Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 6: Transport: Nanoelectronics I - Quantum Dots, Wires, Point Contacts 1
TT 6.9: Vortrag
Montag, 26. März 2012, 11:45–12:00, BH 334
Bunching and anti-bunching in electronic transport — •Christina Pöltl, Clive Emary, Alexander Carmele, Julia Kabuss, Andreas Knorr, and Tobias Brandes — Institut für Theoretische Physik, Hardenbergstr. 36, TU Berlin, D-10623 Berlin, Germany
Current noise has long-since been established as an important tool for studying the physics of transport through mesoscopic and nano-scale conductors. The character of the current noise is typically assessed by considering the Fano factor, the ratio of the zero-frequency noise to the steady state current, and comparing with a Poisson process for which the Fano factor is equal to one. Systems with F<1 are described as sub-Poissonian and systems which have F>1 are called super-Poissonian. The standard physical interpretation of this comparison is that super-Poissonian Fano factors indicate a bunching of electrons which tunnel out of the conductor, whereas sub-Poissonian values indicates anti-bunching.
We directly investigate bunching and anti-bunching in electronic transport as a phenomenon in the time domain through the introduction of a second-order correlation function g(2)(τ), analogous to that found in quantum optics. Our analysis shows that the simple picture relating super-Poissonian Fano factors to bunching and sub-Poissonian ones to anti-bunching is an oversimplification. Timescales can be found for which the electrons bunch, even though the Fano factor is sub-Poissonian and conversely.