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Magneto-tunnelling spectroscopy of many-electron effects in low-dimensional systems based on III-V semiconductor heterostructures

Ziel

The general goal of the project is to study many-electron effects in low-dimensional III-V semiconductor systems, principally quasi-2D systems, using magneto-tunnelling spectroscopy over a wide range of magnetic fields and at low temperatures.

The following experimental and theoretical studies are proposed.

1. Intersubband magnetoplasmon, intrasubband magnetoplasmon and intersubband LO phonon- magnetoplasmon modes. Tunnelling spectroscopy will be employed to probe the properties of these collective excitations and to measure their dispersion curves ((k) for the first time. To achieve these goals, tunnel structures incorporating quasi-2DES, and involving pure vertical transport, will be designed and grown. Tilted magnetic fields will be used for these measurements. Calculations of the dispersion curves ((k) will be carried out and compared with experimental data;
2. 2D-2D magneto-tunnelling and the problem of the "soft" Coulomb gap at the Fermi level in disordered 2D systems. The goal is to investigate the effects of intra- and interlayer Coulomb interactions on the properties of the magnetic field-induced, "soft" linear gap in the single particle DOS of disordered quasi-2DES that has been observed recently by the project participants;
3. Commensurability effects in magneto-tunnelling spectra of quantum wells with self-assembled quantum dots. The starting point is the recent observation by the applicants of a resonance-like perturbation of empty Landau levels in quantum wells containing quantum dots. It is believed that the effect is associated with some kind of commensurability between the size of cyclotron orbits and the size of the quantum dots. This appears to indicate the manifestation of n-electron states in excited Landau levels, n=2,3. The goal is to understand the physical nature of this fundamental phenomenon;
4. Effects of interface structure on tunnelling. The aim is to reveal the effects of the tunnel barrier interface microstructure on the measured electron tunnel spectra of 2D systems and quantum dots. The in-plane anisotropy of the electron effective mass in 2DES will be studied by measurements of the resonant tunnel current in III-V based double-barrier structures as a function of the direction of an in-plane magnetic field. The samples will be grown on a variety of substrate orientations, including (001). A comparison with theoretical results based on a recently developed method, which describes the interface effects in terms of a generalised effective-mass approximation, should provide detailed information about the symmetry and structure of the interfaces.

The work will be carried out by two Western and two Russian research groups within a strong, existing collaboration.

Aufforderung zur Vorschlagseinreichung

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Finanzierungsplan

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Koordinator

UNIVERSITY OF NOTTINGHAM
EU-Beitrag
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Adresse
University Park
NG7 2RD NOTTINGHAM
Vereinigtes Königreich

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Beteiligte (3)