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High resolution photoemission measurements are carried out on non-superconducting SmOFeAs parent compound and superconducting SmFeAs(O1-xFx) (x = 0.12, and 0.15) compounds. The momentum-integrated spectra exhibit a clear Fermi cutoff that shows little leading-edge shift in the superconducting state. A robust feature at 13meV is identified in all these samples. Spectral weight suppression near Ef with decreasing temperature is observed in both undoped and doped samples that points to a possible existence of a pseudogap in these Fe-based compounds.

The structural features of MgB2 superconductors prepared under different conditions have been analysed by means of transmission electron microscopy. The MgB2 crystal is identified to have a hexagonal structure with the space group of P6/mmm. Superconducting materials synthesized under a high pressure of 6 Cpa are made of regularly stacked grains as large as a few microns in sizes. Stacking faults and microstructure properties of grain boundaries, either with or without impurities, appearing in a sample with the critical current density greater than 10(5)/cm(2), have been systematically investigated.

The electronic structures of wurtzite compounds GaN, AlN and strained-layer super-lattice (SLS) (Ga2N2)1(Al2N2)1 (001) constituted by straining GaN-layer to match the lattice constant of AlN according to the elastic theory are studied with the first-principles Linearized-Muffin-Tin-Orbitals band-structure method. The band offsets at the SLS are determined by the frozen potential approach. The results of the bulk materials are in good agreement with available experimental data.

Resistive transitions of the new superconductor MgB2 are carried out under magnetic fields from 0 to 8 T. It is found that the irreversibility field H-irr(T) and the upper critical field H-c2(T) obtained are very close to those determined in the magnetic measurements. By using the Arrhenius activation law p = p(0)exp(- U/k(B) T), the activation barrier U has been determined by the low dissipation part of R(T) curves. It is found that U much greater than k(B)T manifesting a very weak thermal activation and thermal fluctuation effect. This may further indicate that the flux dynamics near H-irr(T) is induced by strong quantum fluctuation and tunnelling of vortices.

The specific heat of the recently discovered superconductor MgB2 has been measured at temperatures ranging from 4.5 to 80 K. The superconducting anomaly ΔC at Tc is clearly observed. The total specific heat in the normal state can be well fitted by electronic and phonon contributions. The Debye temperature θD is found to be 737 K, much larger than other intermetallic superconductors. The normal-state electronic specific heat coefficient γ is found to be 2.48±0.5 mJ/molK2 and ΔC/γTc is between 1.41 and 2.15.

The new superconductor MgB2 has been prepared in two ways, by high pressure and ambient pressure synthesis. The superconducting properties were measured and compared. It is found that the sample prepared by high pressure is much denser than that prepared under ambient pressure. Accordingly the high pressure sample has a very narrow transition width and a much higher bulk critical current density.

The optical-phonon deformation potentials of C, Si, Ge and Sn are calculated by LMTO-ASA approach within the frosen-phonon approximation. The comparisons between our results and those of several present theoretical calculations and experiments demonstrate that our calculation model is reasonable.

The electronic structure of InAs0.25P0.75/InP strained quantum wires grown on InP(001) oriented substrates is studied within the framework of effective-mass envelope-function theory. At the Γ point, the electron and valence subband energy levels with and without spin-split-off band, and the absorption spectra are calculated. The effects of strain and spin-split-off band on valence energy levels are presented. The results show that the uppermost valence subband is almost unaffected by the strain induced coupling between the heavy- and light-hole bands and the spin-split-off bands while the other subbands are more markedly affected in the InAs0.25P0.75/InP strained quantum wires.

Electron structure of three series of alloy heterojunctions (GaAs)x(Ge2)1-x/Ge,(AlAs)x(Ge2)1-x/Ge and AlxG1-xAs/Ge are calculated by linear muffin-tin orbital method with atomic-sphere approximation using the average-bond-energy theory in conjunction with a cluster expansion method. The results indicate the variations of ΔEν(x) at heterojunctions (GeAs)x(Ge2)1-x/Ge and (AlAs)x(Ge2)1-x/Ge are nonlinear, which are very different from that of AlxGa1-xAs/Ge.

Supercell self-consistent calculation of band structures of (ZnS)n/(Si2)n (110) (n = 2, 3, 4, 5) has been performed by means of linear muffin-tin orbitals method. The valence-band offset of such systems is calculated by frozen optential method and their Joint density of states has been computed by tetrahedron method. Our results show that the (ZnS)n/(Si2)n (110) superlattices have a large valence-band offset and their optical properties integrate exellent optical properties of bulk ZnS and that of Si.

We report the superconductivity in iron-based oxyarsenide Sm[O1-xFx]FeAs, with the onset resistivity transition temperature at 55.0K and Meissner transition at 54.6 K. This compound has the same crystal structure as LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the highest critical temperature among all materials besides copper oxides up to now.

We report on the observation of the Josephson effect on the newly discovered superconductor MgB2 with the break-junction technique. Similar to conventional superconductors, the I - V curve can be fitted with the resistively shunted junction model including the noise effect, and a large characteristic voltage V-c = IcRN = 9.6meV was obtained. The energy gap determined by the Ambegaokar-Baratoff relation with the fitted V-c is very consistent with the Bardeen-Cooper-Schrieffer weak-coupling value. Our result implies that the superconductor MgB2 is a promising material for Josephson device applications.

We firstly propose and demonstrate a new economical approach that can correct the wavefront of the petwatt Ti:sapphire laser system with a beam size of 150mm. By using a deformable mirror with 50mm active aperture in the end of the laser, the focal spot size is reduced effectively. The experimental results show that the new approach is simple, less-expensive and valid from a technical and economical point. This technique could be applied to correct the wavefront of a large optical beam with a smaller aperture deformable mirror.

It is demonstrated that defects of any shape or size can be doped in holographic photonic crystals using a cw visible laser and spherical/cylindrical lens. Defects with different sizes at any depth in the material can be obtained by controlling the position of the focal point of the lens and exposure value. We facilitate the implementation of sub-wavelength arbitrary point or line defects in large-size 2D holographic photonic crystals.