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Etude expérimentale de la transition métal-isolant en dimension deux

Abstract : One can make a two dimensional electron system with a tunable electronic density in semiconductor heterostructures at low temperature. At low density, the theory predicts that electron correlations should overcome the quantum fluctuations, leading to a correlated electronic state such as the Wigner crystal. In real systems, disorder can lead to a much intricate problem : the recent observation of a metal-insulator transition has raised the question of interactions and disorder in two dimensions. This study concerns transport and resistance fluctuations measurements, at very low temperature in two-dimensional hole gases formed in GaAs and SiGe quantum wells. The high effective mass and low density in these systems lead to strong interactions that cannot be neglected any more. In the most disordered samples (SiGe), where transport can be explained in the independent particles' approximation, electric field effects are due to carriers heating. On the contrary, in less disordered samples (GaAs), transport laws as a function of the temperature and the electric field at low density can be related to transport in the case of a collective state. In GaAs samples, resistance fluctuations measurements, or 1/f noise, demonstrate the existence of a phase transition at low density. These results are compatible with scenarios predicting that the Wigner transition with disorder could be a percolation transition.
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https://tel.archives-ouvertes.fr/tel-00002374
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Submitted on : Monday, February 10, 2003 - 5:42:50 PM
Last modification on : Monday, February 10, 2020 - 6:12:21 PM
Long-term archiving on: : Tuesday, September 11, 2012 - 7:45:10 PM

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  • HAL Id : tel-00002374, version 1

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Renaud Leturcq. Etude expérimentale de la transition métal-isolant en dimension deux. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 2002. Français. ⟨tel-00002374⟩

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