Atomic tunneling states and low-temperature anomalies of thermal properties in amorphous materials

A general theory of local atomic non-single-well potential in amorphous materials is presented. It is shown that the potentials practically are critical double-well potentials with low spring constants. Two essentially different types of two-level tunneling states in such potentials are found. The spectral density of the states is shown to be smooth under realistic conditions. The respective specific heat logarithmically deviates from the linear temperature dependence and logarithmically or more weakly depends on the measurement time. Both types of the tunneling states can essentially contribute to the specific heat, whereas one of the types is rather more strongly coupled with phonons and determines the phononic thermal conductivity. Some other questions are also discussed.     

The effect of LH wave on the peripheral plasma of TM-1-MH tokamak

The work is devoted to the study of the LH wave effect on the peripheral plasma of the TM-1-MH tokamak. The observed enhancement of the ion saturated current in the limiter shadow is interpreted as heating of the peripheral ions by absorption of decay waves generated in this region due to the nonlinear wave-plasma interaction.     

Degradation of the second critical magnetic field in multilayered composites with nanodimensional layers of niobium and Nb-Ti superconducting alloy

Multilayered tapes containing layers of superconducting niobium alloys with 30 and 31 wt % Ti and separated by niobium layers were investigated. The layers were ∼140 to ∼10 nm thick. Effective pinning of superconducting vortex filaments was observed on the interlayer Nb-NbTi interfaces. It was established that second critical magnetic field H _c2 decreased as the layer thickness decreased. With thin layers, its magnitude depended on the orientation of rolling the tape with respect to the external magnetic field. Results are explained by the proximity effect.     

Electron-hole excitations in CdSe quantum dots under strong and intermediate confinement conditions

The absorption spectrum of cadmium selenide nanocrystals in a glassy fluorophosphate matrix has been investigated in the vicinity of the fundamental absorption edge 400–650 nm. The revealed oscillations of the absorption have been interpreted as a manifestation of the quantum-well effect for electrons and holes under strong and intermediate confinement conditions. The data obtained have demonstrated that the individual discrete confinement states arise from the band and exciton states of the bulk crystal. The results are in good agreement with those obtained from theoretical consideration of the intermediate confinement model.