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High quality and highly conductive n-type Al0.7Ga0.3N films are obtained by using AlN multi-step layers (MSL) with periodical variation of V/III ratios by low-pressure metalorganic chemical vapour deposition (LP-MOCVD). The full-width at half-maximum (FWHM) of (0002) and (1015) rocking curves of the Si-doped Al0.7Ga0.3N layer are 519 and 625 arcsec, respectively. Room temperature (RT) Hall measurement shows a free electron concentration of 2.9 × 1019 cm−3, and mobility of 17.8 cm2V−1s−1, corresponding to a resistivity of 0.0121 ω cm. High conductivity of the Si-doped AlGaN film with such high Al mole fraction is mainly contributed by a remarkable reduction of threading dislocations (TDs) in AlGaN layer. The TD reducing mechanism in AlN MSL growth with periodical variation of V/III ratio is discussed in detail.

Semi-insulating GaN is grown by using a two-step AlN buffer layer by metalorganic chemical vapour deposition. The sheet resistance of as-grown semi-insulating GaN is dramatically increased to 1013 Ω/sq by using two-step AlN buffer instead of the traditional low-temperature GaN buffer. The high sheet resistance of as-grown GaN over 1013 Ω/sq is due to inserting an insulating buffer layer (two-step AlN buffer) between the high-temperature GaN layer and a sapphire substrate which blocks diffusion of oxygen and overcomes the weakness of generating high density carrier near interface of GaN and sapphire when a low-temperature GaN buffer is used. The result suggests that the high conductive feature of unintentionally doped GaN is mainly contributed from the highly conductive channel near interface between GaN and the sapphire substrate, which is indirectly manifested by room-temperature photoluminescence excited by an incident laser beam radiating on growth surface and on the substrate. The functions of the two-step AlN buffer layer in reducing screw dislocation and improving crystal quality of GaN are also discussed.

We show a nonlinear materials equation of superconductors in the form of an extended power law which can be derived from the Ginzburg–Landau (GL) functional. The critical current Jc and ac susceptibility χ are analysed by using this equation, and the puzzling question of the increasing height of the out-of-phase susceptibility peak χ''peak with increasing amplitude hac is explained.

On the basis of the Dirac equation, the analytic continuation in the coupling constant method is employed to investigate the energies and widths of single-particle resonant in square-well, harmonic-oscillator, and Woods-Saxon potentials. The influences of the coupling constant interval and the Pade approximant order are analysed. It is shown that, by properly choosing the coupling constant interval and the Pade approximant order, stable and convergent energies and widths of single-particle resonant states can be obtained, which makes the application of the analytic continuation in the coupling constant for the relativistic mean field theory possible.

We analyse a dynamical swapping of the quantum state in coupled harmonic oscillators. The result can be applied to the interaction of a single-mode field with atomic ensemble in the weak field case. Similar to the case of electromagnetic induced transparency (EIT), a dynamic polariton is formed. Therefore, the quantum state of the field can be completely mapped on to the atomic medium, and vice versa. Using this dynamical swapping and the adiabatic transfer in the EIT between the field and atomic ensemble, we propose a scheme in which both the quantum and the coherent information can be transferred from one field to another.

A statistical study of interhemispheric comparison of dipole tilt angle effect on the latitude of the mid-altitude cusp is preformed by a data set of the Cluster cusp crossings over a 5-year period. The result shows that the dipole tilt angle has a clear control of the cusp latitudinal location. When the dipole tilts sunwards, the cusp is shifted poleward. The northern cusp moves 1° ILAT for every 15.4° increase in the dipole tilt angle, while the southern cusp moves 1° ILAT for every 20.8° increase in the dipole tilt angle. This suggests that an interhemispheric difference appears in the dependence of cusp latitudinal location on the dipole tilt angle.

In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high Tc superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg?Landau (GL) functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I?V data of Strachan et al. [Phys. Rev. Lett.?87?(2001)?067007]. The puzzling question of the derivative plot for the I?V curves and the controversy surrounding the values of critical exponents are discussed.

The Dirac equation for the special case of a spinor in the relativistic potential with the even and odd components related by a constraint is solved exactly when the even component is chosen to be the Hulthen potential. The corresponding radial wavefunctions for two-component spinor are obtained in terms of the hypergeometric function, and the energy spectrum of the bound states is obtained as a solution to a given equation by boundary constraints, in which the nonrelativistic limit reproduces the usual Hulthen potential.

We propose a novel technique for the creation of entangled states of three particles, based upon an adiabatic passage induced by a suitably crafted time-dependent external field. We derive the corresponding adiabatic and bare conditions for the preparation of entangled states. We obtain the time evolutions of the energy of the system and the populations involving the initial state and target entangled state.

Image storage based on photoinduced alignment in azobenzene liquid-crystalline films is reported. Measurements reveal that the liquid-crystalline film possesses large photoinduced birefringence (Δn similar 10-2) and permanent optical storage characteristics. The photoinduced alignment process is used for storing images. It is clearly demonstrated that the alignment of the azo chromophores as well as the stored image can be controlled by choosing the appropriate polarization of the irradiating light.

Bi2Te3 films are grown on (111)-oriented GaAs substrates by using the hot wall epitaxy method and the surface oxidation properties in the films are investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction. The results show that the films are c-axis oriented. Two pairs of new peaks in the XPS spectra involved with the binding energies from Bi 4f and Te 3d electrons correspond to Bi—O—Te bonds. Besides the A11g, E2g and A21g vibration modes from Bi2Te3 films, two new peaks at 93.5cm−1 and 123cm−1 are observed in Raman spectra, which are assigned to α-Bi2O3 and TeO2, respectively. Our results are helpful for analyzing the degradation mechanism of topological surface states in Bi2Te3.

The time evolution of populations of the ground state hyperfine Zeeman levels of 87Rb atoms is analyzed using the Runge—Kutta method for the case that a rubidium beam is optically pumped, under different conditions of polarization, with a weak monochromatic laser and an 87Rb lamp. On the base of the results above, the least estimated laser and 87Rb lamp power for the best population inversion is obtained, aiding further investigations.

We study two families of two-dimensional bright lattice solitons in photovoltaic-photorefractive crystals. It is shown that self-focusing and self-defocusing lattice solitons are possible only when their power level exceeds a critical threshold. It is found that self-focusing lattice solitons exist not only in the semi-infinite band gap, but also in the first band gap, whereas self-defocusing lattice solitons exist only in the first band gap. The structures of these lattice solitons are also analyzed. Our results indicate that a self-focusing lattice soliton in the semi-infinite band gap is more confined than in the first band gap so its tails in the first band gap occupy many lattice sites; when a self-defocusing lattice soliton is close to the second band, the self-defocusing lattice soliton is more confined so its tails occupy a few lattice sites.

Bound and resonant states of the Hulthen potential are studied. The complex scaling method is used to achieve the energy spectrum. The oscillator basis is used to expand the radial wave function. Conforming to the standard feature of the complex scaling method, the bound energies do not change and the continuums change with the rotational angle. With tables and graphs, the interesting properties of the energy spectrum for various physical parameters are presented. The Gauss quadrature integral approximation is used to deal with the potential integral term.

We present explicit unitary transformations for realizing both symmetric and asymmetric one-to-many economical phase-covariant clonings of qudits. We also propose a corresponding telecloning scheme. It is shown that the fidelity of the telecloning with nonmaximally entangled states can be larger than that of the corresponding cloning. This implies that partially entangled states can be better than the maximally entangled states for our economical phase-covariant telecloning scheme.

We propose a method for detecting perfect invisible cloak based on the scattering of the materials of the cloak. The position of the detected cloak can also be determined. The demonstration shows that the detecting effect is obvious, and the accuracy of the detection is high.

The critical phenomena of a Brillouin laser are analyzed theoretically. The results show that the behavior of a Brillouin laser in the threshold region is a second-order phase transition. The critical point of the phase transition is the gain threshold of the Brillouin laser, and the order parameter is the amplitude of the Stokes component in stimulated Brillouin scattering. The critical slow-down phenomenon and the typical characteristics in phase transition are demonstrated. Further work on the combination of nonlinear optics and phase transition in the Brillouin laser may lead to a new view and findings that could be significant for both fields.

The thermal expansion coefficient (TEC) of an ideal crystal is derived by using a method of Boltzmann statistics. The Morse potential energy function is adopted to show the dependence of the TEC on the temperature. By taking the effects of the surface relaxation and the surface energy into consideration, the dimensionless TEC of a nanofilm is derived. It is shown that with decreasing thickness, the TEC can increase or decrease, depending on the surface relaxation of the nanofilm.

AlxGa1-xN epilayers with a wide Al composition range (0.2 ≤ x ≤ 0.68) were grown on AlN/sapphire templates by low-pressure metalorganic chemical vapour deposition (LP-MOCVD). X-ray diffraction results reveal that both the (0002) and (105) full widths at half-maximum (FWHM) of the AlxGa1−xN epilayer decrease with increasing Al composition due to the smaller lattice mismatch to the AlN template. However, the surface morphology becomes rougher with increasing Al composition due to the weak migration ability of Al atoms. Low temperature photoluminescence (PL) spectra show pronounced near band edge (NBE) emission and the NBE FWHM becomes broader with increasing Al composition mainly caused by alloy disorder. Meanwhile, possible causes of the low energy peaks in the PL spectra are discussed.

We study the icosahedral transformations of solid Cu–Co clusters with different initial configurations by using molecular dynamics with the embedded atom method. It is found that the formation of symmetric icosahedral cluster is strongly related to the atomic number and initial configuration. The transformation originates from the surface into the interior of the cluster and is a structural change which is rapid and diffusionless. The icosahedral clusters with any composition and configuration, such as core-shell or three-shell cluster, can be prepared by the means of solid-solid phase transition in bimetallic clusters.

Starting from the free energy of a moving vortex, we obtain the extended power law form of longitudinal resistivity ρxx and the analytical form of Hall resistivity ρxy. Based on them, we obtain a scaling relation which agrees well with the experimental data of different kinds of high-temperature superconductors. Furthermore, the theoretical results well fit the scaling results.