Mid Sweden University

We theoretically study the wavelength and the propagation length of the edge magnetoplasmons (EMP's), running along the edge of a two-dimensional (2D) electron layer in a semiconductor quantum-well structure with and without metallic gates. We show that the metallic gate suppresses the propagation of the EMP's, but the quality factor of the wave (q'/q '', where q' and q '' are the real and imaginary parts of the complex EMP wavevector) can be larger in the gated structures as compared to the structures without the gate. The results may be useful for analysis of operation of the recently discovered microwave detectors and spectrometers operating at liquid nitrogen temperatures (Kukushkin et al., Appl. Phys. Lett. 86, 044101 (2005)).

We consider the scattering of an incident electromagnetic radiation on a two-dimensional (2D) electron layer with an imbedded metallic contact. We show that the incident wave excites in the system the 2D plasmon polaritons running along the 2D layer and localized near it, and electromagnetic waves reflected back from the system. The ratio of the energy transformed to the 2D plasmon polaritons and reflected back from the layer depends on the frequency and the value of a retardation parameter, which characterizes the importance of retardation effects. When the retardation parameter is large, the energy of the incident radiation is mainly reflected from the 2D electron system and the excitation of the 2D plasmon polaritons is less effective. The results obtained are discussed in connection with recent experiments on the microwave response of the 2D electron systems.

Microwave response of a two-dimensional (2D) electron stripe, supplied by two semi-infinite side contacts, is theoretically studied taking into account retardation and radiative effects. Absorption spectra of the stripe are calculated as a function of the microwave frequency omega, magnetic field B, parameters of the 2D electron gas and of the contacts. It is shown that the contacts substantially modify the position, the linewidth and the strength of the absorption resonances, leading for instance to the inversion of the absorption maxima of the right and left circularly polarized radiation in magnetic fields.

Using an exact diagonalization technique, we calculate the distribution of electrons n(nu) over single-particle quantum states in few-electron parabolic quantum dots. We show that n(nu) is a function of quantum numbers nu, but not of the energy of the states E-nu, n(nu) not equal n(E-nu). The common property n(nu) = n(E-nu) remains valid only if electron-electron interaction is neglected. For certain cases in the strong interaction regime, the occupation numbers of higher-energy levels may be larger than those of the lower-energy states: n(nu) > n(nu ') at E-nu > E-nu '.

Electromagnetic response of a finite-width two-dimensional electron stripe with attached metallic side contacts is theoretically studied. It is shown that contacts substantially influence the position, the linewidth, and the amplitude of plasmon-polariton resonances in the stripe. In finite magnetic fields, absorption of the wave with the inactive circular polarization (which is not absorbed in an infinite system without contacts) may become larger than that of the wave with the active polarization. The results are discussed in view of recent microwave experiments in two-dimensional electron systems.

The wavelength and the propagation length of the edge magnetoplasmons, running along the edge of a two-dimensional electron layer in a semiconductor quantum-well structure, are theoretically studied as a function of frequency, magnetic field, electron density, mobility, and geometry of the structure. The results are intended to be used for analysis and optimization of operation of recently invented quantum-well microwave spectrometers operating at liquid-nitrogen temperatures [I. V. Kukushkin , Appl. Phys. Lett. 86, 044101 (2005)].

Electromagnetic response of a finite-width two-dimensional electron stripe is theoretically studied. It is shown that retardation and radiative effects substantially modify the absorption spectrum of the system at microwave frequencies, leading to a nontrivial zigzag behavior of the magnetoplasmon-polariton modes in magnetic fields, similar to that recently observed by Kukushkin [Phys. Rev. Lett. 90, 156801 (2003)].

We demonstrate that a two-dimensional electron system fabricated from a GaAs/AlGaAs quantum well in the presence of a magnetic field B possesses the ability to detect electromagnetic radiation in a broad frequency range. Irradiation of the sample with microwaves produces a dc-photovoltage which oscillates as a function of B. The amplitude and the period of the oscillations are proportional to the radiation power and the wavelength, respectively. Successful operation of such a detector/spectrometer is reported for microwave frequencies up to similar to150 GHz and temperatures up to similar to80 K. We do not anticipate any principal difficulties in extending the operation frequency further into the terahertz region.

We discuss possible origins of recently discovered microwave induced photoresistance oscillations in very-high-electron-mobility two-dimensional electron systems. We show that electrodynamic effects-the radiative decay, plasma oscillations, and retardation effects-are important under the experimental conditions, and that their inclusion in the theory is essential for understanding the discussed and related microwave induced magnetotransport phenomena.