Measurement of Counting Statistics of Electron Transport in a Tunnel Junction

We present measurements of the time-dependent fluctuations in electrical current in a voltage-biased tunnel junction. We were able to simultaneously extract the first three moments of the tunnel current counting statistics. Detailed comparison of the second and the third moment reveals that counting statistics is accurately described by the Poissonian distribution expected for spontaneous current fluctuations due to electron charge discreteness, realized in tunneling transport at negligible coupling to environment.Comment: bibliography expande

c-axis penetration depth in Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta} single crystals measured by ac-susceptibility and cavity perturbation technique

The $c$-axis penetration depth $\Delta\lambda_c$ in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (BSCCO) single crystals as a function of temperature has been determined using two techniques, namely, measurements of the ac-susceptibility at a frequency of 100 kHz and the surface impedance at 9.4 GHz. Both techniques yield an almost linear function $\Delta\lambda_c(T)\propto T$ in the temperature range T<0.5 T_c. Electrodynamic analysis of the impedance anisotropy has allowed us to estimate $\lambda_c(0)\approx 50 \mu$m in BSCCO crystals overdoped with oxygen ($T_c\approx 84$ K) and $\lambda_c(0)\approx 150 \mu$m at the optimal doping level ($T_c\approx 90$ K).Comment: 5 pages, 4 figure

Full counting statistics of a chaotic cavity with asymmetric leads

We study the statistics of charge transport in a chaotic cavity attached to external reservoirs by two openings of different size which transmit non-equal number of quantum channels. An exact formula for the cumulant generating function has been derived by means of the Keldysh-Green function technique within the circuit theory of mesoscopic transport. The derived formula determines the full counting statistics of charge transport, i.e., the probability distribution and all-order cumulants of current noise. It is found that, for asymmetric cavities, in contrast to other mesoscopic systems, the third-order cumulant changes the sign at high biases. This effect is attributed to the skewness of the distribution of transmission eigenvalues with respect to forward/backward scattering. For a symmetric cavity we find that the third cumulant approaches a voltage-independent constant proportional to the temperature and the number of quantum channels in the leads.Comment: new section on probability distribution and new references adde