Fermi edge polaritons in a microcavity containing a high density two-dimensional electron gas

Sharp, near band gap lines are observed in the reflection and photoluminescence spectra of GaAs/AlGaAs structures consisting of a modulation doped quantum well (MDQW) that contains a high density two-dimensional electron gas (2DEG) and is embedded in a microcavity (MC). The energy dependence of these lines on the MC-confined photon energy shows level anticrossings and Rabi splittings very similar to those observed in systems of undoped QW's embedded in a MC. The spectra are analyzed by calculating the optical susceptibility of the MDQW in the near band gap spectral range and using it within the transfer matrix method. The calculated reflection spectra indicate that the sharp spectral lines are due to k{ parallel}=0 cavity polaritons that are composed of e-h pair excitations just above the 2DEG Fermi edge and are strongly coupled to the MC-confined photons.     

Trions in quantum-well structures with two-dimensional electron gas

A study has been made of bound exciton-electron complexes (trions) and unbound exciton-electron states (combined exciton-cyclotron resonance) from reflectance spectra obtained from modulation-doped CdTe/CdMgTe quantum-well structures. It has been established that the contribution of trions to dielectric permittivity is comparable to that of excitons. An analysis is made of the magnetic-field dependence of the parameters describing the contribution to dielectric permittivity due to exciton-cyclotron-resonance states. Fiz. Tverd. Tela (St. Petersburg) 40, 813–815 (May 1998)     

Photonic bandgap structures for long-range surface plasmon polaritons

Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm-size thickness variations result in the pronounced band gap effect, and obtain very good agreement between measured and simulated (transmission and reflection) spectra. This effect is exploited to realize a compact wavelength add-drop filter with the bandwidth of 20 nm centered at 1550 nm. The possibilities of achieving a full bandgap (in the surface plane) for LR-SPPs are also discussed.     

Dispersion of cylindrical surface plasmon polaritons in layered structures

The problem of the existence of cylindrical surface plasmon polaritons on thin metal conductors is considered. A dispersion relation is obtained and analyzed, the domain of existence of dispersion curve with a maximum is found, and parametric relations are derived.     

Formation of high-frequency two-dimensional interference patterns of surface plasmon polaritons

The formation of high-frequency two-dimensional interference patterns of surface plasmon polaritons in a structure consisting of four diffraction gratings with one-dimensional periodicity in a metallic film has been studied numerically and experimentally. It has been shown that change of linear polarization of the incident radiation to its circular polarization makes it possible to reduce the period of the formed pattern at a fixed wavelength. A similar change in the form of the pattern can be achieved by introducing an equivalent shift to the geometry of the structure.     

Coupled-mode approach to surface plasmon polaritons in nonlinear periodic structures

We present a coupled-mode theory describing light propagation in an array of nonlinear plasmonic waveguides. Our model predicts a two-band dependence of the propagation constant versus transverse quasi-momentum and existence of discrete and gap plasmon solitons.     

Solitons in a two-dimensional electron gas

The non-linear spectrum of a two-dimensional electron gas (2-DEG) formed at the interface of a heterostructure is investigated. This spectrum is found to contain a new type of localized excitation exhibiting soliton behavior. A matrix formulation of the model equations permits the extraction of the equation of evolution in space for these excitations. Results are presented for the boundary value problem excited by temporal Gaussian pulses.     

Propagation of surface plasmon polaritons in anisotropic MIM and IMI structures

Electromagnetic wave propagation through waveguide structures consisting of anisotropic dielectric layers, assisted by surface plasmon-polaritons (SPPs) is theoretically studied. Dispersion relations corresponding to both short range and long range coupled SPP modes in metal/insulator/metal (MIM) and insulator/metal/insulator (IMI) structures, taking into consideration the anisotropy of the insulator, are derived and numerically solved. The dispersion has a prominent dependence on the anisotropy of the dielectric environment. The dependence of propagation on the misalignments of the optic axes of the insulator has also been investigated.     

Solitons in semiconductor microstructures with a two-dimensional electron gas

Nonlinear waves in a two-dimensional electronic plasma with metal screening gates are investigated. It is shown that solitons described by the KdV equation exist in such a system. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 7, 479–481 (10 October 1999)     

Edge plasmon polaritons on a half-plane

The effect of electromagnetic retardation on the spectrum of edge plasmons in a semi-infinite two-dimensional electron system is considered. The problem is reduced to complicated integral equations for the potentials, which are solved upon a major simplification of the kernel. The spatial distribution of the potentials, charges, and currents is analyzed. It is shown that edge plasmon polaritons in the high-conductivity two-dimensional system are characterized by a high Q factor at all frequencies, including those lower than the reciprocal electron relaxation time τ^-1.     

Magnetotransport in a modulated two-dimensional electron gas

We propose a semiclassical theory of dc magnetotransport in a two-dimensional electron gas modulated along one direction with weak electrostatic modulations. We show that oscillations of the magnetoresistivity ρ_∥ corresponding to the current driven along the modulation lines observed at moderately low magnetic fields can be explained as commensurability oscillations.     

High-frequency conductivity of a two-dimensional electron gas with impurity electron states

The high-frequency conductivity tensor for a two-dimensional electron gas with short-range-acting impurity atoms has been computed. Spatial dispersion of the conductivity was taken into account. The threshold and maxima of the dissipative part of the conductivity arising from ionization of the impurity atoms by the field of electromagnetic waves were found. Numerical calculations of the conductivity were carried out for semiconductor structures with a two-dimensional electron gas. Khar’kov State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 91–94, July, 1997.     

Propagation of surface plasmon polaritons through gradient index and periodic structures

We study propagation of surface electromagnetic waves along a metallic surface covered by various layered dielectric structures. We show that strong radiative losses, typical for scattering of a surface wave, can be considerably suppressed when a single dielectric step is substituted by gradient index or periodic layered structure.     

Quantum magnetotransport in a modulated two-dimensional electron gas

Quantum mechanical calculations of the magnetotransport coefficients of a modulated two-dimensional electron gas in a perpendicular magnetic field are presented using the Kubo method. The model modulation potential used is such that the effect of the steepness of the potential and its strength on the band part of the longitudinal resistivity ρ_xxand the Hall resistivity ρ_xycould be studied. In the extreme limit of a very steep potential, a two-dimensional square array of antidots is simulated. Impurity scattering is included in the self-consistent t-matrix approximation. The results show that for a strong lateral superlattice potential, ρ_xyis quenched in the low magnetic field regime and as the magnetic field increases there is a large negative Hall resistivity. The intensity of this negative peak is suppressed as the strength of the modulation potential is decreased. It is also shown that the height of the negative peak depends on the steepness of the potential. The longitudinal resistivity also has some interesting features. There are Aharonov–Bohm oscillations and a double peak structure which depends on both the strength of the modulation potential as well as its slope. The numerical results show that the position and intensity of the lower peak is not very sensitive to a change in the strength of the lattice potential or its steepness. However, the upper peak is greatly reduced when the lattice potential is diminished in strength. The double peak feature in ρ_xxand the negative peak and quenching of the Hall effect at low magnetic fields have been observed experimentally for antidots in both the quasiclassical and quantum regimes.     

Magnetic ratchet effects in a two-dimensional electron gas

The effect of the magnetic field on the generation of an electric current in a two-dimensional electronic ratchet is theoretically studied. Mechanisms of the formation of magnetically induced photocurrent are proposed for a structure with a two-dimensional electron gas (quantum well, graphene, or topological insulator) with a lateral asymmetric superlattice consisting of metallic strips on the external surface of the structure. The ratchet with the spatially oscillating magnetic field generated by the ferromagnetic lattice, as well as the nonmagnetic ratchet placed in the uniform magnetic field both classically weak and strong quantizing, is considered. It is established that the ratio of the amplitude of the magnetic oscillations of photocurrent to the ratchet photocurrent in zero field can exceed two orders of magnitude.     

Commensurability oscillations in a stripe-shaped two-dimensional electron gas

We have studied the commensurability oscillations for a nonplanar, two-dimensional electron gas which is confined to a surface spatially modulated both in the transverse and longitudinal directions. We show, numerically, that coupling the drift in both directions causes the motion to be chaotic. The channeling tori, responsible for conduction along the stripes, are destroyed and the averaged squared drift velocities decrease.