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Trapping of lattice polarons by impurities  [PDF]
J. P. Hague,P. E. Kornilovitch,A. S. Alexandrov
Physics , 2008, DOI: 10.1103/PhysRevB.78.092302
Abstract: We consider the effects of single impurities on polarons in three-dimensions (3D) using a continuous time quantum Monte-Carlo algorithm. An exact treatment of the phonon degrees of freedom leads to a very efficient algorithm and we are able to compute the polaron dynamics on an infinite lattice using an auxiliary weighting scheme. The magnitude of the impurity potential, the electron-phonon coupling and the phonon frequency are varied. We determine the magnitude of the impurity potential required for polaron trapping. For small electron-phonon coupling the number of phonons increases dramatically on trapping. The polaron binding diagram is computed, showing that intermediate-coupling low-phonon-frequency polarons are localized by exceptionally small impurities.
Nanometric laser trapping based on nanostructured substrates  [PDF]
A. R. Sidorov,Y. Zhang,A. N. Grigorenko,M. R. Dickinson
Physics , 2006, DOI: 10.1016/j.optcom.2007.06.027
Abstract: Laser trapping near the surface of a nanostructured substrate is demonstrated. Stable microbubbles with radii of 1-20micrometers have been created and manipulated with sub-micron precision by a focused laser beam in an immersion oil covering arrays of pairs of gold nanopillars deposited on a glass substrate. The threshold for bubble creation and trapping characteristics depended on near-field coupling of nanopillars. The nanometric laser tweezers showed giant trapping efficiency of Q~50 for the trapped microbubbles.
The structure of fluids with impurities  [PDF]
M. Bier,L. Harnau
Physics , 2012, DOI: 10.1524/zpch.2012.0260
Abstract: The influence of dilute impurities on the structure of a fluid solvent is investigated theoretically. General arguments, which do not rely on particular models, are used to derive an extension of the Ornstein-Zernike form for the solvent structure factor at small scattering vectors. It is shown that dilute impurities can influence the solvent structure only if they are composed of ions with significantly different sizes. Non-ionic impurities or ions of similar size are shown to not alter the solvent structure qualitatively. This picture is compatible with available experimental data. The derived form of the solvent structure factor is expected to be useful to infer information on the impurity-solvent interactions form measured scattering intensities.
Nanostructured optical nanofibres for atom trapping  [PDF]
Mark Daly,Viet Giang Truong,Ciarán Phelan,Kieran Deasy,Síle Nic Chormaic
Physics , 2013, DOI: 10.1088/1367-2630/16/5/053052
Abstract: We propose an optical dipole trap for cold neutral atoms based on the electric field produced from the evanescent fields in a hollow rectangular slot cut through an optical nanofibre. In particular, we discuss the trap performance in relation to laser-cooled rubidium atoms and show that a far off-resonance, blue-detuned field combined with the attractive surface-atom interaction potential from the dielectric material forms a stable trapping configuration. With the addition of a red-detuned field, we demonstrate how three dimensional confinement of the atoms at a distance of 140 - 200 nm from the fibre surface within the slot can be accomplished. This scheme facilitates optical coupling between the atoms and the nanofibre that could be exploited for quantum communication schemes using ensembles of laser-cooled atoms.
Magnetic impurities in a superconductor: Effect of domain walls and interference  [PDF]
P. D. Sacramento,V. K. Dugaev,V. R. Vieira
Physics , 2007, DOI: 10.1103/PhysRevB.76.014512
Abstract: We consider the effect of magnetic impurities, modeled by classical spins, in a conventional superconductor. We study their effect on the quasiparticles, specifically on the spin density and local density of states (LDOS). As previously emphasized, the impurities induce multiple scatterings of the quasiparticle wave functions leading to complex interference phenomena. Also, the impurities induce quantum phase transitions in the many-body system. Previous authors studied the effect of either a small number of impurities (from one to three) or a finite concentration of impurities, typically in a disordered distribution. In this work we assume a regular set of spins distributed inside the superconductor in such a way that the spins are oriented, forming different types of domain walls, assumed stable. This situation may be particularly interesting in the context of spin transfer due to polarized currents traversing the material.
Cosmology in a Test Tube: Theory of Domain Walls Formation in Binary Fluids  [PDF]
Jacek Dziarmaga,Mariusz Sadzikowski
Physics , 1999,
Abstract: Formation of domain walls during a rapid phase transition in a quasi one dimensional Cahn-Hiliard equation describing binary fluids in a thin tube is studied. Density of kinks scales like a sixth root of quench rate for equal concentrations and like a square root of quench rate for unequal concentrations of fluids. For a slow inhomogeneous transition the density is linear in velocity of temperature front. This paper is first theoretical study of topological defects formation in a system with conserved order parameter.
Fluids in porous media: The case of neutral walls  [PDF]
Giuseppe Pellicane,Richard L. C. Vink,Bruno Russo,Paolo V. Giaquinta
Physics , 2013, DOI: 10.1103/PhysRevE.88.042131
Abstract: The bulk phase behavior of a fluid is typically altered when the fluid is brought into confinement by the walls of a random porous medium. Inside the porous medium, phase transition points are shifted, or may disappear altogether. A crucial determinant is how the walls interact with the fluid particles. In this work, we consider the situation whereby the walls are neutral with respect to the liquid and vapor phase. In order to realize the condition of strict neutrality, we use a symmetric binary mixture inside a porous medium that interacts identically with both of the mixture species. Monte Carlo simulations are then used to obtain the phase behavior. Our main finding is that, in the presence of the porous medium, a liquid-vapor type transition still occurs, but with critical exponents that deviate from bulk Ising values. In addition, we observe clear violations of self-averaging. These findings provide further evidence that random confinement by neutral walls induces critical behavior of the random Ising model (i.e. Ising models with dilution type disorder, where the disorder couples to the energy).
The trapping and escape of buoyant vortex rings in sharply stratified fluids  [PDF]
R. Camassa,S. Khatri,R. McLaughlin,K. Mertens,E. Monbureau,D. Nenon,C. Smith,C. Viotti,B. White
Physics , 2011,
Abstract: In this fluid dynamics video we study the dynamics of miscible vortex rings falling in ambient strongly (near two-layer) stratified fluid. Experiments and direct numerical simulations using the variable density Navier-Stokes (VARDEN) solver are presented and compared. Critical phenomena are identified depending upon the key parameters of the experiment (fluid and ring densities, upper layer vortex travel distance, etc) in which the descending dense vortex ring may experience complete trapping, partial trapping, or fissioning into a cascade of smaller vortices. The interaction of the vortex ring with the upper layer fluids leads to viscous entrainment which alters the effective buoyancy of the ring. Upon impinging on a density transition, the entrained fluid imparts different dynamics as it attempts to regain equilibrium leading to the critical behaviors.
MOS Capacitance–Voltage Characteristics: IV. Trapping Capacitance from 3-Charge-State Impurities
半导体学报 , 2012,
Abstract: Metal-Oxide-Semiconductor Capacitance-Voltage (MOSCV) characteristics containing giant carrier trapping capacitances from 3-charge-state or 2-energy-level impurities are presented for not-doped, n-doped, p-doped and compensated silicon containing the double-donor sulfur and iron, the double-acceptor zinc, and the amphoteric or one-donor and one-acceptor gold and silver impurities. These impurities provide giant trapping capacitances at trapping energies from 200 to 800 meV (50 to 200 THz and 6 to 1.5 μm), which suggest potential sub-millimeter, far-infrared and spin electronics applications.
Fluorescence Associated with Impurities in Nanostructured Al_2O_3
Lide ZHANGt,GuoZhong WANGChimei MOTienan ZHAO,

材料科学技术学报 , 1996,
Abstract: The fluorescent spectra of nanostructured Al2O3 after heat-treating at different temperatureshave been systematically investigated. The results show that for η-Al2O3 and γ-Al2O3, two broadfluorescent bands P1 and P2 appear in the wavenumber range of 20000 cm-1 to 11500 cm-1,and P1 and P2 bands are located in the wavenumber range of 20000 cm-1 to 14500 cm-1 and14500 cm-1 to 11500 cm-1, respectively The P1 band can be attributed to the impurity Cr3+luminescence. This is consistent with other author's result for the Cr doped Al2O3. The P2band is a new fluorescent phenomenon, which has not been reported previously. In this paper,the condition of the appearance of P2 and its mechanism is discussed in detail.
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