2,053 research outputs found
Features of electronic transport in relaxed Si/Si1-X GeX heterostructures with high doping level
The low-temperature electrical and magnetotransport characteristics of partially relaxed Si/Si1-x Gex heterostructures with two-dimensional electron channel (ne≥1012 cm-2) in an elastically strained silicon layer of nanometer thickness have been studied. The detailed calculation of the potential and of the electrons distribution in layers of the structure was carried out to understand the observed phenomena. The dependence of the tunneling transparency of the barrier separating the 2D and 3D transport channels in the structure, was studied as a function of the doping level, the degree of blurring boundaries, layer thickness, degree of relaxation of elastic stresses in the layers of the structure. Tunnel characteristics of the barrier between the layers were manifested by the appearance of a tunneling component in the current-voltage characteristics of real structures. Instabilities, manifested during the magnetotransport measurements using both weak and strong magnetic fields are explained by the transitions of charge carriers from the two-dimensional into three-dimensional state, due to interlayer tunneling transitions of electrons. © 2013 Elsevier B.V. All rights reserved
Change in stability of solid solution at radiation influence
Stability of solid solution at radiation influence has been investigated. Expressions for diffusion streams of binary alloy components, which specify the existence of temperature interval in which the phenomenon of ascending diffusion of elements is observed, were received. Vacancy characters of diffusion, configuration entropy, and potential energy of atomic bonds were considered at derivation. The ascending diffusion testifies to stability infringement of homogeneous solid solution - stratification. Influence of radiation is connected with increase in concentration of vacancies which changes the energy of atomic bonds and, simultaneously, accelerates diffusion processes. The condition of alloy stability with regard to stratification at radiating influence was obtaine
Recommended from our members
Evolution of the eyes of vipers with and without infrared-sensing pit organs
We examined lens and brille transmittance, photoreceptors, visual pigments, and visual opsin gene sequences of viperid snakes with and without infrared-sensing pit organs. Ocular media transmittance is high in both groups. Contrary to previous reports, small as well as large single cones occur in pit vipers. Non-pit vipers differ from pit vipers in having a twotiered retina, but few taxa have been examined for this poorly understood feature. All vipers sampled express rh1, sws1 and lws visual opsin genes. Opsin spectral tuning varies but not in accordance with the presence/absence of pit organs, and not always as predicted from gene sequences. The visual opsin genes were generally under purifying selection, with positive selection at spectral tuning amino acids in RH1 and SWS1 opsins, and at retinal pocket stabilization sites in RH1 or LWS (and without substantial differences between pit and nonpit vipers). Lack of evidence for sensory trade-off between viperid eyes (in the aspects examined) and pit organs might be explained by the high degree of neural integration of vision and infrared detection; the latter representing an elaboration of an existing sense with addition of a novel sense organ, rather than involving the evolution of a wholly novel sensory system
Dispersionful analogues of Benney's equations and -wave systems
We recall Krichever's construction of additional flows to Benney's hierarchy,
attached to poles at finite distance of the Lax operator. Then we construct a
``dispersionful'' analogue of this hierarchy, in which the role of poles at
finite distance is played by Miura fields. We connect this hierarchy with
-wave systems, and prove several facts about the latter (Lax representation,
Chern-Simons-type Lagrangian, connection with Liouville equation,
-functions).Comment: 12 pages, latex, no figure
Effect of Coulomb Forces on the Position of the Pole in the Scattering Amplitude and on Its Residue
Explicit expressions of the vertex constant for the decay of a nucleus into
two charged particles for an arbitrary orbital momentum are derived for the
standard expansion of the effective-range function , as well as when
the function has a pole. As physical examples, we consider the bound
state of the nucleus and the resonant states of the nuclei
He and He in the s-wave, and those of and
in the p-wave. For the systems and the pole
trajectories are constructed in the complex planes of the momentum and of the
renormalized vertex constant. They correspond to a transition from the
resonance state to the virtual state while the Coulomb forces gradually
decrease to zero.Comment: 17 pages, 5 figure
Critical behavior of two-dimensional cubic and MN models in the five-loop renormalization-group approximation
The critical thermodynamics of the two-dimensional N-vector cubic and MN
models is studied within the field-theoretical renormalization-group (RG)
approach. The beta functions and critical exponents are calculated in the
five-loop approximation and the RG series obtained are resummed using the
Borel-Leroy transformation combined with the generalized Pad\'e approximant and
conformal mapping techniques. For the cubic model, the RG flows for various N
are investigated. For N=2 it is found that the continuous line of fixed points
running from the XY fixed point to the Ising one is well reproduced by the
resummed RG series and an account for the five-loop terms makes the lines of
zeros of both beta functions closer to each another. For the cubic model with
N\geq 3, the five-loop contributions are shown to shift the cubic fixed point,
given by the four-loop approximation, towards the Ising fixed point. This
confirms the idea that the existence of the cubic fixed point in two dimensions
under N>2 is an artifact of the perturbative analysis. For the quenched dilute
O(M) models ( models with N=0) the results are compatible with a stable
pure fixed point for M\geq1. For the MN model with M,N\geq2 all the
non-perturbative results are reproduced. In addition a new stable fixed point
is found for moderate values of M and N.Comment: 26 pages, 3 figure
Renormalization Group Functions for Two-Dimensional Phase Transitions: To the Problem of Singular Contributions
According to the available publications, the field theoretical
renormalization group (RG) approach in the two-dimensional case gives the
critical exponents that differ from the known exact values. This fact was
attempted to explain by the existence of nonanalytic contributions in the RG
functions. The situation is analysed in this work using a new algorithm for
summing divergent series that makes it possible to analyse dependence of the
results for the critical exponents on the expansion coefficients for RG
functions. It has been shown that the exact values of all the exponents can be
obtained with a reasonable form of the coefficient functions. These functions
have small nonmonotonities or inflections, which are poorly reproduced in
natural interpolations. It is not necessary to assume the existence of singular
contributions in RG functions.Comment: PDF, 11 page
Direct and Inverse Variational Problems on Time Scales: A Survey
We deal with direct and inverse problems of the calculus of variations on
arbitrary time scales. Firstly, using the Euler-Lagrange equation and the
strengthened Legendre condition, we give a general form for a variational
functional to attain a local minimum at a given point of the vector space.
Furthermore, we provide a necessary condition for a dynamic
integro-differential equation to be an Euler-Lagrange equation (Helmholtz's
problem of the calculus of variations on time scales). New and interesting
results for the discrete and quantum settings are obtained as particular cases.
Finally, we consider very general problems of the calculus of variations given
by the composition of a certain scalar function with delta and nabla integrals
of a vector valued field.Comment: This is a preprint of a paper whose final and definite form will be
published in the Springer Volume 'Modeling, Dynamics, Optimization and
Bioeconomics II', Edited by A. A. Pinto and D. Zilberman (Eds.), Springer
Proceedings in Mathematics & Statistics. Submitted 03/Sept/2014; Accepted,
after a revision, 19/Jan/201
Difference Operator Approach to the Moyal Quantization and Its Application to Integrable Systems
Inspired by the fact that the Moyal quantization is related with nonlocal
operation, I define a difference analogue of vector fields and rephrase quantum
description on the phase space. Applying this prescription to the theory of the
KP-hierarchy, I show that their integrability follows to the nature of their
Wigner distribution. Furthermore the definition of the ``expectation value''
clarifies the relation between our approach and the Hamiltonian structure of
the KP-hierarchy. A trial of the explicit construction of the Moyal bracket
structure in the integrable system is also made.Comment: 19 pages, to appear in J. Phys. Soc. Jp
- …