Pauli spin susceptibility of a strongly correlated two-dimensional electron liquid

Thermodynamic measurements reveal that the Pauli spin susceptibility of strongly correlated two-dimensional electrons in silicon grows critically at low electron densities--behavior that is characteristic of the existence of a phase transition.     

Interference of ballistic electrons in an open quantum dot at high temperatures

The Aharonov-Bohm-type oscillations in the ballistic magnetoconductivity of an open quantum dot ～1 μm in size created in the GaAs/AlGaAs heterostructure by local anode oxidation have been studied. The measurements have been performed at temperatures of 4.2 and 1.5 K, which are high enough to expect a considerable suppression of the oscillations with period h/e (in magnetic flux units). The magnetoconductivity oscillations with a period less than the quantum h/e with respect to the magnetic field are observed at 1.5 K. The explanation is proposed on the basis of the interference of the electrons moving along the time-reversed paths inscribed into the quantum dot that have their initial and final points at one of the contacts, i.e., corresponding to a period of h/2e.     

Filling factor dependence of the fractional quantum Hall effect gap

We directly measure the chemical potential jump in the low-temperature limit when the filling factor traverses the nu=1/3 and nu=2/5 fractional gaps in two-dimensional (2D) electron system in GaAs/AlGaAs single heterojunctions. In high magnetic fields B, both gaps are linear functions of B with slopes proportional to the inverse fraction denominator, 1/q. The fractional gaps close partially when the Fermi level lies outside. An empirical analysis indicates that the chemical potential jump for an ideal 2D electron system, in the highest accessible magnetic fields, is proportional to q(-1) B(1/2).     

Effective electron mass in high-mobility SiGe/Si/SiGe quantum wells

The effective mass m* of the electrons confined in high-mobility SiGe/Si/SiGe quantum wells has been measured by the analysis of the temperature dependence of the Shubnikov-de Haas oscillations. In the accessible range of electron densities, n _s , the effective mass has been found to grow with decreasing n _s , obeying the relation m*/m _b = n _s /(n _s ? n _c ), where m _b is the electron band mass and n _c ≈ 0.54 × 10¹¹ cm^?2. In samples with maximum mobilities ranging between 90 and 220 m²/(V s), the dependence of the effective mass on the electron density has been found to be identical suggesting that the effective mass is disorder-independent, at least in the most perfect samples.     

Magnetoresistance of inversion and accumulation layers in MOS structures on pSi (100)

The magnetoresistance of two-dimensional electron and hole gases in MOS structures onpSi (100) was studied in inversion and accumulation regimes, respectively, measurements being made without contacts using a new experimental technique. In the magnetic field (h < 7 T) parallel to the sample surface the positive magnetoresistance was established to depend on a combination H/T^α (α ≈ 0.5, 1.7 ? T ? 4.2 K), that is unexplainable in terms of modern theories of electron localization and electron-electron interaction. In the perpendicular field, the magnetoresistance of p-accumulation layer is positive and comparable in magnitude with that in the parallel field.     

Two-dimensional electrons in (100)-oriented silicon field-effect structures in the region of low concentrations and high mobilities

A comparative analysis of experimental data on electron transport in Si (100) MOSFETs in the region of high mobilities and strong electron-electron interaction is carried out. It is shown that electrons can be described by the model of a noninteracting gas with the renormalized mass and Lande factor, which allows experimentally verifiable predictions.     

Sizes of solvated ion-clusters in salt solutions

Sizes of solvated ion-clusters were estimated in the approximation of oriented association of polarized solvent molecules around ions and in the approximation of the existence of a self-consistent field in the solution volume. It was shown that the salt concentration in the solution controls the applicability of this or that approximation. The cluster size strongly depends on the concentration at its high values. An increase in the concentration causes an increase in the frequency of the maximum manifestation of the effect of electroinduced selective drift of solvated ions.