Coulomb Plasmon-Excitons in Planar Nanostructures Metal-Semiconductor

Physics of the Solid State - A theory of Coulomb (non-radiative) plasmons-excitons in a semiconductor with adjacent quantum well and ultrathin metal film is presented. The equations of motion are...     

典型金属纳米结构的电子能量损失谱研究

利用格林函数推导出金属纳米结构电子能量损失谱的计算公式,基于时域有限差分方法对几种典型的结构进行建模仿真,数值模拟运动电荷和结构的距离、液晶环境材料对电子能量损失谱的调节作用.仿真结果表明:当增加电子与纳米结构的距离时,电子能量损失谱谱峰降低;当添加液晶材料或各向同性衬底材料时,电子能量损失谱的峰值发生明显红移,但液晶的光轴倾角改变对峰值的调制作用有限.通过计算电子能量损失谱研究金属纳米结构表面等离子激元共振特性,为高度复杂的等离子体激元纳米结构的设计提供了理论基础.     

Two-Dimensional Coulomb Plasmon-Excitons: Relaxation of Excitations

Physics of the Solid State - A theory is developed for the relaxation of two-dimensional non-radiative (Coulomb) plasmon-excitons in closely located thin layers of a metal and a semiconductor. In...     

Room-Temperature Level Anticrossing and Cross-Relaxation Spectroscopy of Spin Color Centers in SiC Single Crystals and Nanostructures

A sharp variation of the near infrared photoluminescence intensity for spin-3/2 color centers in hexagonal (4H-, 6H-) and rhombic (15R-) SiC polytypes in the vicinity of level anticrossing (LAC) and cross-relaxation in an external magnetic field at room temperature are observed. This effect can be used for a purely all-optical sensing of the magnetic field with nanoscale spatial resolution. A distinctive feature of the LAC signal is a weak dependence on the magnetic field direction that allows monitoring of the LAC signals in the nonoriented systems, such as powder materials, without need to determine the nanocrystal orientation in the sensing measurements. Furthermore, an LAC-like signal is also observed for the spin color centers (NV centers) in diamond in low magnetic fields with only marginal dependence on the magnetic field direction. This effect is enabled to detect weak magnetic fields using nanodiamond samples in the form of disordered mixture. In addition, the optically detected magnetic resonance and LAC techniques are suggested to serve as a simple method to determine the local stress in nanodiamonds under ambient conditions.     

Carbon Nanostructures

An overview of the various carbon structures with characteristic sizes in the nanoscale region is presented, with special attention devoted to the structures and properties of ‘nanodiamond’ and carbon nanotubes. The term ‘nanodiamond’ is used broadly for a variety of diamond-based materials at the nanoscale ranging from single diamond clusters to bulk nanocrystalline films. Only selected properties of carbon nanotubes are discussed, with an aim to summarize the most recent discoveries. Current and potential applications of carbon nanostructures are critically analyzed.     

Particularities of Heat Conduction in Nanostructures

Heat conduction in nanostructures differs significantly from that in macrostructures because the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of nanostructures. In this communication, particularities associated with phonon heat conduction in nanostructures, the applicability of the Fourier law, and the implications of nanoscale heat transfer effects on nanotechnology are discussed.     

Phonon-induced Quantum Entanglement in Diamond Nanostructures

We consider the quantum entanglement such as spin squeezing and the reciprocal of the mean quantum Fisher information per particle(RMQFIP) resulted from the phonon-induced spin-spin interactions in diamond nanoresonator. The entangled state can be generated by adjusting the near-resonant coupling and the single phonon coupling strength and the better entanglement and a longer entangled time interval can be achieved by increasing the number of charged nitrogen-vacancy (NV) centers.     

Modelling of Abrikosov Vortices in Three-Dimensional Nanostructures

Russian Physics Journal - COMSOL was used for the modelling of Abrikosov vortices in three-dimensional micro- and nano-sized structures. When modelling, boundary conditions were introduced into the...     

Intracluster and Intercluster Interactions in Nanostructures

The formation and properties of three types of nanostructures: solid-state nanostructures, matrix nanostructures and nanostructures under high pressure with shear were studied. Nanocluster peculiarities: solid-liquid state and first-order (jump-wise) magnetic phase transitions were considered. The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Néel points and the character of magnetic phase transitions were investigated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nanostructures in a nematic liquid crystal

The effect of nanoobjects, molecular objects, and α particles introduced into a liquid-crystal matrix that is placed in a dc electric field is studied theoretically and experimentally. The introduced particles form a charged defect, the radius of which is much larger than the particle sizes, in the orientational structure of the liquid crystal. This defect is easily observed under an optical microscope, and its image agrees with calculated data. It is suggested that this effect be used for detection and diagnostics of small objects and for design of ionizing radiation detectors. The phenomena revealed in this work can help in producing new charged-defect-saturated liquid-crystal structures formed by introducing nanoparticles in a medium or by irradiating a medium by ionizing radiation. A nonmechanical principle of transport of nanoparticles and their regular incorporation into the lattice is implemented. The essence of this principle is control of molecular orientations in a liquid crystal by quasi-stationary electric fields.     

氮掺杂石墨烯纳米结构的等离激元激发（英文）

基于含时密度泛函理论,研究了氮掺杂石墨烯纳米结构的等离激元特性。吡啶型氮掺杂不影响石墨烯纳米结构的等离激元激发特性,而取代型氮掺杂主要基于石墨烯纳米结构对称性的改变和体系中电子密度的增加来影响石墨烯纳米结构的等离激元共振。相对于纯六角石墨烯纳米结构,在低能共振区,取代型氮掺杂六角石墨烯纳米结构的等离激元共振能量发生了红移。相对于纯矩形石墨烯纳米结构,在低能共振区,取代型氮掺杂矩形石墨烯纳米结构沿扶手椅型边界方向激发时,其等离激元共振能量发生了蓝移;沿Z字型边界激发时,其主要的等离激元共振模式受掺杂氮的影响较小。     

纳构件加工后的力学特性

"采用分子动力学模拟的方法,运用镶嵌原子模型,研究了经过刻划后的单晶铜纳构件在不同拉伸速度条件下的力学行为. 通过原子位图、缺陷原子透视图、径向分布函数及应力-应变关系研究加工后纳构件在拉伸负载作用下的变化特性,并与理想单晶铜纳构件进行对比分析．模拟结果表明,加工后的纳构件的屈服强度较理想纳构件的屈服强度有明显下降,屈服强度随着刻槽深度的增加而下降,而且屈服强度对刻槽方向和拉伸速度敏感;纳结构在拉伸负载作用下,其应力应变关系出现了双峰形式,即工作硬化现象,二次屈服后表现为Z字形逐波下降形式．刻划深度、刻划     

Electron Transport in GaAs Nanostructures under Irradiation

The results of theoretical and experimental investigations into the n-GaAs electrophysical characteristics under irradiation are reported.     

Coherent Resonant Tunneling Model in Double-Barrier Nanostructures

We propose a coherent resonant tunneling model in double-barrier nanostructutes in which besides an interference effect originated from coherent tunneling of single electron through two barriers, the effects of one-electron charging, discrete energy spectrum and electron interactions between barriers are also important. The interference effect, like that for light in Fabry-Perot cavity, will occur no matter whether a magnetic field exists or not, and is shown to have significant effect on the systems' tunneling current. Our model agrees
surprisingly well with all the main experimental features of the phenomenon discovered by Scott Thomas et al.     

Delay of Spatial Quantum Correlations in Magnetic Nanostructures

Simultaneous quantum correlations between two spins in magnetic nanostructures are considered in the model of a linear chain of a finite number of atoms with exchange interaction between electron spins of neighboring atoms in the framework of the Heisenberg ferromagnetism theory. We assume that in the initial state, the spins of all chain atoms except the first two are oriented along the same direction. The spins of the first two atoms are flipped. Due to the exchange interaction, this initial state generates a spin flip wave along the chain. The expressions obtained for nonstationary quantum amplitudes of the flip probability waves for an even number of spins can be used for calculating quantum correlations between two spins separated by a large distance in a chain. Numerical calculations of the spin correlator reveal that the correlation between two spins in the chain occurs with a delay on the order of the time of propagation of the exchange interaction along the spin chain. After the delay, the spin correlation amplitude abruptly increases followed by subsequent oscillatory temporal behavior.     

Magnetic Phase Transitions in Nanoclusters and Nanostructures

New phenomena – the first order magnetic phase transitions were observed in nanoclusters and nanostructures. For isolated ferrihydrite nanoclusters (d ～ 1–2 nm) in porous materials, for α-,γ-Fe₂O₃ nanoclusters (d ～ 20–50 nm) and for composites of nanostructured metallic Eu with additives of α-, γ-Fe₂O₃ nanoclusters and adamantane the critical temperatures (T _C, T _N) and magnetic cluster critical sizes (R _cr) were determined by means of thermodynamic models and Mössbauer spectroscopy. The first order magnetic phase transitions (jump-like) proceed by such a way when magnetization and magnetic order disappear by jump without superparamagnetic relaxation. According to thermodynamic model predictions the cluster and interface defects were suggested to play the main role in magnetic behavior. Thus, for the defective α-, γ-Fe₂O₃ nanoclusters, at R ≤ R _cr, the presence of the first order (jump-like) magnetic phase transition was described in terms of magnetic critical size of cluster. The action of high pressure (up to 2 GPa) with shear (120–240°) was effective for defect generation and nanostructure formation. For nanosystems including iron oxide nanoclusters, adamantane and metallic europium and subjected to shear stress under high pressure loading the critical value of defect density was estimated by the study of the character of magnetic phase transition. First-to-second-order (nanostructured metallic Eu) and second-to-first-order (α-, γ-ferric oxide nanoclusters) changes of the character of magnetic phase transition were shown to accompany by the variation of critical temperatures compared to the corresponding bulk values.