A graphene quantum dot with a single electron transistor as an integrated charge sensor

Wang, Linjun; Cao, Gang; Tu, Tao; Li, Haiou; Zhou, Cheng; Hao, Xinjun; Su, Zhan; Guo, Guang‐Can; Jiang, Hong-Wen; Guo, Guo-Ping

doi:10.1063/1.3533021

Cited by 122 publications

(92 citation statements)

References 29 publications

(21 reference statements)

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“…However, it is difficult to control and identify the energy structure of graphene QDs by traditional transport methods such as PAT, possibly because of edge states and puddles [33][34][35]. The sensitive microwave-based metrology used here allows us to study the dephasing rates in graphene DQDs, and whether they depend on the charge number in a DQD.…”

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confidence: 99%

“…Because the dephasing rate in grapheme DQDs has not been obtained by any other means namely photon-assisted tunneling (PAT), a traditional method, we now speculate here a possible reason. Using traditional methods involving charge transport, determining γ 2 is easily masked by the puddle and edge states [33][34][35] in an etched graphene structure. However, the resonant cavity here is mostly sensitive to the electrical dipole of the DQD and is affected much less by electrostatic disorder in the etched grapheme structure.…”

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Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture

et al. 2015

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We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots (DQDs) at microwave frequencies. Specifically, we investigate the charge dephasing rates in a circuit quantum electrodynamics (cQED) architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this four-fold periodicity in dephasing rates is an open problem, our observations hint at the four-fold degeneracy expected in graphene from its spin and valley degrees of freedom.In recent years, on-chip microwave resonators have emerged as a useful tool both for coupling distant qubits and for sensitive metrology [1]. For example, many experimental studies have recently been performed to study the interaction between quantum dots (QDs) and resonators, in gate-defined carbon-nanotubes [2-4], GaAs [5,6] and InAs nanowire [7,8] structures. Such studies are motivated by considering QDs as promising candidates for quantum information processing. Graphene has also attracted considerable attention in recent years because of its interesting physical properties and potential applications [9]. Like semiconductors, graphene-based QDs have been proposed as potential quantum bits [10]. Various experiments are now underway to study the coherence properties of graphene QDs. For example, using pulsed-gate transient spectroscopy, Volk et al.[11] measured a charge relaxation time of 100 ns in a graphene QD device. However, the dephasing times of grapheme QDs, which benchmark their quantum coherence and may be significantly shorter than their relaxation times, have not yet been measured. In addition, graphene has both spin and valley degrees of freedom, similar to carbon nanotubes [12,13] and Si-based QDs [14]. Spin qubits formed by graphene QDs have been theoretically studied [10], and various valley-related phenomena such as shell filling in carbon nanotubes [12] and valley splitting in silicon [15] have been explored. However, there are no experimental reports on the effects of the four-fold degeneracy caused by the spin and valley degrees in graphene devices.Here, we present an experimental study of a graphene DQD device, which can be considered as a charge qubit that contains a large number of well-defined charge * Corresponding author: gpguo@ustc.edu.cn states. Using the sensitive dispersive readout of a microwave resonator, we measured the charge-state dephasing rates of this DQD in an integrated grapheneresonator device. Applying a quantum model describing the hybrid system, we simultaneously extracted: the DQD-resonator coupling strength, the tunneling rate between each quantum dot, and the charge-state dephasing rates. This microwave spectroscopy overcomes the difficulties of conventional transport techniques and allows us to study DQD dynamics in a large parameter space. In these experiments, we found that the dephasing rates depend on the number of charges in t...

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Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture

et al. 2015

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“…Instead, the most viable way to confine charge carriers in graphene nowadays is based on etching nanostructures into graphene flakes [15]. So far, Coulomb blockade [16][17][18][19], excited states [20][21][22], charge sensing [23,24], and spin-filling sequences [25] have been studied in detail in etched graphene quantum dot devices. More recently, also charge pumps [26] and charge relaxation times of excited states [27] in graphene quantum dots have been investigated experimentally.…”

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confidence: 99%

Modeling charge relaxation in graphene quantum dots induced by electron-phonon interaction

Reichardt

Stampfer

2016

Phys. Rev. B

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We study and compare two analytic models of graphene quantum dots for calculating charge relaxation times due to electron-phonon interaction. Recently, charge relaxation processes in graphene quantum dots have been probed experimentally and here we provide a theoretical estimate of relaxation times. By comparing a model with pure edge confinement to a model with electrostatic confinement, we find that the latter features much larger relaxation times. Interestingly, relaxation times in electrostatically defined quantum dots are predicted to exceed the experimentally observed lower bound of ∼100 ns.

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“…This can be overcome by nanostructuring graphene, where it has been shown that an etching-based "paper cutting" technique leads to graphene nanodevices where transport is dominated by a disorder-induced energy gap. Consequently, graphene nanoribbons [4][5][6][7][8][9][10][11][12], single-electron transistors (SETs) [13][14][15], graphene quantum dots (QD) [16][17][18] even with charge detectors [16,19,20] and graphene double quantum dots [21][22][23][24][25] have been demonstrated successfully. These devices allowed the experimental observation of excited states [22,26], spin states [27] and the very few carrier regime [28].…”

Section: Introductionmentioning

confidence: 99%

Tunable capacitive inter‐dot coupling in a bilayer graphene double quantum dot

Fringes

Volk

Terrés

et al. 2011

Phys. Status Solidi C

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We report on a double quantum dot which is formed in a width-modulated etched bilayer graphene nanoribbon. A number of lateral graphene gates enable us to tune the quantum dot energy levels and the tunneling barriers of the device over a wide energy range. Charge stability diagrams and in particular individual triple point pairs allow to study the tunable capacitive inter-dot coupling energy as well as the spectrum of the electronic excited states on a number of individual triple points. We extract a mutual capacitive inter-dot coupling in the range of 2 -6 meV and an inter-dot tunnel coupling on the order of 1.5 µeV.

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A graphene quantum dot with a single electron transistor as an integrated charge sensor

Cited by 122 publications

References 29 publications

Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture

Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture

Modeling charge relaxation in graphene quantum dots induced by electron-phonon interaction

Tunable capacitive inter‐dot coupling in a bilayer graphene double quantum dot

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