A. Jacobsen, P. Simonet, K. Ensslin, T. Ihn
We investigate transport in a three-terminal graphene quantum dot. All nine
elements of the conductance matrix have been independently measured. In the
Coulomb blockade regime accurate measurements of individual conductance
resonances reveal slightly different resonance energies depending on which pair
of leads is used for probing. Rapid changes in the tunneling coupling between
the leads and the dot due to localized states in the constrictions has been
excluded by tuning the difference in resonance energies using in-plane gates
which couple preferentially to individual constrictions. The interpretation of
the different resonance energies is then based on the presence of a number of
levels in the dot with an energy spacing of the order of the measurement
temperature. In this multi-level transport regime the three-terminal device
offers the opportunity to sense if the individual levels couple with different
strengths to the different leads. This in turn gives qualitative insight into
the spatial profile of the corresponding quantum dot wave functions.
View original:
http://arxiv.org/abs/1202.5166
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