Particle-two-particle interaction in configuration space

The problem of three identical particles with zero-range two-particle interaction is considered. An explicit expression for the effective potential between one particle and the remaining two-particle system is obtained in the coordinate representation. It is shown that for arbitrary energies, at small and, for zero energy, at large distances ρ between the one particle and centre of mass of the other two particles the diagonal matrix element of the effective potential is attractive and proportional to 1/ρ². This property of the effective potential explains both the Thomas singularity and the Efimov effect. In the case of zero total energy of the system the general form of the solution of the three-particle integral equation is found in configuration space.     

Terahertz phonon spectroscopy of doped superconducting cuprates

Facts are presented evidencing a strong electron-phonon interaction in doped BSCCO superconductors. A pronounced fine structure in dI/dV characteristics of Josephson junctions has been observed which is caused by interaction of AC Josephson current with Raman-active optical phonon modes. “Quantization” of the “gap” voltage for natural nanosteps on the cryogenically cleaved surfaces of BSCCO proves the existence of the intrinsic Josephson effect. A sharp extra structure in the current-voltage characteristics of nanosteps is attributed to the presence of the extended van Hove singularity.     

Multiple-Band Andreev Transport in Optimally Doped Superconducting Oxypnictides

JETP Letters - Using multiple Andreev reflections (MAR) effect spectroscopy of SnS junctions, we directly determine temperature dependences of the superconducting order parameters, excess Andreev...     

Multiple Andreev Reflection Spectroscopy of Optimally Doped Ba(Fe,Ni)2As2 Superconducting Pnictides

JETP Letters - The current-voltage characteristics and dynamic conductance spectra of the SnS junction in Ba(Fe, Ni)2As2 superconducting pnictide of almost optimal composition have been obtained. A...     

Tunka-133: Status 2008 and development of methods for data analysis

The activity on creation of a array with an area of 1 km² for recording extensive air showers using Cherenkov light began in the Tunka valley in 2006. The new array will allow one to study cosmic rays in the energy range 10¹⁵–10¹⁸ eV by the unified method. In the winter of 2007–2008, the array operated with 4 clusters, 7 detectors in each cluster. Experimental data obtained during 270 h of fair weather in moonless nights demonstrated unique capabilities of the new array, related with the possibility of recording the pulse shape with a step of 5 ns from each detector.     

Status of the Baikal neutrino project

The status of the Baikal neutrino experiment is briefly reviewed and the results of the search for the natural flux of high-energy neutrinos are reported.     

Doping influence on Sm1 − x Th x OFeAs superconducting properties: Observation of the effect of intrinsic multiple Andreev reflections and determination of the superconducting parameters

We studied SNS and S-N-S-N-...-S contacts (where S is a superconductor and N is a normal metal) formed by “break-junction” technique in polycrystalline Sm_{1 ? x} Th _x OFeAs superconductor samples with critical temperatures T _C = 34–45 K. In such contacts (intrinsic) multiple Andreev reflections effects were observed. Using spectroscopies based on these effects, we detected two independent bulk order parameters and determined their magnitudes. Theoretical analysis of the large and the small gap temperature dependences revealed superconducting properties of Sm_{1 ? x} Th _x OFeAs to be driven by intraband coupling, and $\sqrt {V_{11} V_{22} } /V_{12} \approx 14$ (where V _ij are the electron-boson interaction matrix elements), whereas the ratio between density of states for the bands with the small and the large gap, N ₂/N ₁, correspondingly, was roughly of an order. We estimated “solo” BCS-ratio values in a hypothetic case of zero interband coupling (V _{i ≠ j} = 0) for each condensate as 2Δ_{L, S}/k _B T _C ^L,S ≤ 4.5. The values are constant within the range of critical temperatures studied, and correspond to a case of strong intraband electron-phonon coupling.     

Bose—Einstein Condensation and Spin Superfluidity of Magnons in a Perpendicularly Magnetized Yttrium Iron Garnet Film

JETP Letters - The formation of a Bose—Einstein condensate of magnons in a perpendicularly magnetized iron yttrium garnet film under radio-frequency pumping in a stripline has been studied...     

Experimental study of the resonance reflection of a plane electromagnetic wave from a wide-spaced strip grating

The resonance reflection of a plane electromagnetic wave from a diffraction grating consisting of wide-spaced, thin, tilted metal strips is confirmed and investigated experimentally. Good agreement is obtained between the experimental results and published theoretical data. Zh. Tekh. Fiz. 68, 138–140 (May 1998)