Modern Physics Letters B

We study the effects of low-energy nodal quasiparticles on the classical phase fluctuations in a two-dimensional d-wave superconductor. The singularities of the phase-only action at T→0 are removed in the presence of disorder, which justifies using an extended classical XY-model to describe phase fluctuations at low temperatures.

We propose a model that includes itinerant and localized states to study Bose–Einstein condensation of ultracold atoms in optical lattices (Bose–Anderson model). It is found that the original itinerant and localized states intermix to give rise to a new energy band structure with two quasiparticle energy bands. We have computed the critical temperature T_c of the Bose–Einstein condensation of the quasiparticles in the Bose–Anderson model using our newly developed numerical algorithm and found that T_c increases as na³ (the number density times the lattice constant cubed) increases according to the power law T_c≈18.93(na³)^0.59nK for na³<0.125 and according to the linear relation T_c≈8.75+10.53na³nK for 1.25<na³<12.5 for the given model parameters. With the self-consistent equations for the condensation fractions obtained within the Bogoliubov mean-field approximation, the effects of the on-site repulsion U on the quasiparticle condensation are investigated. We have found that, for values up to several times the zeroth-order critical temperature, U enhances the zeroth-order condensation fraction at intermediate temperatures and effectively raises the critical temperature, while it slightly suppresses the zeroth-order condensation fraction at very low temperatures.

We study quantitatively the variation of the electrical tunneling conductivity in an MOSFET with control gate and floating gate in terms of the oxide-layer width. This study is performed by defining a suitable parameter to evaluate the sensitivity of the above conductivity to the oxide-layer thickness. In addition, this sensitivity is expressed in terms of the electronic density of states.

Chromium-carbon films have been deposited on silicon substrates by magnetron sputtering of chromium and carbon targets in pure argon atmosphere. The composition of the films was examined by Auger electron spectroscopy. Oxygen, nitrogen, and iron were the major impurities incorporated in the films. The mechanical and electrical properties of the films were investigated as a function of negative bias voltage applied to substrates. The hardness and elastic modulus were measured by a nano-indenter and the values are around 17.0±0.9 GPa and 245±11 GPa, respectively. The hardness and elastic modulus of the films increased while the electrical resistivity decreased when the substrate bias voltage was applied. The lowest resistivity (~ 267 μohm-cm) was obtained at the substrate bias voltage of 50 V. The temperature dependence of resistivity of the films was measured in air from room temperature to 673 K. The time dependence of resistivity of the films was also measured in air at 673 K. It was found that the resistivity changed little with temperature or time.

Samples with representative formula Li_0.45Ni_0.1Mn_0.1Fe_2.35O₄ have been sintered by conventional sintering technique and microwave sintering technique. Both the samples showed single-phase with spinel structure. The lattice constant for the microwave sintered (MS) sample showed a lower value than the conventionally sintered (CS) sample. The density of the MS sample has been found to be higher than the CS sample. And MS sample showed a higher value of resistivity and activation energy compared to the CS sample. The possible mechanisms are discussed.