Biomedical subjects

Felix von Oppen

Publications and source records attributed to Felix von Oppen.

8 recordsLinked to original sources

PubMed2006

Fractional shot noise in the kondo regime.

Transport through quantum dots in the Kondo regime obeys an effective low-temperature theory in terms of weakly interacting quasiparticles. Despite the weakness of the interaction, we find that the backscattering current and hence the shot noise are dominated by two-quasiparticle scattering. We show that the simultaneous presence of one- and two-quasiparticle scattering results in a universal average charge 5/3e as measured by shot-noise experiments. An experimental verification of our prediction would constitute a most stringent test of the low-energy theory of the Kondo effect.

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PubMed2006

Pair Tunneling through Single Molecules.

By a polaronic energy shift, the effective charging energy of molecules can become negative, favoring ground states with even numbers of electrons. Here we show that charge transport through such molecules near ground-state degeneracies is dominated by tunneling of electron pairs which coexists with (featureless) single-electron cotunneling. Because of the restricted phase space for pair tunneling, the current-voltage characteristics exhibit striking differences from the conventional Coulomb blockade. In asymmetric junctions, pair tunneling can be used for gate-controlled current rectification and switching.

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PubMed2005

Dynamic correlation functions and Boltzmann-Langevin approach for driven one-dimensional lattice gas.

We study the dynamics of the totally asymmetric exclusion process with open boundaries by phenomenological theories complemented by extensive Monte Carlo simulations. Upon combining domain wall theory with a kinetic approach known as Boltzmann-Langevin theory we are able to give a complete qualitative picture of the dynamics in the low- and high-density regimes and at the corresponding phase boundary. At the coexistence line between high- and low-density phases we observe a time scale separation between local density fluctuations and collective domain wall motion, which are well accounted for by the Boltzmann-Langevin and domain wall theory, respectively. We present Monte Carlo data for the correlation functions and power spectra in the full parameter range of the model.

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PubMed2005

Full counting statistics of strongly non-ohmic transport through single molecules.

We study analytically the full counting statistics of charge transport through single molecules, strongly coupled to a weakly damped vibrational mode. The specifics of transport in this regime--a hierarchical sequence of avalanches of transferred charges, interrupted by "quiet" periods--make the counting statistics strongly non-Gaussian. We support our findings for the counting statistics as well as for the frequency-dependent noise power by numerical simulations, finding excellent agreement.

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PubMed2005

Franck-Condon blockade and giant Fano factors in transport through single molecules.

We show that Franck-Condon physics leads to a significant current suppression at low bias voltages (termed Franck-Condon blockade) in transport through single molecules with strong coupling between electronic and vibrational degrees of freedom. Transport in this regime is characterized by remarkably large Fano factors (10(2)-10(3) for realistic parameters), which arise due to avalanchelike transport of electrons. Avalanches occur in a self-similar manner over a wide range of time scales, leading to power-law dependences of the current noise on frequency and vibrational relaxation rate.

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PubMed2005

Theory of charge sensing in quantum-dot structures.

Charge sensing in quantum-dot structures is studied by an exactly solvable reduced model and numerical density-matrix renormalization-group methods. Charge sensing is characterized by repeated cycling of the occupation of current-carrying states due to the capacitive coupling to trap states. In agreement with recent experiments, it results in characteristic asymmetric Coulomb-blockade peaks as well as sawtooth and domelike structures. Temperature introduces asymmetric smearing of these features and correlations in the conductance provide a fingerprint of charge sensing.

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PubMed2005

Disorder-induced resistive anomaly near ferromagnetic phase transitions.

We show that the resistivity rho(T) of disordered ferromagnets near, and above, the Curie temperature T(c) generically exhibits a stronger anomaly than the scaling-based Fisher-Langer prediction. Treating transport beyond the Boltzmann description, we find that within mean-field theory, drho/dT exhibits a |T - T(c)|(-1/2) singularity near T(c). Our results, being solely due to impurities, are relevant to ferromagnets with low T(c), such as SrRuO(3) or diluted magnetic semiconductors, whose mobility near T(c) is limited by disorder.

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PubMed2003

Universal spectral statistics of Andreev billiards: semiclassical approach.

The symmetry classification of complex quantum systems has recently been extended beyond the Wigner-Dyson classes. Several of the novel symmetry classes can be discussed naturally in the context of superconducting-normal hybrid systems such as Andreev billiards and graphs. In this paper, we give a semiclassical interpretation of their universal spectral form factors in the ergodic limit.

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