Transport in a three-terminal graphene quantum dot in the multi-level regime

Abstract

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.

12 pages, 6 figures

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• Random matrices and quantum chaos in weakly-disordered graphene nanoflakes
• Fast detection of single-charge tunneling to a graphene quantum dot in a multi-level regime
• Interplay of Aharonov-Bohm and Berry phases in gate-defined graphene quantum dots
• Electronic triple-dot transport through a bilayer graphene island with ultrasmall constrictions
• Density of states as a probe of electrostatic confinement in graphene
• Nonequilibrium Kondo effect in a graphene-coupled quantum dot in the presence of a magnetic field
• Finite bias spectroscopy of a three-terminal graphene quantum dot in the multi-level regime
• Phenomenological approach to transport through three-terminal disordered wires
• Lithium doped graphene as spintronic devices