Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 3: Transport: Fluctuations and Noise
TT 3.5: Hauptvortrag
Montag, 25. Februar 2008, 10:30–11:00, H 2053
Noise and current cross-correlations in nano-electromechanical systems — •Christoph Bruder — Department of Physics, University of Basel, Klingelbergstr. 82, CH-4056 Basel, Switzerland
After some general remarks about current cross-correlations in electronic (fermionic) three-terminal devices, I would like to focus on position measurements using the cross-correlated output of two tunnel junction position detectors. The bound on the peak-to-background ratio in a position measurement using a single detector can be overcome using detector cross-correlations. Furthermore, the double-detector setup can be exploited to drastically reduce the added displacement noise of the oscillator [C.B. Doiron, B. Trauzettel, C. Bruder, Phys. Rev. B 76, 195312 (2007)].
I would also like to show that the momentum p of a nanomechanical oscillator can be measured [C.B. Doiron, B. Trauzettel, C. Bruder, arXiv: 0707.2709; accepted in PRL] by two tunnel junctions in an Aharonov-Bohm-type setup. The tunneling amplitude of one of the junctions depends linearly on the position x of the oscillator t(x) = t0 + t1 x. The presence of two junctions can, under certain conditions, lead to an effective imaginary coupling t(x) = t0 + i t1 x. By calculating the equation-of-motion for the density matrix of the coupled (oscillator+tunnel junction) system, we show that in this case the finite-frequency current noise of the detector is proportional to the momentum spectrum of the oscillator.
Work done in collaboration with W. Belzig, C.B. Doiron, and B. Trauzettel.