Spin and Valley States in Gate-defined Bilayer Graphene Quantum Dots

TL;DR

This paper reports on the creation and measurement of gate-defined bilayer graphene quantum dots, revealing detailed spin and valley state properties, including splittings and energy scales, through electronic transport experiments.

Contribution

It demonstrates electrostatic confinement in bilayer graphene quantum dots and characterizes their spin and valley states with high precision, providing new insights into their quantum behavior.

Findings

Charge carriers up to n=50 can be successively filled.

Valley and Zeeman splittings are observed in the lowest quantum states.

Valley splitting varies linearly with magnetic field at low fields.

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.