SEMINAR on Disorder and strong electron correlations: "A few electron triple quantum dot and phonon mediated transport of electrons in nano circuits"

[CM ICTP - Trieste]

CONDENSED MATTER SECTION

	
SEMINAR on

Disorder and strong electron correlations




Thursday, 13 December   -    11:00 hrs.


Seminar Room,  Main Building - First floor





S. LUDWIG
(LMU, Munich)




"A few electron triple quantum dot and phonon mediated transport of 
electrons in nano circuits"


Abstract
Solid state based quantum dots (QD) are heavily discussed for 
applications as qubits, but also provide a beautiful playground for 
basic research on artificial molecules. First, concepts needed to 
understand transport and charge spectroscopy measurements on coupled 
QDs will be developed. Then experimental results on a few electron 
triple QD, a double QD quantum ratchet and interaction mechanisms 
involved are discussed.
Our few electron serial triple QD is electrostatically defined in a 
standard GaAs/AlGaAs heterostructure containing a two-dimensional 
electron system. Ground state stability diagrams detected with a single 
quantum point contact (QPC) demonstrate complete control of the triple 
QDs charge configuration in the few electron regime. The complex 
interplay between charge states of the three coupled QDs near points of 
high degeneracy will be discussed. In this regime we observe electron 
transport through the three QDs reflecting quantum cellular automata 
physics.
The remainder of the talk will be devoted to the interaction of a 
strongly driven QPC with another unbiased QPC or a double QD. These 
experiments can be seen in the context of back-action of a charge 
detector (the QPC) onto a qubit (the double QD). Using the strongly 
driven QPC as non-equilibrium energy source we realize a double QD 
quantum ratchet. A second experiment involving two QPCs illuminates the 
possible role of electron-phonon interaction in such devices.