We observe the suppression of the finite frequency shot noise produced by a voltage biased tunnel junction due to its interaction with a single electromagnetic mode of high impedance. The tunnel junction is embedded in a λ/4 resonator containing a dense SQUID array providing it with a characteristic impedance in the kΩ range and a resonant frequency tunable in the 4-6 GHz range. Such high imped...

We study numerically the influence of strong Coulomb repulsion on the current through molecular wires that are driven by external electromagnetic fields. The molecule is described by a tight-binding model whose first and last site is coupled to a respective lead. The leads are eliminated within a perturbation theory yielding a master equation for the wire. The decomposition into a Floquet basis...

We analyze the dynamical Coulomb blockade of multiple Andreev reflections (MAR) in a superconducting quantum point contact coupled to a macroscopic impedance. We find that at very low transmission the blockade scales as n2 with n = Int(2delta/eV), where V is the bias voltage and delta is the superconducting gap, as it would correspond to the occurrence of shots of charge ne. For higher transmis...

– We present measurements on spin blockade in a laterally integrated quantum dot. The dot is tuned into the regime of strong Coulomb blockade, confining ∼ 50 electrons. At certain electronic states we find an additional mechanism suppressing electron transport. This we identify as spin blockade at zero bias, possibly accompanied by a change in orbital momentum in subsequent dot ground states. W...

Tunneling of single electrons has been thoroughly studied both theoretically and experimentally during last ten years. By the present time the basic physics is well understood, and creation of useful single-electron devices becomes the important issue. Single-electron tunneling seems to be the most promising candidate to be used in the future integrated digital circuits with the typical size sc...

Distributions of Coulomb blockade peak spacings are reported for large ensembles of both unbroken (magnetic field B ­ 0) and broken (B fi 0) time-reversal symmetry in GaAs quantum dots. Both distributions are symmetric and roughly Gaussian with a width of ,2% 6% of the average spacing, with broad, non-Gaussian tails. The distribution is systematically wider at B ­ 0 by a factor of ,1.2 6 0.1. N...

We estimate the fluctuation width of an energy level as a function of the number of electrons added to a Coulomb-blockade quantum dot. A microscopic calculation in the limit of Koopmans’ theorem predicts that the standard deviation of these fluctuations is linear in the number of added electrons, in agreement with a parametric random-matrix approach. We estimate the number of electrons it takes...

We study the equilibrium properties of a quantum dot connected to a bulk lead by a single-mode quantum point contact. The ground state energy and other thermodynamic characteristics of the grain show periodic dependence on the gate voltage (Coulomb blockade). We consider the case of almost perfect transmission, and show that the oscillations exist as long as the transmission coefficient of the ...

Niobium thin film wires were fabricated using electron beam lithography with a four layer liftoff mask system, and subsequently thinned by anodisation. The resistance along the wire was monitored in situ and trimmed by controlling the anodisation voltage. Depending on the room temperature sheet resistance, samples showed either superconducting or insulating behaviour at low temperatures. A Coul...