Effect of temperature on polaron dynamics in poly-DNA

We investigate the effect of temperature on polaron dynamics in the framework of a tight-binding model. The dissociation of a polaron will become fast with the increase of temperature. There exists a crossover of the charge localization time from strong to weak temperature-dependence. Instead of the uniform motion at zero temperature, a polaron moves un-uniformly under a driven field at a finite temperature, which indicates a discrete hopping between base pairs. It is also found that the polaron motion is thermally activated. A high temperature will result in a fast movement of a polaron under a deriving field.     

Nonthermal melting of a charge density wave in TiSe2

We use time-resolved optical reflectivity and x-ray diffraction with femtosecond resolution to study the dynamics of the structural order parameter of the charge density wave phase in TiSe2. We find that the energy density required to melt the charge density wave nonthermally is substantially lower than that required for thermal suppression and is comparable to the charge density wave condensation energy. This observation, together with the fact that the structural dynamics take place on an extremely fast time scale, supports the exciton condensation mechanism for the charge density wave in TiSe2.     

Discrete multivortex solitons

We introduce discrete multivortex solitons in a ring of nonlinear oscillators coupled to a central site. Regular clusters of discrete vortices appear as a result of mode collisions, and we show that their stability is determined by global symmetries rather than the stability of constituent vortices. Stable multivortex solitons support complex vortex dynamics including charge flipping and spiraling.     

Ultrafast melting of a charge-density wave in the Mott insulator 1T-TaS2

Femtosecond time-resolved core-level photoemission spectroscopy with a free-electron laser is used to measure the atomic-site specific charge-order dynamics of the charge-density?wave in the Mott insulator 1T-TaS2. After strong photoexcitation, a prompt loss of charge order and subsequent fast equilibration dynamics of the electron-lattice system are observed. On the time scale of electron-phonon thermalization, about 1?ps, the system is driven across a phase transition from a long-range charge ordered state to a quasiequilibrium state with domainlike short-range charge and lattice order. The experiment opens the way to study the nonequilibrium dynamics of condensed matter systems with full elemental, chemical, and atomic-site selectivity.     

Role of stochastic fluctuations in the charge on macroscopic particles in dusty plasmas

The currents which charge a macroscopic particle placed in a plasma consist of discrete charges; hence, the charge can undergo random fluctuations about its equilibrium value. These random fluctuations can be described by a simple model which, if the mechanisms for charging of macroscopic particles are known, makes it possible to determine the dependence of the temporal and amplitude characteristics of the fluctuations on the plasma parameters. This model can be used to study the effect of charge fluctuations on the dynamics of the macroscopic particles. The case of so-called plasma-dust crystals (i.e., highly ordered structures which develop because of strong interactions among macroscopic particles) in laboratory gaseous discharge plasmas is considered as an example. The molecular dynamics method shows that, under certain conditions, random fluctuations in the charge can effectively heat a system of macroscopic particles, thereby impeding the ordering process. Zh. éksp. Teor. Fiz. 115, 2067–2079 (June 1999)     

Effect of colloidal charge discretization in the primitive model

The effect of fixed discrete colloidal charges in the primitive model is investigated for spherical macroions. Instead of considering a central bare charge, as it is traditionally done, we distribute discrete charges randomly on the sphere. We use molecular dynamics simulations to study this effect on various properties such as overcharging, counterion distribution and diffusion. In the vicinity of the colloid surface the electrostatic potential may considerably differ from the one obtained with a central charge. In the strong Coulomb coupling, we showed that the colloidal charge discretization qualitatively influences the counterion distribution and leads to a strong colloidal charge-counterion pair association. However, we found that charge inversion still persists even if strong pair association is observed. Received 30 June 2000 and Received in final form 28 November 2000     

Fast two‐dimensional detection for X‐ray photon correlation spectroscopy using the PILATUS detector

The first X‐ray photon correlation spectroscopy experiments using the fast single‐photon‐counting detector PILATUS (Paul Scherrer Institut, Switzerland) have been performed. The short readout time of this detector permits access to intensity autocorrelation functions describing dynamics in the millisecond range that are difficult to access with charge‐coupled device detectors with typical readout times of several seconds. Showing no readout noise the PILATUS detector enables measurements of samples that either display fast dynamics or possess only low scattering power with an unprecedented signal‐to‐noise ratio.     

Characteristics of the fast electron emission produced during the cleavage of crystals

The present paper reports the fast electron emission produced during the cleavage of alkali halide crystals and models the dynamics of the process. The mechano-emission arises as a result of the ionization of surface traps at the expense of the energy which is released in the annihilation of the defects which are formed during cleavage. The slow electrons which appear upon the ionization of surface traps are subsequently accelerated in the field of negatively charged segment of the freshly cleaved surface. Considering the basic mechanism of fast electron emission, expressions are derived which are able to explain satisfactorily the temporal, thermal, charge, surface, coloration, water adsorption and other characteristics of the fast electron emission produced during the cleavage of crystals. The decay time of the charges on the newly created surfaces, and the velocity of cracks can be determined from the measurements of fast electron emission produced during the cleavage of crystals. It is shown that two types of diffusing centres are responsible for the charge relaxation and thereby for the emission of fast electrons produced during the cleavage of alkali halide crystals.     

Optimal control of a charge qubit in a double quantum dot with a Coulomb impurity

We study the efficiency of modulated external electric pulses to produce efficient and fast charge localization transitions in a two-electron double quantum dot. We use a configuration interaction method to calculate the electronic structure of a quantum dot model within the effective mass approximation. The interaction with the electric field is considered within the dipole approximation and optimal control theory is applied to design high-fidelity ultrafast pulses in pristine samples. We assessed the influence of the presence of Coulomb charged impurities on the efficiency and speed of the pulses. A protocol based on a two-step optimization is proposed for preserving both advantages of the original pulse. The processes affecting the charge localization is explained from the dipole transitions of the lowest lying two-electron states, as described by a discrete model with an effective electron-electron interaction.     

A new mode to excite a gas-discharge XeCl laser

The charge mode is a new mode to excite a discharge XeCl laser based on the dynamics of a spiker-sustainer circuit with a magnetic pulse compressor. The breakdown voltage is higher than in any other mode, due to a very fast rise time. The higher breakdown voltage provides a wider discharge and we found that more energy can be deposited before discharge instabilities terminate the optical output.     

Solvation beyond the linear response regime

Transient two-dimensional infrared spectroscopy (2D-IR) on a charge transfer model system is used as a nonlinear probe of solvation dynamics. Unlike what is expected in the linear response case, nonequilibrium relaxation and equilibrium spectral diffusion occur on different time scales. Transient 2D-IR spectroscopy is shown to be sensitive to higher order frequency fluctuation correlation functions, and provides evidence for a coupling between commonly observed fast and slow solvation processes.     

正充电聚四氟乙烯薄膜驻极体的电荷储存及其动态特性

研究了栅控恒压正电晕充电的聚四氟乙烯（PTFE）薄膜驻极体的电荷储存与 输运特性.结果显示在100℃以下的较低温区和高于150℃，尤其是高于180℃的较高 温区内慢再俘获效应控制着脱阱电荷的输运；而在约100—150℃的温区内快再俘获效应占主导地位.初始表面电位的增加将导致电荷密度衰减加剧，通过合理控制充电参数和组合 热处理工艺，可使同样储存有足够高的电荷密度的正负充电的PTFE薄膜驻极体既显示出相近 的电荷储存寿命，又具有突出的电荷稳定性. 关键词： 聚四氟乙烯 正充电驻极体 交越现象 电荷稳定性 电荷 输运     

Decoherence and disorder in quantum walks: from ballistic spread to localization

We investigate the impact of decoherence and static disorder on the dynamics of quantum particles moving in a periodic lattice. Our experiment relies on the photonic implementation of a one-dimensional quantum walk. The pure quantum evolution is characterized by a ballistic spread of a photon's wave packet along 28 steps. By applying controlled time-dependent operations we simulate three different environmental influences on the system, resulting in a fast ballistic spread, a diffusive classical walk, and the first Anderson localization in a discrete quantum walk architecture.     

不连续Co/SiO2多层膜的结构及其输运性质的研究

用射频磁控溅射方法制备了系列Co/SiO2不连续磁性金属绝缘体多层膜（DMIM） .经研究发现：对［SiO2(2.4 nm)/Co(t)］20体系，在Co层厚度小于2.5 nm时，Co层由连续变为不连续；Co层不连续时，其导电机理为热激发的电子隧穿导电，lnR与T-1/2接近正比关系; 隧道磁电阻（TMR）在Co层厚度为1.4 nm时出现极大值-3%.DMIM 的性质 不仅与磁性金属层厚度密切相关，而且与绝缘层厚度有密切的关系.在固定Co层厚度为 1.9 nm的情况下，研究了TMR随SiO2层厚度的变化 关键词： 不连续磁性金属/绝缘体多层膜 隧道磁电阻效应     

Freezing of triangulations

Zero temperature dynamics of two dimensional triangulations of a torus with curvature energy is described. Numerical simulations strongly suggest that the model get frozen in metastable states, made of topological defects on flat surfaces, that group into clusters of same topological charge. It is conjectured that freezing is related to high temperature structure of baby universes.Received: 6 February 2004, Published online: 28 May 2004PACS: 61.20. Lc Time-dependent properties of liquid structure; relaxation - 05.70. Ln Nonequilibrium and irreversible thermodynamics - 04.60. Nc Lattice and discrete methods in quantum gravity     

Application of real space Kerker method in simulating gate-all-around nanowire transistors with realistic discrete dopants

We adopt a self-consistent real space Kerker method to prevent the divergence from charge sloshing in the simulating transistors with realistic discrete dopants in the source and drain regions. The method achieves efficient convergence by avoiding unrealistic long range charge sloshing but keeping effects from short range charge sloshing. Numerical results show that discrete dopants in the source and drain regions could have a bigger influence on the electrical variability than the usual continuous doping without considering charge sloshing. Few discrete dopants and the narrow geometry create a situation with short range Coulomb screening and oscillations of charge density in real space. The dopants induced quasilocalized defect modes in the source region experience short range oscillations in order to reach the drain end of the device.The charging of the defect modes and the oscillations of the charge density are identified by the simulation of the electron density.     

Direct evidence for conduction pathways in a solid electrolyte

The emission of silver ions from the apex of an amorphous electrolyte tip has been investigated by field ion microscopy. The ion emission patterns show discrete nanometer-sized spots. We present evidence that they represent the termination of bulk ion conduction pathways at the solid-vacuum interface. The analysis of the signals from individual emission sites suggests the existence of a network of such pathways in the solid. Auto- and cross-correlation measurements of the currents from individual sites provide quantitative information on the microscopic dynamics of charge transport in solid electrolytes as well as on the lateral extent of the pathway network.     

Dynamics of neutralized charged particle beams in external magnetic and self fields

The dynamics of charged particle beams under the influence of their self-magnetic field and an external magnetic field is examined on the basis of equations for the trajectory of a boundary particle. A study is made of the change in the dynamics of fast particles due to the influence of the electric field of the partially neutralized space charge of the beam, the stationary electric field, and the field of the oscillations in the quasineutral beam plasma. Changes in the total beam energy caused by the self-electric field and in the longitudinal velocity owing to the self-magnetic field are taken into account. Zh. Tekh. Fiz. 68, 106–109 (August 1998)     

瞬态荧光方法研究溶剂诱导的三苯胺衍生物的对称性破缺电荷转移动力学

在缺乏特征红外振动的情况下追踪具有四极或八极对称性分子的激发态对称性破缺电荷转移通常是很困难的.本文以一种具有八极对称性的三苯胺衍生物为研究对象,利用飞秒时间分辨瞬态荧光光谱方法获得发光跃迁偶极矩的演化动力学,进而实时表征了其溶剂诱导对称性破缺电荷转移的动力学过程.当该分子处于弱极性甲苯溶液中时,在激发态弛豫过程中其发射偶极矩变化较小;当处于较强极性的四氢呋喃溶液中时,其发射偶极矩在数皮秒内快速减小.在对比单体偶极分子的荧光动力学后,推断八极分子的发光态在强极性溶剂中经历溶剂诱导的结构变化,由激子耦合的八极对称性降低至激发定域的偶极对称性;而在较弱极性的溶剂中,其八极对称性在溶剂化稳定中得以较大程度的保持.     

Thermalization of Fermionic Quantum Walkers

We consider the discrete time dynamics of an ensemble of fermionic quantum walkers moving on a finite discrete sample, interacting with a reservoir of infinitely many quantum particles on the one dimensional lattice. The reservoir is given by a fermionic quasifree state, with free discrete dynamics given by the shift, whereas the free dynamics of the non-interacting quantum walkers in the sample is defined by means of a unitary matrix. The reservoir and the sample exchange particles at specific sites by a unitary coupling and we study the discrete dynamics of the coupled system defined by the iteration of the free discrete dynamics acting on the unitary coupling, in a variety of situations. In particular, in absence of correlation within the particles of the reservoir and under natural assumptions on the sample’s dynamics, we prove that the one- and two-body reduced density matrices of the sample admit large times limits characterized by the state of the reservoir which are independent of the free dynamics of the quantum walkers and of the coupling strength. Moreover, the corresponding asymptotic density profile in the sample is flat and the correlations of number operators have no structure, a manifestation of thermalization.