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arXiv · 2103.04864

Kondo effect and spin-orbit coupling in graphene quantum dots

Annika Kurzmann·Yaakov Kleeorin·Chuyao Tong·Rebekka Garreis·Angelika Knothe·Marius Eich·Christopher Mittag·Carolin Gold·Folkert K. de Vries·Kenji Watanabe·Takashi Taniguchi·Vladimir Fal'ko·Yigal Meir·Thomas Ihn·Klaus Ensslin
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Abstract

The Kondo effect is a cornerstone in the study of strongly correlated fermions. The coherent exchange coupling of conduction electrons to local magnetic moments gives rise to a Kondo cloud that screens the impurity spin. Whereas complete Kondo screening has been explored widely, realizations of the underscreened scenario - where only some of several Kondo channels participate in the screening - remain rare. Here we report the observation of fully screened and underscreened Kondo effects in quantum dots in bilayer graphene. More generally, we introduce a unique platform for studying Kondo physics. In contrast to carbon nanotubes, whose curved surfaces give rise to strong spin-orbit coupling breaking the SU(4) symmetry of the electronic states relevant for the Kondo effect, we study a nominally flat carbon material with small spin-orbit coupling. Moreover, the unusual two-electron triplet ground state in bilayer graphene dots provides a route to exploring the underscreened spin-1 Kondo effect.

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Annika Kurzmann, Yaakov Kleeorin, Chuyao Tong, Rebekka Garreis, Angelika Knothe, Marius Eich, Christopher Mittag, Carolin Gold, Folkert K. de Vries, Kenji Watanabe, Takashi Taniguchi, Vladimir Fal'ko, Yigal Meir, Thomas Ihn, Klaus Ensslin. 2021-03-08. Kondo effect and spin-orbit coupling in graphene quantum dots. https://doi.org/10.1038/s41467-021-26149-3

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