Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 22: Transport - Nanoelectronics II: Quantum Dots and Wires, Point Contacts
TT 22.2: Vortrag
Montag, 7. März 2005, 14:15–14:30, TU H2053
Giant super-poissonian Fano factors in shuttle devices — •Andrea Donarini1,2, Tomaš Novotný2, Christian Flindt2, and Antti-Pekka Jauho2 — 1Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany — 2MIC - Department of Micro and Nanotechnology,Technical University of Denmark
Shuttle devices are a particular kind of NEMS characterized by a nanometer scale oscillating quantum dot that transfers electrons one-by-one from the source to the drain lead. We study the dynamics of an archetypal model device in the density matrix formalism and represent the numerical results by means of phase space distribution (Wigner function), current and current noise (Fano factor). The device presents tunnelling and shuttling as limiting operating regimes for respectively high and low mechanical damping conditions. In the transition region between the tunnelling and shuttling regime the system is characterized by a giant super-poissonian Fano factor (F ≈ 100).
This feature is the signature of a coexistence regime: i.e. a slow switching dichotomous process between the tunnelling and the shuttling current modes. For this regime we propose a simplified description in terms of a bistable effective potential. This description captures the main features of the coexistence regime (confirmed by the quantitative agreement with the numerical results) and gives also a more transparent physical insight of the device dynamics.