YBCO薄膜的织构和孪晶的XRD分析

采用多元电子束物理气相沉积法在｛001｝ LAO衬底上制备了YBCO薄膜,采用X射线衍射分析了其取向和孪晶结构,结果表明,薄膜中除了8％C取向的四方相外;其余为正交相,而正交相中存在27％的a取向,3％的b取向以及62％的C取向,且C取向晶粒存在面内90°±0.81°＜110＞孪晶.四方到正交相变不完全引起四方相残留、...     

Atomistic simulation study on twin orientation and spacing distribution effects on nanotwinned Cu films

Affected by twin orientation and spacing distribution, different deformation and failure mechanisms of nanotwinned (NT) Cu films are discovered. For films with the same twin spacing, transition from brittle to ductile and ductile to localized necking with the increase of the slanted angle of twin boundary (TB) from 0° to 90° is examined. Two dominant slip mechanisms: (1) slip intersecting with the TBs; (2) slip parallel to the TBs can uncover the transition mechanisms with consideration of twin orientation. To maintain both relatively high strength and good ductility, the slanted angle can be set close to the ductile to localized necking transition border. Besides, the stress–strain curves obtained in this article show that the mechanical responses on both sides of the turning point 45° are asymmetric. On the other hand, the twin spacing distributions affect the ductility of NT Cu films and have almost no contribution to strengthening. The strength of the NT Cu films mainly depends on the twin density. NT Cu films with different twin spacing have worse ductility than equal twin spacing films due to the local twin spacing asymmetry. The failures can be predicted appearing at TBs adjacent to large twin spacing regions, and the failure propagation direction can also be predicted by knowing the obtuse angle decided by stacking faults and TBs.     

Pair production of neutral Higgs bosons from the left-right twin Higgs model via γγ collisions

The left-right twin Higgs (LRTH) model predicts the existence of the neutral Higgs bosons (h, φ<'0>), which can be produced in pairs (φ<'0>φ<'0>, hh, φ<'0>h) via γγ collisions at the next generation e<'+>e<'-> International Linear Collider (ILC). Our numerical results show that the production cross section of the neutral Higgs boson pair φ<'0>φ<'0> can reach 8.8 fb. The subprocess γγ→φ<'0>φ<'0> might be used to test the LRTH model in future ILC experiments.     

Associated ZH and WH Production in Left-Right Twin Higgs Model at LHC

At the CERN large hadron collider (LHC), production of the Higgs boson in association with Z or W bosons provides a dramatic experimental signal for detecting the standard model (SM) Higgs boson. In this paper, we consider the contributions of the left-right twin Higgs (LRTH) model to the processes q\bar{q}→Z(W)H. Our numerical results show that, in the favorable parameter spaces, the cross sections deviate distinctly from the predictions
of the SM. The possible signals of the LRTH model can be detected via these processes at the LHC experiments.     

Electronic structure of twinned ZnS nanowires

The electronic properties of twinned ZnS nanowires (NWs) with different diameters were investigated based on first-principles calculations. The energy band structures, projected density of states and the spatial distributions of the bottom of conduction band and the top of the valence band were presented. The results show that the twinned nanowires exhibit a semiconducting character and the band gap decreases with increasing nanowire diameter due to quantum confinement effects. The valence band maximum and conduction band minimum originate mainly from the S-p and Zn-s orbitals at the core of the nanowires, respectively, which was confirmed by their spatial charge density distribution. We also found that no heterostructure is formed in the twinned ZnS NWs since the valence band maximum and conduction band minimum states are distributed along the NW axis uniformly. We suggest that the hexagonal (2H) stacking inside the cubic (3C) stacking has no effect on the electronic properties of thin ZnS NWs.     

Generation of quantum‐entangled twin photons by waveguide nonlinear‐optic devices

This paper reviews the quasi‐phase‐matched (QPM) waveguide nonlinear‐optic device technologies for generation of quantum‐entangled twin photons indispensable for quantum‐information techniques. After a brief introduction to the concept of entanglement, quantum theory analysis of twin‐photon generation (TPG) is outlined to clarify the properties of twin photons. Then, methods for entangled‐photon generation are discussed. Practical design and theoretical performances of LiNbO₃ waveguide QPM TPG devices, as well as the fabrication techniques, are described. Finally, experimental demonstrations of polarization‐entangled twin‐photon generation by waveguide Type‐I and Type‐II QPM TPG devices are presented.