Time-resolved charge detection in graphene quantum dots

Abstract

We present real-time detection measurements of electron tunneling in a graphene quantum dot. By counting single electron charging events on the dot, the tunneling process in a graphene constriction and the role of localized states are studied in detail. In the regime of low charge detector bias we see only a single time-dependent process in the tunneling rate which can be modeled using a Fermi-broadened energy distribution of the carriers in the lead. We find a non-monotonic gate dependence of the tunneling coupling attributed to the formation of localized states in the constriction. Increasing the detector bias above 2 mV results in an increase of the dot-lead transition rate related to back-action of the charge detector current on the dot.Comment: 8 pages, 6 figure

Measurement Back-Action in Stacked Graphene Quantum Dots

“…2a). This indicates that the tunneling rates change non-monotonically as a function of energy 25 , which is well-known for Coulomb blockade in graphene nanoribbons. [25][26][27] This behavior is schematically depicted by the energy dependent tunneling barriers in Fig.…”

“…24 We show that this current results from mutual gating of the quantum dots 24 as well as from additional quantum-mechanical contributions. 14 This observation is only possible due to the strongly non-monotonic energy dependence of the quantum dots' tunneling coupling [25][26][27] resulting in a spatial breaking of the quantum dot symmetry. Such energy dependent tunneling barriers are readily available in graphene nanodevices.…”

“…2a and with previous experiments. 25 An accurate extraction of the tunneling rates is however not possible due to the many unknown parameters.…”

“…Such energy dependent tunneling barriers are readily available in graphene nanodevices. [25][26][27] The investigated device is schematically shown in Fig. 1a.…”

Charging graphene nanoribbon quantum dots

“…The spontaneous disorder-induced quantum dots and the ones defined electrostatically are characterized by Coulomb diamonds in the charge stability diagrams 13,14,20 . In part of the studies the nanoribbons contain an additional inline graphene flake 14,15,20,[24][25][26] in the gated region, which is useful in separation 20 of the charging effects due to the intentionally introduced quantum dot and the spontaneous Coulomb islands along the ribbon.…”