Nonlinear AC and DC Conductivities in a Two-Subband n-GaAs/AlAs Heterostructure

JETP Letters - The DC and AC conductivities of the n-GaAs/AlAs heterostructure with two filled size quantization levels are studied within a wide magnetic field range. The electron spectrum of such...     

Forces along Equidistant Particle Paths

Two particles on the sphere leave the equator moving due south and travel at a constant and equal speed along a geodesic colliding at the south pole. An observer who is unaware of the curvature of the space will conclude that there is an attractive force acting between the particles. On the other hand, if particles travel at the same speed (initially parallel) along geodesics in the hyperbolic plane, then the particle paths diverge. Imagine two particles in the hyperbolic plane that are bound together at a constant distance with their center of mass traveling along a geodesic path at a constant velocity, then the force due to the curvature of the space acts to break the bond and increases as a quadratic function of the velocity. We consider this problem for the sphere and the hyperbolic plane and we give the exact formula for the apparent force between the particles. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of the system polydispersity on voltammograms of nanoparticles electrooxidation

The paper proposes a mathematical model describing electrooxidation of a polydisperse system of metal nanoparticles from the surface of an indifferent macro-electrode. It is shown that the degree of dispersion of a nanoparticle ensemble affects the shape of oxidation voltammograms. When the degree of dispersion rises and the average size of nanoparticles becomes smaller, the range of oxidation potentials increases. The results of the experimental study of electrooxidation of gold nanoparticles with different degrees of dispersion are given. The particles were localized on the surface of graphite screen-printed electrodes. A good agreement between the parameters of the experimental and calculated voltammograms confirms the correctness of the proposed model.     

Kondo temperature for the two-channel Kondo models of tunneling centers

A two-channel Kondo (2CK) non-Fermi liquid state in a metal resulting from the interaction between electrons and structural defects modeled by double-well potentials (DWP) is revisited. Account only of the two lowest states in DWP is known to lead to rather low Kondo temperature, T(K). We prove that the contribution of higher excited states reduces T(K), if all of the intermediate states are taken into account. Prefactor in T(K) is shown to be determined by the spacing between the second and the third levels epsilon(3) in DWP rather than by the electron Fermi energy epsilon(F). Since epsilon(3)相似文献   

Giant Nonlinear Absorption by an Ensemble of Metallic Grains

We have investigated the nonlinear low-frequency microwave absorption of an ensemble of small metallic grains. Earlier Zhou et al. [Phys. Rev. Lett. 77, 1958 (1996)] have proved that linear absorption by such a system is due to a mesoscopic relaxation mechanism for which important contribution is from the grains with small level spacings between the ground state and the first excited state. Here we have shown further that such grains are anomalously sensitive to the field amplitude and the distribution of level spacings. Since such a behavior depends on external magnetic field, we expect the appearance of a giant nonlinear magnetoresistance, as well as a very strong temperature dependence of the nonlinear microwave conductivity.     

Nonlinear high-frequency hopping conduction in two-dimensional arrays of Ge-in-Si quantum dots: Acoustic methods

Using acoustic methods we have measured nonlinear AC conductance in 2D arrays of Ge-in-Si quantum dots. The combination of experimental results and modeling of AC conductance of a dense lattice of localized states leads us to the conclusion that the main mechanism of AC conduction in hopping systems with large localization length is due to the charge transfer within large clusters, while the main mechanism behind its non-Ohmic behavior is charge heating by absorbed power.