Non-rigid Shell Model and Correlational Mechanism of the Local Pairing

The Hartree-Fock states of the many-electron atomic system can be unstable with respect to a static or dynamic shift of the electron shells. An appropriate non-rigid shell model for atomic clusters is developed. It permits to formulate a convenient approach to the semiempirical description of the different correlation effects and to reveal some new effects.Comment: 3 pages, 2 ".gif" figures, LaTeX; will be published in Physica C in Materials of Int.Conf. HTSC-V. (1997, Beijing, China

The Growth of CdTe Layer on GaAs Substrate by MBE

We present the results of growth of CdTe layer on (013)GaAs substrate. The sequence processes include the preparation of GaAs surface by chemical etching and annealing in ultra-high vacuum, the growth of ZnTe layer on atomically clean GaAs surface and then the growth of CdTe layer on ZnTe/GaAs. All processes were carried out without removing GaAs substrate from MBE set. The processes were controlled by RHEED and single wavelength ellipsometry. We found that the evaporation of arsenic oxides and gallium oxides from the (001)GaAs surface were observed at over 400 and 500°C, respectively. The growth of CdTe on (001)GaAs leads to appearance of mixture orientations because of large mismatch of lattice parameters. We study the growth of ZnTe on (001)GaAs and (013)GaAs substrates to prevent the growth of mixture orientations. We study the influence of cadmium and tellurium ratio in molecular fluxes and temperature on the growth mechanism of ZnTe and CdTe, crystal perfection, surface roughness and defects density. The optimal condition for growth of high quality thick CdTe on GaAs substrate were found

Experimental and theoretical investigation of the Preglow in ECRIS

International audienceA careful study of pulsed mode operation of the PHOENIX ECR ion source has clearly demonstrated the reality of an unexpected transient current peak occurring at the very beginning of the gas breakdown. This regime was named the Preglow, as an explicit reference to the classical Afterglow occurring at the microwave pulse end. After the transient Preglow peak, the plasma regime relaxes to the classical steady state one. Argon Preglow experiments performed at LPSC are presented. A theoretical 0-dimension model of ECR gas breakdown in a magnetic trap, developed at IAP RAS, is presented in detail. Results of the simulation are compared with the experimental Preglow peaks and discussed

Anomalous specific heat jump in the heavy fermion superconductor CeCoIn5_5

We study the anomalously large specific heat jump and its systematic change with pressure in CeCoIn$_5$ superconductor. Starting with the general free energy functional of the superconductor for a coupled electron boson system, we derived the analytic result of the specific heat jump of the strong coupling superconductivity occurring in the coupled electron boson system. Then using the two component spin-fermion model we calculate the specific heat coefficient $C(T)/T$ both for the normal and superconducting states and show a good agreement with the experiment of CeCoIn$_5$. Our result also clearly demonstrated that the specific heat coefficient $C(T)/T$ of a coupled electron boson system can be freely interpreted as a renormalization either of the electronic or of the bosonic degrees of freedom.Comment: 5 pages, 2 figure

Kondo lattice model with a direct exchange interaction between localized moments

We study the Kondo lattice model with a direct antiferromagnetic exchange interaction between localized moments. Ferromagnetically long-range ordered state coexisting with the Kondo screening shows a continuous quantum phase transition to the Kondo singlet state. We obtain the value of the critical point where the magnetizations of the localized moments and the conduction electrons vanish. The magnetization curves yield a universal critical exponent independent of the filling factors and the strength of the interaction between localized moments. It is shown that the direct exchange interaction between localized moments introduces another phase transition from an antiferromagnetic ordering to a ferromagnetic ordering for small Kondo exchange interaction. We also explain the local minimum of the Kondo temperature in recent experiments.Comment: 6 pages, 5 figures, final versio

HgCdTe quantum wells grown by molecular beam epitaxy

CdxHg₁₋xTe-based (x = 0 – 0.25) quantum wells (QWs) of 8 – 22 nm in thickness were grown on (013) CdTe/ZnTe/GaAs substrates by molecular beam epitaxy. The composition and thickness (d) of wide-gap layers (spacers) were x ∼ 0.7 mol.frac. and d ∼ 35 nm, respectively, at both sides of the quantum well. The thickness and composition of epilayers during the growth were controlled by ellipsometry in situ. It was shown that the accuracy of thickness and composition were ∆x = ± 0.002, ∆d = ± 0.5 nm. The central part of spacers (10 nm thick) was doped by indium up to a carrier concentration of ∼10¹⁵ cm⁻³ . A CdTe cap layer 40 nm in thickness was grown to protect QW. The compositions of the spacer and QWs were determined by measuring the Е₁ and Е₁+∆₁ peaks in reflection spectra using layer-by-layer chemical etching. The galvanomagnetic investigations (the range of magnetic fields was 0 – 13 T) of the grown QW showed the presence of a 2D electron gas in all the samples. The 2D electron mobility µe = (2.4 – 3.5)×10⁵ cm² /(V·s) for the concentrations N = (1.5 – 3)×10¹¹ cm⁻² (x < 0.11) that confirms a high quality of the grown QWs

High Precision Mass Measurements in Ψ\Psi and Υ\Upsilon Families Revisited

High precision mass measurements in $\Psi$ and $\Upsilon$ families performed in 1980-1984 at the VEPP-4 collider with OLYA and MD-1 detectors are revisited. The corrections for the new value of the electron mass are presented. The effect of the updated radiative corrections has been calculated for the $J/\Psi(1S)$ and $\Psi(2S)$ mass measurements.Comment: 5 pages, 1 table, submitted to Phys. Lett.

Study of pulsed ECRIS plasma near breakdown: the Preglow

International audienceA careful study of pulsed mode operation of the PHOENIX ECR ion source has clearly demonstrated the reality of an unexpected transient current peak, occurring at the very beginning of the plasma breakdown. This regime was named the Preglow, as an explicit reference to the Afterglow occurring at the microwave pulse end. After the transient Preglow peak, the plasma regime relaxes to the classical steady state one. Argon Preglow experiments performed at LPSC are presented. A theoretical model of ECR gas breakdown in a magnetic trap, developed at IAP, showing satisfactory agreement with the experimental results is suggested

Radiative decays of light vector mesons

The new data on $\rho,\omega,\phi$ radiative decays into $\pi^0\gamma,\eta\gamma,\eta'\gamma$ from SND experiment at VEPP-2M $e^+e^-$ collider are presented.Comment: 5 pages, 2 figures, talk given at 8th International Conference on Hadron Spectroscopy (HADRON 99), Beijing, China, 24-28 Aug 199