Probing two-electron multiplets in bilayer graphene quantum dots

Abstract

We report on finite bias spectroscopy measurements of the two-electron spectrum in a gate defined bilayer graphene (BLG) quantum dot for varying magnetic fields. The spin and valley degree of freedom in BLG give rise to multiplets of 6 orbital symmetric and 10 orbital anti-symmetric states. We find that orbital symmetric states are lower in energy and separated by ≈ 0.4 − 0.8 meV from orbital anti-symmetric states. The symmetric multiplet exhibits an additional energy splitting of its 6 states of ≈ 0.15 − 0.5 meV due to lattice scale interactions. The experimental observations are supported by theoretical calculations, which allow to determine that inter-valley scattering and 'current-current' interaction constants are of the same magnitude in BLG.

Wannier Diagram and Brown-Zak Fermions of Graphene on Hexagonal Boron-Nitride

“…We emphasize that such complexity emerges from a realistic simulation of graphene on hBN within a single-particle description on the DFT level without invoking any many-body effects. The energy scale for the latter, Δ MB , can be estimated from the flat bands in "magic angle twisted bilayer graphene" [46,47] and from measurements on bilayer graphene quantum dots [48] to be Δ MB ≲ 1 meV and, thus, smaller than the energy scales shaping the structures in the Wannier diagram (Fig. 4) in the present case.…”

Single-shot readout in graphene quantum dots

“…Compared to the mature Si-based technology, the development of quantum devices in graphene is in its infancy. Recent advances in the controllability of individual states in single QDs [17][18][19][20] and double QDs [21,22], as well as the implementation of charge detection [23], enable the realization of spin qubits based on electrostatically defined QDs in bilayer graphene. Major milestones such as qubit manipulation and detection have yet to be achieved to unlock the qubit potential of graphene.…”