We report on ground- and excited state transport through an electrostatically defined few-hole quantum dot in bilayer graphene in both parallel and perpendicular applied magnetic fields. A remarkably clear level scheme for the two-particle spectra is found by analyzing finite bias spectroscopy data within a two-particle model including spin and valley degrees of freedom. We identify the two-hole ground-state to be a spin-triplet and valley-singlet state. This spin alignment can be seen as Hund's rule for a valley-degenerate system, which is fundamentally different to quantum dots in carbon nano tubes and GaAs-based quantum dots. The spin-singlet excited states are found to be valley-triplet states by tilting the magnetic field with respect to the sample plane. We quantify the exchange energy to be 0.35meV and measure a valley and spin g-factor of 36 and 2, respectively.
@article{arxiv.1904.07185,
title = {Excited states in bilayer graphene quantum dots},
author = {A. Kurzmann and M. Eich and H. Overweg and M. Mangold and F. Herman and P. Rickhaus and R. Pisoni and Y. Lee and R. Garreis and C. Tong and K. Watanabe and T. Taniguchi and K. Ensslin and T. Ihn},
journal= {arXiv preprint arXiv:1904.07185},
year = {2019}
}