International Journal of Modern Physics B

We review the topic of quantized vortices in multicomponent Bose–Einstein condensates of dilute atomic gases, with an emphasis on the two-component condensates. First, we review the fundamental structure, stability and dynamics of a single vortex state in a slowly rotating two-component condensates. To understand recent experimental results, we use the coupled Gross–Pitaevskii equations and the generalized nonlinear sigma model. An axisymmetric vortex state, which was observed by the JILA group, can be regarded as a topologically trivial skyrmion in the pseudospin representation. The internal, coherent coupling between the two components breaks the axisymmetry of the vortex state, resulting in a stable vortex molecule (a meron pair). We also mention unconventional vortex states and monopole excitations in a spin-1 Bose–Einstein condensate. Next, we discuss a rich variety of vortex states realized in rapidly rotating two-component Bose–Einstein condensates. We introduce a phase diagram with axes of rotation frequency and the intercomponent coupling strength. This phase diagram reveals unconventional vortex states such as a square lattice, a double-core lattice, vortex stripes and vortex sheets, all of which are in an experimentally accessible parameter regime. The coherent coupling leads to an effective attractive interaction between two components, providing not only a promising candidate to tune the intercomponent interaction to study the rich vortex phases but also a new regime to explore vortex states consisting of vortex molecules characterized by anisotropic vorticity. A recent experiment by the JILA group vindicated the formation of a square vortex lattice in this system.

A new explicit expressions of self-energies Π_μν and Σ are introduced for photons and electrons based on the particle-hole-antiparticle representation (PHA) of Atomic Schwinger–Dyson formalism (ASD). The PHA representation describes exactly the physical processes such as particle-hole excitations (electron-hole) and particle-antiparticle excitations (electron-positron). The self-energy Σ includes both the quantum component and the classical component (classical external field and Coulomb's field), which are divided into the scalar part Σ_s and 4-dimensional vector parts Σ₀, Σ_j. The electron propagators are composed of the particle part, hole part and antiparticle part in PHA representation. The general representation of photon self-energy Π_μν with 16 elements is expressed in terms of only two components (transverse and longitudinal) Π^t and Π^l. The general form of the photon propagators are written in terms of free propagator D⁰ and two independent propagators D^l and D^t, which include two independent photon self-energies. The tensor part of the electron self-energy does not appear in ASD formalism which makes perfectly the closed self-consistent system, when we take the bare vertex approximation, Γ^μ→γ^μ.

Amorphous carbon nitride films (a-CN_x) were deposited by pulsed laser deposition of camphoric carbon target at different substrate temperatures (ST). The influence of ST on the bonding properties of a-CN_x films was investigated. The nitrogen to carbon (N/C) atomic ratio and oxygen to carbon (O/C) atomic ratio, bonding state and microstructure of the deposited a-CN_x films were characterized by X-ray photoelectron spectroscopy and confirmed by other standard measurement techniques. The bonding states between the C and N, and C and O in the deposited films are found significantly influenced by the ST during deposition process. The N/C and O/C atomic ratio of the a-CN_x films reached the maximum value at 400°C. The ST of 400°C was proposed to promote the desired sp³-hybridized C and the C₃N₄ phase. The C–N bonding of C–N, C=N and C–N were observed in the deposited a-CN_x films.

The concept of nth-order amplitude squeezing is introduced in the fundamental mode in Raman process as a generalization of the higher-order squeezing under short-time approximation based on a fully quantum mechanical approach. The condition for occurrence of nth-order squeezing is obtained from which higher-order squeezing up to n = 5 are studied. The coupled Heisenberg equation of motion involving real and imaginary parts of the quadrature operators is established. Dependence of squeezing on photon number is also established.

Electron penetration in semi-infinite Au for normal and oblique angles of incidence at energies between 0.5 and 4 keV is simulated within a Monte-Carlo frame work. The elastic scattering cross sections have been obtained from a modified Rutherford differential cross section, whereas inelastic core and valence electron excitation are calculated using the Gryzinski's expression. The dependence of the backscattering coefficient, mean implantation depth and stopping profiles on the angle of incidence has been examined. These quantities are found to be significantly enhanced as the angle of incidence becomes higher which is generally in consistent with previous simulations.

In this paper we consider two distant mesoscopic superconducting quantum interference device (SQUID) rings A and B in the presence of two-mode squeezed vacuum state field, and aim to see the effect of the field on the correlation of supercurrents in the two rings. We know the degree of entanglement of the two-mode squeezed vacuum state increases with the squeezing parameter r. In this paper we find that the correlation of the supercurrents increases with the parameter r too, meaning that the correlation of the supercurrents increases with the degree of entanglement of the field.