Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 89: Transport: Quantum Dots, Quantum Wires, Point Contacts 1 (jointly with HL)

TT 89.4: Talk

Thursday, March 19, 2015, 11:45–12:00, A 053

Shot noise of a triple quantum dot transistor: Blurred polygons and enhancement at blockade — •Andreas Trottmann, Michael Niklas, Andrea Donarini, and Milena Grifoni — Institute for Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany

A single-electron transistor model with triangular triple quantum dot as central element is studied by means of a Bloch-Redfield-type method with counting fields. Such a device is known to exhibit Coulomb as well as interference blockade due to the presence of orbital degeneracies [1]. Computed Fano factors follow a blurred polygonal pattern as function of the voltages, tend to behave oppositely as against average current, and are enhanced in certain blockade regions in particular. Expressions in an interference blockade region elucidate a counteraction between real and virtual transitions, a blocking condition, and a loss of purity. These effects can be captured describing the orbitally degenerate states based on a pseudospin within a Bloch sphere. Gate and bias thresholds in the Fano factor pattern reflect disparate connectivities, especially a lifting of an interference blockade due to the reachability of a second orbitally degenerate level in the latter case. Blurring is caused by the voltages dependence of axes and frequencies controlling the precession of the pseudospin.

[1] A. Donarini, G. Begemann, and M. Grifoni,

Phys. Rev. B 82, 125451 (2010).