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Quantum coherence in the integer quantum Hall regime

Abstract : This work is devoted to the study of decoherence process in the integer quantum Hall regime. In this regime, the current is carried by one dimensional chiral edge channel. These electronic beams are then controlled with mesoscopic beam splitters, the quantum point contacts (QPC). A precise tuning of these QPC enables us to obtain interferences of the conductance. The study of the visibility of these oscillations probes the coherence of the system. In a first part, we have studied the visibility as a function of the bias when the inner edge state is reflected and have observed a lobe structure. We have shown that for a single side lobe, a Gaussian phase averaging can explain this lobe structure. When the inner edge state is transmitted, the visibility decreases monotonously as a function of the bias: we have shown that it resulted from coupling between the inner and outer edge state. In a second part, we have studied the temperature dependence of the visibility in MZIs of different sizes, have extracted for the first time a measurement of the coherence length in the quantum Hall regime and have shown its proportionality to 1/T. We were interested then in the origin of this finite coherence length. We have shown that thermal fluctuations of the inner edge state combined with the coupling between the inner and outer edge state were the source of decoherence. In a last experiment, we have achieved the first experimental realization of the theoretically widely used voltage probe.
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Contributor : Preden Roulleau <>
Submitted on : Sunday, January 3, 2010 - 7:43:00 PM
Last modification on : Thursday, December 10, 2020 - 10:52:45 AM
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  • HAL Id : tel-00348151, version 2

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Preden Roulleau. Quantum coherence in the integer quantum Hall regime. Condensed Matter [cond-mat]. Université Pierre et Marie Curie - Paris VI, 2008. English. ⟨tel-00348151v2⟩

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