We present experimental and theoretical studies of the magnetoresistance oscillations induced by resonance transitions of electrons between tunnel-coupled states in double quantum wells. The suppression of these oscillations with increasing temperature is irrelevant to the thermal broadening of the Fermi distribution and reflects the temperature dependence of the quantum lifetime of electrons. The gate control of the period and amplitude of the oscillations is demonstrated.Comment: 5 pages 4 figures, to be published in the Physical Review

We observe oscillatory magnetoresistance in double quantum wells under microwave irradiation. The results are explained in terms of the influence of subband coupling on the frequency-dependent photoinduced part of the electron distribution function. As a consequence, the magnetoresistance demonstrates the interference of magneto-intersubband oscillations and conventional microwaveinduced resistance oscillations. 73.43.Qt, 73.50.Pz The phenomenon of microwave-induced resistance oscillations 1−3 (MIRO) in two-dimensional (2D) electron systems under perpendicular magnetic fields has attracted much interest. 4 These oscillations are periodic in the inverse magnetic field with a period determined by the ratio of the microwave radiation frequency ω to the cyclotron frequency ω c and survive at high temperatures. Basically, the observed oscillatory photoconductivity is caused by the Landau quantization of electron states, though different microscopic mechanisms of this phenomenon are still under discussion.The influence of microwave irradiation on the magnetotransport properties is currently under investigation in quantum wells with a single occupied subband. In our paper, we underline the importance of similar studies for the systems with two occupied 2D subbands, where the magnetotransport shows special new features as compared to the single-subband case. Apart from the commonly known Shubnikov-de Haas oscillations (SdHO), there exist the magneto-intersubband (MIS) oscillations of resistivity caused by periodic modulation of the probability of intersubband transitions by the magnetic field 5,6 (see Ref. 7 for more references). These oscillations survive at high temperatures, because they are not related to the position of the Landau levels with respect to the Fermi surface. Our recent observation 7 of large-amplitude MIS oscillations at magnetic fields below 1 T in high-mobility double quantum wells (DQWs) has established that these oscillations are a well-reproducible feature of magnetotransport in such systems. The present measurements, supported by a theoretical analysis, suggest that the behavior of oscillating magnetoresistance in DQWs under microwave irradiation is caused by an interference of the physical mechanisms responsible for the MIS oscillations and con- * Permanent address: Institute of Semiconductor Physics, Prospekt Nauki 45, 03028, Kiev, Ukraine † Permanent address: Institute of Semiconductor Physics, Novosibirsk 630090, Russia ventional MIRO. We have studied dependence of the resistance of symmetric balanced GaAs DQWs with wells widths of 14 nm and different barrier widths d b = 1.4, 2, and 3 nm on the magnetic field B in the presence of microwave irradiation of different frequencies and at different temperatures and intensities of radiation. 0.1 0.2 0.3 0.4 0.9

The nonlinear regime of low-temperature magnetoresistance of double quantum wells in the region of magnetic fields below 1 T is studied both experimentally and theoretically. The observed inversion of the magnetointersubband oscillation peaks with increasing electric current and splitting of these peaks are described by the theory based on the kinetic equation for the isotropic nonequilibrium part of electron distribution function. The inelastic-scattering time of electrons is determined from the current dependence of the inversion field.

InAs quantum dots grown by molecular-beam epitaxy on GaAs substrates are demonstrated to be suitable structures to achieve an optical emission in the 1.3–1.5-μm range. Their tuning towards such long wavelengths was made possible by combining an extreme reduction of the InAs growth rate and a fast growth of the GaAs cap layer at low temperature. Our results create perspectives for the fabrication of GaAs-based devices operating in the most important telecommunications window.

Extracorporeal life support (ECLS) for severe respiratory failure has seen an exponential growth in recent years. Extracorporeal membrane oxygenation (ECMO) and extracorporeal CO2 removal (ECCO2R) represent two modalities that can provide full or partial support of the native lung function, when mechanical ventilation is either unable to achieve sufficient gas exchange to meet metabolic demands, or when its intensity is considered injurious. While the use of ECMO has defined indications in clinical practice, ECCO2R remains a promising technique, whose safety and efficacy are still being investigated. Understanding the physiological principles of gas exchange during respiratory ECLS and the interactions with native gas exchange and haemodynamics are essential for the safe applications of these techniques in clinical practice. In this review, we will present the physiological basis of gas exchange in ECMO and ECCO2R, and the implications of their interaction with native lung function. We will also discuss the rationale for their use in clinical practice, their current advances, and future directions.