Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 8: Postersession Transport: Graphene and Carbon Nanotubes
TT 8.8: Poster
Montag, 23. März 2009, 13:00–16:45, P1B
Towards entanglement in carbon nanotube based double quantum dots — •Lorenz Herrmann1,2, Fabien Portier3, Patrice Roche3, Christian Glattli2,3, Takis Kontos2, and Christoph Strunk1 — 1Inst. for Exp. and Appl. Physics, Univ. Regensburg, Germany — 2Lab. Pierre Aigrain, ENS Paris, France — 3SPEC, CEA Saclay, France
We investigate carbon nanotube-based double quantum dots with two normal (Ti/Au) and one central superconducting (Al) contact. The characterization of the devices via the normal contacts reveals that the superconducting electrode splits the carbon nanotube into two coupled quantum dots. As an additional feature compared to ordinary double dot systems, we can use our middle electrode (Al) not only to split the nanotube into two dots, but also to inject Cooper pairs into our double dot system. By sending a current from the superconducting to the normal contacts it is possible to divide the current into the two output branches. Since Coulomb charging energy prevents double occupation of one dot, the splitting of a pair into the two different normal contacts is favoured if the gate configuration is such that Coulomb interaction between the dots is strong. That is the case at the so called triple points of the initial stability diagram of the double dot. The splitting of the Cooper pairs thus occurs via a co-tunneling process. We find an enhanced subgap conductance at the triple points, which possibly reflects correlated Andreev processes.