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JONCYIONS HYBRIDES SUPRACONDUCTRICES SEMICONDUCTRICES VERS LA MANIPULATION D'ETATS CORRELES

Abstract : We have studied superconductor/ ballistic normal metal hybrid junctions, with GaAs/AlGaAs heterojunction for the normal part, and indium for the superconductor part. This system allows, thanks to its long coherence length and the possibility to use a gate, to investigate the manipulation of correlated pair in the normal part : a new approach of quantum bits.
We have set up a process to make SN junctions with very good transparencies, within mesoscopic dimensions, using diffused indium. The essential problem was the inhomogeneity of indium diffusion. We have characterized the interface with different types of transport measurements at very low temperature. We have shown that, in one hand indium diffuses in a directional way, and on the other hand, it is neither a diffusive junction nor a dirty one, but a tunnel junction with a small number of channels taking part of the conduction. We have shown the presence of a disordered region near the interface which spread on a few hundreds of nanometers. The presence of diffused indium filaments has been corroborated by the observation of a supercurrent carried by the filaments in short SNS junctions. We have finaly achieved a first tentative of manipulation of Cooper pairs with the aim of a QPC : we have observed conductance plateaus versus the gate voltage, with a height divided by two when applying a weak magnetic field.
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Submitted on : Tuesday, January 30, 2007 - 6:45:46 PM
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Sanae Boulay. JONCYIONS HYBRIDES SUPRACONDUCTRICES SEMICONDUCTRICES VERS LA MANIPULATION D'ETATS CORRELES. Supraconductivité [cond-mat.supr-con]. Université Paris Sud - Paris XI, 2005. Français. ⟨tel-00128140⟩

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