Specific Heat of a Two-Layer Magnetic Superlattice

The specific heats of both a two-layer ferromagnetic superlattice and a two-layer ferrimagnetic one are studied. It is found that the spin quantum numbers, the interlayer and intralayer exchange couplings, the anisotropy, the applied magnetic field, and the temperature all affect the specific heat of these superlattices. For both the ferromagnetic and ferrimagnetic superlattices, the specific heat decreases with increasing the spin quantum number, the absolute value of interlayer exchange coupling, intralayer exchange coupling, and anisotropy, while it increases with increasing temperature at low temperatures. When an applied magnetic field is enhanced, the specific heat decreases in the twolayer ferromagnetic superlattice, while it is almost unchanged in the two-layer ferrimagnetic superlattice at low field range at low temperatures.     

Ultrafast Electron Diffraction with Spatiotemporal Resolution of Atomic Motion

Ultrafast electron diffraction （UED） is a rapidly advancing technique capable of recording the atomic-detail structural dynamics in real time. We report the establishment of the first UED system in China. Employing this UED apparatus, both the coherent and the concurrent thermal lattice motions in an aluminium thin-film, trigged by ultrafast laser heating, have been observed. These results demonstrate its ability to directly measure a sub-milli-angstrom lattice spacing change on a sub-picosecond time scale.     

Modified Josephson Equation for Mesoscopic Parallel LC Circuit Including a Josephson Junction

By introducing the entangled state representation, parallel LC circuit including a 3osephson junction equation associated with the modification of the motion equation. the Cooper-pair number-phase quantization of the mesoscopic is realized. In the Heisenberg picture, the modified Josephson Faraday equation about the inductance is deduced from the     

Temperature Insensitivity of Optical Properties of InAs/GaAs Quantum Dots due to a Pregrown InGaAs Quantum Well

Both the peak position and linewidth in the photoluminescence spectrum of the InAs/GaAs quantum dots usually vary in an anomalous way with increasing temperature. Such anomalous optical behaviour is eliminated by inserting an In0.2Ga0.8As quantum well below the quantum dot layer in molecular beam epitaxy. The insensitivity of the photoluminescence spectra to temperature is explained in terms of the effective carrier redistribution between quantum dots through the In0.2Ga0.8As quantum well.     

Phase Transition in Acoustic Localization in a Soft Medium Permeated with Air Bubbles

Propagation of an acoustic wave in a soft medium permeated with air bubbles is theoretically investigated by using a self-consistent approach. The soft medium is assumed to be viscoelastic to estimate the effect of acoustic absorption on the acoustic localization in such a medium. The oscillation phases of bubbles are examined by employing a phase diagram method. A collective oscillation of the bubbles is observed once the acoustic localization occurs, which is known as a phenomenon of ＇phase transition ＇, and such a phenomenon persists as we manually increase the viscosity factor of the soft medium. Therefore it is proven that the phenomenon of phase transition may serve as a unique criterion to effectively identify acoustic localization in a bubbly soft medium even in the presence of viscosity, and the directions of the phase vectors help to determine the extent of localization. This is of practical significance for experimental research studying the acoustic localization in such a medium, for which the presence of viscosity generally causes great ambiguity in distinguishing the effects of localization and acoustic absorption.     

Measurement of Magnetic Properties of an Inertial Sensor with a Torsion Balance

A torsion balance is constructed to accurately measure the magnetic properties of the real proof mass of the inertial sensor. The magnetic susceptibility and remnant moment of a titanium proof mass are measured in the first experiment, and further improvements and the potential sensitivity are also discussed. This is significant for choosing the material of the proof mass and investigating the magnetic disturbances acting on the proof mass.     

Effect of Different Substrate Temperature on Phosphorus-Doped ZnO Thin Films Prepared by PLD on Sapphire Substrates

Phosphorus-doped ZnO （ZnO：P） thin films are deposited on a c-plane sapphire in oxygen at 350℃, 450℃, 550℃ and 650℃, respectively, by pulsed laser deposition （PLD）, then all the ZnO：P samples are annealed at 650℃ in oxygen with a pressure of 1 × 10^5 Pa. X-ray diffraction measurements indicate that the crystalline quality of the ZnO：P thin films is improved with the increasing substrate temperature from 350℃ to 550℃. With a further increase of the deposition temperature, the crystalline quality of the ZnO：P sample is degraded. The measurements of low-temperature photoluminescence spectra demonstrate that the samples deposited at the substrate temperatures of 350℃ and 450℃ show a strong acceptor-bound exciton （A^0X） emission. The electrical properties of ZnO：P films strongly depend on the deposition temperature. The ZnO：P samples deposited at 350℃ and 450℃ exhibit p-type conductivity. The p-type ZnO：P film deposited at 450℃ shows a resistivity of 1.846Ω·cm and a relatively high hole concentration of 5.100 × 10^17 cm^-3 at room temperature.     

Bulk Modulus and Electronic Band Structure of ZnGa2X4(X=S,Se): a First-Principles Study

First-principles local density functional calculations are presented for the compounds ZnGa₂X₄ (X=S,Se). We investigate the bulk moduli and electronic band structures in a defect chalcopyrite structure. The lattice constants and internal parameters are optimized. The electronic structures are analysed with the help of total and partial density of states. The relation between the cohesive energy and the unit cell volume is obtained by fully relaxed structures. We derive the bulk modulus of ZnGa₂X₄ by fitting the Birch-Murnaghan's equation of state. The extended Cohen's empirical formula agrees well with our ab initio results.     

Spatial Soliton Solutions in a Harmonic Potential

The F-expansion technique and the homogeneous nonlinear balance principle have been applied for solving a general （19-1）-dimensional nonlinear Schrodinger equation （NLSE） with varying coetficients and a harmonic potential. A family of （1＋1）D spatial solitons has been obtained. The evolution features of exact solutions have been investigated.     

Bulk Modulus and Electronic Band Structure of ZnGa2Xa （X=S,Se）： a First-Principles Study

First-principles local density functional calculations are presented for the compounds ZnGa2X4 （X = S, Se）. We investigate the bulk moduli and electronic band structures in a defect chalcopyrite structure. The lattice constants and internal parameters are optimized. The electronic structures are analysed with the help of total and partial density of states. The relation between the cohesive energy and the unit cell volume is obtained by fully relaxed structures. We derive the bulk modulus of ZnGa2Xa by fitting the Birch-Murnaghan＇s equation of state. The extended Cohen＇s empirical formula agrees well with our ab initio results.