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Content archived on 2022-12-23

High magnetic fields and low-temperature peculiarities of the properties of highly disordered two-dimensional systems

Objective



The low-temperature properties of semiconductors are determined by quantum coherent effects. However, recent studies of transport properties in the extreme quantum limit (EQL) and in highly disordered systems revealed new additional peculiarities which are not yet explained. The main aim of this project is to study the influence of common action of high magnetic field, especially extreme quantum limit, and strong disorder on quantum transport effects in 2D systems.

The following peculiarities will be studied: quantum corrections to 2D conductivity in EQL but out of quantum Hall regime; quantum corrections to ultrasonic absorption; peculiarities of the QHE due to its competition with metal insulator transition (MIT); and finally the electron phase diagram in magnetic field. The quantum oscillations of intensity and velocity of surface acoustic waves are expected and will be studied in the regime of quantum Hall effect. In the insulating state the structure of upper Hubbard band will be studied under magnetic field action to reveal the nature of both giant and double-dip negative magnetoresistance.

Measurements will be performed in various 2D and quasi-2D semiconducting structures such as strained and unstrained heterostructures, superlattices and delta-doped epitaxial layers based on GaAs/GaInAs, GaAs/GaInP, GaAs but mainly on the Ge-Si system. The Ge-Si system enables a wide range of tunable effective masses to be accessed making it a unique system for the study of 2D properties. Recent dramatic developments in Ge-Si technology have made this possible. This material system is very promising for the above investigations and has potential advantages in the study of Wigner crystallisation.

All measurements will be combined with studies of random potential characteristics by various methods such as X-ray diffraction and reflectivity, transmission electron microscopy (TEM), cross-section transmission electron microscopy (XTEM), photoluminescence and field effect. It may provide the means to obtain new information on the role of disorder.

Call for proposal

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Funding Scheme

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Coordinator

Centre National de la Recherche Scientifique
EU contribution
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Address
Avenue de Rangueil
31077 Toulouse
France

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Participants (5)