Discrete Hubbard-Stratonovich transformations for systems with orbital degeneracy

A discrete Hubbard-Stratonovich transformation is presented for systerns with an orbital degeneracy N and a Hubbard Coulomb interaction. An exact transformation is obtained by introducing an external field which takes N + 1 values. Alternative approximate transformations are presented, where the field takes fewer values, for instance two values corresponding to an Ising spin.     

A trans-ortho asymmetrically di-strapped metalloporphyrin integrating three key structural features of ligand in heme

Heme responsible for the dioxygen fixation, transport and conversion is a metalloporphyrin complex highly dependent on its diverse geometry of ligand. In this work, a trans-ortho-di-strapped zinc porphyrin with dome-like deformation was synthesized by thermodynamically controlling the formation of trans-precursor of porphyrinogen. Its single-crystal structure demonstrated that the asymmetric treatment of porphyrin achieves three goals of creating two secondary coordination sphere (SCS) bulks, maintaining a unique dome deformation, and making atomic out-of-plane deviation. In this way, this metallic complex integrates at least three key features of the pocket structure, the differentiated axial ligations, and the ring distortion, making it an ideal heme analog.     

Simultaneous monitoring of the fluorescence and refractive index by surface plasmon coupled emission: A proof-of-concept study

Simultaneous acquisition of fluorescence property and refractive index using a single surface plasmon coupled emission (SPCE) measurement has been achieved, thus achieving synchronicity in real time. The SPCE sensor was employed for monitoring the adsorption of volatile organic compounds (VOCs) by dye-encapsulated metal-organic frameworks (Dye@MOFs). Refractive index can reveal surface molecular adsorption and the fluorescence with information on refractive index can provide a comprehensive analysis of the adsorption events of VOCs on the interface. Meantime, the signal intensity can be amplified by combining the responses caused by changes in refractive index and the fluorescence property in parallel. This all-in-one method opens up a route to monitoring multiple processes simultaneously occurring on the interface.     

Multi-window visual saliency extraction for fusion of visible and infrared images

Fusion for visible and infrared images aims to combine the source images of the same scene into a single image with more feature information and better visual performance. In this paper, the authors propose a fusion method based on multi-window visual saliency extraction for visible and infrared images. To extract feature information from infrared and visible images, we design local-window-based frequency-tuned method. With this idea, visual saliency maps are calculated for variable feature information under different local window. These maps show the weights of people’s attention upon images for each pixel and region. Enhanced fusion is done using simple weight combination way. Compared with the classical and state-of-the-art approaches, the experimental results demonstrate the proposed approach runs efficiently and performs better than other methods, especially in visual performance and details enhancement.     

Continuous-variable multimode entanglement in multi-wave mixing

We present a scheme to obtain continuous-variable multimode entanglement via multi-wave mixing. For a four-level atomic system in a diamond configuration, four strong coherence fields are applied to the four dipole-allowed transitions to amplify eight sidebands as cavity fields, respectively. Due to the atomic coherence, the eight side modes constitute a pair of double quantum-beats and combine into two quantum-beat collective modes, which are in a four-wave mixing parametric interaction. As a result, the entanglement occurs between these two collective modes. Correspondingly, any two individual modes from two different collective modes are entangled with each other. This gives rise to continuous-variable eight-mode entanglement with different frequencies, which has extensively application in quantum communication and quantum network.     

Effect of hole doping and antiferromagnetic coupling on the itinerant ferromagnetism of through Cu substitution at Ru site

Systematic studies on the structural, transport and magnetic properties of SrRu_1−xCu_xO₃ (x=0.0–0.2) compounds have been performed. SrRu_0.8Cu_0.2O₃ shows a tetragonal structure unlike the other compositions which exhibit a pseudo-cubic structure. Low temperature powder X-ray diffraction data of SrRu_0.8Cu_0.2O₃ collected at a synchrotron beam line reveals that the tetragonal structure is stable down to 8 K. Ferromagnetic transition temperatures (T_c) are significantly reduced from 160 to 34 K with Cu doping. All the compositions exhibit irreversibilities in M_ZFC(T) and M_FC(T) curves ascribable to the presence of domain structures. Magnetic susceptibility measurements show that the copper ions are anti-ferromagnetically coupled for concentrations higher than x=0.16. The antiparallel arrangement of Ru⁵⁺ ions with its neighboring cations also contributes to the large reduction in the observed magnetic moment. X-ray photoemission spectroscopy measurements show evidence for both tetravalent and pentavalent Ru ions while copper is in a divalent state. We conclude from our resistivity data that Cu²⁺ substitution promotes a polaronic type of conductivity.     

Common features in high Tc cuprates and diborides

The normal state of magnesium diboride, the simplest metallic system showing the macroscopic quantum coherence at high temperature (high T_c superconductivity––HTcS) shows some features that are common with the cuprates, shedding light on the pairing mechanism for T_c amplification in HTcS: (1) two or more electronic components associated with multiple Fermi surface portions; (2) crossing of electronic topological transitions (ETT) where the Fermi surface changes its topology and (3) phonon softening in extended Kohn anomalies (EKA) over a large wave-vector range.     

铜位锌替代对DyBa_2Cu_3O_(7-δ)体系超导电性的影响

利用X射线衍射(XRD)技术对DyBa2Cu3-xZnxO7-δ(x=0.0~0.4)系列样品的晶体结构进行探测,研究体系相结构的掺杂效应。结果发现,在整个掺杂范围体系保持了正交相的晶体结构。采用四引线法对掺杂样品DyBa2Cu3-xZnxO7-δ的超导电性能进行了系统测量,发现随着Zn掺杂量的增加,样品的超导转变温度总体呈明显降低趋势,分析了铜位锌掺杂对超导电性抑制的原因。     

Impurity characteristics of group V and VII element-doped two-dimensional ZrSe2 monolayer

Through first-principles calculations, we investigate the electronic structures, formation energy and transition level of the selected group V and VII impurities in the two-dimensional ZrSe₂ monolayer. Our results indicate that group V and VII atoms substituting Se atom can be easier under Zr-rich experiment conditions. Moreover, group V element substituting doping can induce p-type carrier due to their negative formation energy and shallow transition level, while group VII doping can not be effective to induce the n-type impurities. In particular, N substituting Se exhibits the lowest formation energy and shallowest transition level, which indicates that N impurities can offer effective p-type carriers in the ZrSe₂ monolayer.