ERA NANOSCI: Characterization of electronic nanodevices by noise measurements
Zusammenfassung der Projektergebnisse
The characterization of nano‐devices via measurements of the statistics of current fluctuations requires both, an efficient noise detector and a well developed theory of non‐Gaussian current noise necessary for the data analysis. The theory should provide a detailed understanding of the basic mechanisms underlying the noise detection scheme. Furthermore, it is essential to gain a solid understanding of nanoscopic prototype systems for which the noise can be predicted precisely. These devices provide a test bench for the detector and the theory of higher order noise cumulants (full counting statistics). Within this project we have contributed to both aspects. A central result is a comprehensive theoretical approach to model and calculate the dynamics of the so‐called Josephson junction noise detector, an efficient on‐chip detector implemented by our experimental partner group in Saclay. The theory is based on a description of irreversible processes and fluctuations in terms of state variables and conjugate forces and yields exact results for the rate of escape of the detector Josephson junction from the zero voltage state in the weak noise limit for all values of the damping strength. Also the feedback of the detector on the noise generating conductor is fully taken into account by treating the coupled nano‐devices on an equal footing. Moreover, we have investigated in detail the charge transfer statistics for a particular prototype system, a single molecule contacted by two metallic leads. This system, which can be described within the Anderson‐Holstein model, displays effects of the electron‐phonon interaction in the noise statistics. In collaboration with the Madrid partner group, we have been able to determine the feedback of the nonequilibrium phonon distribution on the transport and noise properties of the molecular junction. The phenomenon of current bistability in the Anderson‐Holstein model has been examined by a formally exact diagrammatic quantum Monte Carlo algorithm developed in our group. Despite the considerable progress attained, the experimental study of higher order noise cumulants of nanoscopic devices remains challenging and alternative noise detection schemes need to be explored in the future.
Projektbezogene Publikationen (Auswahl)
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Theory of a Josephson junction detector of non‐Gaussian noise. Physical Review B 77, 205315 (2008)
H. Grabert
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Feedback and rate asymmetry of the Josephson junction noise detector. Physical Review B 79, 113102 (2009)
D.F. Urban and H. Grabert
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Nonlinear effects of phonon fluctuations on transport through nanoscale junctions. Physical Review B 82, 121414 (2010)
D.F.Urban, R. Avriller and A. Levy‐Yeyati
