laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Séminaire - 19 Janvier 2009

Julien GABELLI, Laboratoire de Physique des Solides<br class='autobr' />UMR8502 bâtiment 510, Université Paris-Sud 91405 ORSAY Cedex France
Dynamics and Third Cumulant of Quantum Noise

The existence of the third cumulant S3 of voltage fluctuations has demonstrated the non-Gaussian aspect of shot noise in electronic transport. Until now, measurements have been performed at low frequency, i.e. in the classical regime 1ω eV, kBT . In this regime, experiment cannot be seen as a charge counting statistics problem anymore. It raises central questions of the statistics of quantum noise, in particular :

1. The electromagnetic environment of the sample has been proven to strongly influence the measure¬ment, through the possible modulation of the noise of the sample. What happens to this mechanism in the quantum regime ?

2. For eV < 1ω, the noise is due to zero point fluctuations and keeps its equilibrium value : S2 = G1ω with G the conductance of the sample. Therefore, S2 is independent of the bias voltage and no photon is emitted by the conductor. It is possible, as suggested by some theories [1, 2], that S3 =0 in this regime ?

With regard to these questions, we give theoretical and experimental answers to the environmental effects showing they involve dynamics of the quantum noise. Using these results, we investigate the question of the third cumulant of quantum noise in the a tunnel junction.

[1] A. Galaktionov, D. Golubev, and A. Zaikin, Statistics of current fluctuations in mesoscopic coherent conductors at nonzero frequencies, Phys. Rev. B 68 pp. 235333 (2003)

[2] J. Salo, F. W. J. Hekking, and J. P. Pekola , Frequency-dependent current correlation functions from scattering theory, Phys. Rev. B 74 pp. 125427 (2006)