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161.
I. V. Kukushkin D. V. Kulakovskii S. A. Mikhailov J. H. Smet K. von Klitzing 《JETP Letters》2003,77(9):497-501
A manifestation of retardation effects, which were predicted theoretically more than 35 years ago, is revealed for the first time in the plasma excitation spectrum of a two-dimensional electron system with a high electron mobility. It is shown that a significant decrease in the resonant plasma frequency due to a hybridization of the plasma and light modes is observed in zero magnetic field. An unusual dependence of the frequency of the hybrid cyclotron-plasmon mode on the magnetic field has been observed in a perpendicular magnetic field. The experimental results are in good quantitative agreement with the theory. 相似文献
162.
A. S. Plaut S. Patel W. G. Stallard P. Hawrylak H. Lage P. Grambow D. Heitmann K. von Klitzing S. Thoms M. C. Holland S. P. Beaumont C. R. Stanley M. Hopkinson J. P. Harbison L. T. Florez 《Physica E: Low-dimensional Systems and Nanostructures》1998,1(1-4)
Photoluminescence spectroscopy has been used to probe the occupied electron states below the Fermi energy of zero-dimensional electron systems (0DESs) in both zero and finite magnetic fields. The arrays of modulation-doped quantum dots investigated were fabricated by both reactive-ion etching and strain-confining GaAs heterojunctions with a
-layer of Be present in the GaAs, in order to improve luminescence efficiency. For the etched quantum dots we show that the low magnetic field dispersion
T) of the acceptor recombination line is directly related to the magnetic field dependence of the total ground-state energy of interacting electrons in the quantum dots. For the strain-confined 0DESs we have mapped the magneto-dispersion of the quantum confined electron states to reveal 15 electrons per dot. 相似文献
163.
Yu. B. Vasilyev K. V. Klitzing K. Eberl 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
Far-infrared magnetotransmission measurements in magnetic fields are carried out on asymmetric coupled double wells. We observe a splitting in the cyclotron resonance (CR) line for a wide range of intermediate magnetic fields and only one line at high magnetic fields. Two peaks observed in the CR spectra correspond to transitions between Landau levels in individual wells. We propose that phase transition between weak and strong coupling regimes may be responsible for the features. The characteristics of the transition are studied via an analysis of CR masses, CR splitting and line widths as a function of the magnetic field. 相似文献
164.
S. V. Tovstonog L. V. Kulik V. E. Kirpichev I. V. Kukushkin W. Dietsche K. von Klitzing 《JETP Letters》2003,78(10):654-658
A new class of single-particle excitations in tunnel-coupled electron bilayers is investigated by inelastic light scattering. The dispersion law and the dependence of the energies of these excitations on the degree of unbalance between the layers have been measured. A new spectroscopic method is proposed for determining the degree of unbalance between bilayers. 相似文献
165.
S. V. Tovstonog L. V. Kulik V. E. Kirpichev I. V. Kukushkin W. Dietsche K. von Klitzing 《JETP Letters》2004,79(1):48-52
Spectra of collective and magnetic excitations in symmetric double quantum wells with strong tunnel coupling were studied by inelastic scattering. Gaps in the spectrum of collective and single-particle excitations associated with tunnel interwell splitting were measured. New excitation modes, namely, tunnel Bernstein modes, were detected in a magnetic field. Based on the dispersion and magnetic-field dependences of the energies of inelastic light scattering lines, a classification of excitations and magnetic excitations was given. 相似文献
166.
Supercritical fluid chromatography (SFC) has become popular in the field of enantioselective separations. Many works have been reported during the last years. This review covers the period from 2000 till August 2013. The article is divided into three main chapters. The first one comprises a basic introduction to SFC. The authors provide a brief explanation of general principles and possibilities of this method. The advantages and drawbacks are also listed. Next part deals with chiral separation systems available in SFC, namely with the commonly used chiral stationary phases. Properties and interaction possibilities of the chiral separation systems are described. Recent theoretical papers are emphasized in this chapter. The last part of the paper gives an overview of applications of enantioselective SFC in analytical chemistry, in both analytical and preparative scales. Separation systems and conditions are summed up in tables so that they provide a helpful tool for analysts who search for a particular method of analysis. 相似文献
167.
The coupling of subsystems in a hierarchical modelling approach leads to different time constants in the dynamical simulation of technical systems. Multirate schemes exploit the different time scales by using different time steps for the subsystems. The stiffness of the system or at least of some subsystems in chemical reaction kinetics or network analysis, for example, forbids the use of explicit integration schemes. To cope with stiff problems, we introduce multirate schemes based on partitioned Runge—Kutta methods which avoid the coupling between active and latent components based on interpolating and extrapolating state variables. Order conditions and test results for such a lower order MPRK method are presented.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
168.
D. Quirion J. Weis Klaus v. Klitzing 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(3):413-419
The transport properties of a single quantum dot were
measured at low temperature in a regime of strong asymmetric
tunnel coupling to leads. By tuning this asymmetry, the two
parameters of the Kondo effect in a quantum dot, the Kondo
temperature and the zero-bias zero-temperature conductance, were
independently controlled. A careful analysis of the Coulomb
energies and of the tunnel couplings was performed. It allowed an
estimate of the Kondo temperature independently of its value
obtained via the temperature dependence of the conductance. Both
are in good agreement. We finally compared our experimental data
with an exact solution of the Kondo problem which provides the
dependence of the differential conductance on temperature and
source-drain voltage. Theoretical expectations fit quite well our
experimental data in the equilibrium and out-of-equilibrium
regimes. 相似文献
169.
R.D. Wiersma J.G.S. Lok S. Kraus W. Dietsche K. von Klitzing D. Schuh M. Bichler H.-P. Tranitz W. Wegscheider 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):16
We observe the total filling factor νT=1 exciton condensate in independently contacted bilayer two-dimensional electron systems in samples with minute tunnel coupling. At balanced electron densities in the layers, we find for both drag and counter-flow current configurations, thermally activated transport with a monotonic increase of the activation energy for d/ℓB<1.65 with activation energies up to 0.4 K. In the imbalanced system the activation energies show a striking asymmetry around the balance point, implying that the gap to charge excitations is considerably different in the separate layers that form the bilayer condensate. This indicates that the measured activation energy is neither the binding energy of the excitons, nor their condensation energy. 相似文献
170.
H. Rubel A. Fischer W. Dietsche C. Jrger K. von Klitzing K. Eberl 《Physica E: Low-dimensional Systems and Nanostructures》1998,1(1-4)
The coupling between systems of two spatially separated two-dimensional (2D) electron gases and between systems of a separated 2D electron gas and a 2D hole gas is studied as a function of magnetic field
. The small barrier (30 nm) separated coupled electron gases showed a transition from a phonon dominated interaction at
to a Coulomb dominated one at quantising fields. For large barriers (190 nm) phonons have been found to be the dominant coupling mechanism both at zero and finite fields. However, for all barriers investigated we could observe novel screening effects manifested in a suppression of the coupling at half-filled Landau levels. For the coupled electron–hole gases we have investigated samples with large barriers (
) so that the coupling is both in zero and finite fields dominated by phonon mediated processes. The enhanced screening effects could not be observed in those samples possibly due to the less pronounced quantisation of the hole gas. 相似文献