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Properties of excitations in two-dimensional electron systems in quantizing magnetic fields

Ziel

The objectives of the experimental part of the project are
(i) to determine the quasiparticle charge for different fractional-quantum-Hall-effect states by two different methods;
(ii) to study spin polarization of the two-dimensional electron system in the GaAs/AlGaAs heterostructures in a wide range of filling factors;
(iii) to identify variations of the spin polarization, caused by particular quantum-Hall-effect states;
(iv) to investigate the electron spin resonance in the states with different spin polarization;
(v) to search for signatures of the incompressible quantum-Hall-effect strips in real inhomogeneous systems by the capacitance technique;
(vi) to check theoretical predictions obtained within this project by the theoretical group.

The aims of the theoretical part of the project are
(i) to investigate the dynamics of the skyrmions,
(ii) to study the nature of the lowest neutral excitations with finite wave vectors at filling factor 1;
(iii) to develop approaches to calculations of the ground state energy and the excitation spectrum at non-integer filling factors.

To achieve these objectives the following experiments will be carried out on two-dimensional electron systems of GaAs/AlGaAs heterojunctions
(i) The dependence of the shot noise power on the backscattering current will be measured in devices with the constrictions under fractional-quantum-Hall-effect regime;
(ii) The chemical potential discontinuities will be measured by the capacitance spectroscopy method in situ with the activation energy of the dissipative conductivity for the fractional-quantum-Hall-effect states at filling factors 2/3, 4/3, 2/5, and 3/5;
(iii) The effect of the in-plane magnetic field component on the capacitance between the electron system and the gate will be studied in a wide range of filling factors (including 1, 3, 5, 1/3, 2/3, and 4/3) for different sets of quantum-Hall-effect states present;
(iv) Both resonant and nonresonant photoresponse in the magnetoresistance and capacitance of a two-dimensional electron system on the microwave irradiation will be investigated;
(v) The capacitance of the samples with the artificially produced carrier density gradient will be measured. The skyrmions and the spin waves will be analyzed in the framework of the same approach based on the Hartree-Fock approximation and the linear momentum representation. The next leading time derivative in the kinetic part of the action will be determined in order to study the dynamics of the skyrmions. New approaches will be searched for to describe both the ground state and the excited states at non-integer filling factors.

Investigations of these points promises a better understanding and a more complete view of the properties of these fascinating systems.

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Weizmann Institute of Science
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Herzel St.
76100 Rehovot
Israel

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Letzte Aktualisierung: 30 Oktober 2002

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Permalink: https://cordis.europa.eu/project/id/INTAS-1997-00076/de

European Union, 2024