title: Probing relaxation times in graphene quantum dots.
abstract: Graphene quantum dots are attractive candidates for solid-state quantum bits. In fact, the predicted weak spin-orbit and hyperfine interaction promise spin qubits with long coherence times. Graphene quantum dots have been extensively investigated with respect to their excitation spectrum, spin-filling sequence and electron-hole crossover. However, their relaxation dynamics remain largely unexplored. This is mainly due to challenges in device fabrication, in particular concerning the control of carrier confinement and the tunability of the tunnelling barriers, both crucial to experimentally investigate decoherence times. Here we report pulsed-gate transient current spectroscopy and relaxation time measurements of excited states in graphene quantum dots. This is achieved by an advanced device design that allows to individually tune the tunnelling barriers down to the low megahertz regime, while monitoring their asymmetry. Measuring transient currents through electronic excited states, we estimate a lower bound for charge relaxation times on the order of 60-100 ns.
authors.affiliation: JARA-FIT and II Institute of Physics B, RWTH Aachen, 52074 Aachen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Volk
authors.forename: Christoph
authors.initials: C
authors.lastname: Neumann
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kazarski
authors.forename: Stefan
authors.initials: S
authors.lastname: Fringes
authors.forename: Stephan
authors.initials: S
authors.lastname: Engels
authors.forename: Federica
authors.initials: F
authors.lastname: Haupt
authors.forename: André
authors.initials: A
authors.lastname: Müller
authors.forename: Christoph
authors.initials: C
authors.lastname: Stampfer