Archive ouverte UNIGE | last documents for author 'Heidi Forster'https://archive-ouverte.unige.ch/Latest objects deposited in the Archive ouverte UNIGE for author 'Heidi Forster'engVoltage and dephasing probes in mesoscopic conductors : a study of full-counting statisticshttps://archive-ouverte.unige.ch/unige:4208https://archive-ouverte.unige.ch/unige:4208Voltage and dephasing probes introduce incoherent inelastic and incoherent quasielastic scattering into a coherent mesoscopic conductor. We discuss in detail the concepts of voltage and dephasing probes and develop a full-counting statistics approach to investigate their effect on the transport statistics. The formalism is applied to several experimentally relevant examples. A comparison of different probe models and with procedures like phase averaging over an appropriate phase distribution shows that there is a perfect equivalence between the models for the case of one single-channel probe. Interestingly, the appropriate phase-distribution function is found to be uniform. A uniform distribution is provided by a chaotic cavity with a long dwell time. The dwell time of a chaotic cavity plays a role similar to the charge response time of a voltage or dephasing probe. For multichannel or multiple probes the transport statistics of voltage and dephasing probes differs and the equivalence with phase averaging is similarly lost.Mon, 30 Nov 2009 16:07:14 +0100Current-voltage correlations in interferometershttps://archive-ouverte.unige.ch/unige:4202https://archive-ouverte.unige.ch/unige:4202We investigate correlations of current at contacts and voltage fluctuations at voltage probes coupled to interferometers. The results are compared with correlations of current and occupation number fluctuations at dephasing probes. We use a quantum Langevin approach for the average quantities and their fluctuations. For higher order correlations we develop a stochastic path integral approach and find the generating functions of voltage or occupation number fluctuations. We also derive a generating function for the joint distribution of voltage or occupation number at the probe and current fluctuations at a terminal of a conductor. For energy independent scattering we found earlier that the generating function of current cumulants in interferometers with a one-channel dephasing or voltage probe are identical. Nevertheless, the distribution function for voltage and the distribution function for occupation number fluctuations differ, the latter being broader than that of the former in all examples considered here.Mon, 30 Nov 2009 16:07:05 +0100Full-counting statistics for voltage and dephasing probeshttps://archive-ouverte.unige.ch/unige:4183https://archive-ouverte.unige.ch/unige:4183We present a stochastic path integral method to calculate the full-counting statistics of conductors with energy conserving dephasing probes and dissipative voltage probes. The approach is explained for the experimentally important case of a Mach-Zehnder interferometer, but is easily generalized to more complicated setups. For all geometries where dephasing may be modeled by a single one-channel dephasing probe we prove that our method yields the same full-counting statistics as phase averaging of the cumulant generating function.Mon, 30 Nov 2009 16:06:41 +0100Decoherence and full counting statistics in a Mach-Zehnder interferometerhttps://archive-ouverte.unige.ch/unige:4177https://archive-ouverte.unige.ch/unige:4177We investigate the Full Counting Statistics of an electrical Mach-Zehnder interferometer penetrated by an Aharonov-Bohm flux, and in the presence of a classical fluctuating potential. Of interest is the suppression of the Aharonov-Bohm oscillations in the distribution function of the transmitted charge. For a Gaussian fluctuating field we calculate the first three cumulants. The fluctuating potential causes a modulation of the conductance leading in the third cumulant to a term cubic in voltage and to a contribution correlating modulation of current and noise. In the high voltage regime we present an approximation of the generating function.Mon, 30 Nov 2009 16:06:31 +0100Full counting statistics in interferometers : PROBE models and fluctuation relationshttps://archive-ouverte.unige.ch/unige:627https://archive-ouverte.unige.ch/unige:627This work deals with current fluctuations in mesoscopic conductors. The current fluctuations are investigated in the framework of the full counting statistics, and as an example of experimental relevance we chose the electronic Mach-Zehnder interferometer. A powerful method of introducing decoherence into a coherent conductor is the model of voltage and dephasing probes. We develope a formalism for the full counting statistics of the electronic transport through conductors coupled to voltage and dephasing probes. We compare these models to alternative procedures like phase averaging and find that there is perfect agreement between the models for the case of one probe with a single transport channel. The probe gives additional information on internal properties of the conductor via the fluctuations at the probe. We present the joint counting statistics of current at contacts and voltage at voltage probes coupled to the conductor, as well as the joint counting statistics of current at contacts and occupation number at dephasing probes. In linear transport, the Onsager relations and the fluctuation-dissipation theorem are valid. Beyond the linear regime, there exist fluctuation relations for the full counting statistics which rely on microscopic reversibility away from equilibrium. However, both theory and experiments have shown deviations from micro-reversiblity in the form of magnetic field asymmetric current-voltage relations. We present novel fluctuation relations for non linear transport in the presence of magnetic fields that relate current correlation functions at any order at equilibrium to response coefficients of current cumulants at lower order.Wed, 03 Dec 2008 18:35:05 +0100