Quantum Shot Noise in Graphene

Abstract : We have conducted an experimental study of the quantum shot noise in a mono-layer graphene device. Conductance of the device and the quantum Hall effect were also investigated. A theoretical model, describing conductance and quantum shot noise in ideal (ballistic) graphene was proposed by Tworzydlo et al., 2006. In diffusive graphene, that is much easier achievable experimentally, shot noise was investigated numerically by several authors (San-Jose et al., 2007, Lewenkopf et al., 2008, Logoteta et al., 2013). Conclusions of the first experimental works (DiCarlo et al., 2008 and Danneau et al., 2008), addressing this problem, didn’t lead to an enough broad understanding of it and a further investigation was required. In our experiment we intended to maximally reduce the contributions of the measurement system to the detected signal by performing four-point voltage noise measurement as well as by using cross-correlation detection. In addition to that, our measurement system include home-made cryogenic low-noise amplifiers combined with band-pass filters, while our experimental device carries a constriction in the center of graphene layer and side-gates are used instead of back-gate. First, using the results of the conductance and of the quantum Hall effect measurements we determined the mean free path in our sample and concluded that it was in diffusive regime. The extracted values of the Fano factor show a good agreement with the above-mentioned simulations for this regime, in particular, the peak at Dirac point, predicted by Lewenkopf et al., was observed. Moreover our results are consistent with those of Danneau et al. and DiCarlo et al.
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Andrey Mostovov. Quantum Shot Noise in Graphene. Other [cond-mat.other]. Université Pierre et Marie Curie - Paris VI, 2014. English. ⟨NNT : 2014PA066061⟩. ⟨tel-01023003⟩

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