SKM 2023 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 14: Focus Session: Graphene Quantum Dots (joint session HL/TT)
TT 14.5: Hauptvortrag
Montag, 27. März 2023, 17:15–17:45, POT 251
Particle-hole symmetry protects spin-valley blockade in graphene quantum dots — •Christian Volk1,2, Luca Banszerus1,2, Samuel Möller1,2, Katrin Hecker1,2, Eike Icking1,2, Kenji Watanabe3, Takashi Taniguchi4, Fabian Hassler5, and Christoph Stampfer1,2 — 1JARA-FIT and 2nd Institute of Physics, RWTH Aachen University — 2Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich — 3Research Center for Functional Materials, NIMS, Tsukuba, Japan — 4International Center for Materials Nanoarchitectonics, NIMS, Tsukuba, Japan — 5JARA-Institute for Quantum Information, RWTH Aachen University
Particle-hole symmetry plays an important role for the characterization of topological phases in solid-state systems. Graphene is a prime example of a gapless particle-hole symmetric system. The intrinsic Kane-Mele spin-orbit coupling in graphene leads to a lifting of the spin-valley degeneracy and renders graphene a topological insulator in a quantum spin-Hall phase while preserving particle-hole symmetry.
Here, we show that the Kane-Mele spin-orbit gap leads to a lifting of the spin-valley degeneracy in bilayer graphene quantum dots, resulting in Kramer's doublets with different ordering for electron and hole states preserving particle-hole symmetry. We observe the creation of single electron-hole pairs with opposite quantum numbers and use the electron-hole symmetry to achieve a protected spin-valley blockade in electron-hole double quantum dots. The latter will allow spin-to-charge and valley-to-charge conversion, which is essential for the operation of spin and valley qubits.