Current cross-correlations in mesoscopic devices

Christoph Bruder

Department of Physics and Astronomy and Center for Quantum Computing and Quantum Coherence (QC2),
University of Basel, Switzerland

In this talk, I would like to present two examples of electronic (fermionic) systems that exhibit positive current cross correlations.

The first example is a three-terminal device with one superconducting terminal and two normal-metal terminals. We calculate the full distribution of transmitted charges into the two symmetrically biased normal terminals. In a wide parameter range, we find large positive crosscorrelations between the currents in the two normal arms. We also determine the third cumulant that provides additional information on the statistics not contained in the current noise.

As a second example, we study current fluctuations in an interacting three-terminal quantum dot with ferromagnetic leads. For appropriately polarized contacts, the transport through the dot is governed by a novel dynamical spin blockade, i.e., a spin-dependent bunching of tunneling events not present in the paramagnetic case. This leads for instance to positive zero-frequency cross-correlations of the currents in the output leads even in the absence of spin accumulation on the dot. We include the influence of spin-flip scattering and identify favorable conditions for the experimental observation of this effect with respect to polarization of the contacts and tunneling rates.

Work done in collaboration with W. Belzig, J. Boerlin, and A. Cottet