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Register a new userDispersion of Volume Relativistic Magnetoplasma Excitation in a Gated Two-Dimensional Electron System
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Added by
Viacheslav Muravev Dr.
Publication date
2015
fields
Physics
and research's language is
English
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The dispersion of the volume relativistic magnetoplasma mode in a gated GaAs/AlGaAs quantum well is measured using a coupled resonators detection technique. The weakly damped relativistic mode exhibits an unusual zigzag-shaped magnetodispersion dependence dictated by the diagonal component of the resistivity tensor $rho_{xx}$. The plasma excitation easily hybridizes with photon modes due to a large spatial delocalization of its electromagnetic field. The effects of electron density and structure geometry on the excitation spectrum have been investigated.
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The dipolar (magnetostatic) interaction dominates the behavior of spin waves in magnetic films in the long-wavelength regime. In an in-plane magnetized film, volume modes exist with a negative group velocity (backward volume magnetostatic spin waves), in addition to the forward surface-localized mode (Damon-Eshbach). Inside the film of finite thickness $L$, the volume modes have a nontrivial spatial dependence, and their two-dimensional dispersion relations $omega(mathbf{k})$ can be calculated only numerically. We present explicit perturbative expressions for the profiles and frequencies of the volume modes, taking into account an in-plane applied field and uniaxial anisotropy, for the regimes $lVert mathbf{k}L rVert gg 1$ and $lVert mathbf{k}L rVert ll 1$, which together provide a good indication of the behavior of the modes for arbitrary wavevector $mathbf{k}$. Moreover, we derive a very accurate semianalytical expression for the dispersion relation $omega(mathbf{k})$ of the lowest-frequency mode that is straightforward to evaluate using standard numerical routines. Our results are useful to quickly interpret and control the excitation and propagation of spin waves in (opto-)magnetic experiments.
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The spectra of plasma and magnetoplasma excitations in a two-dimensional system of anisotropic heavy fermions were investigated for the first time. The spectrum of microwave absorption by disk-like samples of stressed AlAs quantum wells at low electron densities showed two plasma resonances separated by a frequency gap. These two plasma resonances correspond to electron mass principle values of $(1.10 pm 0.05) m_0$ and $(0.20 pm 0.01) m_0$. The observed results correspond to the case of a single valley strongly anisotropic Fermi surface. It was established that electron density increase results in population of the second valley, manifesting itself as a drastic modification of the plasma spectrum. We directly determined the electron densities in each valley and the inter-valley splitting energy from the ratio of the two plasma frequencies.
We study the effect of magnetic field on the properties of a high mobility gated two-dimensional electron gas in a field effect transistor with the Hall bar geometry. When approaching the current saturation when the drain side of the channel becomes strongly depleted, we see a number of unusual effects related to the magnetic field induced re-distribution of the electron density in the conducting channel. The experimental results obtained in the non-linear regime have been interpreted based on the results obtained in the linear regime by a simple theoretical model, which describes quite well our observations.
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