Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 78: Transport: Graphene 1 (jointly with TT, MA, DY, DS, O)
HL 78.10: Vortrag
Donnerstag, 29. März 2012, 12:00–12:15, BH 334
Relaxation in graphene quantum dots — •Christoph Neumann1, Christian Volk1,2, Sebastian Kazarski1, Stefan Fringes1, Stephan Engels1,2, Bernat Terres1,2, Jan Dauber1,2, Stefan Trellenkamp2, and Christoph Stampfer1,2 — 1JARA-FIT and II. Institute of Physics B, RWTH Aachen, 52074 Aachen, Germany — 2Peter Grünberg Institut (PGI-8/9), Forschungszentrum Jülich, 52425 Jülich, Germany
Graphene quantum dots (QDs) have received increasing attention over the last years as interesting candidates for the future implementation of spin qbits. Compared to GaAs-based QDs, their smaller hyperfine and spin-orbit coupling promises more favorable spin coherence times. However, while the preparation, manipulation, and read-out of single spins has been demonstrated in GaAs structures, research on graphene QDs is still at an early stage. Although Coulomb blockade phenomena and excited state spectroscopy is already well established, experimental signatures allowing the identification of relaxation times have been hard to trace. Here we report on pulse gating experiments on graphene quantum devices. We will present measurements of the relaxation rates in single-layer graphene QDs. The investigated devices consist of an island with a diameter of 120 nm, 4 lateral graphene gates and 2 charge detectors. From so-called diamond measurements we extract a charging energy of 11 meV and excited state level spacings of 2-4 meV. The gates enable us to tune the tunnelling rates from the GHz down to the low MHz regime. Finally low-bias pulse gate measurements allow us to extract relaxation rates on the order of 50 ns.