Abstract
In bilayer graphene, electrostatic confinement can be realized by a suitable design of top and back gate electrodes. We measure electronic transport through a bilayer graphene quantum dot, which is laterally confined by gapped regions and connected to the leads via p-n junctions. Single electron and hole occupancy is realized and charge carriers $n = 1, 2,\dots 50$ can be filled successively into the quantum system with charging energies exceeding $10 \ \mathrm{meV}$. For the lowest quantum states, we can clearly observe valley and Zeeman splittings with a spin g-factor of $g_{s}\approx 2$. In the low field-limit, the valley splitting depends linearly on the perpendicular magnetic field and is in qualitative agreement with calculations.
Highlights
Graphene has been recognized early on as a prime candidate to host spin qubits [1]
We measure electronic transport through a bilayer graphene quantum dot, which is laterally confined by gapped regions and connected to the leads via p-n junctions
We demonstrate charging of a bilayer graphene quantum dots (QDs) with a single and a few holes when coupling the QD to n-type source and drain leads through p-n tunnel barriers
Summary
Graphene has been recognized early on as a prime candidate to host spin qubits [1]. With carbon being one of the lightest elements in the periodic table, spin-orbit interactions are expected to be weak. The two main spin decoherence mechanisms for spin qubits, namely, spin-orbit interactions and hyperfine coupling of nuclear and electronic spins, should be strongly suppressed in any carbon-based solid state system. These theoretical considerations have not come to fruition in experiments. While many of the basic quantum transport properties such as Coulomb blockade [2,3], charge detection [7], and electronic phase coherence [8,9] have been experimentally demonstrated, the understanding of the orbital and spin character of specific states has remained elusive. Our demonstration of excellent control and reproducibility opens up a wide field of possibilities for carbon-based quantum electronics
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