Quantum nature of the critical points of substances

Thermodynamics of chemical elements, based on the two-component electron-nuclear plasma model shows that the critical parameters for the liquid-vapor transition are the quantum values for which the classical limit is absent.Comment: 4 pages, no figure

True Dielectric and Ideal Conductor in Theory of the Dielectric Function for Coulomb System

On the basis of the exact relations the general formula for the static dielectric permittivity e(q,0) for Coulomb system is found in the region of small wave vectors q. The obtained formuladescribes the dielectric function e(q,0) of the Coulomb system in both states in the "metallic" state and in the "dielectric" one. The parameter which determines possible states of the Coulomb system - from the "true" dielectric till the "ideal" conductor is found. The exact relation for the pair correlation function for two-component system of electrons and nuclei g_ei(r) is found for the arbitrary thermodynamic parameters.Comment: 5 pages, no figure

Angular Schmidt Modes in Spontaneous Parametric Down-Conversion

We report a proof-of-principle experiment demonstrating that appropriately chosen set of Hermite-Gaussian modes constitutes a Schmidt decomposition for transverse momentum states of biphotons generated in the process of spontaneous parametric down conversion. We experimentally realize projective measurements in Schmidt basis and observe correlations between appropriate pairs of modes. We perform tomographical state reconstruction in the Schmidt basis, by direct measurement of single-photon density matrix eigenvalues.Comment: 5 pages, 4 figure

Point-contact study of the LuNi2B2C borocarbide superconducting film

We present point-contact (PC) Andreev-reflection measurements of a superconducting epitaxial c-axis oriented nickel borocarbide film LuNi2B2C (Tc=15.9 K). The averaged value of the superconducting gap is found to be 2.6 +/-0.2 meV in the one-gap approach, whereas the two-gap approach results in 2.14+/-0.36 meV and 3.0+/-0.27 meV. The better fit of the Andreev-reflection spectra for the LuNi2B2C - Cu PC obtained by the two-gap approach provides evidence for multiband superconductivity in LuNi2B2C. For the first time, PC electron-phonon interaction (EPI) spectra have been measured for this compound. They demonstrate pronounced phonon maximum at 8.5+/-0.4meV and a second shallow one at 15.8+/-0.6 meV. The electron-phonon coupling constant estimated from the PC EPI spectra turned out to be small (~ 0.1), like in other superconducting rare-earth nickel borocarbides. Possible reasons for this are discussed.Comment: 5 pages, 5 figures, V2: figs. 2 & 5 captions are corrected, and new Refs. 4, 6, 12, 13, 14 are adde

Identity of electrons and ionization equilibrium

It is perhaps appropriate that, in a year marking the 90th anniversary of Meghnad Saha seminal paper (1920), new developments should call fresh attention to the problem of ionization equilibrium in gases. Ionization equilibrium is considered in the simplest "physical" model for an electronic subsystem of matter in a rarefied state, consisting of one localized electronic state in each nucleus and delocalized electronic states considered as free ones. It is shown that, despite the qualitative agreement, there is a significant quantitative difference from the results of applying the Saha formula to the degree of ionization. This is caused by the fact that the Saha formula corresponds to the "chemical" model of matter.Comment: 9 pages, 2 figure