有机半导体/金属杂化纳米结构中的强耦合相互作用及超快动力学特性

有源表面等离光子学(active plasmonics)是目前表面等离子体光子学研究的一个重要分支,其基本思想是利用“增益”物质和纳米金属结构相结合形成杂化金属纳米结构,从而克服表面等离子体激元(surface plasmon polariton,SPP)的耗散问题以及实现对SPP光子的外部操作和调制。本文主要针对有机半导体/金属杂化纳米结构,介绍其相关研究结果。结合色散补偿的光谱相干法和超快泵浦-探测瞬态光谱测量技术,分析了J-凝聚/光栅杂化金属纳米结构的静态和瞬态光学特性,揭示了X-SPP的强耦合过程中的相干和非相干相互作用通道,杂化能态的sub/super-radiance现象,以及有机半导体染料中的激子和SPP之间的瞬态相干能量交换过程：“拉比”振荡。实现了10 fs量级的SPP光学特性的外部相干调制。

     

Crossover between weak and strong coupling in 2D superconductors

We study the crossover between weak coupling and strong coupling in two-dimensional (2D) superconductors atT⊋0 in the weak coupling regime, described by the BCS state, and we calculate the order parameter and the chemical potential atT=0 andT⊋0 for the model of a 2D superconductor. In the strong coupling regime the energy excitation has the scale of the pairs generated by the attractive interaction. The order parameter and the chemical potential atT⊋0 are calculated, and we show that there is a continuous transition between the two regimes.     

光合细菌液中动态膜的过滤特性

以旋叶膜滤机作为过滤设备对光合细菌发酵液过滤物料进行动态微孔膜膜过滤特性的研究.研究了操作条件如压力、转速、浓度等对微孔膜过滤中的速率和阻力大小及分布情况的影响,发现整个过滤过程分为两个阶段,过滤初始阶段和稳态过滤阶段.在第二个阶段过滤阻力和过滤时间呈线形变化.     

Mcmillan-Rowell resonance in the strong-coupling NS tunneling junctions with reflecting boundary

A proximity junction with strong-coupling N, S and a reflecting NS boundary is considered. Using the formula derived in the framework of the Eliashberg and quasiclassical theories in the step approximation, the tunneling density of states is calculated for a model system, and the effects of the reflecting boundary and the phonons in the N, as well as S, layers on the McMillan-Rowell oscillation in the tunneling density of states are discussed.This work was supported by the SERC.     

Plasmon enhancement for Vernier coupled single-mode lasing from ZnO/Pt hybrid microcavities

It is essential to develop a single mode operation and improve the performance of lasing in order to ensure practical applicability of microlasers and nanolasers.In this paper,two hexagonal microteeth with varied nanoscaled air-gaps of a ZnO microcomb are used to construct coupled whispering-gallery cavities.This is done to achieve a stable single mode lasing based on Vernier effect without requiring any complicated or sophisticated manipulation to achieve positioning with nanoscale precision.Optical gain and the corresponding ultraviolet lasing performance were improved greatly through coupling with localized surface plasmons of Pt nanoparticles.The ZnO/Pt hybrid microcavities achieved a seven-fold enhancement of intensity of single mode lasing with higher sidemode suppression ratio and lower threshold.The mechanism that led to this enhancement has been described in detail.     

Electron-phonon locking and superconductivity

The electron-phonon vertex part is investigated as a function of real frequencies in a narrow-band electron system coupled with local phonons. Even though the bare electron-phonon coupling is not very strong, is found to diverge at some characteristic frequencies _l. The divergence induces the vanishment of the electron Green's function at _l. This phenomenon can be interpreted as the locking of an electron by such local phonons. By including this effect in the theory of superconductivity, we suggest an anomalous behavior in the tunneling spectroscopy.     

Material design and structural color inspired by biomimetic approach

Abstract

Generation of structural color is one of the essential functions realized by living organisms, and its industrial reproduction can result in numerous applications. From this viewpoint, the mechanisms, materials, analytical methods and fabrication technologies of the structural color are reviewed in this paper. In particular, the basic principles of natural photonic materials, the ideas developed from these principles, the directions of applications and practical industrial realizations are presented by summarizing the recent research results.     

A review of the size of the energy gap in superconducting oxides

An attempt has been made to summarize a large body of data dealing with measurements of the energy gap in superconducting oxides like La_2–x Sr _x CuO_4–y , YBa₂Cu₃O_7–y , and related compounds. A plot of available data of the energy gap 2 as a function of the superconducting transition temperatureT _c revealed a large dispersion of some data from 2/k _B T _c =3.53 for the weak coupling BCS prediction. Nevertheless, we could conclude that the size of the energy gap in these exotic materials is within the weak coupling BCS prediction, in view of some controversial issues that could be responsible for the dispersion, such as the gap anisotropy as well as identification of the energy gap.     

The indirect attraction between holes in the extended hubbard model

The extended Hubbard model [V. J. Emery,Phys. Rev. Lett. 58, 2794 (1987)] is used to study the copper-oxide plane of the high-T _c superconducting material. Due to the Coulomb repulsion between the holes on oxygen and copper atoms, there exists an indirect attraction between oxygen holes. Correlation among holes will enhance rather than screen the attraction. Calculation based on the Hartree-Fock and random-phase approximations show that it is quite large. A comparison with direct Coulomb repulsion shows that it is greater in a certain range of momentum transfer. It is sufficient to provide the pairing mechanism to give high critical temperature.