Statistics of electron tunneling in normal tunnel junctions: An analytical and numerical study including circuit effects

Statistics of electron tunneling in normal tunnel junctions is studied analytically and numerically taking into account circuit (environment) effects. Full counting statistics, as well as full statistics of voltage and phase have been found for arbitrary times of observation. The theoretical analysis was based on the classical master equation, whereas the numerical simulations employed standard Monte-Carlo methods.Peer reviewe

Thermal shot noise in top-gated single carbon nanotube field effect transistors

The high-frequency transconductance and current noise of top-gated single carbon nanotube transistors have been measured and used to investigate hot electron effects in one-dimensional transistors. Results are in good agreement with a theory of 1-dimensional nano-transistor. In particular the prediction of a large transconductance correction to the Johnson-Nyquist thermal noise formula is confirmed experimentally. Experiment shows that nanotube transistors can be used as fast charge detectors for quantum coherent electronics with a resolution of $13\mathrm{\mu e/\sqrt{Hz}}$ in the 0.2-$0.8 \mathrm{GHz}$ band.Comment: 3 pages, 4 figure

Energy relaxation in graphene and its measurement with supercurrent

We study inelastic energy relaxation in graphene for low energies to find out how electrons scatter with acoustic phonons and other electrons. By coupling the graphene to superconductors, we create a strong dependence of the measured signal, i.e.,\ critical Josephson current, on the electron population on different energy states. Since the relative population of high- and low-energy states is determined by the inelastic scattering processes, the critical current becomes an effective probe for their strength. We argue that the electron-electron interaction is the dominant relaxation method and, in our model of two-dimensional electron-electron scattering, we find a scattering time $\tau_{e-e}=5... 13$ ps at T=500 mK, 1-2 orders of magnitude smaller than predicted by theory.Comment: 10 pages, 13 figures submitted to Physical Review

Tuning of a hypersonic surface phononic band gap using a nanoscale two-dimensional lattice of pillars

We present experimental and theoretical evidence of a phononic band gap in a hypersonic range for thermally activated surface acoustic waves in two-dimensional (2D) phononic crystals. Surface Brillouin light scattering experiments were performed on the (001) surface of silicon, loaded with a 2D square lattice of 100- or 150-nm-high aluminum pillars with a spacing of 500nm. The surface Brillouin light scattering spectra revealed a different type of surface mode, related to the modulation of the lattice structure and the mechanical eigenmodes of the pillars. The experimental data were in excellent agreement with theoretical calculations performed using the finite-element method.Peer reviewe

Observation of shot-noise-induced asymmetry in the Coulomb blockaded Josephson junction

We have investigated the influence of shot noise on the IV-curves of a single mesoscopic Josephson junction. We observe a linear enhancement of zero-bias conductance of the Josephson junction with increasing shot noise power. Moreover, the IV-curves become increasingly asymmetric. Our analysis on the asymmetry shows that the Coulomb blockade of Cooper pairs is strongly influenced by the non-Gaussian character of the shot noise.Comment: 4 pages, 5 figures, RevTE

Heat switch and thermoelectric effects based on Cooper-pair splitting and elastic cotunneling

In this paper, we demonstrate that the hybrid normal-superconducting-normal (NSN) structure has potential for a multifunctional thermal device which could serve for heat flux control and cooling of microstructures. By adopting the scattering matrix approach, we theoretically investigate thermal and electrical effects emerging in such structures due to the Cooper pair splitting (CPS) and elastic cotunneling phenomena. We show that a finite superconductor can, in principle, mediate heat flow between normal leads, and we further clarify special cases when this seems contradictory to the second law of thermodynamics. Among other things, we demonstrate that the CPS phenomenon can appear even in the simple case of a ballistic NSN structure.Comment: 10 pages, 5 figure

Cooper Pair Splitting by Means of Graphene Quantum Dots

A split Cooper pair is a natural source for entangled electrons which is a basic ingredient for quantum information in the solid state. We report an experiment on a superconductor-graphene double quantum dot (QD) system, in which we observe Cooper pair splitting (CPS) up to a CPS efficiency of ∼10%. With bias on both QDs, we are able to detect a positive conductance correlation across the two distinctly decoupled QDs. Furthermore, with bias only on one QD, CPS and elastic cotunneling can be distinguished by tuning the energy levels of the QDs to be asymmetric or symmetric with respect to the Fermi level in the superconductor.Peer reviewe