Terahertz radiation-induced magnetoresistance oscillations of a high-density and high-mobility two-dimensional electron gas

The terahertz response of a high-density and high-mobility two-dimensional electron gas in 13-nm GaAs quantum wells at frequencies of 0.7 and 1.63 THz has been investigated. Terahertz radiation-induced magnetoresistance oscillations have been discovered. The oscillation maxima coincide with the harmonics of cyclotron resonance. It has been shown that a large number of harmonics (up to the ninth) appear under irradiation at a frequency of 0.7 THz. In this case, the effect is the analogue of microwave-induced oscillations. At a higher frequency, the oscillation amplitude decreases drastically with an increase in the harmonic number. This indicates a transition to the regime of ordinary cyclotron harmonics.     

Effect of nonstationarity in the motion of an open fluid flow

A way of taking the effects of unsteady motion into consideration in boundary layer theory has been found recently [1]. In the meantime, in hydraulics ever-increasing interest is being shown in the application of the ideas and methods of boundary layer theory to the study channel flows. We have attempted here to apply this hydrodynamic approach in deriving the law of resistance for turbulent unsteady flows in open channels.     

Two-Dimensional Semimetal HgTe in 14-nm-Thick Quantum Wells

JETP Letters - A two-dimensional semimetal is discovered in the (013) HgTe quantum well with a thickness of d = 14 nm, which is much smaller than those previously studied. It is found that such...     

Electrostatic potential, energy spectrum, and Fano resonances in a ballistic ring interferometer based on an AlGaAs/GaAs heterojunction

For a ballistic ring interferometer based on high-mobility two-dimensional electron gas in an AlGaAs/GaAs heterojunction, the electrostatic potential and the energy spectrum are determined. It is shown that the splitting points in such an interferometer have the form of triangular potential wells. Calculation is performed for the two-dimensional electron transmission through the ring, and the Fano resonances caused by the coupling of the transmitted waves with the levels of higher transverse modes in triangular wells are predicted. These resonances are observed in the experiment.     

Two-dimensional electron-hole system in a HgTe-based quantum well

A two-dimensional electron-hole system consisting of light high-mobility electrons with a density of N _s = (4–7) × 10¹⁰ cm^?2 and a mobility of μ _n = (4–6) × 10⁵ cm²/V s and heavier low-mobility holes with a density of P _s = (0.7–1.6) × 10¹¹ cm^?2 and a mobility of μ _p = (3–7) × 10⁴ cm²/V s has been discovered in a quantum well based on mercury telluride with the (013) surface orientation. The system exhibits a number of specific magnetotransport properties in both the classical magnetotransport (positive magnetoresistance and alternating Hall effect) and the quantum Hall effect regime. These properties are associated with the coexistence of two-dimensional electrons and holes.     

Coherent scattering in a small quantum dot

Ballistic transport in an open small (100 nm) three-terminal quantum dot has been analyzed. The dot is based on the high-mobility 2D electron gas of the AlGaAs/GaAs heterojunction. It has been shown that the gate oscillations of the resistance of such a dot arise due to the coherent scattering of electrons on its quasidiscrete levels and these oscillations are suppressed by a weak magnetic field.     

XPS and STM study of carbon deposits at the surface of platinum (110)

The deposition of carbon due to high temperature ethylene decomposition at Pt(110) was studied by XPS and STM techniques. In the temperature range 700–1400 K no graphite species were observed. Instead, two carbon states were distinguished by XPS. At temperatures 700–850 K chemisorbed carbon layer is formed with BE(C1s) = 284.2 eV, this carbon state reacting readily with both oxygen and hydrogen. At T> 850 K carbon layer with BE(C1s) = 284.6–284.9 eV is formed. Further study showed this carbon species to be stable up to 1150 K and to be inert towards both hydrogen and oxygen up to 1000 K. This state was attributed to diamond-like carbon (DLC). STM study of DLC on Pt(110) revealed the patched pseudo-C-(3 × 1) structure. This reconstruction is believed to account for the DLC formation at platinum (110) surface.     

Scattering processes in a two-dimensional semimetal

The scattering mechanisms in a two-dimensional semimetal based on a HgTe quantum well, where the electron and hole densities are controlled over a wide range by applying the gate voltage, have been studied. It is shown that impurity scattering prevails in this system at low temperatures. Interparticle scattering (in this case, electrons and holes) has been observed to directly affect the resistance of the metal.     

Observation of the second subband occupation in the p-type (1 1 1) Si inversion layer

We report our observations of the features in the conductivity and the anomalous magnetoresistance of a two-dimensional hole gas near (1 1 1) silicon surface, which gives the evidence for the onset of the second subband occupation at hole density p_s ≈ 5.3 × 10¹² cm^-2.