Raman spectral imaging of a carbon nanotube intramolecular junction

Confocal Raman spectral imaging results are presented for a metal-to-semiconductor intramolecular junction (IMJ) on an isolated carbon nanotube. Spectra observed at the junction are consistent with the symmetry lowering expected from the occurrence of pentagon-heptagon defects to produce the chirality shift. The IMJ transition zone is sharp and preserves the nanotube diameter. These results have significant implications for the future use of IMJs as electronic devices, including how prevalent these structures are and how their growth may be rationally targeted. Raman imaging has been demonstrated to be a powerful tool for IMJ studies and provides a more accessible method for further studies of IMJ structure and growth.     

Airy Equation for the Topological String Partition Function in a Scaling Limit

We use the polynomial formulation of the holomorphic anomaly equations governing perturbative topological string theory to derive the free energies in a scaling limit to all orders in perturbation theory for any Calabi–Yau threefold. The partition function in this limit satisfies an Airy differential equation in a rescaled topological string coupling. One of the two solutions of this equation gives the perturbative expansion and the other solution provides geometric hints of the non-perturbative structure of topological string theory. Both solutions can be expanded naturally around strong coupling.     

Electrochemical performance of modified artificial graphite as anode material for lithium ion batteries

Artificial graphite anode material was modified by coating an amorphous carbon layer on the particle surface via a sol-gel and pyrolysis route. The electrochemical measurements demonstrate that appropriate carbon coating can increase the specific capacity and the initial coulombic efficiency of the graphite material, while excessive carbon coating leads to the decrease in specific capacity. Thick coating layer is obviously unfavorable for the lithium ion diffusion due to the increased diffusion distance, but the decreased specific surface area caused by carbon coating is beneficial to the decrease of initial irreversible capacity loss. The sample coated with 5 wt.% glucose exhibits a stable specific capacity of 340 mAhg^?1. Carbon coating can remarkably enhance the rate capability of the graphite anode material, which is mainly attributed to the increased diffusion coefficient of lithium ion.     

Novel Wronskian Solutions to Boussinesq Equation

The new method for constructing the Wronskian entries is applied to the Boussinesq equation. The novel Wronskian solutions to it are obtained, including solitons, rational solutions, Matveev solutions, and complexitons.     

一种简单的干涉光路

介绍了用反射镜和立方棱镜实现两束光相干涉的光路。     

Hybrid binary subtracted joint transform correlator for a large number of reference patterns using a Bi12SiO20(BSO) spatial light modulator and a laser scanner

A hybrid binary subtracted joint transform correlator was constructed using a Bi₁₂SiO₁₂ (BSO) spatial light modulator and a laser scanner. The usefulness of this system was confirmed experimentally using a large number of binary and halL-tone images as the reference patterns.     

双缺陷模一维光子晶体的双光子吸收增强研究

采用真空镀膜工艺制备了具有762 nm和800 nm双缺陷模的含两个CdS缺陷层的TiO2/SiO2一维光子晶体,运用抽运探测技术测量了其双光子吸收。对于两个缺陷模,双光子吸收均得到很大的增强,其中缺陷模为800nm时的双光子吸收系数307 cm/GW要大于缺陷模为762 nm时的116 cm/GW,分别为单层CdS薄膜的48倍和18倍。这种双光子吸收的增强是由于光局域化导致一维光子晶体缺陷层内的电场强度增大而形成的。通过传输矩阵法计算了一维光子晶体的内部场强,发现800 nm波长光入射时缺陷层内的电场强度要大于762 nm波长光入射时的电场强度值。     

The effect of thermal reactor neutron irradiation on semi-insulating GaN

Semi-insulating Gallium nitride was irradiated by fast and thermal neutrons with fluences from 10¹⁴ to 10¹⁶ n/cm². Depth-resolved cathodoluminescence spectroscopy was used to determine defects changes before and after irradiation. The results revealed two kinds of defects affected near-band emission recombination from two opposite directions. One was attributed to irradiation-induced N vacancies that contribute to near-band emission recombination. Another was attributed to irradiation-induced deep level defects that contribute to sub-band gap recombination and thus decrease the near-band emission recombination.     

Structural phase transition,antiferromagnetism and two superconducting domes in LaFeAsO_(1-x)F_x(0<x≤0.75)

We report~(75) As nuclear magnetic resonance(NMR)/nuclear quadrupole resonance(NQR) and transmission electron microscopy(TEM) studies on LaFeAsO_(1-x)F_x. There are two superconducting domes in this material. The first one appears at 0.03 ≤ x ≤0.2 with T_c~(max) = 27 K, and the second one at 0.25 ≤x≤0.75 with T_c~(max) = 30 K. By NMR and TEM, we demonstrate that a C4-to-C2 structural phase transition(SPT) takes place above both domes, with the transition temperature T_s varying strongly with x. In the first dome, the SPT is followed by an antiferromagnetic(AF) transition, but neither AF order nor low-energy spin fluctuations are found in the second dome. By ~(75) As nuclear spin-lattice relaxation rate(1/T_1) measurements, we find that AF order and superconductivity coexist microscopically in LaFeAsO_(0.97) F_(0.03). In the coexisting region, 1/T_1 decreases at T_c but becomes proportional to T below 0.6 T_c, indicating gapless excitations. Therefore, in contrast to the early reports, the obtained phase diagram for x ≤ 0.2 is quite similar to the doped BaFe_2As_2 system. The electrical resistivity p in the second dome can be fitted by ρ = ρ0 + AT~n with n = 1 and a maximal coefficient A at around xopt = 0.5-0.55 at which T_s extrapolates to zero and Tc is the maximal, which suggests the importance of quantum critical fluctuations associated with the SPT. We have constructed a complete phase diagram of LaFeAsO_(1-x)F_x, which provides insight into the relationship between SPT, antiferromagnetism and superconductivity.