Andrea Donarini

Publications (33) View all

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  Available from: Andrea Donarini

  Article: A benzene interference single-electron transistor

  D. Darau, G. Begemann, A. Donarini, M. Grifoni
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  ABSTRACT: Interference effects strongly affect the transport characteristics of a benzene single-electron transistor (SET) and for this reason we call it interference SET (I-SET). We focus on the effects of degeneracies between many-body states of the isolated benzene. We show that the particular current blocking and selective conductance suppression occurring in the benzene I-SET are due to interference effects between the orbitally degenerate states. Further we study the impact of reduced symmetry due to anchor groups or potential drop over the molecule. We identify in the quasi-degeneracy of the involved molecular states the necessary condition for the robustness of the results. Comment: 17pages, 9 figures, revised version
  10/2008;
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  Available from: Andrea Donarini

  Article: Simple models suffice for the single dot quantum shuttle

  A. Donarini, T. Novotný, A. -P. Jauho
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  ABSTRACT: A quantum shuttle is an archetypical nanoelectromechanical device, where the mechanical degree of freedom is quantized. Using a full-scale numerical solution of the generalized master equation describing the shuttle, we have recently shown [Novotn\'{y} {\it et al.}, Phys. Rev. Lett. {\bf 92}, 248302 (2004)] that for certain limits of the shuttle parameters one can distinguish three distinct charge transport mechanisms: (i) an incoherent tunneling regime, (ii) a shuttling regime, where the charge transport is synchronous with the mechanical motion, and (iii) a coexistence regime, where the device switches between the tunneling and shuttling regimes. While a study of the cross-over between these three regimes requires the full numerics, we show here that by identifying the appropriate time-scales it is possible to derive vastly simpler equations for each of the three regimes. The simplified equations allow a clear physical interpretation, are easily solved, and are in good agreement with the full numerics in their respective domains of validity.
  08/2005;
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  Available from: Andrea Donarini

  Article: Many-body localized molecular orbital approach to molecular transport

  Dmitry A. Ryndyk, Andrea Donarini, Milena Grifoni, Klaus Richter
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  ABSTRACT: An ab initio based theoretical approach to describe nonequilibrium many-body effects in molecular transport is developed. We introduce a basis of localized molecular orbitals and formulate the many-body model in this basis. In particular, the Hubbard-Anderson Hamiltonian is derived for single-molecule junctions with intermediate coupling to the leads. As an example we consider a benzenedithiol junction with gold electrodes. An effective few-level model is obtained, from which spectral and transport properties are computed and analyzed. Electron-electron interaction crucially affects transport and induces multiscale Coulomb blockade at low biases. At large bias, transport through asymmetrically coupled molecular edge states results in the occurrence of "anomalous" conductance features, i.e., of peaks with unexpectedly large/small height or even not located at the expected resonance energies.
  10/2012;
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  Available from: Andrea Donarini

  Article: Topographical fingerprints of many-body interference blocking in STM junctions on thin insulating films

  Andrea Donarini, Sandra Sobczyk, Benjamin Siegert, Milena Grifoni
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  ABSTRACT: Negative differential conductance (NDC) is a non-linear transport phenomenon ubiquitous in molecular nanojunctions. Its physical origin can be the most diverse. In rotationally symmetric molecules with orbitally degenerate many-body states, it can be ascribed to interference effects. We establish in this paper a criterion to identify the interference blocking scenario by correlating the spectral and the topographical information achievable in an STM single molecule measurement. Simulations of current voltage characteristics and current maps for a Cu-Phthalocyanine (CuPc) on a thin insulating film are presented as experimentally relevant examples.
  06/2012;
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  Available from: Andrea Donarini

  Article: Vibration induced memory effects and switching in ac-driven molecular nanojunctions

  Andrea Donarini, Abdullah Yar, Milena Grifoni
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  ABSTRACT: We investigate bistability and memory effects in a molecular junction weakly coupled to metallic leads with the latter being subject to an adiabatic periodic change of the bias voltage. The system is described by a simple Anderson-Holstein model and its dynamics is calculated via a master equation approach. The controlled electrical switching between the many-body states of the system is achieved due to polaron shift and Franck-Condon blockade in the presence of strong electron-vibron interaction. Particular emphasis is given to the role played by the excited vibronic states in the bistability and hysteretic switching dynamics as a function of the voltage sweeping rates. In general, both the occupation probabilities of the vibronic states and the associated vibron energy show hysteretic behaviour for driving frequencies in a range set by the minimum and maximum lifetimes of the system. The consequences on the transport properties for various driving frequencies and in the limit of DC-bias are also investigated.
  05/2012;