G. Remenyi

Spin splitting of the Landau levels and exchange interaction of a non-ideal two-dimensional electron gas in heterostructures

Shubnikov - de Haas oscillations corresponding to the spin-resolved Landau levels of the two-dimensional electron gas at an heterointerface were studied in wide ranges of magnetic fields (up to 22 T) and tilt angles. Dependences of the spin splitting on the parallel component of magnetic field were investigated for half-filled Landau levels , , , and . The exchange interaction was shown to be strongly dependent on the broadening and overlapping of adjacent Landau levels. On the basis of this model, the experimental magnetic field dependences of were described. As a result, the absolute value of bare g-factor , exchange energy and Landau level broadening were obtained.

STRONG-PINNING EFFECTS IN LOW-TEMPERATURE CREEP: CHARGE-DENSITY WAVES IN TAS3

Nonlinear conduction in the quasi-one dimensional conductor o-TaS_3 has been studied in the low-temperature region down to 30 mK. It was found that at temperatures below a few Kelvins the current-voltage (I-V) characteristics consist of several branches. The temperature evolution of the I-V curve proceeds through sequential freezing-out of the branches. The origin of each branch is attributed to a particular strong pinning impurity type. Similar behavior is expected for other physical systems with collective transport (spin-density waves, Wigner crystals, vortex lattices in type-II superconductors etc.) in the presence of strong pinning centers.

Magnetic Field Induced Insulating Phase in Two-Dimensional Electron Gas in InGaAs/InP: The Wigner Solid

We review the results of our study of the properties of the magnetic field induced insulating phase in a two-dimensional electron gas in modulation-doped In0.53Ga0.47As/InP heterostructures. The experiments were performed in the millikelvin range of temperatures in very high magnetic fields. The results can be explained by the assumption of the formation of a glassy Wigner solid.

Magnetostriction Of Charge Density Wave Superconductor

Single crystals of layered niobium diselenide (2H‐NbSe2) compound with hexagonally packed layers were studied in a range of temperature 1.5–300 K by measuring magnetostricrtion and magnetization in field up to 20 T. The data are compared with magnetic susceptibility measurements. Specific features of measured temperature and field dependences were observed near CDW transition temperature (32.5 K) and superconducting transition (7.2 K), sensitive to magnetic field direction and strength.

Wigner-like phase transition in the strong disorder limit

We report on experiments on low temperature (mK range) quantum magnetotransport in InGaAs/InP with strong disorder, which can be explained by the assumption of the formation of Wigner-glass in the two-dimensional electron system. Varying the magnetic field, the temperature and the electron concentration, we have determined a part of the corresponding phase diagram.

Non-universal scaling in the integer quantum Hall effect regime in two-dimensional electron gas in InGaAs/InP heterostructures

We report on temperature scaling experiments on the integer quantum Hall effect plateau-to-plateau transitions as well as on the i = 1 plateau-to-insulating phase transitions in two-dimensional electron gas in In0.53Ga0.47As/InP modulation-doped heterostructures. We have measured the longitudinal ρxx and Hall ρxy resistivities as a function of magnetic field in the temperature range 40 mK - 4.2 K. It was found that for both types of transitions the scaling exponent has the same value κ ≈ 0.6-0.7. The scaling exponent obtained in our experiments is significantly greater than κ = 0.42, the value generally considered to be universal.

Interaction of low-density 2DEG with acoustic phonons

The energy relaxation of two-dimensional electron gas (2DEG) with low density (2.2 × 1010 cm-2) in selectively-doped In0.53Ga0.47As/InP heterostructures has been studied over a range of electron temperatures 0.1<Te<2 K. The Joule power of the dc current was employed for heating the electron gas, with the four terminal ac resistance of the sample used as electron thermometer. We found that the interaction with a screened small-angle piezoelectric potential of the acoustic phonons dominates in the temperature range 0.1<Te<0.4 K. At higher temperatures 0.5<Te<1.5 K, the change of energy balance equation is associated with a gradual transition from the small-angle interaction to a quasi-elastic one. The screening of the electron-phonon interaction and the deformation potential of acoustic phonons must be taken into consideration in this temperature range. The best fit to the data was obtained with piezoelectric constant h14 = (0.95 ±0.05) × 107 V cm-1 and deformation potential ED = (6 ±1) eV for both temperature ranges.

Quantum magnetotransport in 2D electron gas in InGaAs/InP heterostructures

Quantum magnetotransport measurements were performed on liquid phase epitaxially grown In0.35Ga0.47As/InP heterostructures at 4.2 K temperature in magnetic fields up to 22 Tesla. Measurements in tilted magnetic field, in conjunction with the analysis of the derivatives with respect to the magnetic field of the magnetoresistance curves, allowed the resolution of spin-splitting of the Landau levels up to N equals 3. The spin-splitting energy ESPIN was deduced for the half-filled Landau levels 0

Quantum and classical phenomena in low-temperature creep of the charge-density waves in o-TaS3

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Zero-temperature limits of nonlinear conduction of the quasi-one-dimensional conductor TaS 3 with charge-density waves

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