Electron transport through double quantum dots

Wiel, W. G. van der; Franceschi, S. De; Elzerman, J. M.; Fujisawa, Toshimasa; Tarucha, Seigo; Kouwenhoven, Leo P.

doi:10.1103/revmodphys.75.1

Cited by 1,782 publications

(2,159 citation statements)

References 68 publications

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“…These results indicate that interdot coupling can be controlled by varying V g1 and V g2 , because the side gates affect the central barrier through the existing capacitances between the side gates and the central barrier [30]. Thus, in the range V g1 < 1.25 V, a double-quantum-dot system behaves as a single-quantum-dot system, and in the range 1.25 V < V g1 < 1.5 V, the two dots are in a weak electrostatic coupling regime [26]. Interdot coupling changes continuously and non-monotonically as a function of gate voltages V g1 and V g2 in our measured device.…”

Section: Electrical Propertiesmentioning

confidence: 99%

“…The system can be controlled by adjusting V sd and gate voltages V g1 and V g2 , which are capacitively coupled to each dot. Figure 4(b) shows a charge stability diagram of the system [26], where (n, m) pairs indicate the excess charges in dots 1 and 2. Inside the hexagonal lattices, the number of charges on the two dots is constant in the Coulomb blockade regime, so no current flows.…”

Section: Electrical Propertiesmentioning

confidence: 99%

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Fabrication of quantum-dot devices in graphene

Moriyama

Morita

Watanabe³

et al. 2010

Science and Technology of Advanced Materials

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We describe our recent experimental results on the fabrication of quantum-dot devices in a graphene-based two-dimensional system. Graphene samples were prepared by micromechanical cleavage of graphite crystals on a SiO 2 /Si substrate. We performed micro-Raman spectroscopy measurements to determine the number of layers of graphene flakes during the device fabrication process. By applying a nanofabrication process to the identified graphene flakes, we prepared a double-quantum-dot device structure comprising two lateral quantum dots coupled in series. Measurements of low-temperature electrical transport show the device to be a series-coupled double-dot system with varied interdot tunnel coupling, the strength of which changes continuously and non-monotonically as a function of gate voltage.

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Section: Electrical Propertiesmentioning

confidence: 99%

Section: Electrical Propertiesmentioning

confidence: 99%

Fabrication of quantum-dot devices in graphene

Moriyama

Morita

Watanabe³

et al. 2010

Science and Technology of Advanced Materials

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show abstract

“…3b) [34]. The lever arm between the left (right) gate and the left (right) dot is α L lg = V b /δV lg = 0.056 (α R rg = 0.019) [7,34]. This allows to extract the singledot addition energies E L a = α L lg · ∆V lg = 23 meV and E R a = α R rg · ∆V rg = 13 meV, which reflect an asymmetry in the QD island sizes.…”

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confidence: 99%

Electronic Excited States in Bilayer Graphene Double Quantum Dots

et al. 2011

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We report tunneling spectroscopy experiments on a bilayer graphene double quantum dot device that can be tuned by all-graphene lateral gates. The diameter of the two quantum dots are around 50 nm and the constrictions acting as tunneling barriers are 30 nm in width. The double quantum dot features addition energies on the order of 20 meV. Charge stability diagrams allow us to study the tunable interdot coupling energy as well as the spectrum of the electronic excited states on a number of individual triple points over a large energy range. The obtained constant level spacing of 1.75 meV over a wide energy range is in good agreement with the expected single-particle energy spacing in bilayer graphene quantum dots. Finally, we investigate the evolution of the electronic excited states in a parallel magnetic field.Keywords: graphene, bilayer graphene, quantum dot, double quantum dot, excited states Graphene quantum dots (QDs) are interesting candidates for spin qubits with long coherence times [1]. The suppressed hyperfine interaction and weak spin-orbit coupling [2, 3] make graphene and flat carbon structures in general, promising for future quantum information technology [4]. Significant progress has been made recently in the fabrication and understanding of graphene quantum devices. A "paper-cutting" technique enables the fabrication of graphene nanoribbons [5][6][7][8][9][10][11][12][13], quantum dots [14][15][16][17][18][19], and double quantum dot devices [20][21][22][23], where a disorder-induced energy gap allows confinement of individual carriers in graphene. These devices allowed the experimental investigation of excited states [16,21], spin states [19] and the electron-hole crossover [17]. However, all of these studies were based on single-layer graphene and showed a number of device limitations related to the presence of disorder, vibrational excitations and to the fact that the missing band gap makes it difficult to realize soft confinement potentials and "well-behaving" tunneling barriers. In particular, it has been shown that intrinsic ripples and corrugations in single-layer graphene can lead to unintended vibrational degrees of freedom [24] and to a coherent electron-vibron coupling in graphene QDs [25]. Bilayer graphene is a promising candidate to overcome some of these limitations. In particular it allows to open a band gap by an out-of-plane electric field [26][27][28], which may enable a soft confinement potential and may reduce the influence of localized edge states. More importantly, it has been shown that ripples and substrate-induced disorder are reduced in bilayer graphene [29], which increases the mechanical stability and suppresses unwanted vibrational modes.Here, we present a bilayer graphene double quantum dot (DQD) device, with a number of lateral gates. These local gates allow to tune transport from hole to electron dominated regimes and they enable to access different device configurations. We focus on the DQD configuration and show characteristic honeycomb-like charge stability dia...

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“…4b, cross-coupling of plunger gates, which would skew the square pattern into rhombus shapes, appears to be quite small. We note that these measurements were conducted at T ~ 1.5K, higher than the typical temperature where double dots based on semiconductor heterostructures have been measured [13].…”

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confidence: 99%

Gate-Defined Quantum Dots on Carbon Nanotubes

et al. 2005

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were defined either by tunnel barriers at the metal-nanotube interface [4,5], or by intrinsic [6,7] or induced [8,9] defects along the tube. These devices demonstrated the potential of nanotube-based quantum devices but did not allow independent control over device parameters (e.g., charge number and tunnel barrier transparency), and also placed stringent geometric constraints on device design. In the present study, we address some of these challenges by forming the quantum dots on the nanotube using only patterned gates, while the contacts to the nanotube remain highly transparent. This design allows multiple quantum dots to be arbitrarily positioned along a tube (quantum dots connected

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Electron transport through double quantum dots

Cited by 1,782 publications

References 68 publications

Fabrication of quantum-dot devices in graphene

Fabrication of quantum-dot devices in graphene

Electronic Excited States in Bilayer Graphene Double Quantum Dots

Gate-Defined Quantum Dots on Carbon Nanotubes

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