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HL: Fachverband Halbleiterphysik
HL 69: Quantum dots and wires III
HL 69.9: Vortrag
Donnerstag, 19. März 2020, 17:45–18:00, POT 151
Shell-filling and spin-valley coupling in gate-defined BLG quantum dots — Luca Banszerus1,2, •Samuel Möller1, Eike Icking1, Christian Volk1, Kenji Watanabe3, Takashi Taniguchi3, and Christoph Stampfer1,2 — 12.Physikalisches Institut A, RWTH Aachen University, Germany — 2Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Germany — 3National Institute for Materials Science,1-1 Namiki, Tsukuba, 305-0044, Japan
We present a gate-defined single quantum dot in electrostatically gapped bilayer graphene with full occupational control up to the first electron. Quantum dot states are examined by applying perpendicular and in-plane magnetic fields to the sample at low and high bias, allowing to extract addition energies and g-factors. We obtain the electron g-factor of 2 and valley g-factors in the order of 30, depending on the orbital state. Each orbital state (shell) is occupied four times due to the spin and valley degrees of freedom in graphene. Single particle states are found sufficient to describe the ground state (excited states) of the quantum dot up to occupations of 12(8) electrons. The order of states in which electrons enter the quantum dot is extracted and found to be constant across shells. Remarkably, we find the fourfold degeneracy at zero magnetic field is lifted. Instead, two pairs each with two states of opposite spin and valley form. We denote this phenomenon to an effective spin-valley coupling of 0.5 meV.