Tenfold magnetoconductance in a nonmagnetic metal film

We present magnetoconductance (MC) measurements of homogeneously disordered Be films whose zero field sheet conductance ( G) is described by the Efros-Shklovskii hopping law G(T) = (2e(2)/h)exp-(T0/T)(1/2). The low field MC of the films is negative with G decreasing a factor of 2 below 1 T. In contrast the MC above 1 T is strongly positive. At 8 T, G increases tenfold in perpendicular field and fivefold in parallel field. In the simpler parallel case, we observe field enhanced variable range hopping characterized by an attenuation of T0 via the Zeeman interaction.     

Sample size dependence of magnetoconductance fluctuations in narrow n+-GaAs wires

Submicron sized n⁺-GaAs wires are fabricated using MOCVD and electron beam lithography techniques, and effects of sample size on magnetoconductance fluctuations have been investigated. It is found that the magnitude of the fluctuation decreases by ensemble averaging with increasing sample size in wires with the width and the length larger than the inelastic scattering length. It is found that the fluctuation becomes larger than the predicted value in wires with the width narrower than the scattering length.     

Microwave-induced dephasing in one-dimensional metal wires

We report on the effect of monochromatic microwave (MW) radiation on the weak-localization corrections to the conductivity of quasi-one-dimensional silver wires. Because of the improved electron cooling in the wires, the MW-induced dephasing is observed without a concomitant overheating of electrons over wide ranges of the MW power P(MW) and frequency f. The observed dependences of the conductivity and MW-induced dephasing rate on P(MW) and f are in agreement with the theory by Altshuler, Aronov, and Khmelnitsky [Solid State Commun. 39, 619 (1981)]. Our results suggest that in the low-temperature experiments with 1D wires, saturation of the temperature dependence of the dephasing time can be caused by an MW electromagnetic noise with a sub-pW power.     

金属微结构纳米线中等离激元传播和分光特性

本文从理论和实验两方面探讨了具有微结构的金属纳米线系统中表面等离激元传播规律和分光特性. 我们由麦克斯韦方程组出发, 利用严格耦合波近似和有限元差分等方法首先从理论上给出了金属纳米线系统中等离激元的色散关系和能带特征, 然后基于微结构的银纳米线及其等离激元能带结构, 设计并制备出等离激元分光原型器件, 实验展示其将不同频率的光在微小空间分离的特性. 该研究结果是我们前期相关工作的延续和补充, 可应用于构造多功能集成的光子芯片和新型亚波长光电材料和器件.     

Fermi energy and optical conductivity of metal quantum wires

The size dependence of the Fermi energy of conduction electrons has been analytically evaluated and its oscillations have been calculated in the framework of the cylindrical well model. The conductivity tensor components for a metal wire with the radius ρ₀ have been calculated with the use of the expansion in powers of ρ₀/λ, where λ is the wavelength of incident light. The influence of the dimension of the systems has been established by comparing the results of the calculations of the optical conductivity of thin wires and films for Au, Al, and Pb metals. According to the results of the calculations, the real and imaginary parts of the conductivity depend substantially on the size and frequency. The difference between the results obtained for Pb and Au metals has been explained by the different relaxation times of electrons in nanowires that are homogeneous in the thickness.     

Formation of chemical compounds in the electrical explosion of metal wires in liquids

The results of investigations of the products of the electrical explosion of aluminum and tungsten wires in liquid media (water and decane) are presented. It is shown that the phase composition of the powders formed depends on the energy characteristics of the explosion. The mechanism by which the products of the explosion are formed is discussed. NIIVN, Tomsk Polytechnical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 9–13, June, 1996.     

Geometry effects in the magnetoconductance of normal and Andreev Sinai billiards

We study the transport properties of low-energy (quasi)particles ballistically traversingnormal and Andreev two-dimensional open cavities with a Sinai-billiard shape. We considerfour different geometrical setups and focus on the dependence of transport on the strengthof an applied magnetic field. By solving the classical equations of motion for each setupwe calculate the magnetoconductance in terms of transmission and reflection coefficientsfor both the normal and Andreev versions of the billiard, calculating in the latter thecritical field value above which the outgoing current of holes becomes zero.     

Dispersion of surface plasmon polaritons on metal wires in the terahertz frequency range

We report the experimental and theoretical study of the dispersive behavior of surface plasmon polaritons (SPPs) on cylindrical metal surfaces in the terahertz frequency range. Time-domain measurements of terahertz SPPs propagating on metal wires reveal a unique structure that is inconsistent with a simple extrapolation of the high frequency portion of the dispersion diagram for SPPs on a planar metal surface, and also distinct from that of SPPs on metal nanowires observed at visible and near-infrared frequencies. The results are consistent with a numerical solution of Maxwell's equations, showing that the dispersive behavior of SPPs on a cylindrical metal surface at terahertz frequencies is quite different from that of SPPs on a flat surface. These findings indicate the increasing importance of skin effects for SPPs in the terahertz range, as well as the enhancement of such effects on curved surfaces.     

Low temperature thermal magnetoconductance of metals

A low temperature transverse thermal magnetoconductance of metals and semimetals is treated theoretically. It is shown that its high magnetic field behavior is determined by the characteristic time τ_ɛ of jumps from one cyclotron circle to another due to electron-phonon collisions rather than by the transport time τ_tr that determines the conductance. The phonon-electron drag contribution to the magnetoconductance is also discussed.     

Positive magnetoconductance and dephasing in strongly localized black phosphorus

We study the magnetoconductance and dephasing in a strongly localized regime in black phosphorus (BP) devices. The phase coherence length, l_φ obtained from the magnetoconductance follows a temperature dependence of T^–1/3 in the strongly localized regime with k_Fl_e < 1 (ξ < l_φ) based on the Ioffe–Regel criterion. Here k_F, l_e and ξ are the Fermi wave vector, mean free path and localization length, respectively. The conductance behavior as a function of temperature confirms that the transport regime of our BP is in a variable‐range‐hopping regime, which results in the strongly localized regime.     

有机发光二极管的光致磁电导效应

制备了结构为ITO/CuPc/NPB/Alq₃/LiF/Al的常规有机发光二极管, 之后对器件采用波长为442 nm和325 nm的激光线进行照射产生激子, 并在小偏压下(保证器件没有开启)对激子的演化过程进行控制, 同时测量器件的光致磁电导(photo-induced magneto-conductance, PIMC). 实验发现, 不同于电注入产生激子的磁电导效应, PIMC在正、反小偏压下表现出明显不同的磁响应结果. 当给器件加上正向小偏压时, 器件的PIMC在0-40 mT范围内迅速上升; 随着磁场的进一步增大, 该PIMC增加缓慢, 并逐渐趋于饱和. 反向小偏压时, 器件的PIMC随着磁场也是先迅速增大(0-40 mT), 但达到最大值后却又逐渐减小. 通过分析外加磁场对器件光生载流子微观过程的影响, 采用'电子-空穴对'模型和超精细相互作用理论对正向偏压下的PIMC进行了解释; 反向偏压下因各有机层的能级关系, 为激子与电荷相互作用提供了必要条件, 运用三重态激子与电荷的反应机制可以解释PIMC出现高场下降的实验现象.     

Carrier and field dependences of the magnetoconductance of two-dimensional electron systems

The magnetoconductivity of a two-dimensional electron system is evaluated for weak/intermediate magnetic fields as a function of carrier density. The magnetoconductance shows a maximum which is reduced and shifted towards a higher carrier concentration when the magnetic field is increased The oscillating pattern changes also with the concentration. These variations agree with the data of Fang, Fowler and Hartstein.