Modern Physics Letters B

We discuss the construction of the exactly solvable pairing models for bosons in the framework of the Quantum Inverse Scattering method. It is stressed that this class of models naturally appears in the quasiclassical limit of the algebraic Bethe ansatz transfer matrix. We propose the new pairing Hamiltonians for bosons, depending on the additional parameters. It is pointed out that the new class of the pairing models can be obtained from the fundamental transfer-matrix. The possible new application of the pairing models for confined bosons in the physics of helium nanodroplets is pointed out.

Using the invariant operator method and the unitary transformation method together, we obtained discrete and continuous solutions of the quantum damped driven harmonic oscillator. The wave function of the underdamped harmonic oscillator is expressed in terms of the Hermite polynomial while that of the overdamped harmonic oscillator is expressed in terms of the parabolic cylinder function. The eigenvalues of the underdamped harmonic oscillator are discrete while that of the critically damped and the overdamped harmonic oscillators are continuous. We derived the exact phases of the wave function for the underdamped, critically damped and overdamped driven harmonic oscillator. They are described in terms of the particular solutions of the classical equation of motion.

In the bilayer quantum Hall coherent state for ν_T deviating slightly from unity, we show that, instead of the global order parameter, the periodic domain structure accompanying the charged meron pairs spontaneously breaks the pseudospin U(1) rotational symmetry. The motion of meron pairs induces a novel pseudospin wave. The long-range order of the periodic domains in a low bias voltage range leads to the residual zero-bias peak in the tunneling conductance, which can be distinct from the pseudopsin Goldstone feature in a high bias voltage range.

We investigate the coexistence of ferromagnetism and superconductivity in UGe₂ and Sr₂RuO₄ in analogy with our previous model³ for high transition temperature superconductivity (HTSC). The Coulomb interaction for triplet electron pairs is reduced by a difference of the exchange interaction. If the electron–electron interaction U_sf for UGe₂ and U_sd for Sr₂RuO₄ are larger than the reduced Coulomb interaction, superconductivity must happen. Under the same conditions, the coexistence of superconductivity and ferromagnetism is impossible in the case of our scheme, but changing phonons by pressures makes the coexistence possible for UGe₂.

We have investigated the cohesive and thermodynamic properties of (KBr)_1-x(KCN)_x using an extended three-body force shell model (ETSM), which has been found to be adequately suitable for the description of orientationally disordered mixed cyanide-halide crystals. The specific heat of (KBr)_1-x(KCN)_x for compositions (x=0.53, 0.65, 0.73, 0.84 and 0.93) at temperature 10 K≤T≤150 K have been computed using the ETSM for the first time. The paper also reports the calculated results on Debye temperature (Θ_D), cohesive energy (Φ), compressibility (β), molecular force constant (f) and Restrahlen frequency (ν₀) of (KBr)_1-x(KCN)_x. The results on specific heat and some other thermal properties are in good agreement with their available experimental data.

The oxygen concentration of tantalum powder is critical for the fabrication of solid electrolyte tantalum capacitors. In the present paper an attempt has been made to study the influence of milling time, milling speed (rotations per minute (RPM)) of the vibratory disc mill and average particle size of tantalum powder on oxygen concentrations. It was observed that milling time is directly related to the oxygen content of the powder mass. However, the rotational speed of the mill also contributes to the particle size distribution and ambience gas content of the particles.