma}}/{xi}{sub 2{gamma}}=2P{sub error}{sup 2}/{pi}{sup 2}, which is significantly improved compared to previous approaches. Again based on the quantum Zeno effect, as well as coherent excitations, we present a possibility to fulfill this requirement in an otherwise linear optics setup.

Brinke, Nicolai ten; Osterloh, Andreas; Schuetzhold, Ralf [Fakultaet fuer Physik, Universitaet Duisburg-Essen, Lotharstrasse 1, D-47057 Duisburg (Germany)

2011-08-15

280

SU(4) Kondo effect in carbon nanotube quantum dots  

NASA Astrophysics Data System (ADS)

We investigate theoretically the non-equilibrium transport properties of carbon nanotube quantum dots. Owing to the two-dimensional band structure of graphene, a double orbital degeneracy plays the role of a pseudo-spin, which is entangled with the spin. Quantum fluctuations between these four degrees of freedom result in an SU(4) Kondo effect at low temperatures. This exotic Kondo effect manifests as a four-peak splitting in the non-linear conductance when an axial magnetic field is applied [1]. Recent transport experiments in carbon nanotube quantum dots [2] clearly support our theoretical findings. [1] M. S. Choi, R. Lopez and R. Aguado, cond-mat/0411665 (2004). [2] P. Jarillo-Herrero, J. Kong, H. S. J. van der Zant, C. Dekker, L. P. Kouwenhoven and S. De Franceschi, to be published (2004).

Aguado, Ramon; Choi, Mahn-Soo; Lopez, Rosa

2005-03-01

281

Effects of reservoir squeezing on quantum systems and work extraction  

NASA Astrophysics Data System (ADS)

We establish a quantum Otto engine cycle in which the working substance contacts with squeezed reservoirs during the two quantum isochoric processes. We consider two working substances: (1) a qubit and (2) two coupled qubits. Due to the effects of squeezing, the working substance can be heated to a higher effective temperature, which leads to many interesting features different from the ordinary ones, such as (1) for the qubit as working substance, if we choose the squeezed parameters properly, the positive work can be exported even when THquantum fuel is more efficient than the classical one.

Huang, X. L.; Wang, Tao; Yi, X. X.

2012-11-01

282

The spin Hall effect in a quantum gas.  

PubMed

Electronic properties such as current flow are generally independent of the electron's spin angular momentum, an internal degree of freedom possessed by quantum particles. The spin Hall effect, first proposed 40 years ago, is an unusual class of phenomena in which flowing particles experience orthogonally directed, spin-dependent forces--analogous to the conventional Lorentz force that gives the Hall effect, but opposite in sign for two spin states. Spin Hall effects have been observed for electrons flowing in spin-orbit-coupled materials such as GaAs and InGaAs (refs 2, 3) and for laser light traversing dielectric junctions. Here we observe the spin Hall effect in a quantum-degenerate Bose gas, and use the resulting spin-dependent Lorentz forces to realize a cold-atom spin transistor. By engineering a spatially inhomogeneous spin-orbit coupling field for our quantum gas, we explicitly introduce and measure the requisite spin-dependent Lorentz forces, finding them to be in excellent agreement with our calculations. This 'atomtronic' transistor behaves as a type of velocity-insensitive adiabatic spin selector, with potential application in devices such as magnetic or inertial sensors. In addition, such techniques for creating and measuring the spin Hall effect are clear prerequisites for engineering topological insulators and detecting their associated quantized spin Hall effects in quantum gases. As implemented, our system realizes a laser-actuated analogue to the archetypal semiconductor spintronic device, the Datta-Das spin transistor. PMID:23739329

Beeler, M C; Williams, R A; Jiménez-García, K; LeBlanc, L J; Perry, A R; Spielman, I B

2013-06-05

283

Loss of coherence and memory effects in quantum dynamics Loss of coherence and memory effects in quantum dynamics  

NASA Astrophysics Data System (ADS)

The last years have witnessed fast growing developments in the use of quantum mechanics in technology-oriented and information-related fields, especially in metrology, in the developments of nano-devices and in understanding highly efficient transport processes. The consequent theoretical and experimental outcomes are now driving new experimental tests of quantum mechanical effects with unprecedented accuracies that carry with themselves the concrete possibility of novel technological spin-offs. Indeed, the manifold advances in quantum optics, atom and ion manipulations, spintronics and nano-technologies are allowing direct experimental verifications of new ideas and their applications to a large variety of fields. All of these activities have revitalized interest in quantum mechanics and created a unique framework in which theoretical and experimental physics have become fruitfully tangled with information theory, computer, material and life sciences. This special issue aims to provide an overview of what is currently being pursued in the field and of what kind of theoretical reference frame is being developed together with the experimental and theoretical results. It consists of three sections: 1. Memory effects in quantum dynamics and quantum channels 2. Driven open quantum systems 3. Experiments concerning quantum coherence and/or decoherence The first two sections are theoretical and concerned with open quantum systems. In all of the above mentioned topics, the presence of an external environment needs to be taken into account, possibly in the presence of external controls and/or forcing, leading to driven open quantum systems. The open system paradigm has proven to be central in the analysis and understanding of many basic issues of quantum mechanics, such as the measurement problem, quantum communication and coherence, as well as for an ever growing number of applications. The theory is, however, well-settled only when the so-called Markovian or memoryless, approximation applies. When strong coupling or long environmental relaxation times make memory effects important for a realistic description of the dynamics, new strategies are asked for and the assessment of the general structure of non-Markovian dynamical equations for realistic systems is a crucial issue. The impact of quantum phenomena such as coherence and entanglement in biology has recently started to be considered as a possible source of the high efficiency of certain biological mechanisms, including e.g. light harvesting in photosynthesis and enzyme catalysis. In this effort, the relatively unknown territory of driven open quantum systems is being explored from various directions, with special attention to the creation and stability of coherent structures away from thermal equilibrium. These investigations are likely to advance our understanding of the scope and role of quantum mechanics in living systems; at the same time they provide new ideas for the developments of next generations of devices implementing highly efficient energy harvesting and conversion. The third section concerns experimental studies that are currently being pursued. Multidimensional nonlinear spectroscopy, in particular, has played an important role in enabling experimental detection of the signatures of coherence. Recent remarkable results suggest that coherence—both electronic and vibrational—survive for substantial timescales even in complex biological systems. The papers reported in this issue describe work at the forefront of this field, where researchers are seeking a detailed understanding of the experimental signatures of coherence and its implications for light-induced processes in biology and chemistry.

Benatti, Fabio; Floreanini, Roberto; Scholes, Greg

2012-08-01

284

Effects of quantum coherence in metalloprotein electron transfer.  

PubMed

Many intramolecular electron transfer (ET) reactions in biology are mediated by metal centers in proteins. This process is commonly described by a model of diffusive hopping according to the semiclassical theories of Marcus and Hopfield. However, recent studies have raised the possibility that nontrivial quantum mechanical effects play a functioning role in certain biomolecular processes. Here, we investigate the potential effects of quantum coherence in biological ET by extending the semiclassical model to allow for the possibility of quantum coherent phenomena using a quantum master equation based on the Holstein Hamiltonian. We test the model on the structurally defined chain of seven iron-sulfur clusters in nicotinamide adenine dinucleotide plus hydrogen:ubiquinone oxidoreductase (complex I), a crucial respiratory enzyme and one of the longest chains of metal centers in biology. Using experimental parameters where possible, we find that, in limited circumstances, a small quantum mechanical contribution can provide a marked increase in the ET rate above the semiclassical diffusive-hopping rate. Under typical biological conditions, our model reduces to well-known diffusive behavior. PMID:23030959

Dorner, Ross; Goold, John; Heaney, Libby; Farrow, Tristan; Vedral, Vlatko

2012-09-26

285

Effects of quantum coherence in metalloprotein electron transfer  

NASA Astrophysics Data System (ADS)

Many intramolecular electron transfer (ET) reactions in biology are mediated by metal centers in proteins. This process is commonly described by a model of diffusive hopping according to the semiclassical theories of Marcus and Hopfield. However, recent studies have raised the possibility that nontrivial quantum mechanical effects play a functioning role in certain biomolecular processes. Here, we investigate the potential effects of quantum coherence in biological ET by extending the semiclassical model to allow for the possibility of quantum coherent phenomena using a quantum master equation based on the Holstein Hamiltonian. We test the model on the structurally defined chain of seven iron-sulfur clusters in nicotinamide adenine dinucleotide plus hydrogen:ubiquinone oxidoreductase (complex I), a crucial respiratory enzyme and one of the longest chains of metal centers in biology. Using experimental parameters where possible, we find that, in limited circumstances, a small quantum mechanical contribution can provide a marked increase in the ET rate above the semiclassical diffusive-hopping rate. Under typical biological conditions, our model reduces to well-known diffusive behavior.

Dorner, Ross; Goold, John; Heaney, Libby; Farrow, Tristan; Vedral, Vlatko

2012-09-01

286

Quantum interference effects in linear and nonlinear optics  

NASA Astrophysics Data System (ADS)

In this thesis, the effects of quantum interference on the linear and nonlinear optical properties of various media are investigated. The first part deals with the implementation of the well- known induced transparency in semiconductor structures. Quantum interference is realized by coherent resonant tunneling between collective intersubband resonances. The first observation of destructive quantum interference of such transitions in the GaAs/AlGaAs material system is reported. According to the means of coherent coupling, the phenomenon is termed tunneling induced transparency. It is shown that interference occurs between eigenstates of collective excitations rather than single electron states. It is shown that the strength of the effect is limited by interface roughness of the quantum wells. The temperature dependence of the interference is investigated and reduced absorption is shown to persist up to room temperature. Intersubband emission measurements in the midinfrared are presented. The results and problems associated with the observation of quantum interference in emission are discussed. The theory for quantum interference in the second order nonlinear response of coherently coupled quantum wells is developed. The existence of constructive interference for the second order susceptibility is demonstrated for several types of structures. A comparison with conventional nonlinear intersubband schemes is carried out and the conditions for improvement due to interference are derived. Second harmonic generation measurements on a sample with quantum interference are described. A novel nonlinear measurement technique for second harmonic experiments in semiconductors is introduced. In the second part, a novel quantum interference scheme for third order nonlinearities is described. It is demonstrated that Kerr nonlinearities in a two photon absorption limited scheme are resonantly enhanced and improve efficiencies by many orders of magnitude. The cw and bandwidth dependent properties of such giant Kerr nonlinearities are determined in detail and compared to a conventional scheme. Significant improvement is found for bandwidths up to the GHz range. Finally, the application of these nonlinearities for strong photon-photon interactions in a nonlinear cavity is discussed. Using Monte Carlo wave function simulations, the effects of photon blockade, nonclassical detector statistics, and photonic pi-pulses are demonstrated.

Schmidt, Holger

1999-10-01

287

Robust generation of entanglement in Bose-Einstein condensates by collective atomic recoil  

SciTech Connect

We address the dynamics induced by collective atomic recoil in a Bose-Einstein condensate in the presence of radiation losses and atomic decoherence. In particular, we focus on the linear regime of the lasing mechanism, and analyze the effects of losses and decoherence on the generation of entanglement. The dynamics is that of three bosons, two atomic modes interacting with a single-mode radiation field, coupled with a bath of oscillators. The resulting three-mode dissipative Master equation is solved analytically in terms of the Wigner function. We examine in details the two complementary limits of high-Q cavity and bad cavity, the latter corresponding to the so-called superradiant regime, both in the quasiclassical and quantum regimes. We found that three-mode entanglement as well as two-mode atom-atom and atom-radiation entanglement is generally robust against losses and decoherence, thus making the present system a good candidate for the experimental observation of entanglement in condensate systems. In particular, steady-state entanglement may be obtained both between atoms with opposite momenta and between atoms and photons.

Cola, Mary M.; Paris, Matteo G.A.; Piovella, Nicola [Dipartimento di Fisica dell'Universita di Milano and INFN and INFM at Universita di Milano, Via Celoria 16, Milan I-20133 (Italy)

2004-10-01

288

Universal Binding and Recoil Corrections to Bound State g Factors in Hydrogenlike Ions  

SciTech Connect

The leading relativistic and recoil corrections to bound state g factors of particles with arbitrary spin are calculated. It is shown that these corrections are universal for any spin and depend only on the free particle gyromagnetic ratios. To prove this universality we develop nonrelativistic quantum electrodynamics (NRQED) for charged particles with an arbitrary spin. The coefficients in the NRQED Hamiltonian for higher spin particles are determined only by the requirements of Lorentz invariance and local charge conservation in the respective relativistic theory. For spin one charged particles, the NRQED Hamiltonian follows from the renormalizable QED of the charged vector bosons. We show that universality of the leading relativistic and recoil corrections can be explained with the help of the Bargmann-Michael-Telegdi equation.

Eides, Michael I.; Martin, Timothy J. S. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States)

2010-09-03

289

Anisotropic intrinsic spin Hall effect in quantum wires.  

PubMed

We use numerical simulations to investigate the spin Hall effect in quantum wires in the presence of both Rashba and Dresselhaus spin-orbit coupling. We find that the intrinsic spin Hall effect is highly anisotropic with respect to the orientation of the wire, and that the nature of this anisotropy depends strongly on the electron density and the relative strengths of the Rashba and Dresselhaus spin-orbit couplings. In particular, at low densities, when only one subband of the quantum wire is occupied, the spin Hall effect is strongest for electron momentum along the [N110] axis, which is the opposite of what is expected for the purely 2D case. In addition, when more than one subband is occupied, the strength and anisotropy of the spin Hall effect can vary greatly over relatively small changes in electron density, which makes it difficult to predict which wire orientation will maximize the strength of the spin Hall effect. These results help to illuminate the role of quantum confinement in spin-orbit-coupled systems, and can serve as a guide for future experimental work on the use of quantum wires for spin-Hall-based spintronic applications. PMID:22052818

Cummings, A W; Akis, R; Ferry, D K

2011-11-03

290

Vector correlations in photodissociation of polarized polyatomic molecules beyond the axial recoil limit.  

PubMed

We present the full quantum mechanical theory of the angular momentum distributions of photofragments produced in photolysis of oriented/aligned parent polyatomic molecules beyond the axial recoil limit. This paper generalizes the results of Underwood and Powis(28,29) to the case of non-axial recoil photodissociation of an arbitrary polyatomic molecule. The spherical tensor approach is used throughout this paper. We show that the recoil angular distribution of the angular momentum polarization of each of the photofragments can be presented in a universal spherical tensor form valid for photolysis in diatomic or polyatomic molecules, irrespective of the reaction mechanism. The angular distribution can be written as an expansion over the Wigner D-functions in terms of the set of the anisotropy-transforming coefficients c(K(i)q(i))(K) (k(d), K(0)) which contain all of the information about the photodissociation dynamics and can be either determined from experiment, or computed from quantum mechanical theory. An important new conservation rule is revealed through the analysis, namely that the component q(i) of the initial reagent polarization rank K(i) and the photofragment polarization rank K onto the photofragment recoil direction k is preserved in any photolysis reaction. Both laboratory and body frame expressions for the recoil angle dependence of the photofragment angular momentum polarization are presented. The parent molecule polarization is shown to lead to new terms in the obtained photofragment angular distributions compared with the isotropic case. In particular, the terms with |q(i)| > 2 can appear which are shown to manifest angular momentum helicity non-conservation in the reaction. The expressions for the coefficients c(K(i)q(i))(K) (k(d), K(0)) have been simplified using the quasiclassical approximation in the high-J limit which allows for introducing the dynamical functions and the rotation factors which describe the decreasing of the photofragment angular momentum orientation and alignment due to the rotation of the molecular axis during photodissociation. In this case, the resultant recoil angle dependence is also presented in a form where the anisotropy of the parent molecular ensemble is expressed in terms of the molecular axis distribution, rather than in terms of the molecular density matrix. PMID:21152623

Krasilnikov, Mikhail B; Kuznetsov, Vladislav V; Suits, Arthur G; Vasyutinskii, Oleg S

2010-12-13

291

Surface Termination Effects on Zinc Oxide Quantum Dots.  

NASA Astrophysics Data System (ADS)

We investigate the effects of surface terminations on the optical properties of 2-6 nm ZnO quantum dots. Nanocrystals were grown by wet chemical synthesis in a short-chain alcohol solvent from zinc acetate and sodium hydroxide. Quenching of particle growth with various capping agents is necessary to maintain and enhance the unique characteristics of the nanocrystals. We reproduce results of previous work and expand on characterization of naked and surface terminated ZnO quantum dots. The nanoparticle properties were investigated by UV absorption spectrophotometry, photoluminescence, infrared spectroscopy, scanning electron microscopy , and atomic force microscopy techniques.

Whitesell, Steve; Spalenka, Joe; Jack, Christopher; Allen, Cary; Collins, Reuben; Furtak, Thomas

2007-03-01

292

Nuclear Quantum Vibrational Effects in Shock Hugoniot Temperatures  

SciTech Connect

We present a straightforward method for the inclusion of quantum nuclear vibrational effects in molecular dynamics calculations of shock Hugoniot temperatures. Using a Grueneisen equation of state and a quasiharmonic approximation to the vibrational energies, we derive a simple, post-processing method for calculation of the quantum corrected Hugoniot temperatures. We have used our novel technique on ab initio simulations of shock compressed water. Our results indicate significantly closer agreement with all available experimental temperature data. Our formalism and technique can be easily applied to a number of different shock compressed molecular liquids or solids.

Goldman, N; Reed, E; Fried, L E

2009-07-23

293

Macroscopic quantum tunneling and the 'cosmic' Josephson effect  

SciTech Connect

We discuss the possible influence of a cosmic magnetic field on the macroscopic quantum tunneling process associated, in a cosmological context, to the decay of the 'false vacuum'. We find a close analogy with the effects of an external magnetic field applied to a Josephson junction in the context of low-temperature/high-temperature superconducting devices.

Barone, A. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', CNR-SPIN, Piazzale Tecchio 21, 80125 Napoli (Italy); Gasperini, M. [Dipartimento di Fisica, Universita di Bari, Via G. Amendola 173, 70126 Bari (Italy); INFN, Sezione di Bari, Bari (Italy); Rotoli, G. [Dipartimento di Ingegneria dell'Informazione, Seconda Universita di Napoli (SUN), Via Roma 29, 81031 Aversa (CE) (Italy)

2010-10-15

294

Three dimensional quantum effects in NanoMOSFETs  

Microsoft Academic Search

In this paper, a three dimensional numerical model of a uniformly doped nanoscale MOSFET device considering the quantum-mechanical effects has been presented. The 3D Poissonpsilas equation in the space charge region coupled with 3D Schrodinger equation has been solved numerically using Leibmannpsilas iteration method. The exact potential profile and electric field profile were estimated from the set of physics based

R. Ramesh; M. Madheswaran; K. Kannan

2008-01-01

295

Anomalous Kondo Effect in a Quantum Dot at Nonzero Bias  

Microsoft Academic Search

We present measurements on the Kondo effect in a small quantum dot connected strongly to one lead and weakly to the other. The conductance of the dot reveals an offset of the Kondo resonance at zero magnetic field. While the resonance persists in the negative bias regime, it is suppressed in the opposite direction. This demonstrates the pinning of the

F. Simmel; R. H. Blick; J. P. Kotthaus; W. Wegscheider; M. Bichler

1999-01-01

296

Strong supersymmetric quantum effects on the top quark width  

Microsoft Academic Search

We compute the one-loop supersymmetric QCD quantum effects on the width ?(t ? W+b) of the canonical main decay of the top quark within the framework of the MSSM. The corrections can be of either sign depending on whether the stop squark mass is above or below the top quark decay threshold into stop and gluino ?(t ? tg). For

Andreas Dabelstein; Wolfgang Hollik; Christoph Jünger; Ricardo A. Jiménez; Joan Solà

1995-01-01

297

The noncommutative geometry of the quantum Hall effect  

Microsoft Academic Search

We give an overview of the Integer Quantum Hall Effect. We propose a mathematical framework using Non-Commutative Geometry as defined by A. Connes. Within this framework, it is proved that the Hall conductivity is quantized and that plateaux occur when the Fermi energy varies in a region of localized states.

J. Bellissard; A. van Elst; H. Schulz-Baldes

1994-01-01

298

Quantum tunnelling effect for the inverted Caldirola-Kanai Hamiltonian  

Microsoft Academic Search

In order to study the behaviour of the inverted Caldirola-Kanai Hamiltonian in the quantum tunnelling effect, the authors consider a wavepacket as the initial state and they calculate exactly the probability density. They also obtain the transmission and reflection probability, the expectation value of the particle's energy and the sojourn time which appears to be an increasing function of the

S. Baskoutas; A. Jannussis

1992-01-01

299

CT-Invariant Quantum Spin Hall Effect in Ferromagnetic Graphene  

Microsoft Academic Search

We predict a quantum spin Hall effect (QSHE) in ferromagnetic graphene under a magnetic field. Unlike the previous QSHE, this QSHE appears in the absence of spin-orbit interaction and thus, is arrived at from a different physical origin. The previous QSHE is protected by the time-reversal (T) invariance. This new QSHE is protected by CT invariance, where C is the

Qing-Feng Sun; X. C. Xie

2010-01-01

300

Mesoscopic effects in quantum phases of ultracold quantum gases in optical lattices  

NASA Astrophysics Data System (ADS)

We present a wide array of quantum measures on numerical solutions of one-dimensional Bose- and Fermi-Hubbard Hamiltonians for finite-size systems with open boundary conditions. Finite-size effects are highly relevant to ultracold quantum gases in optical lattices, where an external trap creates smaller effective regions in the form of the celebrated “wedding cake” structure and the local density approximation is often not applicable. Specifically, for the Bose-Hubbard Hamiltonian we calculate number, quantum depletion, local von Neumann entropy, generalized entanglement or Q measure, fidelity, and fidelity susceptibility; for the Fermi-Hubbard Hamiltonian we also calculate the pairing correlations, magnetization, charge-density correlations, and antiferromagnetic structure factor. Our numerical method is imaginary time propagation via time-evolving block decimation. As part of our study we provide a careful comparison of canonical versus grand canonical ensembles and Gutzwiller versus entangled simulations. The most striking effect of finite size occurs for bosons: we observe a strong blurring of the tips of the Mott lobes accompanied by higher depletion, and show how the location of the first Mott lobe tip approaches the thermodynamic value as a function of system size.

Carr, L. D.; Wall, M. L.; Schirmer, D. G.; Brown, R. C.; Williams, J. E.; Clark, Charles W.

2010-01-01

301

Effect of uniform acceleration on multiplayer quantum game  

NASA Astrophysics Data System (ADS)

We investigate the influence of the Unruh effect on three-qubit quantum games. In particular, we interpret the quantum Prisoners’ Dilemma, which is a famous, non-zero sum game both for entangled and unentangled initial states and show that the acceleration of non-inertial frames disturbs the symmetry of the game. Using the various strategies, the novel Nash equilibrium is obtained at infinite acceleration (r = ?/4). As a remarkable point, it is shown that in our three-player system, in contrast to the two-player quantum game in non-inertial frames (see Khan et al 2011 J. Phys. A: Math. Theor. 44 355302), there is not a dominant strategy (even classical strategy) in the game and choosing the quantum strategy by each player can be the dominant strategy depending on the kind of strategy chosen by others. Since the entangled states of particles play an important role in the quantum game, finally we argue that the results of the players depend on the degree of entanglement in the initial state of the game.

Goudarzi, H.; Beyrami, S.

2012-06-01

302

Unification of dynamical decoupling and the quantum Zeno effect  

SciTech Connect

We unify the quantum Zeno effect (QZE) and the 'bang-bang' (BB) decoupling method for suppressing decoherence in open quantum systems: in both cases strong coupling to an external system or apparatus induces a dynamical superselection rule that partitions the open system's Hilbert space into quantum Zeno subspaces. Our unification makes use of von Neumann' s ergodic theorem and avoids making any of the symmetry assumptions usually made in discussions of BB. Thus we are able to generalize the BB to arbitrary fast and strong pulse sequences, requiring no symmetry, and to show the existence of two alternatives to a pulsed BB: continuous decoupling and pulsed measurements. Our unified treatment enables us to derive limits on the efficacy of the BB method: we explicitly show that the inverse QZE implies that the BB can in some cases accelerate, rather than inhibit, decoherence.

Facchi, P.; Pascazio, S. [Dipartimento di Fisica, Universita di Bari I-70126 Bari (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Bari, I-70126 Bari (Italy); Lidar, D.A. [Chemical Physics Theory Group, Chemistry Department, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6 (Canada)

2004-03-01

303

Linear and nonlinear electrostatic modes in a strongly coupled quantum plasma  

SciTech Connect

The properties of linear and nonlinear electrostatic waves in a strongly coupled electron-ion quantum plasma are investigated. In this study, the inertialess electrons are degenerate, while non-degenerate inertial ions are strongly correlated. The ion dynamics is governed by the continuity and the generalized viscoelastic momentum equations. The quantum forces associated with the quantum statistical pressure and the quantum recoil effect act on the degenerate electron fluid, whereas strong ion correlation effects are embedded in generalized viscoelastic momentum equation through the viscoelastic relaxation of ion correlations and ion fluid shear viscosities. Hence, the spectra of linear electrostatic modes are significantly affected by the strong ion coupling effect. In the weakly nonlinear limit, due to ion-ion correlations, the quantum plasma supports a dispersive shock wave, the dynamics of which is governed by the Korteweg-de Vries Burgers' equation. For a particular value of the quantum recoil effect, only monotonic shock structure is observed. Possible applications of our investigation are briefly mentioned.

Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064 (India); Shukla, P. K. [International Center for Advanced Studies in Physical Sciences and Institute for Theoretical Physics, Faculty of Physics and Astronomy, Ruhr University Bochum, D-44780 Bochum, Germany and Department of Mechanical and Aerospace Engineering and Centre for Energy Research, University of California San Diego, La Jolla, California 92093 (United States)

2012-07-15

304

Semi-inclusive deep-inelastic scattering off few-nucleon systems: Tagging the EMC effect and hadronization mechanisms with detection of slow recoiling nuclei  

NASA Astrophysics Data System (ADS)

The semi-inclusive deep-inelastic scattering of electrons off H2 and He3 with detection of slow protons and deuterons, respectively, i.e., the processes 2H(e,e'p)X and 3He(e,e'd)X, are calculated within the spectator mechanism, taking into account the final state interaction of the nucleon debris with the detected protons and deuterons. It is shown that by a proper choice of the kinematics the origin of the EMC effect and the details of the interaction between the hadronizing quark and the nuclear medium can be investigated at a level which cannot be reached by inclusive deep-inelastic scattering. A comparison of the results of our calculations, containing no adjustable parameters, with recently available experimental data on the process 2H(e,e'p)X shows a good agreement in the backward hemisphere of the emitted nucleons. Theoretical predictions at energies that will be available at the upgraded Thomas Jefferson National Accelerator Facility are presented, and the possibility to investigate the proposed semi-inclusive processes at electron-ion colliders is briefly discussed.

Ciofi Degli Atti, C.; Kaptari, L. P.

2011-04-01

305

The Distribution of Recoil Velocities from Merging Black Holes  

NASA Astrophysics Data System (ADS)

We calculate the linear momentum flux from merging black holes (BHs) with arbitrary masses and spin orientations, using the effective-one-body (EOB) model. This model includes an analytic description of the inspiral phase, a short merger, and a superposition of exponentially damped quasi-normal ring-down modes of a Kerr BH. By varying the matching point between inspiral and ring-down, we can estimate the systematic errors generated with this method. Within these confidence limits, we find close agreement with previously reported results from numerical relativity. Using a Monte Carlo implementation of the EOB model, we are able to sample a large volume of BH parameter space and estimate the distribution of recoil velocities. For a range of mass ratios 1<=m1/m2<=10, spin magnitudes of a1,2=0.9, and uniform random spin orientations, we find that a fraction f500=0.12+0.06-0.05 of binaries have recoil velocities greater than 500 km s-1 and that a fraction f1000=0.027+0.021-0.014 of binaries have kicks greater than 1000 km s-1. These velocities likely are capable of ejecting the final BH from its host galaxy. Limiting the sample to comparable-mass binaries with m1/m2<=4, the typical kicks are even larger, with f500=0.31+0.13-0.12 and f1000=0.079+0.062-0.042.

Schnittman, Jeremy D.; Buonanno, Alessandra

2007-06-01

306

Large size self-assembled quantum rings: quantum size effect and modulation on the surface diffusion  

NASA Astrophysics Data System (ADS)

We demonstrate experimentally the submicron size self-assembled (SA) GaAs quantum rings (QRs) by quantum size effect (QSE). An ultrathin In0.1 Ga0.9As layer with different thickness is deposited on the GaAs to modulate the surface nucleus diffusion barrier, and then the SA QRs are grown. It is found that the density of QRs is affected significantly by the thickness of inserted In0.1 Ga0.9As, and the diffusion barrier modulation reflects mainly on the first five monolayer . The physical mechanism behind is discussed. The further analysis shows that about 160 meV decrease in diffusion barrier can be achieved, which allows the SA QRs with density of as low as one QR per 6 ?m2. Finally, the QRs with diameters of 438 nm and outer diameters of 736 nm are fabricated using QSE.

Tong, Cunzhu; Yoon, Soon Fatt; Wang, Lijun

2012-09-01

307

Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve  

PubMed Central

Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively. PACS numbers:

2011-01-01

308

On the Existence of Quantum Wave Function and Quantum Interference Effects in Mental States: An Experimental Confirmation during Perception and Cognition in Humans  

Microsoft Academic Search

We introduce the quantum theoretical formulation to determine a posteriori, if existing, the quantum wave functions and to estimate the quantum interference effects of mental states. Such quantum features are actually found in the case of an experiment involving the perception and the cognition in humans. Also some specific psychological variables are introduced and it is obtained that they characterize

Elio Conte; Andrei Yuri Khrennikov; Orlando Todarello; Antonio Federici; Joseph P. Zbilut

2008-01-01

309

Thermal recoil force, telemetry, and the Pioneer anomaly  

SciTech Connect

Precision navigation of spacecraft requires accurate knowledge of small forces, including the recoil force due to anisotropies of thermal radiation emitted by spacecraft systems. We develop a formalism to derive the thermal recoil force from the basic principles of radiative heat exchange and energy-momentum conservation. The thermal power emitted by the spacecraft can be computed from engineering data obtained from flight telemetry, which yields a practical approach to incorporate the thermal recoil force into precision spacecraft navigation. Alternatively, orbit determination can be used to estimate the contribution of the thermal recoil force. We apply this approach to the Pioneer anomaly using a simulated Pioneer 10 Doppler data set.

Toth, Viktor T.; Turyshev, Slava G. [Ottawa, Ontario K1N 9H5 (Canada); Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States)

2009-02-15

310

A novel method for modeling the recoil in W boson events at hadron colliders  

Microsoft Academic Search

We present a new method for modeling the hadronic recoil in W??? events produced at hadron colliders. The recoil is chosen from a library of recoils in Z??? data events and overlaid on a simulated W??? event. Implementation of this method requires that the data recoil library describe the properties of the measured recoil as a function of the true,

Victor Mukhamedovich Abazov; Braden Keim Abbott; Maris A. Abolins; Bannanje Sripath Acharya; Mark Raymond Adams; Todd Adams; Ernest Aguilo; Mahsana Ahsan; Guennadi D. Alexeev; Georgiy D. Alkhazov; Andrew K. Alton; G. Alverson; L. S. Ancu; T. Andeen; M. S. Anzelc; M. Aoki; Y. Arnoud; M. Arov; M. Arthaud; A. Askew; B. Åsman; O. Atramentov; C. Avila; J. BackusMayes; F. Badaud; L. Bagby; B. Baldin; D. V. Bandurin; S. Banerjee; E. Barberis; A.-F. Barfuss; P. Bargassa; J. Barreto; J. F. Bartlett; U. Bassler; D. Bauer; S. Beale; A. Bean; M. Begalli; C. Belanger-Champagne; L. Bellantoni; A. Bellavance; J. A. Benitez; S. B. Beri; G. Bernardi; R. Bernhard; I. Bertram; M. Besançon; R. Beuselinck; V. A. Bezzubov; P. C. Bhat; V. Bhatnagar; G. Blazey; S. Blessing; K. Bloom; A. Boehnlein; D. Boline; T. A. Bolton; E. E. Boos; G. Borissov; T. Bose; A. Brandt; R. Brock; G. Brooijmans; A. Bross; D. Brown; X. B. Bu; D. Buchholz; M. Buehler; V. Buescher; V. Bunichev; S. Burdin; T. H. Burnett; C. P. Buszello; P. Calfayan; B. Calpas; S. Calvet; J. Cammin; M. A. Carrasco-Lizarraga; E. Carrera; W. Carvalho; B. C. K. Casey; H. Castilla-Valdez; S. Chakrabarti; D. Chakraborty; K. M. Chan; A. Chandra; E. Cheu; D. K. Cho; S. W. Cho; S. Choi; B. Choudhary; T. Christoudias; S. Cihangir; D. Claes; J. Clutter; M. Cooke; W. E. Cooper; M. Corcoran; F. Couderc; M.-C. Cousinou; D. Cutts; M. ?wiok; A. Das; G. Davies; K. De; S. J. de Jong; E. De La Cruz-Burelo; K. DeVaughan; F. Déliot; M. Demarteau; R. Demina; D. Denisov; S. P. Denisov; S. Desai; H. T. Diehl; M. Diesburg; A. Dominguez; T. Dorland; A. Dubey; L. V. Dudko; D. Duggan; A. Duperrin; S. Dutt; A. Dyshkant; M. Eads; D. Edmunds; J. Ellison; V. D. Elvira; Y. Enari; S. Eno; M. Escalier; H. Evans; A. Evdokimov; V. N. Evdokimov; G. Facini; A. V. Ferapontov; T. Ferbel; F. Fiedler; F. Filthaut; W. Fisher; H. E. Fisk; M. Fortner; H. Fox; S. Fu; S. Fuess; T. Gadfort; C. F. Galea; A. Garcia-Bellido; V. Gavrilov; P. Gay; W. Geist; C. E. Gerber; Y. Gershtein; D. Gillberg; G. Ginther; B. Gómez; A. Goussiou; P. D. Grannis; S. Greder; H. Greenlee; Z. D. Greenwood; E. M. Gregores; G. Grenier; Ph. Gris; J.-F. Grivaz; A. Grohsjean; S. Grünendahl; M. W. Grünewald; F. Guo; J. Guo; G. Gutierrez; P. Gutierrez; A. Haas; P. Haefner; S. Hagopian; J. Haley; I. Hall; R. E. Hall; L. Han; K. Harder; A. Harel; J. M. Hauptman; J. Hays; T. Hebbeker; D. Hedin; J. G. Hegeman; A. P. Heinson; U. Heintz; C. Hensel; I. Heredia-De La Cruz; K. Herner; G. Hesketh; M. D. Hildreth; R. Hirosky; T. Hoang; J. D. Hobbs; B. Hoeneisen; M. Hohlfeld; S. Hossain; P. Houben; Y. Hu; Z. Hubacek; N. Huske; V. Hynek; I. Iashvili; R. Illingworth; A. S. Ito; S. Jabeen; M. Jaffré; S. Jain; K. Jakobs; D. Jamin; R. Jesik; K. Johns; C. Johnson; M. Johnson; D. Johnston; A. Jonckheere; P. Jonsson; A. Juste; E. Kajfasz; D. Karmanov; P. A. Kasper; I. Katsanos; V. Kaushik; R. Kehoe; S. Kermiche; N. Khalatyan; A. Khanov; A. Kharchilava; Y. N. Kharzheev; D. Khatidze; M. H. Kirby; M. Kirsch; B. Klima; J. M. Kohli; J.-P. Konrath; A. V. Kozelov; J. Kraus; T. Kuhl; A. Kumar; A. Kumar; T. Kur?a; V. A. Kuzmin; J. Kvita; F. Lacroix; D. Lam; S. Lammers; G. Landsberg; P. Lebrun; H. S. Lee; W. M. Lee; A. Leflat; J. Lellouch; L. Li; Q. Z. Li; S. M. Lietti; J. K. Lim; D. Lincoln; J. Linnemann; V. V. Lipaev; R. Lipton; Y. Liu; Z. Liu; A. Lobodenko; M. Lokajicek; P. Love; H. J. Lubatti; R. Luna-Garcia; A. L. Lyon; A. K. A. Maciel; D. Mackin; P. Mättig; R. Magaña-Villalba; P. K. Mal; S. Malik; V. L. Malyshev; Y. Maravin; B. Martin; R. McCarthy; C. L. McGivern; M. M. Meijer; A. Melnitchouk; L. Mendoza; D. Menezes; P. G. Mercadante; M. Merkin; K. W. Merritt; A. Meyer; J. Meyer; N. K. Mondal; H. E. Montgomery; R. W. Moore; T. Moulik; G. S. Muanza; M. Mulhearn; O. Mundal; L. Mundim; E. Nagy; M. Naimuddin; H. A. Neal; J. P. Negret; P. Neustroev; H. Nilsen; S. F. Novaes; T. Nunnemann; G. Obrant; C. Ochando; D. Onoprienko; J. Orduna; N. Oshima; J. Osta; R. Otec; G. J. Otero y Garzón; M. Owen; M. Padilla; P. Padley; M. Pangilinan; N. Parashar; S.-J. Park; J. Parsons; R. Partridge; N. Parua; A. Patwa; B. Penning; M. Perfilov; K. Peters; Y. Peters; P. Pétroff; R. Piegaia; J. Piper; M.-A. Pleier; P. L. M. Podesta-Lerma; V. M. Podstavkov; Y. Pogorelov; M.-E. Pol; P. Polozov; A. V. Popov; M. Prewitt; S. Protopopescu; J. Qian; A. Quadt; B. Quinn; A. Rakitine; M. S. Rangel; K. Ranjan; P. N. Ratoff; P. Renkel; M. Rijssenbeek; I. Ripp-Baudot; F. Rizatdinova; S. Robinson; M. Rominsky; C. Royon; P. Rubinov; R. Ruchti; G. Safronov; A. Sánchez-Hernández; M. P. Sanders; B. Sanghi; G. Savage; L. Sawyer; T. Scanlon; D. Schaile; R. D. Schamberger; Y. Scheglov; H. Schellman; T. Schliephake; S. Schlobohm; C. Schwanenberger; R. Schwienhorst; J. Sekaric; H. Severini; E. Shabalina; M. Shamim; V. Shary; A. A. Shchukin; R. K. Shivpuri

2009-01-01

311

Quantum spin Hall effect in nanostructures based on cadmium fluoride  

SciTech Connect

Tunneling current-voltage (I-V) characteristics and temperature dependences of static magnetic susceptibility and specific heat of the CdB{sub x}F{sub 2-x}/p-CdF{sub 2}-QW/CdB{sub x}F{sub 2-x} planar sandwich structures formed on the surface of an n-CdF{sub 2} crystal have been studied in order to identify superconducting properties of the CdB{sub x}F{sub 2-x} {delta} barriers confining the p-type CdF{sub 2} ultranarrow quantum well. Comparative analysis of current-voltage (I-V) characteristics and conductance-voltage dependences (measured at the temperatures, respectively, below and above the critical temperature of superconducting transition) indicates that there is an interrelation between quantization of supercurrent and dimensional quantization of holes in the p-CdF{sub 2} ultranarrow quantum well. It is noteworthy that detection of the Josephson peak of current in each hole subband is accompanied by the appearance of the spectrum of the multiple Andreev reflection (MAR). A high degree of spin polarization of holes in the edge channels along the perimeter of the p-CdF{sub 2} ultranarrow quantum well appears as a result of MAR and makes it possible to identify the quantum spin Hall effect I-V characteristics; this effect becomes pronounced in the case of detection of nonzero conductance at the zero voltage applied to the vertical gate in the Hall geometry of the experiment. Within the energy range of superconducting gap, the I-V characteristics of the spin transistor and quantum spin Hall effect are controlled by the MAR spectrum appearing as the voltage applied to the vertical gate is varied. Beyond the range of the superconducting gap, the observed I-V characteristic of the quantum spin Hall effect is represented by a quantum conductance staircase with a height of the steps equal to e{sub 2}/h; this height is interrelated with the Aharonov-Casher oscillations of longitudinal and depends on the voltage applied to the vertical gate.

Bagraev, N. T., E-mail: Bagraev@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Guimbitskaya, O. N. [St. Petersburg State Polytechnical University (Russian Federation); Klyachkin, L. E.; Koudryavtsev, A. A.; Malyarenko, A. M. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Romanov, V. V. [St. Petersburg State Polytechnical University (Russian Federation); Ryskin, A. I.; Shcheulin, A. S. [St. Petersburg State University of Information Technologies, Mechanics, and Optics (Russian Federation)

2010-10-15

312

Quantum effects in five-dimensional Kaluza-Klein theory  

Microsoft Academic Search

The role of quantum effects in five-dimensional Kaluza-Klein theory is discussed. We concentrate in particular on the evaluation of terms in the one-loop effective action which look like the Maxwell action. A detailed discussion of the reduction of the five-dimensional gravitational action to an equivalent four-dimensional form is given. Self-consistent solutions of the form R4 x S1 are examined. We

S. R. Huggins; D. J. Toms

1986-01-01

313

``Interaction--free'' interaction: entangling evolution via quantum Zeno effect  

Microsoft Academic Search

The effect of entangling evolution induced by frequently repeated quantum\\u000ameasurement is presented. The interesting possibility of conditional freezing\\u000athe system in maximally entangled state out of Zeno effect regime is also\\u000arevealed. The illustration of the phenomena in terms of dynamical version of\\u000a``interaction free'' measurement is presented. Some general conclusions are\\u000aprovided.

Pawel Horodecki

1998-01-01

314

An effective quantum parameter for strongly correlated metallic ferromagnets.  

PubMed

The correlated motion of electrons in metallic ferromagnets is investigated in terms of a realistic interacting-electron model with N-fold orbital degeneracy and intra-orbital (U) and inter-orbital (J) Coulomb interactions. Correlation-induced self-energy and vertex corrections are incorporated systematically to provide a non-perturbative Goldstone-mode-preserving scheme. An effective quantum parameter [U2+(N-1)J2]/[U+(N-1)J]2 is obtained which determines, in analogy with 1/S for quantum spin systems and 1/N for the N-orbital Hubbard model, the strength of correlation-induced quantum corrections to magnetic excitations. The rapid suppression of this quantum parameter with Hund's coupling J, especially for large N, provides fundamental insight into the phenomenon of strong stabilization of metallic ferromagnetism by orbital degeneracy and Hund's coupling. Correlation effects are investigated for spin stiffness, magnon dispersion, electronic spectral function, density of states, and finite-temperature spin dynamics using realistic bandwidth, interaction, and lattice parameters for iron. PMID:22277778

Kamble, Bhaskar; Singh, Avinash

2012-01-26

315

Unraveling quantum mechanical effects in water using isotopic fractionation  

PubMed Central

When two phases of water are at equilibrium, the ratio of hydrogen isotopes in each is slightly altered because of their different phase affinities. This isotopic fractionation process can be utilized to analyze water’s movement in the world’s climate. Here we show that equilibrium fractionation ratios, an entirely quantum mechanical property, also provide a sensitive probe to assess the magnitude of nuclear quantum fluctuations in water. By comparing the predictions of a series of water models, we show that those describing the OH chemical bond as rigid or harmonic greatly overpredict the magnitude of isotope fractionation. Models that account for anharmonicity in this coordinate are shown to provide much more accurate results because of their ability to give partial cancellation between inter- and intramolecular quantum effects. These results give evidence of the existence of competing quantum effects in water and allow us to identify how this cancellation varies across a wide-range of temperatures. In addition, this work demonstrates that simulation can provide accurate predictions and insights into hydrogen fractionation.

Markland, Thomas E.; Berne, B. J.

2012-01-01

316

Additional Dirac Matrix in Quantum Hall Effect  

SciTech Connect

We find that the predictions of the Dirac equation agree with the idea of fractional charges. We have introduced the combination of spin and orbital quantum numbers, including the negative sign for spin, in such a way that there occur fractional charges through the Bohr magneton. This leads to doubling of eigen values so that we define an additional matrix the properties of which are important when magnetic field is present. There is a spin-charge coupling so that spin (1/2) particle can have the zero or one charge. The Dirac equation can accommodate not only charges of 0 and {+-}e but also fractional values such as 1/3 and 2/3. For spin (1/2) there are two eigen values, {+-}(1/2)g{mu}{sub B}H but when two different g values are taken into account, there are four eigen values, {+-}(1/2)g{+-}{mu}{sub B}H, which are fractionally charged. The Hall resistivity becomes spin dependent. The spin (1/2) particle with zero orbital angular momentum, has two values of resistivity, 3h/e{sup 2} and 3h/(2e{sup 2}) which means that when magnetic field is varied the resistivity can change by a factor of 2. If the spin is 3/2, the value of (1/2)g+ = (1/2)+(3/2) so that g = 4 arises which substituted in the series, {+-}(1/2)g{mu}{sub B}H, {+-}(3/2)g{mu}{sub B}H, {+-}(5/2)g{mu}{sub B}H, ..., gives 2, 6, 10, etc which are the correct numbers found experimentally.

Shrivastava, Keshav N. [Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia); School of Physics, University of Hyderabad, Hyderabad 500046 (India)

2008-05-20

317

Recoil-Induced-Resonances in Nonlinear, Ground-State, Pump-Probe Spectroscopy.  

National Technical Information Service (NTIS)

A theory of pump-probe spectroscopy is developed in which optical fields drive two-photon Raman transitions between ground states of an ensemble of three-level atoms. Effects related to the recoil the atoms undergo as a result of their interactions with t...

C. P. Search P. R. Berman

2001-01-01

318

Experimental superradiance and slow-light effects for quantum memories  

SciTech Connect

The effects of high optical depth phenomena, such as superradiance, are investigated in potential quantum memory materials. The results may have relevance for several schemes, including controlled reversible inhomogeneous broadening, atomic frequency combs, and quantum memories based on electromagnetically induced transparency, which are based on using ensembles as storage media. It is shown that strong superradiant effects manifested as decay rates larger than 1/T{sub 2}* are present even for moderate values of {alpha}L{<=}5 and increases as a function of {alpha}L. For even higher {alpha}L, effects such as off-resonant slow light is demonstrated and discussed and, finally, the efficiency of time-reversed optimized input pulses is tested. A maximum retrieval efficiency of {approx}20% is reached and agreement with the theoretically expected result is discussed.

Walther, A.; Amari, A.; Kroell, S.; Kalachev, A. [Department of Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund (Sweden); Zavoisky Physical-Technical Institute of the Russian Academy of Sciences, Sibirsky Trakt 10/7, Kazan 420029 (Russian Federation)

2009-07-15

319

Influence of nuclear quantum effects on nonadiabatic dynamics in the condensed phase  

Microsoft Academic Search

Mixing quantum and classical prescriptions of dynamics is an attractive way to approach condensed phase problems in which only a few of the degrees of freedom need to be treated with quantum mechanics while the rest are treated using an effective classical description. The way in which the full quantum problem is reduced so that some variables are treated effectively

David Coker

1998-01-01

320

Controllable effects of quantum fluctuations on spin free-induction decay at room temperature  

Microsoft Academic Search

Fluctuations of local fields cause decoherence of quantum objects. It is generally believed that at high temperatures, thermal noises are much stronger than quantum fluctuations unless the thermal effects are suppressed by certain techniques such as spin echo. Here we report the discovery of strong quantum-fluctuation effects of nuclear spin baths on free-induction decay of single electron spins in solids

Xin-Yu Pan; Gang-Qin Liu; Dong-Qi Liu; Zhan-Feng Jiang; Nan Zhao; Ren-Bao Liu

2011-01-01

321

Synchrotron-radiation experiments with recoil ions  

SciTech Connect

Studies of atoms, ions and molecules with synchrotron radiation have generally focused on measurements of properties of the electrons ejected during, or after, the photoionization process. Much can also be learned, however, about the atomic or molecular relaxation process by studies of the residual ions or molecular fragments following inner-shell photoionization. Measurements are reported of mean kinetic energies of highly charged argon, krypton, and xenon recoil ions produced by vacancy cascades following inner-shell photoionization using white and monochromatic synchrotron x radiation. Energies are much lower than for the same charge-state ions produced by charged-particle impact. The results may be applicable to design of future angle-resolved ion-atom collision experiments. Photoion charge distributions are presented and compared with other measurements and calculations. Related experiments with synchrotron-radiation produced recoil ion, including photoionization of stored ions and measurement of shakeoff in near-threshold excitation, are briefly discussed. 24 refs., 6 figs., 1 tab.

Levin, J.C.

1989-01-01

322

Effective Masses for Donor Binding Energies in Quantum Well Systems  

NASA Astrophysics Data System (ADS)

The donor ionization energies in a quantum well and quantum dot with finite and infinite barriers are estimated for different well dimensions. Using the effective mass (EM) approximation, calculations are presented with constant effective mass and position dependent effective masses that are different for finite and infinite cases. Our results reduce to an approximate form used by X. H. Qi et al., Phys. Rev. B 58 (1998) 10578 in the finite barrier model and that of L. E. Oliveira and L. M. Falicov, Phys. Rev. B 34 (1986) 8676 in the infinite barrier case. Results are presented by taking the GaAs quantum well as an example. The use of constant effective mass of 0.067m0 is justified for well dimensions ?a* where a* is an effective Bohr radius which is about 100 Å. While Qi et al. found a maximum of 22% variation in the binding energies due to mass variation, we obtained nearly 100% variation when mass variations are included correctly.

Rajashabala, S.; Navaneethakrishnan, K.

323

Gravitational recoils of supermassive black holes in hydrodynamical simulations of gas-rich galaxies  

NASA Astrophysics Data System (ADS)

We study the evolution of gravitationally recoiled supermassive black holes (BHs) in massive gas-rich galaxies by means of high-resolution hydrodynamical simulations. We find that the presence of a massive gaseous disc allows recoiled BHs to return to the centre on a much shorter time-scale than for purely stellar discs. Also, BH accretion and feedback can strongly modify the orbit of recoiled BHs and hence their return time-scale, besides affecting the distribution of gas and stars in the galactic centre. However, the dynamical interaction of kicked BHs with the surrounding medium is in general complex and can facilitate both a fast return to the centre as well as a significant delay. The Bondi-Hoyle-Lyttleton accretion rates of the recoiling BHs in our simulated galaxies are favourably high for the detection of off-centred active galactic nuclei (AGN) if kicked into gas-rich discs - up to a few per cent of the Eddington accretion rate - and are highly variable on time-scales of a few 107 yr. In major merger simulations of gas-rich galaxies, we find that gravitational recoils increase the scatter in the BH mass-host galaxy relationships compared to simulations without kicks, with the BH mass being more sensitive to recoil kicks than the bulge mass. The BH mass can be lowered by a factor of a few due to a recoil, even for a relatively short return time-scale, but the exact magnitude of the effect depends strongly on the BH binary hardening time-scale and on the efficiency of star formation in the central regions. A generic result of our numerical models is that the clumpy massive discs suggested by recent high-redshift observations, as well as the remnants of gas-rich mergers, exhibit a gravitational potential that falls steeply in the central regions, due to the dissipative concentration of baryons. As a result, supermassive BHs should only rarely be able to escape from massive galaxies at high redshifts, which is the epoch where the bulk of BH recoils is expected to occur.

Sijacki, Debora; Springel, Volker; Haehnelt, Martin G.

2011-07-01

324

Plasma wave instability in a quantum field effect transistor with magnetic field effect  

NASA Astrophysics Data System (ADS)

The current-carrying state of a nanometer Field Effect Transistor (FET) may become unstable against the generation of high-frequency plasma waves and lead to generation of terahertz radiation. In this paper, the influences of magnetic field, quantum effects, electron exchange-correlation, and thermal motion of electrons on the instability of the plasma waves in a nanometer FET are reported. We find that, while the electron exchange-correlation suppresses the radiation power, the magnetic field, the quantum effects, and the thermal motion of electrons can enhance the radiation power. The radiation frequency increases with quantum effects and thermal motion of electrons, but decreases with electron exchange-correlation effect. Interestingly, we find that magnetic field can suppress the quantum effects and the thermal motion of electrons and the radiation frequency changes non-monotonely with the magnetic field. These properties could make the nanometer FET advantageous for realization of practical terahertz oscillations.

Zhang, Li-Ping; Xue, Ju-Kui

2013-08-01

325

Efficient semiclassical quantum nuclear effects for shock compression studies  

NASA Astrophysics Data System (ADS)

A fast methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects in a self-consistent fashion. We introduce a modification of the multiscale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new approach are found comparable with existing experimental data. We find that the self-consistent nature of the method results in the onset of chemistry at 40% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature shift associated with quantum heat capacity is determined to be the primary factor in this shift.[4pt] In collaboration with Tingting Qi, Department of Materials Science and Engineering, Stanford University.

Reed, Evan

2013-03-01

326

Effective Degrees of Freedom in Low-Energy Quantum Chromodynamics  

NASA Astrophysics Data System (ADS)

Confinement and spontaneous breaking of chiral symmetry are assumed to generate the governing degrees of freedom of low-energy quantum chromodynamics. On this basis a relativistic constituent-quark model is constructed and formulated along an invariant mass operator within Poincaré-invariant quantum mechanics. The model is effectively applied to the spectroscopy of all known baryons of flavors u, d, s, c and b. The mass-operator eigenstates are furthermore tested with regard to the baryon electromagnetic and axial form factors. Through using the point form of relativistic quantum mechanics, these observables are obtained in a manifestly covariant manner. For all light and strange baryon ground states the electroweak structures are reproduced either in good agreement with phenomenology or, if no experimental data exist, in consistency with results available from lattice quantum chromodynamics. It is concluded that the relativistic constituent-quark model, relying on {QQQ} Fock states only, provides a universal framework for the description of low-energy baryons. The most important ingredients are spontaneous chiral-symmetry breaking and strict relativistic invariance.

Plessas, Willibald

2013-08-01

327

Impurity effects on coupled quantum dot spin qubits in semiconductors  

NASA Astrophysics Data System (ADS)

Localized electron spins confined in semiconductor quantum dots are being studied by many groups as possible elementary qubits for solid-state quantum computation. We theoretically consider the effects of having unintentional charged impurities in laterally coupled two-dimensional double (GaAs) quantum dot systems, where each dot contains one or two electrons and a single charged impurity in the presence of an external magnetic field. We calculate the effect of the impurity on the 2-electron energy spectrum of each individual dot as well as on the spectrum of the coupled-double-dot 2-electron system. We find that the singlet-triplet exchange splitting between the two lowest energy states, both for the individual dots and the coupled dot system, depends sensitively on the location of the impurity and its coupling strength (i.e. the effective charge). We comment on the impurity effect in spin qubit operations in the double dot system based on our numerical results. This work is supported by LPS-CMTC and CNAM.

Nguyen, Nga; Das Sarma, Sankar

2011-03-01

328

Quantum spring from the Casimir effect  

Microsoft Academic Search

The Casimir effect arises not only in the presence of material boundaries but also in space with nontrivial topology. In this Letter, we choose a topology of the flat (D+1)-dimensional spacetime, which causes the helix boundary condition for a Hermitian massless scalar field. Especially, Casimir effect for a massless scalar field on the helix boundary condition is investigated in two

Chao-Jun Feng; Xin-Zhou Li

2010-01-01

329

Heat capacity of water: A signature of nuclear quantum effects  

NASA Astrophysics Data System (ADS)

In this note we present results for the heat capacity at constant pressure for the TIP4PQ/2005 model, as obtained from path-integral simulations. The model does a rather good job of describing both the heat capacity of ice Ih and of liquid water. Classical simulations using the TIP4P/2005, TIP3P, TIP4P, TIP4P-Ew, simple point charge/extended, and TIP5P models are unable to reproduce the heat capacity of water. Given that classical simulations do not satisfy the third law of thermodynamics, one would expect such a failure at low temperatures. However, it seems that for water, nuclear quantum effects influence the heat capacities all the way up to room temperature. The failure of classical simulations to reproduce Cp points to the necessity of incorporating nuclear quantum effects to describe this property accurately.

Vega, C.; Conde, M. M.; McBride, C.; Abascal, J. L. F.; Noya, E. G.; Ramirez, R.; Sesé, L. M.

2010-01-01

330

Thermal effect in quantum-dot cellular automata  

NASA Astrophysics Data System (ADS)

We present a theoretical study of thermal effect in quantum-dot cellular automata (QCA). A quantum statistical model has been introduced to obtain the thermal average of polarization of a QCA cell. We have studied the thermal effect on an inverter, a majority gate and planar arrays of different sizes. The theoretical analysis has been approximated for a two-state model where the cells are in any one of the two possible eigenstates of the cell Hamiltonian. Hence, only the ±1 polarization values are taken into account for the statistical analysis. A numerical computational model has been developed to obtain all possible configurations of the cells in an array. In general, the average polarization of each cell decreases with temperature as well as with the distance from the driver cells. We have found the temperatures for thermal breakdown. The results demonstrate the critical nature of temperature dependence for the operation of QCA.

Sturzu, I.; Kanuchok, J. L.; Khatun, M.; Tougaw, P. D.

2005-03-01

331

Higher-Dimensional Quantum Hall Effect in String Theory  

SciTech Connect

We construct a string theory realization of the 4+1d quantum Hall effect recently discovered by Zhang and Hu. The string theory picture contains coincident D4-branes forming an S{sup 4} and having D0-branes (i.e. instantons) in their world-volume. The charged particles are modeled as string ends. Their configuration space approaches in the large n limit a CP{sup 3}, which is an S{sup 2} fibration over S{sup 4}, the extra S{sup 2} being made out of the Chan-Paton degrees of freedom. An alternative matrix theory description involves the fuzzy S{sup 4}. We also find that there is a hierarchy of quantum Hall effects in odd-dimensional spacetimes, generalizing the known cases in 2 + 1d and 4 + 1d.

Fabinger, Michal

2002-08-08

332

Theory of the thermal Hall effect in quantum magnets.  

PubMed

We present a theory of the thermal Hall effect in insulating quantum magnets, where the heat current is totally carried by charge-neutral objects such as magnons and spinons. Two distinct types of thermal Hall responses are identified. For ordered magnets, the intrinsic thermal Hall effect for magnons arises when certain conditions are satisfied for the lattice geometry and the underlying magnetic order. The other type is allowed in a spin liquid which is a novel quantum state since there is no order even at zero temperature. For this case, the deconfined spinons contribute to the thermal Hall response due to Lorentz force. These results offer a clear experimental method to prove the existence of the deconfined spinons via a thermal transport phenomenon. PMID:20366838

Katsura, Hosho; Nagaosa, Naoto; Lee, Patrick A

2010-02-10

333

Parity effect and phase transitions in quantum Szilard engines.  

PubMed

Quantum Szilard engines with an arbitrary number of identical particles are studied in this paper. Analytical expressions for the total work in the low- and high-temperature limits are obtained. The total work depends on both the particle statistics, the odd-even parity, and the temperature of the system. The parity effect is drastic in fermion systems. An odd number of fermions perform work as if they were a single fermion, and an even number of fermions do not perform any work at all. For bosons, there exists a phase transition at a critical temperature under which work done by the engine is always negative. It is found that only above a certain temperature, bosonic quantum Szilard engine does more work than fermionic one. The possible experimental verification of these effects is discussed. PMID:22400530

Lu, Yao; Long, Gui Lu

2012-01-17

334

Non-Abelian Quantum Hall Effect in Topological Flat Bands  

NASA Astrophysics Data System (ADS)

Inspired by the recent theoretical discovery of robust fractional topological phases without a magnetic field, we search for the non-Abelian quantum Hall effect in lattice models with topological flat bands. Through extensive numerical studies on the Haldane model with three-body hard-core bosons loaded into a topological flat band, we find convincing numerical evidence of a stable ?=1 bosonic non-Abelian quantum Hall effect, with the characteristic threefold quasidegeneracy of ground states on a torus, a quantized Chern number, and a robust spectrum gap. Moreover, the spectrum for two-quasihole states also shows a finite energy gap, with the number of states in the lower-energy sector satisfying the same counting rule as the Moore-Read Pfaffian state.

Wang, Yi-Fei; Yao, Hong; Gu, Zheng-Cheng; Gong, Chang-De; Sheng, D. N.

2012-03-01

335

Effect of Quantum Hall State of Substrate on Single-Electron Transport of Carbon Nanotube Quantum Dots  

Microsoft Academic Search

The effect of the quantum Hall state of a GaAs\\/AlGaAs two-dimensional electron gas (2DEG) substrate on the single-electron transport of carbon nanotube (CNT) quantum dots (QDs) has been investigated when the 2DEG substrate was used as a back gate to CNT QDs. We found that the gating to CNT QDs through the 2DEG was not effective when the transverse resistance

Tomohiro Yamaguchi; Takeo Tsukamoto; Satoshi Moriyama; Masaki Suzuki; Koji Ishibashi

2009-01-01

336

Semiclassical states, effective dynamics, and classical emergence in loop quantum cosmology  

SciTech Connect

We construct physical semiclassical states annihilated by the Hamiltonian constraint operator in the framework of loop quantum cosmology as a method of systematically determining the regime and validity of the semiclassical limit of the quantum theory. Our results indicate that the evolution can be effectively described using continuous classical equations of motion with nonperturbative corrections down to near the Planck scale below which the Universe can only be described by the discrete quantum constraint. These results, for the first time, provide concrete evidence of the emergence of classicality in loop quantum cosmology and also clearly demarcate the domain of validity of different effective theories. We prove the validity of modified Friedmann dynamics incorporating discrete quantum geometry effects which can lead to various new phenomenological applications. Furthermore the understanding of semiclassical states allows for a framework for interpreting the quantum wave functions and understanding questions of a semiclassical nature within the quantum theory of loop quantum cosmology.

Singh, Parampreet [Institute for Gravitational Physics and Geometry, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States); Vandersloot, Kevin [Institute for Gravitational Physics and Geometry, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States); Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, D-14476 Golm (Germany)

2005-10-15

337

Reentrant quantum anomalous Hall effect with in-plane magnetic fields in HgMnTe quantum wells  

NASA Astrophysics Data System (ADS)

The quantum anomalous Hall effect has been predicted in HgMnTe quantum wells with an out-of-plane magnetization of Mn atoms. However, since HgMnTe quantum wells are paramagnetic, an out-of-plane magnetic field is required to polarize magnetic moments of Mn atoms, which inevitably induces Landau levels and makes it difficult to identify the origin of the quantized Hall conductance experimentally. In this work, we study the quantum anomalous Hall effect in the presence of an in-plane magnetic field in Mn-doped HgTe quantum wells. For a small out-of-plane magnetic field, the in-plane magnetic field can drive the system from a normal insulating state to a quantum anomalous Hall state. When the out-of-plane magnetic field is slightly above the transition point, the system shows a reentrant behavior of Hall conductance, varying from ?e2/h to 0 and back to ?e2/h, with increasing in-plane magnetic fields. The reentrant quantum anomalous Hall effect originates from the interplay between the exchange coupling of magnetic moments and the direct Zeeman coupling of magnetic fields. The calculation incorporating Landau levels shows that there is no qualitative change of the reentrant behavior.

Hsu, Hsiu-Chuan; Liu, Xin; Liu, Chao-Xing

2013-08-01

338

WITCH: a recoil spectrometer for beta-decay  

Microsoft Academic Search

The WITCH experiment will measure the recoil energy spectrum of the daughter ions in beta-decay. The main parts of the experiment are two Penning traps and a subsequent retardation spectrometer. The beta-decays take place in the ion cloud in the decay trap. Since the ion cloud is in vacuum and due to the cylindrical structure of the trap, the recoiling

M. Beck; F. Ames; D. Beck; G. Bollen; B. Delauré; J. Deutsch; V. V. Golovko; V. Yu. Kozlov; I. S. Kraev; A. Lindroth; T. Phalet; W. Quint; K. Reisinger; P. Schuurmans; N. Severijns; B. Vereecke; S. Versyck

2003-01-01

339

Compton recoil electron tracking with silicon strip detectors  

Microsoft Academic Search

The application of silicon strip detectors to Compton gamma ray astronomy telescopes is described. The silicon Compton recoil telescope tracks Compton recoil electrons in silicon strip converters to provide an unique direction for Compton scattered gamma rays above 1 MeV. With strip detectors of modest positional and energy resolutions, of 1 mm FWHM and 3% at 662 keV, respectively, true

T. J. O'Neill; F. Ait-Ouamer; I. Schwartz; O. T. Tumer; R. S. White; A. D. Zych

1992-01-01

340

Asymmetry of recoil protons in neutron {beta} decay  

SciTech Connect

A complete analysis of proton recoil asymmetry in neutron decay in the first order of radiative and recoil corrections is presented. The possible contributions from new physics are calculated in terms of low energy coupling constants, and the sensitivity of the measured asymmetry to models beyond the Standard Model are discussed.

Gudkov, V. [Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208 (United States)

2008-04-15

341

Recoil-Proton Fast-Neutron-Counter Telescope.  

National Technical Information Service (NTIS)

A proton-recoil neutron counter telescope is described composed of a solid state silicon transmission detector and a NE 102 A plastic scintillator, measuring the energy loss, the energy of the recoil protons and the time-of-flight between the two detector...

G. Galeazzi P. Pavan D. Toniolo G. Zago R. Zannoni

1981-01-01

342

Radioactive Waste Storage Materials: Their alpha Recoil Aging  

Microsoft Academic Search

Ion implantation experiments suggest that the accumulation of alpha -recoil damage in radioactive waste storage materials, which behave like solid-state track detectors, plays a drastic role in their long-term degradation. The understanding of alpha -recoil ``aging,'' overlooked in earlier studies, offers new guidelines for improving waste storage conditions.

J. C. Dran; M. Maurette; J. C. Petit

1980-01-01

343

Quantum memory in quantum cryptography  

Microsoft Academic Search

[Shortened abstract:] This thesis investigates the importance of quantum memory in quantum cryptography, concentrating on quantum key distribution schemes. In the hands of an eavesdropper -- a quantum memory is a powerful tool, putting in question the security of quantum cryptography; Classical privacy amplification techniques, used to prove security against less powerful eavesdroppers, might not be effective when the eavesdropper

Tal Mor

1999-01-01

344

Electron fluid and quasiparticles in the quantum Hall effect  

Microsoft Academic Search

To explain fractional quantum Hall effect, it is necessary to take into account both the interaction between electrons and\\u000a their interaction with impurities. We propose a simple model, where the Coulomb repulsion is replaced by a short range potential.\\u000a For this model we are able to find many-body wave functions of the electron system interacting with impurities and calculate\\u000a the

V L Pokrovsky; A L Talapov

1987-01-01

345

Phonon effects in molecular transistors: Quantum and classical treatment  

Microsoft Academic Search

A comprehensive theoretical treatment of the effect of electron-phonon interactions on the current-voltage and noise characteristics of a quantum dot is presented, including both classical and quantal limits and the crossover between them. Both direct and cotunnelling contributions are included. I-V and noise are found to depend strongly on whether or not the phonons equilibrate in a time rapid compared

Aditi Mitra; Igor Aleiner; Andrew Millis

2004-01-01

346

Two-dimensional quantum effects in nanoscale MOSFETs  

Microsoft Academic Search

In this paper, a full two-dimensional (2-D) quantum mechanical (QM) device simulator for deep submicron MOSFETs is presented. The model couples a 2-D Schrodinger-Poisson solver with a semiclassical transport model. The validity of the proposed model is first tested against a QM model for transport, developed as a benchmark. Then, QM effects on nanoscale MOSFETs performance are quantitatively addressed and

Agostino Pirovano; Andrea L. Lacaita; Alessandro S. Spinelli

2002-01-01

347

Effect of spins on the quantum entropy of black holes  

Microsoft Academic Search

By using the Newman-Penrose formalism and 't Hooft brick-wall model, the quantum entropies of the Kerr-Newman black hole due to the Dirac and electromagnetic fields are calculated and the effects of the spins of the photons and Dirac particles on the entropies are investigated. It is shown that the entropies depend only on the square of the spins of the

Jiliang Jinga; Mu-Lin Yan

348

Probing Quantum-Vacuum Geometrical Effects with Cold Atoms  

SciTech Connect

The lateral Casimir-Polder force between an atom and a corrugated surface should allow one to study experimentally nontrivial geometrical effects in the electromagnetic quantum vacuum. Here, we derive the theoretical expression of this force in the scattering approach. We show that large corrections to the 'proximity force approximation' could be measured using present-day technology with a Bose-Einstein condensate used as a vacuum field sensor.

Dalvit, Diego A. R. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Neto, Paulo A. Maia [Instituto de Fisica, UFRJ, CP 68528, Rio de Janeiro, RJ, 21941-972 (Brazil); Lambrecht, Astrid; Reynaud, Serge [Laboratoire Kastler Brossel, Case 74, CNRS, ENS, UPMC, Campus Jussieu, F-75252 Paris Cedex 05 (France)

2008-02-01

349

High-Dimensional Quantum Hall Effect in String Theory  

Microsoft Academic Search

We construct a string theory realization of the 4+1d quantum Hall effect recently discovered by Zhang and Hu. The string theory picture contains coincident D4- branes forming an S4 and having D0-branes (i.e. instantons) in their world-volume. The charged particles are modeled as string ends. Their configuration space approaches in the large n limit a CP3, which is an S2

M. Fabinger

2002-01-01

350

Higher-Dimensional Quantum Hall Effect in String Theory  

Microsoft Academic Search

We construct a string theory realization of the 4+1d quantum Hall effect recently discovered by Zhang and Hu. The string theory picture contains coincident D4-branes forming an S⁴ and having D0-branes (i.e. instantons) in their world-volume. The charged particles are modeled as string ends. Their configuration space approaches in the large n limit a CP³, which is an S² fibration

Fabinger; Michal

2002-01-01

351

Higher-Dimensional Quantum Hall Effect in String Theory  

Microsoft Academic Search

We construct a string theory realization of the 4+1d quantum Hall effect recently described by Zhang and Hu. The string theory picture contains coincident D4-branes forming an S4 and having D0-branes (i.e. instantons) in their world-volume. The charged particles are modelled as string ends. Their configuration space approaches in the large-N limit a CP3, which is an S2 fibration over

Michal Fabinger

2002-01-01

352

Quantum effects in the optical activity of alpha-quartz.  

PubMed

An experiment was proposed to probe quantum effects on optical activity. The helical structures in optically active media act as natural microsolenoids for the electromagnetic waves passing through them, which produces a longitudinal magnetic field in the axis of helices. Magnetic flux through a helical crystal structure is quantized. A high number of quanta in the rotatory power was probed in the optical activity of alpha-quartz. PMID:17938658

Tan, C Z; Chen, L

2007-10-15

353

High speed quantum-well lasers and carrier transport effects  

Microsoft Academic Search

Carrier transport can significantly affect the high-speed properties of quantum-well lasers. The authors have developed a model and derived analytical expressions for the modulation response, resonance frequency, damping rate, and K factor to include these effects. They show theoretically and experimentally that carrier transport can lead to significant low-frequency parasitic-like rolloff that reduces the modulation response by as much as

Radhakrishnan Nagarajan; Masayuki Ishikawa; Toru Fukushima; Randall S. Geels; John E. Bowers

1992-01-01

354

Quantum Spin-Hall Effect and Topologically Invariant Chern Numbers  

Microsoft Academic Search

We present a topological description of the quantum spin-Hall effect (QSHE) in a two-dimensional electron system on a honeycomb lattice with both intrinsic and Rashba spin-orbit couplings. We show that the topology of the band insulator can be characterized by a 2x2 matrix of first Chern integers. The nontrivial QSHE phase is identified by the nonzero diagonal matrix elements of

D. N. Sheng; Z. Y. Weng; L. Sheng; F. D. M. Haldane

2006-01-01

355

Quantum Spin-Hall Effect and Topologically Invariant Chern Numbers  

Microsoft Academic Search

We present a topological description of the quantum spin-Hall effect (QSHE) in a two-dimensional electron system on a honeycomb lattice with both intrinsic and Rashba spin-orbit couplings. We show that the topology of the band insulator can be characterized by a 2×2 matrix of first Chern integers. The nontrivial QSHE phase is identified by the nonzero diagonal matrix elements of

D. N. Sheng; Z. Y. Weng; L. Sheng; F. D. M. Haldane

2006-01-01

356

Anomalous spin Hall effects in Dresselhaus (110) quantum wells  

Microsoft Academic Search

Anomalous spin Hall effects that belong to the intrinsic type in Dresselhaus (110) quantum wells are discussed. For the out-of-plane spin component, antisymmetric current-induced spin polarization induces opposite spin Hall accumulation, even though there is no spin-orbit force due to Dresselhaus (110) coupling. A surprising feature of this spin Hall induction is that the spin accumulation sign does not change

Ming-Hao Liuand; Ching-Ray Chang

2010-01-01

357

Quantum Spin-Hall Effect and Topologically Invariant Chern Numbers  

Microsoft Academic Search

We present a topological description of quantum spin Hall effect (QSHE) in a\\u000atwo-dimensional electron system on honeycomb lattice with both intrinsic and\\u000aRashba spin-orbit couplings. We show that the topology of the band insulator\\u000acan be characterized by a $2\\\\times 2$ traceless matrix of first Chern integers.\\u000aThe nontrivial QSHE phase is identified by the nonzero diagonal matrix elements

D. N. Sheng; Z. Y. Weng; L. Sheng; F. D. M. Haldane

2006-01-01

358

Time-Reversal-Symmetry-Broken Quantum Spin Hall Effect  

Microsoft Academic Search

The quantum spin Hall (QSH) state of matter is usually considered to be protected by time-reversal (TR) symmetry. We investigate the fate of the QSH effect in the presence of the Rashba spin-orbit coupling and an exchange field, which break both inversion and TR symmetries. It is found that the QSH state characterized by nonzero spin Chern numbers C±=±1 persists

Yunyou Yang; Zhong Xu; L. Sheng; Baigeng Wang; D. Y. Xing; D. N. Sheng

2011-01-01

359

Surface Termination Effects on Zinc Oxide Quantum Dots  

Microsoft Academic Search

We investigate the effects of surface terminations on the optical properties of 2-6 nm ZnO quantum dots. Nanocrystals were grown by wet chemical synthesis in a short-chain alcohol solvent from zinc acetate and sodium hydroxide. Quenching of particle growth with various capping agents is necessary to maintain and enhance the unique characteristics of the nanocrystals. We reproduce results of previous

Steve Whitesell; Joe Spalenka; Christopher Jack; Cary Allen; Reuben Collins; Thomas Furtak

2007-01-01

360

Electron interaction and spin effects in quantum wires, quantum dots and quantum point contacts: a first-principles mean-field approach  

NASA Astrophysics Data System (ADS)

We have developed a mean-field first-principles approach for studying electronic and transport properties of low dimensional lateral structures in the integer quantum Hall regime. The electron interactions and spin effects are included within the spin density functional theory in the local density approximation where the conductance, the density, the effective potentials and the band structure are calculated on the basis of the Green's function technique. In this paper we present a systematic review of the major results obtained on the energetics, spin polarization, effective g factor, magnetosubband and edge state structure of split-gate and cleaved-edge overgrown quantum wires as well as on the conductance of quantum point contacts (QPCs) and open quantum dots. In particular, we discuss how the spin-resolved subband structure, the current densities, the confining potentials, as well as the spin polarization of the electron and current densities in quantum wires and antidots evolve when an applied magnetic field varies. We also discuss the role of the electron interaction and spin effects in the conductance of open systems focusing our attention on the 0.7 conductance anomaly in the QPCs. Special emphasis is given to the effect of the electron interaction on the conductance oscillations and their statistics in open quantum dots as well as to interpretation of the related experiments on the ultralow temperature saturation of the coherence time in open dots.

Zozoulenko, I. V.; Ihnatsenka, S.

2008-04-01

361

Quantum instanton evaluation of the kinetic isotope effects  

SciTech Connect

A general quantum-mechanical method for computing kinetic isotope effects is presented. The method is based on the quantum instanton approximation for the rate constant and on the path integral Metropolis Monte-Carlo evaluation of the Boltzmann operator matrix elements. It computes the kinetic isotope effect directly, using a thermodynamic integration with respect to the mass of the isotope, thus avoiding the more computationally expensive process of computing the individual rate constants. The method is more accurate than variational transition-state theories or the semiclassical instanton method since it does not assume a single reaction path and does not use a semiclassical approximation of the Boltzmann operator. While the general Monte-Carlo implementation makes the method accessible to systems with a large number of atoms, we present numerical results for the Eckart barrier and for the collinear and full three-dimensional isotope variants of the hydrogen exchange reaction H+H{sub 2} {yields} H{sub 2}+H. In all seven test cases, for temperatures between 250 K and 600 K, the error of the quantum instanton approximation for the kinetic isotope effects is less than {approx}10%.

Vanicek, Jiri; Miller, William H.; Castillo, Jesus F.; Aoiz, F.Javier

2005-04-19

362

Quantum Effects in Heisenberg Spin Chains with Incommensurate Correlations  

NASA Astrophysics Data System (ADS)

We examine the effect of quantum fluctuations in isotropic frustrated Heisenberg chains where the classical ground state favors coplanar spiral incommensurate spin-density wave order, for example, a chain with competing nearest and next-nearest neighbor exchange plus ``biquadratic'' exchange. Because of the non-Abelian symmetry of the order parameter, quantum effects always induce an isotropic spin-singlet ground state with a ``mass gap'' in the excitation spectrum if the wavevector Q of the correlations is incommensurate. However, the system can remain gapless if Q is ``locked in'' to a commensurate value such as 2? /3, as in the spin-1 chain with suffiently strong biquadratic exchange. In this case the low-energy description is the k=4 SU(2) conformal field theory; the couplings which would cause the value of Q to drift have conformal spin 1, and remain irrelevant unless other marginal couplings destroy conformal invariance and open a gap. This system shows the interesting and perhaps counter-intuitive effect that gaplessness of a quantum system with a non-Abelian symmetry can lock the wavevector of its dominant correlations to a commensurate value.

Haldane, F. D. M.; Madhav, Amulya

2001-03-01

363

Topological superconductivity, topological confinement, and the vortex quantum Hall effect  

SciTech Connect

Topological matter is characterized by the presence of a topological BF term in its long-distance effective action. Topological defects due to the compactness of the U(1) gauge fields induce quantum phase transitions between topological insulators, topological superconductors, and topological confinement. In conventional superconductivity, because of spontaneous symmetry breaking, the photon acquires a mass due to the Anderson-Higgs mechanism. In this paper we derive the corresponding effective actions for the electromagnetic field in topological superconductors and topological confinement phases. In topological superconductors magnetic flux is confined and the photon acquires a topological mass through the BF mechanism: no symmetry breaking is involved, the ground state has topological order, and the transition is induced by quantum fluctuations. In topological confinement, instead, electric charge is linearly confined and the photon becomes a massive antisymmetric tensor via the Stueckelberg mechanism. Oblique confinement phases arise when the string condensate carries both magnetic and electric flux (dyonic strings). Such phases are characterized by a vortex quantum Hall effect potentially relevant for the dissipationless transport of information stored on vortices.

Diamantini, M. Cristina; Trugenberger, Carlo A. [INFN and Dipartimento di Fisica, University of Perugia, via A. Pascoli, I-06100 Perugia (Italy); SwissScientific, chemin Diodati 10, CH-1223 Cologny (Switzerland)

2011-09-01

364

Zel'Dovich Effect in Quantum Mechanics.  

National Technical Information Service (NTIS)

In systems bound by the Coulomb potential with a short-range distortion, the reconstruction of atomic spectrum (or Zel'dovich effect) can appear. Some peculiarities of this phenomenon for the state of nonzero angular momentum are discussed. Analytical pro...

B. M. Karnakov V. D. Mur A. E. Kudryavtsev V. S. Popov

1985-01-01

365

Nuclear astrophysics at the DRAGON recoil separator  

NASA Astrophysics Data System (ADS)

The DRAGON recoil separator facility at TRIUMF measures radiative alpha and proton capture reactions of astrophysical importance in inverse kinematics. This is done using radioactive and stable ion beams produced and accelerated using the ISAC (Isotope Separator and ACcelerator) facility in conjunction with a windowless gas target. Over the last few years, the DRAGON collaboration has embarked on a programme to measure a variety of reactions considered vital to the understanding of various astrophysical scenarios. An overview of DRAGON's separation, beam suppression, and detection capabilities will be given. In addition, examples of recent reaction cross section measurements will be discussed, such as the ^16O(?,?)^20Ne reaction, which plays an important part in the He-burning in massive stars.

Hager, Ulrike

2011-10-01

366

Recoil corrections in highly charged ions  

SciTech Connect

A recently introduced Bethe-Salpeter formalism is applied to the calculation of recoil corrections to the energy levels of all n=1, 2, and 3 states of hydrogenic ions. Finite basis set techniques are shown to allow the accurate evaluation of expressions that sum all orders of Z{alpha}, which are rederived in the formalism using combinatoric techniques. A comparison of the all-order results with one-loop calculations and known terms of the perturbation expansion in Z{alpha} is made. Good agreement of the results of the present work with previous calculations is shown, and a discussion of issues that will have to be treated for the many-electron case, where highly accurate experiments have been carried out, is given.

Adkins, G. S.; Morrison, S.; Sapirstein, J. [Department of Physics, Franklin and Marshall College, Lancaster, Pennsylvania 17604 (United States); Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

2007-10-15

367

Semileptonic b decay at intermediate recoil  

SciTech Connect

We compute the O({alpha}{sub s}{sup 2}) corrections to the differential rate of the semileptonic decay b{yields}cl{nu}{sub l} at the 'intermediate recoil' point, where the c-quark mass and the invariant mass of the leptons are equal. The calculation is based on an expansion around two opposite limits of the quark masses m{sub b,c}: m{sub c}{approx_equal}m{sub b} and m{sub c}<

Dowling, Matthew; Pak, Alexey; Czarnecki, Andrzej [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada)

2008-10-01

368

Correcting quantum errors with the Zeno effect  

SciTech Connect

In order to reduce errors, error correction codes need to be implemented fast. They can correct the errors corresponding to the first few orders in the Taylor expansion of the time evolution operator corresponding to the Hamiltonian of the interaction with the environment. If implemented fast enough, the zeroth order error predominates and the dominant effect is of error prevention by measurement (Zeno effect) rather than correction. In this 'Zeno regime', codes with less redundancy are sufficient for protection. We describe such a simple scheme, which uses two 'noiseless' qubits to protect a large number, n, of information qubits from noise from the environment. The 'noisless qubits' can be realized by treating them as logical qubits to be encoded by one of the previously introduced encoding schemes.

Erez, Noam [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States); Aharonov, Yakir [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Department of Physics, University of South Carolina, Columbia, South Carolina 29208 (United States); Reznik, Benni; Vaidman, Lev [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

2004-06-01

369

Quantum amplification effect in a horizon fluctuation  

NASA Astrophysics Data System (ADS)

The appearance of a few unevenly spaced bright flashes of light on top of Hawking radiation is the sign of the amplification effect in black hole horizon fluctuations. Previous studies on this problem suffer from the lack of considering all emitted photons in the theoretical spectroscopy of these fluctuations. In this paper, we include all of the physical transition weights and present a consistent intensity formula. This modifies a black hole radiation pattern.

Ansari, Mohammad H.

2010-05-01

370

Kondo Effect at a Quantum Critical Point  

NASA Astrophysics Data System (ADS)

The Kondo effect in a metal on the verge of a zero-temperature magnetic instability provides a fascinating example of interference between local and long-range correlations. (A. I. Larkin and V. I. Mel'nikov, Sov. Phys. JETP 34, 656 (1972)) (P. Coleman and A. M. Tsvelik, cond-mat/9707003) (A. Sengupta, cond-mat/9707316) We discuss possible consequences of this interference, including the breakdown of the Fermi liquid state.

Ramazashvili, Revaz; Coleman, Piers

1998-03-01

371

Scattering approach to quantum transport and many body effects  

NASA Astrophysics Data System (ADS)

We review a series of works discussing how the scattering approach to quantum transport developed by Landauer and Buttiker for one body elastic scatterers can be extended to the case where electron-electron interactions act inside the scattering region and give rise to many body scattering. Firstly, we give an exact numerical result showing that at zero temperature a many body scatterer behaves as an effective one body scatterer, with an interaction dependent transmission. Secondly, we underline that this effective scatterer depends on the presence of external scatterers put in its vicinity. The implications of this non local scattering are illustrated studying the conductance of a quantum point contact where electrons interact with a scanning gate microscope. Thirdly, using the numerical renormalization group developed by Wilson for the Kondo problem, we study a double dot spinless model with an inter-dot interaction U and inter-dot hopping td, coupled to leads by hopping terms tc. We show that the quantum conductance as a function of td is given by a universal function, independently of the values of U and tc, if one measures td in units of a characteristic scale ?(U,tc). Mapping the double dot system without spin onto a single dot Anderson model with spin and magnetic field, we show that ?(U,tc) = 2TK, where TK is the Kondo temperature of the Anderson model.

Pichard, Jean-Louis; Freyn, Axel

2010-12-01

372

Cancer proliferation and therapy: the Warburg effect and quantum metabolism  

PubMed Central

Background Most cancer cells, in contrast to normal differentiated cells, rely on aerobic glycolysis instead of oxidative phosphorylation to generate metabolic energy, a phenomenon called the Warburg effect. Model Quantum metabolism is an analytic theory of metabolic regulation which exploits the methodology of quantum mechanics to derive allometric rules relating cellular metabolic rate and cell size. This theory explains differences in the metabolic rates of cells utilizing OxPhos and cells utilizing glycolysis. This article appeals to an analytic relation between metabolic rate and evolutionary entropy - a demographic measure of Darwinian fitness - to: (a) provide an evolutionary rationale for the Warburg effect, and (b) propose methods based on entropic principles of natural selection for regulating the incidence of OxPhos and glycolysis in cancer cells. Conclusion The regulatory interventions proposed on the basis of quantum metabolism have applications in therapeutic strategies to combat cancer. These procedures, based on metabolic regulation, are non-invasive, and complement the standard therapeutic methods involving radiation and chemotherapy

2010-01-01

373

Nuclear quantum effects and hydrogen bond fluctuations in water.  

PubMed

The hydrogen bond (HB) is central to our understanding of the properties of water. However, despite intense theoretical and experimental study, it continues to hold some surprises. Here, we show from an analysis of ab initio simulations that take proper account of nuclear quantum effects that the hydrogen-bonded protons in liquid water experience significant excursions in the direction of the acceptor oxygen atoms. This generates a small but nonnegligible fraction of transient autoprotolysis events that are not seen in simulations with classical nuclei. These events are associated with major rearrangements of the electronic density, as revealed by an analysis of the computed Wannier centers and (1)H chemical shifts. We also show that the quantum fluctuations exhibit significant correlations across neighboring HBs, consistent with an ephemeral shuttling of protons along water wires. We end by suggesting possible implications for our understanding of how perturbations (solvated ions, interfaces, and confinement) might affect the HB network in water. PMID:24014589

Ceriotti, Michele; Cuny, Jérôme; Parrinello, Michele; Manolopoulos, David E

2013-09-06

374

Time-reversal-symmetry-broken quantum spin Hall effect.  

PubMed

The quantum spin Hall (QSH) state of matter is usually considered to be protected by time-reversal (TR) symmetry. We investigate the fate of the QSH effect in the presence of the Rashba spin-orbit coupling and an exchange field, which break both inversion and TR symmetries. It is found that the QSH state characterized by nonzero spin Chern numbers C(±) = ±1 persists when the TR symmetry is broken. A topological phase transition from the TR-symmetry-broken QSH phase to a quantum anomalous Hall phase occurs at a critical exchange field, where the bulk band gap just closes. It is also shown that the transition from the TR-symmetry-broken QSH phase to an ordinary insulator state cannot happen without closing the band gap. PMID:21902351

Yang, Yunyou; Xu, Zhong; Sheng, L; Wang, Baigeng; Xing, D Y; Sheng, D N

2011-08-02

375

CT-invariant quantum spin Hall effect in ferromagnetic graphene.  

PubMed

We predict a quantum spin Hall effect (QSHE) in ferromagnetic graphene under a magnetic field. Unlike the previous QSHE, this QSHE appears in the absence of spin-orbit interaction and thus, is arrived at from a different physical origin. The previous QSHE is protected by the time-reversal (T) invariance. This new QSHE is protected by CT invariance, where C is the charge conjugation operation. Because of this QSHE, the longitudinal resistance exhibits quantum plateaus. The plateau values are at 1/2, 1/6, 3/28, ..., (in units of h/e2), depending on the filling factors of the spin-up and spin-down carriers. The spin Hall resistance is also investigated and is found to be robust against the disorder. PMID:20366848

Sun, Qing-feng; Xie, X C

2010-02-12

376

Enhanced Stark effects of coupled quantum wells and their application to tunable IR photodetectors  

Microsoft Academic Search

Traditional multi-quantum-well photodetectors exhibited no evidence of the Stark shift, and absorption resonance cannot be tuned by the applied electric field. Coupled quantum wells with a significant Stark effect can be employed to fabricate tunable photodetectors. The tunability was measured by the self-consistent technique, and the absorption coefficient of coupled-quantum-well was investigated. An Al(x)Ga(1-x)As\\/GaAs asymmetric coupled-quantum-well photodetector and a high-low

Yimin Huang; Chenhsin Lien; Tan-Fu Lei

1993-01-01

377

Quantum Effects in Plasma Dielectric Response: Plasmons and Shielding in Normal Systems and Graphene  

Microsoft Academic Search

\\u000a A brief review of quantum plasma theory and phenomenology in solid-state plasmas is presented here, with attention to dynamic\\u000a and nonlocal features of dielectric response. Focussing on the random-phase approximation, we discuss the RPA screening and\\u000a dielectric functions in three, two, and one dimensions corresponding to bulk, quantum well, and quantum wire plasmas, respectively,\\u000a taking care to distinguish quantum effects

Norman J. M. Horing

378

Photon-number-discriminating detection using a quantum-dot, optically gated, field-effect transistor  

Microsoft Academic Search

Detectors with the capability to directly measure the photon number of a pulse of light enable linear optics quantum computing, affect the security of quantum communications, and can be used to characterize and herald non-classical states of light. Here, we demonstrate the photon-number-resolving capabilities of a quantum-dot, optically gated, field-effect transistor that uses quantum dots as optically addressable floating gates

M. A. Rowe; M. B. Greene; D. Rosenberg; T. E. Harvey; M. Y. Su; R. H. Hadfield; S. W. Nam; R. P. Mirin; E. J. Gansen

2007-01-01

379

Quantum confinement effects in semiconductor clusters  

SciTech Connect

The band gaps, band structure, and excited-state (exciton) energies of CdS, GaAs, and GaP semiconductor clusters are calculated using pseudopotentials. In addition, the sensitivity of the exciton energies to the size, shape, crystal structure, and lattice constant of the unit cell are investigated. The calculated exciton energies of CdS clusters are in excellent agreement with experiment over a wide range of cluster sizes. Also, the exciton states of small CdS clusters are sensitive to whether their crystal structure is zinc blende or hexagonal. Such a sensitivity is absent in large CdS clusters. Furthermore, small GaAs clusters are shown to exhibit anomalous redshift of their absorption spectra, in sharp contrast to CdS and large GaAs clusters whose spectra always shift to blue with decreasing cluster size. Finally, the lowest-energy non-Franck--Condon transition in GaP clusters always shifts to blue with decreasing cluster size, whereas the higher-energy Franck--Condon transition in small clusters exhibits the anomalous redshift. These novel findings reveal that (1) the optical spectroscopy of semiconductor clusters is strongly material and crystal structure dependent; (2) the spectroscopy of small clusters is dramatically different from those of large clusters and bulk; and (3) these effects cannot be explained, even qualitatively, using the effective-mass approximation.

Rama Krishna, M.V.; Friesner, R.A. (The Department of Chemistry, Columbia University, New York, New York (USA))

1991-12-01

380

Numerical simulation of quantum effects in high-k gate dielectric MOS structures using quantum mechanical models  

Microsoft Academic Search

In this paper the electrical characteristics of metal oxide semiconductor (MOS) capacitors with high-k gate dielectric are investigated with quantum mechanical models. Both the self-consistent Schrödinger–Poisson (SP) model and the density gradient (DG) model are solved simultaneously to study quantum confinement effects (QCEs) for MOS capacitors. A computationally efficient parallel eigenvalue solution algorithm and a robust monotone iterative (MI) finite volume

Yiming Li; Jam-Wem Lee; Ting-Wei Tang; Tien-Sheng Chao; Tan-Fu Lei; S. M. Sze

2002-01-01

381

Quantum transport through a quantum wire coupled with a quantum ring: Effects of in-plane electric field  

Microsoft Academic Search

Transport through a quantum wire sandwiched between two metallic electrodes and coupled to a quantum ring, threaded by a magnetic flux ?, is studied. An analytic approach for the electron transport through the bridge system is presented based on the tight-binding model. The electronic transport properties are discussed in three aspects: (a) the presence of external magnetic filed, (b) the

Santanu K. Maiti

2007-01-01

382

Quantum transport through a quantum wire coupled with a quantum ring: Effects of in-plane electric field  

Microsoft Academic Search

Transport through a quantum wire sandwiched between two metallic electrodes and coupled to a quantum ring, threaded by a magnetic flux varphi, is studied. An analytic approach for the electron transport through the bridge system is presented based on the tight-binding model. The electronic transport properties are discussed in three aspects: (a) the presence of external magnetic filed, (b) the

Santanu K. Maiti

2007-01-01

383

Antibody-quantum dot conjugates exhibit enhanced antibacterial effect vs. unconjugated quantum dots.  

PubMed

The effect of a 20-min exposure to antibody-quantum dot (Ab-QD) conjugates on colony counts of Escherichia coli was assessed by the spread-plate method and compared with exposure to unconjugated QDs having only amine or carboxyl groups on their surfaces. Under these conditions, Ab-QD conjugates generally exhibited >90% reduction in colony-forming units as compared to untreated E. coli and E. coli treated with unconjugated QDs after incubation for as long as 41 h. The antibacterial effect of Ab-QD conjugates vs. unconjugated QDs on Salmonella enterica subsp. enterica serovar Typhimurium was also assessed by means of a disk-diffusion technique which demonstrated greater growth inhibition (approximately 3 mm greater) by Ab-QD conjugate-impregnated disks than by unconjugated-QD-only-impregnated disks at a 10-microg disk load. At a 25-microg disk load, both treatment groups exhibited nearly equal growth inhibition. PMID:17571792

Dwarakanatha, S; Bruno, J G; Athmaram, T N; Bali, G; Vattem, D; Rao, P

2007-01-01

384

Separation of the alpha-emitting radioisotopes actinium-225 and bismuth-213 from thorium-229 using alpha recoil methods  

NASA Astrophysics Data System (ADS)

An innovative method has been demonstrated for separating alpha-emitting isotopes for medical radiotherapy applications. The method relies on recoil-ion separation rather than on conventional wet chemistry techniques to separate medical isotopes from their precursor sources. The isotopes 225Ac and 213Bi have been separated from electro-deposited sources of 229ThO2. Separations of 225Ac were carried out by placing nickel recoil collector foils in firm contact with the 229ThO2 sources. One-stage recoil-ion separations of 225Ac from 229Th have been performed as well as two-stage separations of 213Bi from previously recoil separated 225Ac. In addition, a direct recoil separation of 213Bi from 229Th has been demonstrated. The 213Bi from the one-stage direct separation has a high isotopic purity, but contains small amounts of long-lived 225Ac alpha activity. The two-stage separations of 213Bi produce high isotopic purity material (>99.9999%), but result in lower isotopic yields. Range-energy calculations have been carried out to determine the yields of recoil ions as a function of alpha-particle energy and ThO2 thickness. The results of the calculations have been benchmarked with recoil separation measurements carried out using ThO2 electro-deposits over a range of thickness. A computer code based on the generalized Bateman equations has been developed to allow calculations of the amounts of any isotope in the 229Th decay chain as a function of recoil separation exposure time and elapsed time after the separation. An excellent match has been obtained between the predictions of the Bateman calculations and the results of recoil separation measurements. The recoil separation method has proven to be a simple and effective way of separating medically useful isotopes such as 213Bi. In addition, the method has been shown to produce no chemical or radioactive wastes, in contrast to radiochemical separation methods, which generate mixed (chemical and radioactive) waste.

Ruddy, F. H.; Dulloo, A. R.; Seidel, J. G.; Petrovi?, B.

2004-01-01

385

Magnetoelectric effects in an organometallic quantum magnet  

NASA Astrophysics Data System (ADS)

Metal-organic materials constitute a new field in which to search for ferroelectricity and coupling between electricity and magnetism. We observe a magnetic field-induced change in the electric polarization, ?P(H), that reaches 50 ?C/m2 in single crystals of NiCl2-4SC(NH2)2 (DTN). DTN forms a tetragonal structure that breaks inversion symmetry with the electrically polar thiourea molecules [SC(NH2)] all tilted in the same direction along the c axis. The field H induces canted antiferromagnetism of the Ni S=1 spins between 2 and 12 T and our measurements show that the electric polarization increases monotonically in this range, saturating above 12 T. By modeling the microscopic origin of this magnetoelectric effect, we find that the leading contribution to ?P comes from the change in the crystal electric field, with a smaller contribution from magnetic exchange striction. The finite value of ?P induced by magnetostriction results from the polar nature of the thiourea molecules bonded to the Ni atoms, and it is amplified by the softness of these organic molecules.

Zapf, V. S.; Sengupta, P.; Batista, C. D.; Nasreen, F.; Wolff-Fabris, F.; Paduan-Filho, A.

2011-04-01

386

Quantum Zeno effect by general measurements  

NASA Astrophysics Data System (ADS)

We study the measurement-induced enhancement of the spontaneous decay for a two-level subsystem, where measurements are treated as couplings between the excited state and an auxiliary state rather than the von Neumann's wave function reduction. The photon radiated in a fast decay of the atom, from the auxiliary state to the excited state, triggers a quasi-measurement, as opposed to a projection measurement. Our use of the term ``quasi-measurement'' refers to a ``coupling-based measurement''. Such frequent quasi-measurements result in an exponential decay of the survival probability of atomic initial state with a photon emission following each quasi-measurement. Our calculations show that the effective decay rate is of the same form as the one based on projection measurements. The survival probability of the atomic initial state obtained by tracing over all the photon states is equivalent to that of the atomic initial state with a photon emission following each quasi-measurement.

Ai, Qing; Xu, Dazhi; Yi, Su; Kofman, A. G.; Sun, C. P.; Nori, Franco

2013-05-01

387

On the Existence of Quantum Wave Function and Quantum Interference Effects in Mental States: An Experimental Confirmation during Perception and Cognition in Humans On the Possibility That We Think in a Quantum Mechanical Manner: An Experimental Verification of Existing Quantum Interference Effects In Cognitive Anomaly of Conjunction Fallacy  

Microsoft Academic Search

We introduce the quantum theoretical formulation to determine a posteriori, if existing, the quantum wave functions and to estimate the quantum interference effects of mental states. Such quantum features are actually found in the case of an experiment involving the perception and the cognition in humans. Also some specific psychological variables are introduced and it is obtained that they characterize

Elio Conte; Andrei Yuri Khrennikov; Orlando Todarello; Antonio Federici; Roberta De Robertis; Joseph P. Zbilut

388

Tunable interactions and the fractional quantum Hall effect  

NASA Astrophysics Data System (ADS)

We explore several realistic methods of tuning the interactions in two-dimensional electronic systems in high magnetic fields. We argue that these experimental probes can be useful in studying the interplay of topology, quantum geometry and symmetry breaking in the fractional quantum Hall effect (FQHE). In particular, we show that the mixing of subbands and Landau levels in GaAs wide quantum wells breaks the particle-hole symmetry between the Moore-Read Pfaffian state and its particle-hole conjugate, the anti-Pfaffian, in such a way that the latter is unambiguously favored and generically describes the ground state at 5/2 filling [1]. Furthermore, the tilting of the magnetic field, or more generally variation of the band mass tensor, probes the fluctuation of the intrinsic metric degree of freedom of the incompressible fluids, and ultimately induces the crossover to the broken-symmetry and nematic phases in higher Landau levels [2]. Some of these mechanisms also lead to an enhancement of the excitation gap of the non-Abelian states, as observed in recent experiments. Finally, we compare the tuning capabilities in conventional systems with that in multilayer graphene and related materials with Dirac-type carriers where tuning the band structure and dielectric environment provides a simple and direct method to engineer more robust FQHE states and to study quantum transitions between them [3]. [4pt] [1] Z. Papic, F. D. M. Haldane, and E. H. Rezayi, arXiv:1209.6606 (2012).[0pt] [2] Bo Yang, Z. Papic, E. H. Rezayi, R. N. Bhatt, F. D. M. Haldane, Phys. Rev. B 85, 165318 (2012).[0pt] [3] Z. Papic, R. Thomale, D. A. Abanin, Phys. Rev. Lett. 107, 176602 (2011); Z. Papic, D. A. Abanin, Y. Barlas, and R. N. Bhatt, Phys. Rev. B 84, 241306(R) (2011); D. A. Abanin, Z. Papic, Y. Barlas, and R. N. Bhatt, New J. Phys. 14, 025009 (2012).

Papic, Zlatko

2013-03-01

389

General relativity as an effective field theory: The leading quantum corrections  

SciTech Connect

I describe the treatment of gravity as a quantum effective field theory. This allows a natural separation of the (known) low energy quantum effects from the (unknown) high energy contributions. Within this framework, gravity is a well-behaved quantum field theory at ordinary energies. In studying the class of quantum corrections at low energy, the dominant effects at large distance can be isolated, as these are due to the propagation of the massless particles ( including gravitons) of the theory and are manifested in the nonlocal and/or nonanalytic contributions to vertex functions and propagators. These leading quantum corrections are parameter-free and represent necessary consequences of quantum gravity. The methodology is illustrated by a calculation of the leading quantum corrections to the gravitational interaction of two heavy masses.

Donoghue, J.F. (Department of Physics and Astronomy, University of Massachusetts, Amherst, Massachusetts 01002 (United States))

1994-09-15

390

Landau level mixing and the fractional quantum Hall effect  

NASA Astrophysics Data System (ADS)

We derive effective Hamiltonians for the fractional quantum Hall effect in n=0 and n=1 Landau levels that account perturbatively for Landau-level mixing by electron-electron interactions. To second order in the ratio of electron-electron interaction to cyclotron energy, Landau-level mixing is accounted for by constructing effective interaction Hamiltonians that include two-body and three-body contributions characterized by Haldane pseudopotentials. Our study builds upon previous treatments, using as a stepping stone the observation that the effective Hamiltonian is fully determined by the few-body problem with N=2 and N=3 electrons in the partially filled Landau level. For the n=0 case we use a first quantization approach to provide a compact and transparent derivation of the effective Hamiltonian which captures a class of virtual processes omitted in earlier derivations of Landau-level-mixing corrected Haldane pseudopotentials.

Sodemann, I.; MacDonald, A. H.

2013-06-01

391

Effect Algebras Are Not Adequate Models for Quantum Mechanics  

NASA Astrophysics Data System (ADS)

We show that an effect algebra E possess an order-determining set of states if and only if E is semiclassical; that is, E is essentially a classical effect algebra. We also show that if E possesses at least one state, then E admits hidden variables in the sense that E is homomorphic to an MV-algebra that reproduces the states of E. Both of these results indicate that we cannot distinguish between a quantum mechanical effect algebra and a classical one. Hereditary properties of sharpness and coexistence are discussed and the existence of {0,1} and dispersion-free states are considered. We then discuss a stronger structure called a sequential effect algebra (SEA) that we believe overcomes some of the inadequacies of an effect algebra. We show that a SEA is semiclassical if and only if it possesses an order-determining set of dispersion-free states.

Gudder, Stan

2010-10-01

392

Scintillation of liquid helium for low-energy nuclear recoils  

NASA Astrophysics Data System (ADS)

The scintillation properties of liquid helium upon the recoil of a low-energy helium atom are discussed in the context of the possible use of this medium as a detector of dark matter. It is found that the prompt scintillation yield in the range of recoil energies from a few keV to 100 keV is somewhat higher than that obtained by a linear extrapolation from the measured yield for a 5-MeV ? particle. A comparison is made of both the scintillation yield and the charge separation by an electric field for nuclear recoils and for electrons stopped in helium.

Ito, T. M.; Seidel, G. M.

2013-08-01

393

Autler-Townes splitting and quantum confined Stark effect of sideband peak in asymmetric double quantum wells  

NASA Astrophysics Data System (ADS)

Optical absorption is investigated by self-consistent density matrix approach in asymmetric double quantum wells driven by an intense terahertz field and a direct current electric field polarized along the growth direction. Rich nonlinear dynamic behaviors of sideband absorption peaks are systematically studied in undoped asymmetric double quantum wells. When only in presence of a resonant terahertz field, the Autler-Townes splitting of the sideband peaks becomes pronounced with increasing the strength of the terahertz field. Quantum confined Stark effect of sideband peaks is discussed when an invariant terahertz field and a direct current electric field are simultaneously applied to the quantum well. It is shown that the sideband peaks of the 1s main absorption peak undergo a red-shift and the sideband peaks of the 2s main absorption peak undergo a blue-shift with increasing intensity of the direct current electric field. The presented results have potential applications in electro-optical devices.

Hong-wei, Wu; Xian-wu, Mi; Yong-gang, Huang; Ke-hui, Song

2013-01-01

394

External-field effect on quantum features of radiation emitted by a quantum well in a microcavity  

SciTech Connect

We consider a semiconductor quantum well in a microcavity driven by coherent light and coupled to a squeezed vacuum reservoir. By systematically solving the pertinent quantum Langevin equations in the strong-coupling and low-excitation regimes, we study the effect of exciton-photon detuning, external coherent light, and the squeezed vacuum reservoir on vacuum Rabi splitting and on quantum statistical properties of the light emitted by the quantum well. We show that the exciton-photon detuning leads to a shift in polariton resonance frequencies and a decrease in fluorescence intensity. We also show that the fluorescent light exhibits quadrature squeezing, which predominately depends on the exciton-photon detuning and the degree of the squeezing of the input field.

Sete, Eyob A.; Das, Sumanta; Eleuch, H. [Institute for Quantum Science and Engineering and Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843-4242 (United States); Department of Physics and Astronomy, College of Science, P. O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia)

2011-02-15

395

Tunneling through point contacts in the quantum Hall effect  

NASA Astrophysics Data System (ADS)

We study tunneling through gated point contacts on GaAs/AlGaAs heterojunctions in the regime of the integer (IQHE) and fractional (FQHE) quantum Hall effects. The off-resonant conductance data at bulk filling factor ?=1/3 has a steep temperature dependence that is roughly consistent with the predictions of Luttinger liquid theory for edge states. In the IQHE, we find only weak temperature dependence at ?=1 in the bulk. However, the line shape of tunneling resonances at ?=1 is not well fit by a Fermi-liquid form, perhaps indicating that complex edge structure affects resonant transmission.

Turley, P. J.; Druist, D. P.; Gwinn, E. G.; Maranowski, K.; Campmann, K.; Gossard, A. C.

1998-06-01

396

Role of quantum effects in the glass transition.  

PubMed

It is shown that quantum effects lead to a significant decrease of the glass transition temperature T(g) with respect to the melting temperature T(m), so that the ratio T(g)/T(m) can be much smaller than the typical value of 2/3 in materials where T(g) is near or below ~60 K. Furthermore, it is demonstrated that the viscosity or structural relaxation time in such low temperature glass formers should exhibit highly unusual temperature dependence, namely a decrease of the apparent activation energy upon approaching T(g) (instead of traditional increase). PMID:23432275

Novikov, V N; Sokolov, A P

2013-02-05

397

Nuclear quantum effects on the stability of cationic neon clusters  

NASA Astrophysics Data System (ADS)

The stable structures of cationic neon clusters containing up to 57 atoms have been located using a diatomic-in-molecules potential energy surface and basin-hopping hierarchical optimization. The effects of vibrational delocalization were included either in the harmonic approximation, or by performing Langevin molecular dynamics simulations coupled to a quantum thermal bath at T=0. For most clusters, zero-point motion is sufficiently high to blur the picture of a single well-defined structure. However, structural diversity of the ground state wavefunction is found to be lower at sizes 14, 21, and 56, which correspond to special stabilities in experimental mass spectra.

Calvo, F.; Naumkin, F. Y.; Wales, D. J.

2012-11-01

398

Scalar spin chirality and quantum hall effect on triangular lattices  

SciTech Connect

We study the Kondo Lattice and Hubbard models on a triangular lattice for band filling factor 3/4. We show that a simple non-coplanar chiral spin ordering (scalar spin chirality) is naturally realized in both models due to perfect nesting of the fermi surface. The resulting triple-Q magnetic ordering is a natural counterpart of the collinear Neel ordering of the half-filled square lattice Hubbard model. We show that the obtained chiral phase exhibits a spontaneous quantum Hall-effect with {sigma}{sub xy} = e{sup 2}/h.

Martin, Ivar [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory

2008-01-01

399

The quantum Hall effect: The symmetry and the velocity  

NASA Astrophysics Data System (ADS)

The complete and the correct interpretation of all of the fractions found in the quantum Hall effect of AlGaAs/GaAs heterostructures is presented by use of a specific treatment of spin. Hence the flux quantization depends on spin and the Lande's g value expression is replaced by a linear formula. The fractions occur in pairs of left and right helicities and the velocity of the particles is directed such that if one particle moves upstream then its conjugate moves downstream. The change in the sign of the spin is equivalent to the change in the sign of the velocity.

Shrivastava, Keshav N.

2013-04-01

400

One-dimensional model for the fractional quantum Hall effect  

NASA Astrophysics Data System (ADS)

A simple one-dimensional model is proposed, in which N spinless repulsively interacting fermions occupy M>N degenerate states. It is argued that the energy spectrum and the wavefunctions of this system strongly resemble the spectrum and wavefunctions of 2D electrons in the lowest Landau level (the problem of the Fractional Quantum Hall Effect). In particular, Laughlin-type wavefunctions describe ground states at filling factors v = N/M = 1/q, q odd.. Within this model the complimentary wavefunction for v=1?1/q is found explicitly, and extremely simple ground state wavefunctions for arbitrary odd-denominator filling factors are proposed.

Dyakonov, M. I.

2013-08-01

401

Role of Quantum Effects in the GlassTransition.  

SciTech Connect

It is shown that quantum effects lead to a significant decrease of the glass transition temperature Tg with respect to the melting temperature Tm, so that the ratio Tg=Tm can be much smaller than the typical value of 2=3 in materials where Tg is near or below 60 K. Furthermore, it is demonstrated that the viscosity or structural relaxation time in such low temperature glass formers should exhibit highly unusual temperature dependence, namely a decrease of the apparent activation energy upon approaching Tg (instead of traditional increase).

Novikov, Vladimir [ORNL; Sokolov, Alexei P [ORNL

2013-01-01

402

Systematic Studies of the Fractional Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

A description is given of the occurrence of fractional quantum Hall effects, and how these are influenced by the presence of disorder. It is shown that when electrons are photoexcited into a GaAs-GaAlAs heterojunction, the fractional state existing at a Landau level occupancy of 7/5 can dominate over that at 4/3. Activation energy measurements of the resistivity show how the energy gap of the fractional states is reduced by the presence of disorder. A new method of analysis of the resistivity minima is presented which is used to give information on the correlation length of the many body ground state.

Nicholas, R. J.; Clark, R. G.; Usher, A.; Mallett, J. R.; Suckling, A. M.; Harris, J. J.; Foxon, C. T.

1987-01-01

403

Excitonic collapse of higher Landau level fractional quantum Hall effect  

NASA Astrophysics Data System (ADS)

The scarcity of the fractional quantum Hall effect in higher Landau levels is a most intriguing fact when contrasted with its great abundance in the lowest Landau level. This paper shows that a suppression of the hard core repulsion in going from the lowest Landau level to higher Landau levels leads to a collapse of the energy of the neutral excitation, destabilizing all fractional states in the third and higher Landau levels, and almost all in the second Landau level. The remaining fractions are in agreement with those observed experimentally.

Scarola, V. W.; Park, Kwon; Jain, J. K.

2000-12-01

404

Effects of dissipation on a quantum critical point with disorder.  

PubMed

We study the effects of dissipation on a disordered quantum phase transition with O(N) order-parameter symmetry by applying a strong-disorder renormalization group to the Landau-Ginzburg-Wilson field theory of the problem. We find that Ohmic dissipation results in a nonperturbative infinite-randomness critical point with unconventional activated dynamical scaling while super-Ohmic damping leads to conventional behavior. We discuss applications to the superconductor-metal transition in nanowires and to the Hertz theory of the itinerant antiferromagnetic transition. PMID:18233349

Hoyos, José A; Kotabage, Chetan; Vojta, Thomas

2007-12-04

405

Computational Investigation of Quantum Size Effects in Gold Nanoparticles  

ScienceCinema

Electron density perturbation from carbon monoxide adsorption on a multi-hundred atom gold nanoparticle. The perturbation causes significant quantum size effects in CO catalysis on gold particles. Science: Jeff Greeley and Nick Romero, Argonne National Laboratory; Jesper Kleis, Karsten Jacobsen, Jens Nørskov, Technical University of Denmark? Visualization: Joseph Insley, Argonne National Laboratory This research used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Dept. of Energy under contract DE-AC02-06CH11357.

406

Disentangling the order effect from the context effect: analogies, homologies, and quantum probability.  

PubMed

Although the quantum probability (QP) can be useful to model the context effect, it is not relevant to the order effect, conjunction fallacy, and other related biases. Although the issue of potentiality, which is the intuition behind QP, is involved in the context effect, it is not involved in the other biases. PMID:23673039

Khalil, Elias L

2013-06-01

407

Recoil corrections to the nucleon magnetic moment in the bag model  

NASA Astrophysics Data System (ADS)

It is shown that the recoil correction to the value of the nucleon magnetic moment computed in the static bag model is small and negative. This is due to an over-cancellation of the spin precession effect by the retardation effect. The latter has been ignored in previous calculations, leading to a large positive correction. Permanent address: Service de Physique Théorique, IPN, Bâtiment 210, Université Claude Bernard, 69622 Villeurbanne Cedex, France.

Guichon, P. A. M.

1983-09-01

408

Quantum transport through a quantum wire coupled with a quantum ring: Effects of in-plane electric field  

NASA Astrophysics Data System (ADS)

Transport through a quantum wire sandwiched between two metallic electrodes and coupled to a quantum ring, threaded by a magnetic flux ?, is studied. An analytic approach for the electron transport through the bridge system is presented based on the tight-binding model. The electronic transport properties are discussed in three aspects: (a) the presence of external magnetic filed, (b) the strength of the wire to electrodes coupling and (c) the presence of in-plane electric field.

Maiti, Santanu K.

2007-02-01

409

Momentum Distributions and Final State Effects in Quantum Fluids  

NASA Astrophysics Data System (ADS)

We present and discuss high precision neutron scattering measurements(This work is done in collaboration with W.G. Stirling, P.E. Sokol, S.M. Bennington, K. Guckelsberger, R. Scherm and A.D. Taylor.)^,(R.T. Azuah et al. Phys. Rev. B) 51, 605 (1995); Physica B 213/214, 457 (1995). of the momentum distribution, n(k), and of Final State collision effects in liquid ^4He and ^3He, liquid Ne and solid ^4He. The shape of n(k) is normal liquid ^4He is accurately determined and differs significantly from the classical Maxwell-Boltzmann distribution. States of low momentum in n(k) have significantly higher occupation in a cold Bose quantum liquid than in classical liquids. The n(k) in liquid Ne is found to be nearly Maxwellian. In quantum liquids where n(k) is narrow, Final State effects are best represented by a Final State broadening function as proposed by Gersch and Rodriguez. This is accurately determined and found to be the same in normal ^4He, superfluid ^4He and liquid ^3He within precision. In nearly classical liquids where n(k) is broad, final state effects are better represented as additive corrections. The momentum distribution in solid ^4He, liquid ^3He and the condensate fraction will be discussed.

Azuah, R. T.; Glyde, Henry R.

1996-03-01

410

Interference Effects in the Conductance of Multilevel Quantum Dots  

SciTech Connect

Using exact-diagonalization techniques supplemented by a Dyson equation embedding procedure, the transport properties of multilevel quantum dots are investigated in the Kondo regime. The conductance can be decomposed into the contributions of each level. It is shown that these channels can carry a different phase, and destructive interference processes are observed when the phase difference between them is {+-}{pi}. This effect is very different from those observed in bulk metals with magnetic impurities, where the phase differences play no significant role. The effect is also different from other recent studies of interference processes in dots, as discussed in the text. In particular, no external magnetic field is introduced here, and the dot-leads hopping amplitude for all levels are the same. However, conductance cancellations induced by interactions are still observed. Another interesting effect reported here is the formation of localized states that do not participate in the transport. When one of these states crosses the Fermi level, the electronic occupation of the quantum dot changes, modifying the many-body physics of the system and indirectly affecting the transport properties. Unusual discontinuities between two finite conductance values can occur as the gate voltage is varied, as discussed here.

Busser, Carlos A [ORNL; Martins, G. B. [Oakland University, Rochester, MI; Al Hassanieh, Khaled A [ORNL; Moreo, Adriana [ORNL; Dagotto, Elbio R [ORNL

2004-01-01

411

Charge distributions of alpha-recoil atoms from electrodeposited 210Po source  

Microsoft Academic Search

Charge distributions have been measured for 206Pb recoil atoms emerging from a 210Po source electrodeposited on platinum. It has been found that more than 50% of the recoils are neutrals when the average energy loss of the recoils is about 18 keV. The observed large fraction for the neutrals indicates that a strong neutralization of the recoil ions occurs with

Shin Ito; Nobuhiro Maeda

1987-01-01

412

Scattering approach to quantum transport and many body effects  

SciTech Connect

We review a series of works discussing how the scattering approach to quantum transport developed by Landauer and Buttiker for one body elastic scatterers can be extended to the case where electron-electron interactions act inside the scattering region and give rise to many body scattering. Firstly, we give an exact numerical result showing that at zero temperature a many body scatterer behaves as an effective one body scatterer, with an interaction dependent transmission. Secondly, we underline that this effective scatterer depends on the presence of external scatterers put in its vicinity. The implications of this non local scattering are illustrated studying the conductance of a quantum point contact where electrons interact with a scanning gate microscope. Thirdly, using the numerical renormalization group developed by Wilson for the Kondo problem, we study a double dot spinless model with an inter-dot interaction U and inter-dot hopping t{sub d}, coupled to leads by hopping terms t{sub c}. We show that the quantum conductance as a function of t{sub d} is given by a universal function, independently of the values of U and t{sub c}, if one measures t{sub d} in units of a characteristic scale {tau}(U,t{sub c}). Mapping the double dot system without spin onto a single dot Anderson model with spin and magnetic field, we show that {tau}(U,t{sub c}) 2T{sub K}, where T{sub K} is the Kondo temperature of the Anderson model.

Pichard, Jean-Louis [Service de Physique de l'Etat Condense, (CNRS URA 2464), IRAMIS/SPEC, CEA Saclay, 91191 Gif sur Yvette cedex (France); Freyn, Axel [Service de Physique de l'Etat Condense, (CNRS URA 2464), IRAMIS/SPEC, CEA Saclay, 91191 Gif sur Yvette cedex (France); Institut Neel, 25 avenue des Martyrs, BP 166, 38042 Grenoble Cedex 9 (France)

2010-12-21

413

Compton recoil electron tracking with silicon strip detectors  

SciTech Connect

The application of silicon strip detectors to Compton gamma ray astronomy telescopes is described in this paper. The Silicon Compton Recoil Telescope (SCRT) tracks Compton recoil electrons in silicon strip converters to provide a unique direction for Compton scattered gamma rays above 1 MeV. With strip detectors of modest positional and energy resolutions of 1 mm FWHM and 3% at 662 keV, respectively, 'true imaging' can be achieved to provide an order of magnitude improvement in sensitivity to 1.6 [times] 10[sup [minus] 6] [gamma]/cm[sup 2]-s at 2 MeV. The results of extensive Monte Carlo calculations of recoil electrons traversing multiple layers of 200 micron silicon wafers are presented. Multiple Coulomb scattering of the recoil electron in the silicon wafer of the Compton interaction and the next adjacent wafer is the basic limitation to determining the electron's initial direction.

O'Neill, T.J.; Ait-Ouamer, F.; Schwartz, I.; Tumer, O.T.; White, R.S.; Zych, A.D. (California Univ., Riverside, CA (United States). Inst. of Geophysics and Planetary Physics)

1992-08-01

414

Proton recoil energy and angular distribution of neutron radiative ?- decay  

NASA Astrophysics Data System (ADS)

We analyze the proton recoil energy and angular distribution of the radiative ?- decay of the neutron to leading order in the large baryon mass expansion by taking into account the contributions of the proton-photon correlations. We show that the account for the proton-photon correlations does not contradict the description of the radiative corrections to the lifetime of the neutron and the proton recoil energy spectrum of the neutron ?- decay in terms of the functions (?/?)gn(Ee) and (?/?)fn(Ee), where Ee is the electron energy. In addition we find that the contributions of the proton-photon correlations in the radiative ?- decay of the neutron to the proton recoil asymmetry C are of order 10-4. They make the contributions of the radiative corrections to the proton recoil asymmetry C symmetric with respect to a change A0?B0, where A0 and B0 are the correlation coefficients of the neutron ?- decay.

Ivanov, A. N.; Höllwieser, R.; Troitskaya, N. I.; Wellenzohn, M.

2013-09-01

415

Comparison of recoil-induced resonances and the collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

The theories of recoil-induced resonances (RIR) [J. Guo, P. R. Berman, B. Dubetsky, and G. Grynberg, Phys. Rev. A 46, 1426 (1992)] and the collective atomic recoil laser (CARL) [R. Bonifacio and L. De Salvo, Nucl. Instrum. Methods Phys. Res. A 341, 360 (1994)] are compared. Both theories can be used to derive expressions for the gain experienced by a probe field interacting with an ensemble of two-level atoms that are simultaneously driven by a pump field. It is shown that the underlying formalisms of the RIR and CARL are equivalent. Differences between the RIR and CARL arise because the theories are typically applied for different ranges of the parameters appearing in the theory. The RIR limit is one in which the time derivative of the probe field amplitude, dE2/dt, depends locally on E2(t) and the gain depends linearly on the atomic density, while the CARL limit is one in which dE2/dt=?t0f(t,t')E2(t')dt', where f is a kernel, and the gain has a nonlinear dependence on the atomic density. Validity conditions for the RIR or CARL limits are established in terms of the various parameters characterizing the atom-field interaction. The probe gain for a probe-pump detuning equal to zero is analyzed in some detail, in order to understand how gain arises in a system which, at first glance, appears to have a symmetry that would preclude the possibility for gain. Moreover, it is shown that these calculations, carried out in perturbation theory, have a range of applicability beyond the recoil problem. Experimental possibilities for observing CARL are discussed.

Berman, P. R.

1999-01-01

416

A Proton Recoil Telescope for Neutron Spectroscopy  

NASA Astrophysics Data System (ADS)

The N2P research program funded by the INFN committee for Experimental Nuclear Physics (CSNIII) has among his goals the construction of a Proton Recoil Telescope (PRT), a detector to measure neutron energy spectra. The interest in such a detector is primarily related to the SPES project for rare beams production at the Laboratori Nazionali di Legnaro. For the SPES project it is, in fact, of fundamental importance to have reliable information about energy spectra and yield for neutrons produced by d or p projectiles on thick light targets to model the ''conversion target'' in which the p or d are converted in neutrons. These neutrons, in a second stage, will induce the Uranium fission in the ''production target''. The fission products are subsequently extracted, selected and re-accelerated to produce the exotic beam. The neutron spectra and angular distribution are important parameters to define the final production of fission fragments. In addition, this detector can be used to measure neutron spectra in the field of cancer therapy (this topic is nowadays of particular interest to INFN, for the National Centre for Hadron therapy (CNAO) in Pavia) and space applications.

Cinausero, M.; Barbui, M.; Prete, G.; Rizzi, V.; Andrighetto, A.; Pesente, S.; Fabris, D.; Lunardon, M.; Nebbia, G.; Viesti, G.; Moretto, S.; Morando, M.; Zenoni, A.; Bocci, F.; Donzella, A.; Bonomi, G.; Fontana, A.

2006-05-01

417

Exerpts from the history of alpha recoils.  

PubMed

Any confined air volume holding radon ((222)Rn) gas bears a memory of past radon concentrations due to (210)Pb (T(1/2) = 22 y) and its progenies entrapped in all solid objects in the volume. The efforts of quantifying past radon exposures by means of the left-behind long-lived radon progenies started in 1987 with this author's unsuccessful trials of removing (214)Po from radon exposed glass objects. In this contribution the history and different techniques of assessing radon exposure to man in retrospect will be overviewed. The main focus will be on the implantation of alpha recoils into glass surfaces, but also potential traps in radon dwellings will be discussed. It is concluded that for a successful retrospective application, three crucial imperatives must be met, i.e. firstly, the object must persistently store a certain fraction of the created (210)Pb atoms, secondly, be resistant over decades towards disturbances from the outside and thirdly, all (210)Pb atoms analysed must originate from airborne radon only. For large-scale radon epidemiological studies, non-destructive and inexpensive measurement techniques are essential. Large-scale studies cannot be based on objects rarely found in dwellings or not available for measurements. PMID:21306801

Samuelsson, Christer

2011-02-08

418

From Fractional Chern Insulators to a Fractional Quantum Spin Hall Effect  

Microsoft Academic Search

We investigate the algebraic structure of flat energy bands a partial filling of which may give rise to a fractional quantum anomalous Hall effect (or a fractional Chern insulator) and a fractional quantum spin Hall effect. Both effects arise in the case of a sufficiently flat energy band as well as a roughly flat and homogeneous Berry curvature, such that

M. O. Goerbig

2011-01-01

419

Recoil Studies of Nuclear Reactions Induced by Heavy Ions  

Microsoft Academic Search

The mechanism of nuclear reactions induced by heavy ions was investigated by measuring the recoil ranges of Tb149, At211 and other alpha-emitting isotopes of At and neighboring elements and by determining the cross sections for the formation of Tb149 and At211. Recoil ranges were consistent with compound-nucleus formation at all energies studied for the following reactions: Pr141(C12, 4n)Tb149, Ce(N14, xn)Tb149,

John M. Alexander; Lester Winsberg

1961-01-01

420

SubSurface Neutralization Of Highly Charged, Slow Recoil Ions  

Microsoft Academic Search

X rays from target-recoil atoms in collisions of high-energy heavy ions exhibit rich satellite structures indicating target multiple ionization. Recoil velocities are 10^5-10^6 cm\\/sec. For third row elements, K-shell radiative lifetimes are ~ 10-15 sec, and distances between ionization and X-ray emission are ~ 0.1-1 ÅL-shell vacancy distributions inferred from K-X-ray satellites follow binomial distributions which depend on the electronic

C. R. Vane; S. Datz; J. D. Hunn; N. L. Jones; H. F. Krause

1998-01-01

421

Recoil splitting of x-ray-induced optical fluorescence  

SciTech Connect

We show that the anisotropy of the recoil velocity distribution of x-ray-ionized atoms or molecules leads to observable splittings in subsequent optical fluorescence or absorption when the polarization vector of the x rays is parallel to the momentum of the fluorescent photons. The order of the magnitude of the recoil-induced splitting is about 10 {mu}eV, which can be observed using Fourier or laser-absorption spectroscopic techniques.

Gavrilyuk, S.; Aagren, H.; Gel'mukhanov, F. [Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm (Sweden); Sun, Y.-P. [Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm (Sweden); College of Physics and Electronics, Shandong Normal University, 250014 Jinan (China); Levin, S. [Institute for Physics, St. Petersburg University, Uljanovskaya 1, St. Petersburg RU-198904 (Russian Federation)

2010-03-15

422

Monte Carlo Study on Spontaneous Recoil of Confined DNA Chain  

Microsoft Academic Search

A part of a long DNA chain was driven into a confined environment by an electric field, while the rest remains in the higher-entropy region. Upon removal of the field, the chain recoils to the higher-entropy region spontaneously. This dynamical process was investigated by Monte Carlo simulations. The simulation reproduces the experimentally-observed phenomenon that the recoil of the DNA chain

Yong-jun Xie; Hong-tao Yu; Hai-yang Yang; Yao Wang; Xing-yuan Zhang; Qin-wei Shi

2008-01-01

423

Compton recoil electron tracking with silicon strip detectors  

Microsoft Academic Search

The application of silicon strip detectors to Compton gamma-ray astronomy telescopes is described. The silicon Compton recoil telescope tracks Compton recoil electrons in silicon strip converters to provide a unique direction for Compton-scattered gamma rays above 1 MeV. With strip detectors of modest positional and energy resolutions of 1 mm full width at half maximum (FWHM) and 3% at 662

T. J. O'Neill; F. Ait-Ouamer; I. Schwartz; O. T. Tumer; R. S. White; A. D. Zych

1991-01-01

424

alpha decay and recoil decay tagging studies of 183Tl  

Microsoft Academic Search

High-spin states in the nucleus 183Tl have been studied using the recoil decay tagging and recoil tagging techniques. The data have enabled new structures to be identified which are believed to be based on prolate f7\\/2 , h9\\/2 , and oblate h9\\/2 configurations. In addition, the prolate i3\\/2 structure has also been extended. The systematics of the newly identified structures

P. M. Raddon; D. G. Jenkins; C. D. O'Leary; A. J. Simons; R. Wadsworth; A. N. Andreyev; R. D. Page; M. P. Carpenter; F. G. Kondev; T. Enqvist; P. T. Greenlees; P. M. Jones; R. Julin; S. Juutinen; H. Kettunen; M. Leino; A.-P. Leppänen; P. Nieminen; J. Pakarinen; P. Rahkila; J. Uusitalo; D. T. Joss

2004-01-01

425

Alpha-recoil track dating of Quaternary volcanics  

Microsoft Academic Search

Like fission-track dating, alpha-recoil track (ART) dating is based on the accumulation of nuclear particles that are released by natural radioactivity and produce etchable tracks in solids. ARTs are formed during the alpha-decay of uranium and thorium as well as of their daughter nuclei. When emitting an alpha-particle, the heavy remaining nucleus recoils 30–40 nm, leaving behind a trail of

K. Gögen; G. A. Wagner

2000-01-01

426

Effective vector-field theory and long-wavelength universality of the fractional quantum Hall effect  

NASA Astrophysics Data System (ADS)

We report on an effective vector-field theory of the fractional quantum Hall effect that takes into account projection to Landau levels. The effective theory refers to neither the composite-boson nor composite-fermion picture, but properly reproduces the results consistent with them, thus revealing the universality of the long-wavelength characteristics of the quantum Hall states. In particular, the dual-field Lagrangian of Lee and Zhang is obtained, and an argument is given to verify the identification by Goldhaber and Jain of a composite fermion as a dressed electron. The generalization to double-layer systems is also remarked.

Shizuya, K.

2002-01-01

427

Underscreened Kondo effect in quantum dots coupled to ferromagnetic leads  

NASA Astrophysics Data System (ADS)

We analyze the equilibrium transport properties of underscreened Kondo effect in the case of a two-level quantum dot coupled to ferromagnetic leads. Using the numerical renormalization-group (NRG) method, we have determined the gate voltage dependence of the dot’s spin and level-resolved spectral functions. We have shown that the polarization of the dot is very susceptible to spin imbalance in the leads and changes sign in the middle of the S=1 Coulomb valley. Furthermore, we have also found that by fine tuning an external magnetic field one can compensate for the presence of ferromagnetic leads and restore the Kondo effect in the case of S=(1)/(2) Coulomb valley. The underscreened Kondo effect is, however, extremely sensitive to the magnetic field which hinders the full restoration of the Kondo peak.

Weymann, Ireneusz; Borda, László

2010-03-01

428

Path integral and effective Hamiltonian in loop quantum cosmology  

NASA Astrophysics Data System (ADS)

We study the path integral formulation of Friedmann universe filled with a massless scalar field in loop quantum cosmology. All the isotropic models of k=0,+1,-1 are considered. To construct the path integrals in the timeless framework, a multiple group-averaging approach is proposed. Meanwhile, since the transition amplitude in the deparameterized framework can be expressed in terms of group-averaging, the path integrals can be formulated for both deparameterized and timeless frameworks. Their relation is clarified. It turns out that the effective Hamiltonian derived from the path integral in deparameterized framework is equivalent to the effective Hamiltonian constraint derived from the path integral in timeless framework, since they lead to same equations of motion. Moreover, the effective Hamiltonian constraints of above models derived in canonical theory are confirmed by the path integral formulation.

Qin, Li; Huang, Haiyun; Ma, Yongge

2013-06-01

429

Confined monopoles induced by quantum effects in dense QCD  

SciTech Connect

We analytically show that mesonic bound states of confined monopoles appear inside a non-Abelian vortex string in massless three-flavor QCD at large quark chemical potential {mu}. The orientational modes CP{sup 2} in the internal space of a vortex is described by the low-energy effective world-sheet theory. Mesons of confined monopoles are dynamically generated as bound states of kinks by the quantum effects in the effective theory. The mass of monopoles is shown to be an exponentially soft scale M{approx}{Delta}exp[-c({mu}/{Delta}){sup 2}], with the color superconducting gap {Delta} and some constant c. A possible quark-monopole duality between the hadron phase and the color superconducting phase is also discussed.

Eto, Minoru [Mathematical Physics Laboratory, RIKEN Nishina Center, Saitama 351-0198 (Japan); Nitta, Muneto [Department of Physics, and Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Yokohama, Kanagawa 223-8521 (Japan); Yamamoto, Naoki [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550 (United States)

2011-04-15

430

Mass spectroscopy of recoiled ion investigation of electrode segregation effects during the initial stages of SrBi{sub 2}Ta{sub 2}O{sub 9} film growth.  

SciTech Connect

The thermodynamic stability of Pt/Ti/SiO2/Si, Pt/TiO2/SiO2/Si, Pt/Ta/SiO2/Si, Ir/SiO2/Si, and RuO2/SiO2/Si electrode layers has been studied using mass spectroscopy of recoiled ions (MSRI), a new technique which provides monolayer-specific in situ surface analysis under conditions of modest oxygen partial pressures required for oxide film growth using sputter-deposition. Results of the initial stages of growth of SrBi2Ta2O9 films on the various substrates listed above are presented also. It is found that the initial growth of SrBi2Ta2O9 films strongly depends on the composition of the bottom electrode surface, on diffusion and segregation processes, and the presence of reactive species on the electrode surface.

Im, J.; Krauss, A. R.; Auciello, O.; Gruen, D. M.; Chang, R. P. H.; Northwestern Univ.

1998-01-01

431

Resonant recoil in extreme mass ratio binary black hole mergers  

NASA Astrophysics Data System (ADS)

The inspiral and merger of a binary black hole system generally leads to an asymmetric distribution of emitted radiation, and hence a recoil of the remnant black hole directed opposite to the net linear momentum radiated. The recoil velocity is generally largest for comparable mass black holes and particular spin configurations, and approaches zero in the extreme mass ratio limit. It is generally believed that for extreme mass ratios ??1, the scaling of the recoil velocity is |V|??2, where the proportionality coefficient depends on the spin of the larger hole and the geometry of the system (e.g. orbital inclination). The small recoil velocity is due to cancellations; while the fraction of the total binary mass radiated away in gravitational waves is O(?), most of this energy is emitted during the inspiral phase where the momentum radiated integrates to zero over an orbit. Here, we show that for low but nonzero inclination prograde orbits and very rapidly spinning large holes (spin parameter a?>0.9678) the inspiralling binary can pass through resonances where the orbit-averaged radiation-reaction force is nonzero. These resonance crossings lead to a new contribution to the kick, |V|??3/2. For these configurations and sufficiently extreme mass ratios, this resonant recoil is dominant. While it seems doubtful that the resonant recoil will be astrophysically significant, its existence suggests caution when extrapolating the results of numerical kick results to extreme mass ratios and near-maximal spins.

Hirata, Christopher M.

2011-05-01

432

Cascade quantum teleportation  

NASA Astrophysics Data System (ADS)

In this letter a cascade quantum teleportation scheme is proposed. The proposed scheme needs less local quantum operations than those of quantum multi-teleportation. A quantum teleportation scheme based on entanglement swapping is presented and compared with the cascade quantum teleportation scheme. Those two schemes can effectively teleport quantum information and extend the distance of quantum communication.

Zhou, Nan-Run; Gong, Li-Hua; Liu, Ye

2006-11-01

433

Electron-recoil ion and recoil ion-projectile coincidence techniques applied to obtain absolute partial collision cross sections.  

PubMed

We present in detail an alternative experimental set-up and data analysis, based on the electron-recoil ion and recoil ion-projectile coincidence techniques, that enable the measurement of partial pure ionization and partial charge exchange cross sections for an effusive gas jet set-up, where the absolute target density and recoil ion efficiency cannot be measured directly. The method is applied to the ionization of helium atoms due to collision with partially stripped C(3 +) projectiles. In order to check the method, the results are compared to data available in the literature where the target density and recoil ion detection efficiency were measured directly. The pure ionization channel is compared to the electron capture channel. PMID:23277972

Wolff, W; de Souza, Ihani J; Tavares, André C; de Oliveira, G F S; Luna, H

2012-12-01

434

Interpretation of Fractions in Quantum Hall Effect: Wei Pan's data  

NASA Astrophysics Data System (ADS)

The proof of 101 different fractions which occur in the quantum Hall effect is reported. One factor arises from the Bose-Einstein statistics for Landau levels so that the eigen values are proportional to (n+1/2). Another factor arises from the spin and the orbit. Some of the fractions arise because of a transition to zero-energy state while others arise from the transition's amongst levels. These transitions create quasiparticles in the system so that the moving quasiparticles can combine to make new two or three particle states. The energy spectrum has a variety of quasiparticles so that in a given cluster, the spin can be a fraction like 1/2, 3/2, ... or an integer like, 0, 1, 2, .... The integer spin gives rise to even denominators such as 1/2, 5/2, 7/2, 3/2, 1/6, 5/6, 3/10, 7/10, etc. There is considerable clustering of electrons in the sample. The unit of flux quantum is ?o = hc/e so that flux can quantize in units of n'?o (n' = integer). For n' = 2, the plateaus can occur at 3/8, 5/8 and 29/8. The state at 1/2 is four-fold degenerate and hence can not be described as a paired state. The factor of 8 in the denominator is a result of 1/2 from Bose-Einstein distribution, 1/2 from l and s and 1/2 from the flux quantum. But another 1/2 can arise from the cyclotron frequency. Hence there are four sources of 1/2 out of which only three are needed to obtain 1/8. Hence 3/8, 5/8 and 29/8 can not be described by a Pfaffian determinant which gives only a two particle state. However, some of the states are paired.

Shrivastava, Keshav N.

2009-07-01

435

Waves in a bounded quantum plasma with electron exchange-correlation effects  

SciTech Connect

Within a quantum hydrodynamic model, the collective excitations of the quantum plasma with electron exchange-correlation effects in a nano-cylindrical wave guide are studied both analytically and numerically. The influences of the electron exchange-correlation potential, the radius of the wave guide, and the quantum effect on the dispersion properties of the bounded quantum plasma are discussed. Significant frequency-shift induced by the electron exchange-correlation effect, the radius of the wave guide and the quantum correction are observed. It is found that the influence of the electron exchange-correlation, the radius of the wave guide and the quantum correction on the wave modes in a bounded nano-waveguide are strongly coupled.

Ma Yutng; Mao Shenghng; Xue Juji [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

2011-10-15

436

The quantum transverse-field Ising chain in circuit quantum electrodynamics: effects of disorder on the nonequilibrium dynamics  

NASA Astrophysics Data System (ADS)

We study several dynamical properties of a recently proposed implementation of the quantum transverse-field Ising chain in the framework of circuit quantum electrodynamics (QED). Particular emphasis is placed on the effects of disorder on the nonequilibrium behavior of the system. We show that small amounts of fabrication-induced disorder in the system parameters do not jeopardize the observation of previously predicted phenomena. Based on a numerical extraction of the mean free path of a wave packet in the system, we also provide a simple quantitative estimate for certain disorder effects on the nonequilibrium dynamics of the circuit QED quantum simulator. We discuss the transition from weak to strong disorder, characterized by the onset of Anderson localization of the system's wave functions, and the qualitatively different dynamics it leads to.

Viehmann, Oliver; von Delft, Jan; Marquardt, Florian

2013-03-01

437

Recoil refinements: Implications for the 40 Ar/ 39 Ar dating technique  

NASA Astrophysics Data System (ADS)

Integration of the neutron energy distribution for a water-moderated reactor with the most recent cross-section data yields mean recoil energies of 177 keV for 39 K ( n, p ) 39 Ar, 969 keV for 40 Ca ( n , ) 37 Ar, and 140 eV for 37 Cl ( n , ) 38 Cl ( ) 38 Ar. These estimates are insensitive to the anisotropy of reaction products. Utilizing Monte Carlo simulations of collision cascades, we calculate a mean recoil range of 1620 å for 39 K ( n, p ) 39 Ar, 3780 å for 40 Ca ( n , ) 37 Ar, and 11 å for 37 Cl ( n , ) 38 Cl ( ) 38 Ar. Rutherford backscatter (RBS) measurements of argon implantation experiments into albite confirm the veracity of these estimates. Integration of the recoil range distributions yields a mean depletion depth in a semi-infinite medium of 820 å for 39 Ar, 1950 å for 37 Ar, and 6 å for 38 Ar. The concentration gradients generated by recoil-redistribution between thin slabs were then incorporated into standard diffusion equations. If the exsolution lamellae are the effective diffusion dimension for argon, then the calculations indicate that the argon release rates and age spectrum derived from incremental heating of minerals exsolved at the micron to submicron scale are significantly affected by recoil-redistribution. The age spectra will be discordant even if the feldspar has not experienced a complex or slow cooling history. Incremental step apparent ages will increase with the fraction of 39 Ar released as the potassium poor lamellae degas. The age spectra will exhibit decreasing apparent ages with increasing fraction 39 Ar released as the potassium feldspar lamellae degas. The overall profile of the age spectrum will depend upon the composition of the feldspar and the size distribution of the lamellae, if the lamellae are the effective argon diffusion dimension. In principal, these calculations can be used to discriminate between different models for argon diffusion in minerals. Finally, the 11 å mean recoil distance calculated for 38 Ar indicates that it is not a proxy for anion-sited excess argon. Instead, published correlations of 38 Ar with excess 40 Ar probably reflect the degassing of fine-grained, Cl-rich inclusions.

Onstott, T. C.; Miller, M. L.; Ewing, R. C.; Arnold, G. W.; Walsh, D. S.

1995-05-01

438

Quantum Computer Games: Quantum Minesweeper  

ERIC Educational Resources Information Center

|The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…

Gordon, Michal; Gordon, Goren

2010-01-01

439

Effects of quantum mechanical tunneling on rates of radiative association  

NASA Astrophysics Data System (ADS)

Radiative association in ion-molecular collisions plays an important role in the synthesis of polyatomic species in interstellar clouds. Here, the results of calculations on the radiative association reactions C(+) + H2 - CH2(+) + h(nu) and CH3(+) + H2 - CH5(+) + h(nu) are presented. While these calculations are based on the treatment of collisionally stabilized associations of neutral free radicals originally proposed by Troe, the effects of quantum mechanical tunneling through the centrifugal barriers on the effective potentials are included in the calculations for the first time. At 10 K, the inclusion of tunneling is estimated to increase the rates of association by factors of 2.2 for C(+) + H2 and by 2.0 for CH3(+) + H2.

Smith, Ian W. M.

1989-12-01

440

Quantum size effects in ?-plutonium (020) surface layers  

NASA Astrophysics Data System (ADS)

We present a systematic first principles density functional theory (DFT) based study of the (020) surface of ?-plutonium using the projector-augmented-wave formalism as implemented in the Vienna Ab Initio Simulation Package (VASP). The surface was modeled by a periodic slab geometry comprised of anti-ferromagnetic atomic layers, with a thickness of up to ten atomic layers. The total and cohesive energies indicate a monotonically decreasing and increasing slope to the bulk values, respectively. The surface energies, in contrast to the work functions, exhibit a significant oscillatory pattern indicating persistent quantum size effects and possible magnetic frustration as well as other effects. The 5f electron density of states indicates progressive delocalization with increasing slab thickness.

Hernandez, S. C.; Ray, A. K.; Taylor, C. D.

2013-10-01

441

Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures  

PubMed Central

The effect of electrostatic shielding of the polarization fields in nanostructures at high carrier densities is studied. A simplified analytical model, employing screened, exponentially decaying polarization potentials, localized at the edges of a QW, is introduced for the ES-shielded quantum confined Stark effect (QCSE). Wave function trapping within the Debye-length edge-potential causes blue shifting of energy levels and gradual elimination of the QCSE red-shifting with increasing carrier density. The increase in the e?h wave function overlap and the decrease of the radiative emission time are, however, delayed until the “edge-localization” energy exceeds the peak-voltage of the charged layer. Then the wave function center shifts to the middle of the QW, and behavior becomes similar to that of an unbiased square QW. Our theoretical estimates of the radiative emission time show a complete elimination of the QCSE at doping densities ?1020 cm?3, in quantitative agreement with experimental measurements.

2009-01-01

442

Effective interactions and elementary excitations in quantum liquids  

SciTech Connect

The effective interactions which provide a wavevector and frequency dependent restoring force for collective modes in quantum liquids are derived for the helium liquids by means of physical arguments and sum rule and continuity considerations. A simple model is used to take into account mode-mode coupling between collective and multiparticle excitations, and the results for the zero-temperature liquid /sup 4/He phonon-maxon-roton spectrum are shown to compare favorably with experiment and with microscopic calculation. The role played by spin-dependent backflow in liquid /sup 3/He is analyzed, and a physical interpretation of its variation with density and spin-polarization is presented. A progress report is given on recent work on effective interactions and elementary excitations in nuclear matter, with particular attention to features encountered in the latter system which have no counterparts in the helium liquids.

Pines, D.

1986-01-01

443

Role of electrical field in quantum Hall effect of graphene  

NASA Astrophysics Data System (ADS)

The ballistic motion of carriers of graphene in an orthogonal electromagnetic field is investigated to explain quantum Hall effect of graphene under experimental conditions. With the electrical field, all electronic eigen-states have the same expectation value of the velocity operator, or classically, all carriers move in cycloid-like curves with the same average velocity. This velocity is the origin of the Hall conductance and its magnitude is just appropriate so that the quantized Hall conductance is exactly independent of the external field. Electrical field changes each Landau level into a bundle of energies. Hall conductance plateaus occur in small fields as bundle gaps exist and are destroyed in intermediate fields as bundles overlap. As the electrical field tends to the critical point, all bundles have the same width, and bundle gaps increase to infinity rapidly. As a result, saturation of the Hall conductance may be observed. Electrical field thus demonstrates nonlinear effects on the Hall conductance.

Luo, Ji

2013-01-01

444

Disorder effects in the quantum Hall effect of graphene p-n junctions  

NASA Astrophysics Data System (ADS)

The quantum Hall effect in graphene p-n junctions is studied numerically with emphasis on the effect of disorder at the interface of two adjacent regions. Conductance plateaus are found to be attached to the intensity of the disorder and are accompanied by universal conductance fluctuations in the bipolar regime, which is in good agreement with theoretical predictions of the random matrix theory on quantum chaotic cavities. The calculated Fano factors can be used in an experimental identification of the underlying transport character.

Li, Jian; Shen, Shun-Qing

2008-11-01

445

Band Collapse and the Quantum Hall Effect in Graphene  

SciTech Connect

The recent Quantum Hall experiments in graphene have confirmed the theoretically well-understood picture of the quantum Hall (QH) conductance in fermion systems with continuum Dirac spectrum. In this paper we take into account the lattice, and perform an exact diagonalization of the Landau problem on the hexagonal lattice. At very large magnetic fields the Dirac argument fails completely and the Hall conductance, given by the number of edge states present in the gaps of the spectrum, is dominated by lattice effects. As the field is lowered, the experimentally observed situation is recovered through a phenomenon which we call band collapse. As a corollary, for low magnetic field, graphene will exhibit two qualitatively different QHE's: at low filling, the QHE will be dominated by the 'relativistic' Dirac spectrum and the Hall conductance will be odd-integer; above a certain filling, the QHE will be dominated by a non-relativistic spectrum, and the Hall conductance will span all integers, even and odd.

Bernevig, B.Andrei; Hughes, Taylor L.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.; Chen, Han-Dong; /Illinois U., Urbana; Wu, Congjun; /Santa Barbara, KITP

2010-03-16

446

Quantum Hall Effect near the charge neutrality point in graphene  

NASA Astrophysics Data System (ADS)

The Quantum Hall effect (QHE) of a two-dimensional (2D) electron gas in a strong magnetic field is one of the most fascinating quantum phenomena discovered in condensed matter physics. In this work we propose to study the transport properties of the single layer and bilayer of graphene at the charge neutrality point (CNP) and compare it with random magnetic model developed in theoretical papers in which we argue that at CNP graphene layer is still inhomogeneous, very likely due to random potential of impurities. The random potential fluctuations induce smooth fluctuations in the local filling factor around ?=0. In this case the transport is determined by special class of trajectories, ``the snake states'', propagating along contour ?=0. The situation is very similar to the transport of a two-dimensional particles moving in a spatially modulated random magnetic field with zero mean value. We especially emphasize that our results may be equally relevant to the composite fermions description of the half-filled Landau level.

Leon, Jorge A.; Gusev, Guennadii M.; Plentz, Flavio O.

2013-03-01

447

Effect of anisotropies on magnetic quantum phase transitions  

NASA Astrophysics Data System (ADS)

We consider the effects of superexchange anisotropy and Dzyaloshinskii--Moriya (DM) interactions on the field-- and pressure--driven magnetic phase transitions in quantum dimer systems. These two types of anisotropy term are introduced separately on the intra-- and interdimer bonds, with spatial symmetries both commensurate and incommensurate with the magnetic order, to determine the alterations of the phase diagram and magnetic excitations. Exchange anisotropy causes a general modification of the critical properties at the field--driven transition from the XY universality class (Bose--Einstein condensation) to Ising behaviour. DM interactions may act either to remove the field--driven transition completely or to create a new transition between two different antiferromagnetic states. For certain cases we compute the magnetisation and the evolution of the excitation spectra as functions of field and pressure. Our results are directly relevant to recent measurements on TlCuCl3 and CuHpCl, and may assist in the further understanding of a number of other quantum dimer systems, including BaCuSi2O6, Sr2Cu(BO3)2 and PHCC.

Normand, B.; Zhitomirsky, M. E.

2005-03-01

448

Controllable effects of quantum fluctuations on spin free-induction decay at room temperature  

PubMed Central

Fluctuations of local fields cause decoherence of quantum objects. Usually at high temperatures, thermal noises are much stronger than quantum fluctuations unless the thermal effects are suppressed by certain techniques such as spin echo. Here we report the discovery of strong quantum-fluctuation effects of nuclear spin baths on free-induction decay of single electron spins in solids at room temperature. We find that the competition between the quantum and thermal fluctuations is controllable by an external magnetic field. These findings are based on Ramsey interference measurement of single nitrogen-vacancy center spins in diamond and numerical simulation of the decoherence, which are in excellent agreement.

Liu, Gang-Qin; Pan, Xin-Yu; Jiang, Zhan-Feng; Zhao, Nan; Liu, Ren-Bao

2012-01-01

449

Quantum effects in helimagnets: Disappearance of the soft mode at the wave vector of magnetic order  

Microsoft Academic Search

Usually the quantum nature of spins has only a limited effect on properties like the spin wave spectrum of a system and the S ? ? limit (classical vectorial model) is often considered. On the contrary, we show that in helimagnets the quantum corrections can have dramatic effects. In absence of magnetic anisotropy the spin wave spectrum in the S

E. Rastelli; L. Reatto; A. Tassi

1984-01-01

450

Nuclear quantum effects in ab initio dynamics: Theory and experiments for lithium imide  

Microsoft Academic Search

Owing to their small mass, hydrogen atoms exhibit strong quantum behavior even at room temperature. Including these effects in first-principles calculations is challenging because of the huge computational effort required by conventional techniques. Here we present the first ab initio application of a recently developed stochastic scheme, which allows to approximate nuclear quantum effects inexpensively. The proton momentum distribution of

Michele Ceriotti; Giacomo Miceli; Antonino Pietropaolo; Daniele Colognesi; Angeloclaudio Nale; Michele Catti; Marco Bernasconi; Michele Parrinello

2010-01-01

451

Memory effects in classical and quantum mean-field disordered models  

NASA Astrophysics Data System (ADS)

We apply the Kovacs experimental protocol to classical and quantum p-spin models. We show that these models have memory effects as those observed experimentally in super-cooled polymer melts. We discuss our results in connection to other classical models that capture memory effects. We propose that a similar protocol applied to quantum glassy systems might be useful to understand their dynamics.

Cugliandolo, L. F.; Lozano, G.; Lozza, H.

2004-09-01

452

Unconventional quantum Hall effect and Berry's phase of 2pi in bilayer graphene  

Microsoft Academic Search

There are two known distinct types of the integer quantum Hall effect. One is the conventional quantum Hall effect, characteristic of two-dimensional semiconductor systems, and the other is its relativistic counterpart observed in graphene, where charge carriers mimic Dirac fermions characterized by Berry's phase pi, which results in shifted positions of the Hall plateaus. Here we report a third type

K. S. Novoselov; E. McCann; S. V. Morozov; V. I. Fal'Ko; M. I. Katsnelson; U. Zeitler; D. Jiang; F. Schedin; A. K. Geim

2006-01-01

453

Size effect of quantum conductance in single-walled carbon nanotube quantum dots  

Microsoft Academic Search

The quantum conductance of two kinds of carbon nanotube quantum dots (CNQD) composed of (5,5) and (10,0) tubes, namely (10,0)\\/(5,5)\\/(10,0) and (5,5)\\/(10,0)\\/(5,5) with different quantum sizes, are calculated. It is shown that for (10,0)\\/(5,5)\\/(10,0) CNQD, one on-resonant peak at the Fermi energy exists only for special QD sizes, and the width of the conductance gap increases from 1.0 eV to

H. Liu; Y. Tao

2003-01-01

454

Determination of the Lifetime of the 40-kev Excited State of 81Tl208 Following Alpha Decay Using Recoil Shifts of the Conversion Electrons  

Microsoft Academic Search

The lifetime of the 40-kev excited state of 81Tl208 which is produced after alpha decay has been measured by using recoil shifts of the conversion electrons. By using an alpha-particle-conversion-electron coincidence arrangement, a beam of moving recoil nuclei in vacuum is effectively selected. The momenta of electrons emitted from such moving nuclei into the acceptance angle of a lens spectrometer

J. Burde; S. G. Cohen

1956-01-01

455

Performance of a two-state quantum engine improved by the superposition effect  

NASA Astrophysics Data System (ADS)

The performance of a two-state quantum engine under different conditions is analyzed. It is shown that the efficiency of the quantum engine can be enhanced by superposing the eigenstates at the beginning of the cycle. By employing the finite-time movement of the potential wall, the power output of the quantum engine as well as the efficiency at the maximum power output (EMP) can be obtained. A generalized potential is adopted to describe a class of two-level quantum engines in a unified way. The results obtained show clearly that the performances of these engines depend on the external potential, the geometric configuration of the quantum engines, and the superposition effect. Moreover, it is found that the superposition effect will enlarge the optimally operating region of quantum engines.

Ou, CongJie; Huang, ZhiFu; Lin, BiHong; Chen, JinCan

2013-10-01

456

Polarization dependence of quantum-confined Stark effect in Ge/SiGe quantum well planar waveguides.  

PubMed

We report room-temperature quantum-confined Stark effect in Ge/SiGe multiple quantum wells (MQWs) with light propagating parallel to the plane of the Ge/SiGe MQWs for applications in integrated photonics. Planar waveguides embedded in a p-i-n diode are fabricated in order to investigate the absorption spectra at different reverse bias voltages from optical transmission measurements for both TE and TM polarizations. Polarization dependence of the absorption spectra of the Ge/SiGe MQWs is clearly observed. The planar waveguides exhibit a high extinction ratio and low insertion loss over a wide spectral range for TE polarization. PMID:21593893

Chaisakul, Papichaya; Marris-Morini, Delphine; Isella, Giovanni; Chrastina, Daniel; Le Roux, Xavier; Edmond, Samson; Coudevylle, Jean-René; Cassan, Eric; Vivien, Laurent

2011-05-15

457

The Quantum Hall Effect in Spin Quartets in Graphene  

NASA Astrophysics Data System (ADS)

Using the non-relativistic Schroedinger equation, we find that for (1/2)g=(1/2)±s gives zero charge for negative sign and one charge for positive sign. This explains the conductivity at i = 0 and 1. For s=3/2, (1/2)g=2 for positive sign and hence g=4. The substitution in the series, -(5/2)(g?BH), -(3/2)(g?BH), -(1/2)( g?BH), +(1/2)( g?BH),+(3/2)( g?BH), +(5/2)( g?BH), , etc., g=4 gives, -10, -6, -2, +2, +6, +10, etc. This series is the same as observed in the experimental data of quantum Hall effect in graphene. When we take n=2 in the flux quantization, i.e., 2(hc/e), we generate the plateaus at ±4. Thus the plateaus can occur at 0, 1, 4 and at 2, 6, 10, 14, , etc. Thus the quantum Hall effect in graphene is understood by means of non-relativistic theory. The fractions such as 1/3 or integers such as 0,1,4,, 2,6,10,14, multiply the charge and hence describe the ``effective charge'' of the quasiparticles. This means that there is ``spin-charge locking''. *K. N. Shrivastava, Phys. Lett. A 113, 435(1986); 115, 436(E)(1986); Phys. Lett. A, 326, 469(2004); AIP Conf. Proc. 909, 43(2007);909,50(2007. *Z.Jiang, et al, Phys. Rev. Lett. 98,197403(2007);Y.Zhang et al, Phys. Rev. Lett. 96, 136806(2006).

Shrivastava, Keshav

2008-03-01

458

Characterization of carbon nanotube fiber compressive properties using tensile recoil measurement.  

PubMed

The tensile properties of carbon nanotube (CNT) fibers have been widely studied. However, the knowledge of their compressive properties is still lacking. In this work, the compressive properties of both pure CNT fibers and epoxy infiltrated CNT fibers were studied using the tensile recoil measurement. The compressive strengths were obtained as 416 and 573 MPa for pure CNT fibers and CNT-epoxy composite fibers, respectively. In addition, microscopic analysis of the fiber surface morphologies revealed that the principal recoil compressive failure mode of pure CNT fiber was kinking, while the CNT-epoxy composite fibers exhibited a failure mode in bending with combined tensile and compressive failure morphologies. The effect of resin infiltration on CNT fiber compressive properties, including the compressive strength and the deformation mode, is discussed. This work expands the knowledge base of the overall mechanical properties of CNT fibers, which are essential for their application in multifunctional composites. PMID:22494330

Zu, Mei; Lu, Weibang; Li, Qing-Wen; Zhu, Yuntian; Wang, Guojian; Chou, Tsu-Wei

2012-04-18

459

Recoil velocities from equal-mass binary-black-hole mergers.  

PubMed

The final evolution of a binary-black-hole system gives rise to a recoil velocity if an asymmetry is present in the emitted gravitational radiation. Measurements of this effect for nonspinning binaries with unequal masses have pointed out that kick velocities approximately 175 km/s can be reached for a mass ratio approximately 0.36. However, a larger recoil can be obtained for equal-mass binaries if the asymmetry is provided by the spins. Using two independent methods we show that the merger of such binaries yields velocities as large as approximately 440 km/s for black holes having unequal spins that are antialigned and parallel to the orbital angular momentum. PMID:17678346

Koppitz, Michael; Pollney, Denis; Reisswig, Christian; Rezzolla, Luciano; Thornburg, Jonathan; Diener, Peter; Schnetter, Erik

2007-07-27

460

Helium jet recoil transport setup for chemistry and nuclear applications at VECC  

NASA Astrophysics Data System (ADS)

A gas jet recoil transport facility (GJRT) developed at VECC is described. A maximum transport efficiency of ~ 90% has been obtained for Ni and Cu isotopes using cyclohexane as a dopant to the He carrier gas. A transit time of ~ 1 s has been obtained at a distance of ~ 12 m using a 1.6 mm i.d. tygon capillary and a pressure differential of 1 atm. The effect of various dopants, beam current and fluid dynamical parameters on the transport of different nuclides has been studied. The results indicate the role of the chemical aspects of the dopants and the recoils on the efficiency of transport. The usefulness of this system in determining (reaction) cross sections has been demonstrated for 60Cu, 60Zn, 61Zn and 159mHo.

Chakrabarti, A.; Chowdhury, D. P.; Gangadharan, S.; Arunachalam, J.; Iyer, R. M.

1988-01-01

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