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arXiv · 2008.02585

Electron-hole crossover in gate-controlled bilayer graphene quantum dots

Luca Banszerus·Alexander Rothstein·Thomas Fabian·Samuel Möller·Eike Icking·Stefan Trellenkamp·Florian Lentz·Daniel Neumaier·Kenji Watanabe·Takashi Taniguchi·Florian Libisch·Christian Volk·Christoph Stampfer
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Abstract

Electron and hole Bloch states in gapped bilayer graphene exhibit topological orbital magnetic moments with opposite signs near the band edges, which allows for tunable valley-polarization in an out-of-plane magnetic field. This intrinsic property makes electron and hole quantum dots (QDs) in bilayer graphene interesting for valley and spin-valley qubits. Here we show measurements of the electron-hole crossover in a bilayer graphene QD, demonstrating the opposite sign of the orbital magnetic moments associated with the Berry curvature. Using three layers of metallic top gates, we independently control the tunneling barriers of the QD while tuning the occupation from the few-hole regime to the few-electron regime, crossing the displacement-field controlled band gap. The band gap is around 25 meV, while the charging energies of the electron and hole dots are between 3-5 meV. The extracted valley g-factor is around 17 and leads to opposite valley polarization for electron and hole states at moderate B-fields. Our measurements agree well with tight-binding calculations for our device.

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Luca Banszerus, Alexander Rothstein, Thomas Fabian, Samuel Möller, Eike Icking, Stefan Trellenkamp, Florian Lentz, Daniel Neumaier, Kenji Watanabe, Takashi Taniguchi, Florian Libisch, Christian Volk, Christoph Stampfer. 2020-08-06. Electron-hole crossover in gate-controlled bilayer graphene quantum dots. https://doi.org/10.1021/acs.nanolett.0c03227

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