Cloaks for suppression or enhancement of scattering of diffuse photon density waves

In this paper we investigate the entanglement dynamics between two two-level atoms interacting with two coherent fields in two spatially separated cavities which are filled with a Kerr-like medium. We examine the effect of nonlinear medium on the dynamical properties of entanglement and atomic occupation probabilities in the case of even and odd deformed coherent states. The results show that the deformed fields play important roles in the evolution of entanglement. Also, the results demonstrate that entanglement sudden death, sudden birth and long-distance can be controlled by the deformation and nonlinear parameters.     

Amplification of light and atoms in a bose-einstein condensate

A Bose-Einstein condensate illuminated by a single off-resonant laser beam ("dressed condensate") shows a high gain for matter waves and light. We have characterized the optical and atom-optical properties of the dressed condensate by injecting light or atoms, illuminating the key role of long-lived matter wave gratings produced by the condensate at rest and recoiling atoms. The narrow bandwidth for optical gain gave rise to an extremely slow group velocity of an amplified light pulse ( approximately 1 m/s).     

SUPERRADIANCE EFFECT OF THE CRYSTAL-LIKE-GAS

Crystal-like-gas (CLG) is a new kind of matter in which the atoms are arranged periodically in the space and the electrons are bound to the corresponding atoms. In this paper, we study the superradiance effect of CLG and discuss some interesting new properties due to the periodic structure of CLG. The non-ideal situation is also discussed.     

Computation of elastic moduli of graphene monolayer in nonsymmetric formulation using energy-based approach

In the paper, elastic moduli of finite-sized graphene monolayers are computed in a nonsymmetric formulation using the lattice statics approach. The motion of atoms due to their interaction is not considered, lattice stability is not studied. The presence of covalent binding is assumed to preserve material structure and all atoms are assigned displacements that correspond to a homogeneous deformation gradient tensor. As a result, the deformation kinematics of graphene is strictly controlled and the material response is defined using a variant of the interatomic interaction potential of the Mie family. The dimensionless parameters of the potential are identified using the coincidence criterion of the experimentally determined Poisson ratio of graphene with an estimated value. The obtained potential parameters are used to determine the elastic properties of a graphene monolayer in a nonsymmetric formulation for low strains and low temperatures. It is shown that the graphene monolayer under homogeneous deformation goes to a nonequilibrium state. In order to provide the potential energy minimum of the specimen in the deformed state, it is necessary to assign displacements to a part of graphene atoms that form one of its “triangular” sublattices relative to atoms of another sublattice, with each sublattice being deformed homogeneously.     

Enhancement of phase space density by increasing trap anisotropy in a magneto-optical trap with a large number of atoms

The phase space density of dense, cylindrical clouds of atoms in a 2D magneto-optic trap is investigated. For a large number of trapped atoms (>10(8)), the density of a spherical cloud is limited by photon reabsorption. However, as the atom cloud is deformed to reduce the radial optical density, the temperature of the atoms decreases due to the suppression of multiple scattering leading to an increase in the phase space density. A density of 2 x 10(-4) has been achieved in a magneto-optic trap containing 2 x 10(8) atoms.     

Quantum generation of angular momenta of crystallites in a nanocrystalline material

It is shown that, under the effect of a point force, ordered deformation states of the Fermi type can arise in a nanocrystal. These states are characterized by an angular momentum whose magnitude (estimated in the units of Planck’s constant) depends on the number of atoms in the deformed nanocrystals and can accept macroscopic values. A qualitative explanation is given to the evolution of the strength, diffusive, and damping properties of compact nanocrystalline materials based on the assumption that the quantum generation of angular momenta of crystallites can result in states of rotational motion.     

Segregation of Mo atoms into stacking faults in CrFeCoNiMo alloy

Solute segregation at dislocations can impede the motion of dislocations, strengthening materials. Here, we study the formation and role of solute segregation at dislocations in CrFeCoNiMo high-entropy alloys (HEAs) by high-angle annular dark-field scanning transmission electron microscopy imaging and mechanical testing both deformed and annealed samples. Mo atoms exhibit pronounced segregation into the planar-extended core of dislocations, i.e. stacking faults, causing the increase in the yield strength while the loss of the ductility. This work suggests that mechanical properties of HEAs can be tailored by alloying additional elements that are in favour of segregation into dislocations.     

Experimental evidence of the existence of a nonstationary coherent crystal state in bismuth

The excitation of a bismuth (Bi) crystal by intense ultrashort laser pulses at liquid-helium temperature leads to consistent motion of atoms and variations in the electron density. At various time instants over an interval reaching several dosen picoseconds, atoms in the Bi lattice exhibit sequential pairing in the real and reciprocal spaces. This behavior may correspond to the formation of a coherent crystal—a special state of matter that combines the properties of a solid and quantum fluid. Experimental data showing evidence of the possible existence of this unusual state are presented and analyzed.     

Molecular dynamics simulation of subsurface deformed layers in AFM-based nanometric cutting process

Three-dimensional molecular dynamics simulations of AFM-based nanometric cutting monocrystalline copper with pin tool radius of 0.713 nm are performed to investigate the effect of uncut chip thicknesses (0.1805 nm, 0.361 nm, 0.5415 nm, 0.722 nm, 0.9025 nm, 1.0875 nm, and 1.268 nm) on the depth of subsurface deformed layers. The EAM potential and Morse potential are utilized respectively to compute the interactions between workpiece atoms, the interactions between workpiece atoms and tool atoms. The single-atom potential energy variations of the workpiece atoms within the subsurface regions during the cutting process are obtained and analyzed through a deformation criterion to determine the deformation behaviors of subsurface atoms. The simulation results reveal that the depth of subsurface deformed layers is affected by the AFM pin tool's rake angle. At each uncut chip thickness, the AFM pin tool presents different negative rake angles, consequently different degrees of deformation in the subsurface take place.     

Quantum philosophy

In this, the hundredth year since Einstein first postulated the existence of photons, the successful application of wave - particle duality to matter has seen an explosion of activity in the field of atom optics and Bose - Einstein condensation (BEC). This article provides a brief introduction to atom optics, illustrated with applications taken from experiments using helium atoms in long-lived (metastable) excited states. Metastable helium atoms store the greatest amount of energy (～20 electron volts) in any atomic or molecular system. They behave like nano-hand grenades, making it easy to detect single atoms, opening up promising applications as well as fundamental studies of the quantum statistical properties of atomic systems.     

原子团簇的稳定结构和幻数

原子团簇介于原子分子和宏观凝聚物质之间 ,一般产生于非平衡条件 ,其结构和性质随所含原子数目而变化。当含有某些特定原子数时 ,团簇特别稳定 ,这就是“幻数”。本文重点讨论几种典型团簇的幻数及其演变规律 ,说明“幻数”是团簇的基本属性之一及其与键合方式的关系     

Molecular dynamics simulation of processing using AFM pin tool

A three-dimensional molecular dynamics (MD) model is utilized to investigate the effect of tool geometry on the deformation process of the workpiece and the nature of deformation process at the atomic-scale. Results show that different states exist between the atomic force microscope (AFM) pin tool and the workpiece surface, i.e. the non-wear state, the ploughing state, the state in which ploughing is dominant and the state in which cutting plays a key role. A relationship between the deformation process of the workpiece and the potential energy variation is presented. The potential energy variation of atoms in different deformed regions in the workpiece such as plastically deformed region, elastically deformed region and the mixed deformation region is different. The features of variations of potential energy are discussed.     

The effect of high pressure gaseous He,Ar and N2 on the photoconductivity of deformed Ge

In order to examine the effect of the penetration process of compressed gases on the electrical activity of dislocations, photoconductivity (PC) measurements were carried out on deformed and undeformed germanium samples at 200 K and at high pressures of helium, argon and nitrogen. The results show that dislocations allow the gases to diffuse into the crystal interior more easily. Argon atoms and nitrogen molecules penetrate into dislocations in germanium much less (if at all) than helium atoms. He atoms can be built into the dislocation core, thus changing the electrical activity of the dislocations and causing the reconstruction of some dislocation partials.     

Cluster methods to study the electronic structure of condensed matter

Multiple scattering techniques have been used to study the electronic states (core and continuum states) of condensed matter. The electronic density of states, total energies, charge and spin densities are computed self consistently. The electronic and magnetic properties of the materials are evaluated from this results. The model material is a finite cluster of atoms immersed in the spherical average potential of the rest of the system. The electronic states are then either core states or continuum states. Examples in which the wave functions are given molecular boundary conditions far from the cluster of atoms are also presented.     

Properties of deformed Λ hypernuclei

The properties of Be and B isotopes and the corresponding Λ hypernuclei are studied by using a deformed Skyrme Hartree-Fock approach with realistic nucleonic Skyrme forces, pairing correlations, and a microscopically determined lambda-nucleon interaction based on Brueckner-Hartree-Fock calculations of hypernuclear matter. The results suggest that the core nuclei and the corresponding hypernuclei have similar deformations with the same sign.     

Investigation of the concentration gradient and extraction of helium atoms from copper deformed in a liquid-helium medium

A complex investigation of the penetration, accumulation, and extraction of helium atoms in porous copper samples deformed in a liquid-helium medium has been performed. The experiments have been carried out using three mass spectrometric techniques: (1) ionization of helium atoms by an electron impact in an MSCh-6 mass spectrometer, (2) secondary ion mass spectroscopy, and (3) an original high-resolution method with a sensitivity threshold of ∼10^{9 4}He atoms. The results obtained have made it possible to determine important characteristics of mechanodynamic diffusion of helium atoms, such as their penetration depth, the true concentration of helium trapped under deformation, and its gradient with an increase in the distance from the surface, as well as to estimate the binding energy of helium in traps.     

On the possibility of electronic compression waves in heavy ion collisions

In the collision of heavy atoms compression waves in the atomic electron clouds are predicted. The bulk properties of electronic matter are estimated. Reaction cross sections for electron emission are calculated in a schematic model.     

Relationships between quantum physics and biology

The known facts of quantum physics and biology strongly suggest the following hypotheses: atoms and the fundamental particles have a rudimentary degree of consciousness, volition, or self-activity; the basic features of quantum mechanics are a result of this fact; the quantum mechanical wave properties of matter are actually the conscious properties of matter; and living organisms are a direct result of these properties of matter. These hypotheses are tested by using them to make detailed predictions of new facts, and then by showing that the predictions can be verified. The hypotheses are used to predict successfully that the quantum wave properties of matter are strongly predominant in proteins, to explain the presence and relative abundance of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur in proteins, and to explain diffraction phenomena, the behavior of helium II, the exclusion principle, and causality and determinism in modern science, thus closely relating physics and biology.This article is an outgrowth of the author's thesis work in the Graduate School (Physics Department) of the University of Missouri—Rolla.