316 research outputs found
Nonextensive Thermostatistical Investigation of The Blackbody Radiation
Thermodynamical quantities of the blackbody radiation, such as free energy,
entropy, total radiation energy, specific heat are calculated within the
Tsallis thermostatistics where factorization method is incorparated. It is
shown that basic thermodynamical relation of the blackbody radiation is form
invariant with respect to nonextensivity entropic index q. Furthermore, the
nonextensive thermodynamical quantities related to the blackbody radiation is
seperately be obtained in terms of q and the standard thermodynamical
quantities of the blackbody radiation .It is indicated that the formulation may
give a way to determine the q which determines the degree of the nonextensivity
that is the one of the aims of the present study.Comment: 16 pages,No figures,to be appear in Chaos,Solitons&Fractal
Microscopic theory of the activated behavior of the quantized Hall effect
The thermally activated behavior of the gate defined narrow Hall bars is
studied by analyzing the existence of the incompressible strips within a
Hartree-type approximation. We perform self-consistent calculations considering
the linear response regime, supported by a local conductivity model. We
investigate the variation of the activation energy depending on the width of
samples in the range of . We show that the largest
activation energy of high-mobility narrow samples, is at the low field edge of
Hall filling factor 2 plateau (exceeding half of the cyclotron energy), whereas
for relatively wide samples the higher activation energy is obtained at the
high field edge of Hall plateau. In contrast to the single-particle theories
based on the localization of electronic states, we found that the activation
energy is almost independent of the properties of the density of states.Comment: 8 pages, 4 figure
Evanescent incompressible strips as origin of the observed Hall resistance overshoot
In this work we provide a systematic explanation to the unusual non-monotonic
behavior of the Hall resistance observed at two-dimensional electron systems.
We use a semi-analytical model based on the interaction theory of the integer
quantized Hall effect to investigate the existence of the anomalous, \emph{i.e}
overshoot, Hall resistance . The observation of the overshoot resistance
at low magnetic field edge of the plateaus is elucidated by means of
overlapping evanescent incompressible strips, formed due to strong magnetic
fields and interactions. Utilizing a self-consistent numerical scheme we also
show that, if the magnetic field is decreased the decreases to its
expected value. The effects of the sample width, temperature, disorder strength
and magnetic field on the overshoot peaks are investigated in detail. Based on
our findings, we predict a controllable procedure to manipulate the maxima of
the peaks, which can be tested experimentally. Our model does not depend on
specific and intrinsic properties of the material, provided that a single
particle gap exists.Comment: A theoretical follow-up paper of arXiv:1007.258
Exchange-correlation enhancement of the Lande-g* factor in integer quantized Hall plateaus
We study the emergent role of many-body effects on a two dimensional electron
gas (2DEG) within the Thomas-Fermi-Poisson approximation, including both the
exchange and correlation interactions in the presence of a strong perpendicular
magnetic field. It is shown that, the indirect interactions widen the
odd-integer incompressible strips spatially, whereas the even-integer filling
factors almost remain unaffected.Comment: 8 pages,4 figure
Quantum Hall Resistance Overshoot in 2-Dimensional Electron Gases - Theory and Experiment
We present a systematical experimental investigation of an unusual transport
phenomenon observed in two dimensional electron gases in Si/SiGe
heterostructures under integer quantum Hall effect (IQHE) conditions. This
phenomenon emerges under specific experimental conditions and in different
material systems. It is commonly referred to as Hall resistance overshoot,
however, lacks a consistent explanation so far. Based on our experimental
findings we are able to develop a model that accounts for all of our
observations in the framework of a screening theory for the IQHE. Within this
model the origin of the overshoot is attributed to a transport regime where
current is confined to co-existing evanescent incompressible strips of
different filling factors.Comment: 26 pages, 10 figure
Interaction mediated asymmetries of the quantized Hall effect
Experimental and theoretical investigations on the integer quantized Hall
effect in gate defined narrow Hall bars are presented. At low electron mobility
the classical (high temperature) Hall resistance line RH(B) cuts through the
center of all Hall plateaus. In contrast, for our high mobility samples the
intersection point, at even filling factors \nu = 2; 4 ..., is clearly shifted
towards larger magnetic fields B. This asymmetry is in good agreement with
predictions of the screening theory, i. e. taking Coulomb interaction into
account. The observed effect is directly related to the formation of
incompressible strips in the Hall bar. The spin-split plateau at \nu= 1 is
found to be almost symmetric regardless of the mobility. We explain this within
the so-called effective g-model.Comment: 4 pages, 3 figure
Effect of exchange-correlation potential on the plasmon dispersions in a doped symmetrical double quantum well
We have calculated the plasmon dispersion relations in a doped double quantum well with and without exchange-correlation potential added to the effective potential of the system. The calculations were done for high and low doping densities by solving the Schrödinger and Poisson equations self-consistently. Our numerical results show that the exchange-correlation potential is quite important at high doping densities of donor impurities for plasmon dispersions at large wave vectors. On the other hand, the ratio of subband populations nl to donor density ND is more affected at low densities. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA
Theoretical investigation of InAs/GaSb type-II pin superlattice infrared detector in the mid wavelength infrared range
In this study, we present the theoretical investigation of type-II InAs/GaSb superlattice p-i-n detector. Kronig-Penney and envelope function approximation is used to calculate band gap energy and superlattice minibands. Variational method is also used to calculate exciton binding energies. Our results show that carriers overlap increases at GaSb/InAs interface on the higher energy side while it decreases at InAs/GaSb interface on the lower energy side with increasing reverse bias due to shifting the hole wavefunction toward to the GaSb/InAs interface decisively. Binding energies increase with increasing electric field due to overall overlap of electron and hole wave functions at the both interfaces in contrast with type I superlattices. This predicts that optical absorption is enhanced with increasing electric field. © 2013 American Institute of Physics
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