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Transport through a strongly coupled graphene quantum dot in perpendicular magnetic field.

Güttinger J, Stampfer C, Frey T, Ihn T, Ensslin K - Nanoscale Res Lett (2011)

Bottom Line: Lateral graphene gates are used to electrostatically tune the device.We show the evolution of Coulomb resonances as a function of perpendicular magnetic field, which provides indications of the formation of the graphene specific 0th Landau level.Finally, we demonstrate that the complex pattern superimposing the quantum dot energy spectra is due to the formation of additional localized states with increasing magnetic field.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland. guettinj@phys.ethz.ch.

ABSTRACT
We present transport measurements on a strongly coupled graphene quantum dot in a perpendicular magnetic field. The device consists of an etched single-layer graphene flake with two narrow constrictions separating a 140 nm diameter island from source and drain graphene contacts. Lateral graphene gates are used to electrostatically tune the device. Measurements of Coulomb resonances, including constriction resonances and Coulomb diamonds prove the functionality of the graphene quantum dot with a charging energy of approximately 4.5 meV. We show the evolution of Coulomb resonances as a function of perpendicular magnetic field, which provides indications of the formation of the graphene specific 0th Landau level. Finally, we demonstrate that the complex pattern superimposing the quantum dot energy spectra is due to the formation of additional localized states with increasing magnetic field.

No MeSH data available.


Related in: MedlinePlus

Dot conductance as a function of right gate and back gate voltage at a magnetic field of (a) 0 T and (b) 7 T. The spectrum is dominated by dot resonances marked with the solid line in (a) with a relative lever arm of  (see also Figure 2). (b) At a magnetic field of 7 T a hexagon pattern with two characteristic slopes is observed. Their corresponding lever arms are  attributed to the dot and  origin around the right constriction.
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Figure 4: Dot conductance as a function of right gate and back gate voltage at a magnetic field of (a) 0 T and (b) 7 T. The spectrum is dominated by dot resonances marked with the solid line in (a) with a relative lever arm of (see also Figure 2). (b) At a magnetic field of 7 T a hexagon pattern with two characteristic slopes is observed. Their corresponding lever arms are attributed to the dot and origin around the right constriction.

Mentions: In Figure 4a we show an example of a sequence of dot Coulomb resonances in the Vrg-Vbg plane. The slope corresponding to and the spacing of ΔVbg ≈ 0.1 V are in good agreement with Figure 2, and lead to the conclusion that we observe single quantum dot behaviour over a large parameter range. However, if we measure the current in the very same Vrg - Vbg parameter space at B = 7 T the pattern changes significantly and the diagonal lines are substituted by a strong hexagonal pattern (see dashed lines) typical for two coupled quantum dots [40]. The two states forming the hexagon pattern show relative lever arms of and . While the resonances with are attributed to the original dot, corresponds to a new and strongly coupled localization formed close to the right constriction. Additional resonances from the right constriction with (see above) are still visible.


Transport through a strongly coupled graphene quantum dot in perpendicular magnetic field.

Güttinger J, Stampfer C, Frey T, Ihn T, Ensslin K - Nanoscale Res Lett (2011)

Dot conductance as a function of right gate and back gate voltage at a magnetic field of (a) 0 T and (b) 7 T. The spectrum is dominated by dot resonances marked with the solid line in (a) with a relative lever arm of  (see also Figure 2). (b) At a magnetic field of 7 T a hexagon pattern with two characteristic slopes is observed. Their corresponding lever arms are  attributed to the dot and  origin around the right constriction.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211315&req=5

Figure 4: Dot conductance as a function of right gate and back gate voltage at a magnetic field of (a) 0 T and (b) 7 T. The spectrum is dominated by dot resonances marked with the solid line in (a) with a relative lever arm of (see also Figure 2). (b) At a magnetic field of 7 T a hexagon pattern with two characteristic slopes is observed. Their corresponding lever arms are attributed to the dot and origin around the right constriction.
Mentions: In Figure 4a we show an example of a sequence of dot Coulomb resonances in the Vrg-Vbg plane. The slope corresponding to and the spacing of ΔVbg ≈ 0.1 V are in good agreement with Figure 2, and lead to the conclusion that we observe single quantum dot behaviour over a large parameter range. However, if we measure the current in the very same Vrg - Vbg parameter space at B = 7 T the pattern changes significantly and the diagonal lines are substituted by a strong hexagonal pattern (see dashed lines) typical for two coupled quantum dots [40]. The two states forming the hexagon pattern show relative lever arms of and . While the resonances with are attributed to the original dot, corresponds to a new and strongly coupled localization formed close to the right constriction. Additional resonances from the right constriction with (see above) are still visible.

Bottom Line: Lateral graphene gates are used to electrostatically tune the device.We show the evolution of Coulomb resonances as a function of perpendicular magnetic field, which provides indications of the formation of the graphene specific 0th Landau level.Finally, we demonstrate that the complex pattern superimposing the quantum dot energy spectra is due to the formation of additional localized states with increasing magnetic field.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland. guettinj@phys.ethz.ch.

ABSTRACT
We present transport measurements on a strongly coupled graphene quantum dot in a perpendicular magnetic field. The device consists of an etched single-layer graphene flake with two narrow constrictions separating a 140 nm diameter island from source and drain graphene contacts. Lateral graphene gates are used to electrostatically tune the device. Measurements of Coulomb resonances, including constriction resonances and Coulomb diamonds prove the functionality of the graphene quantum dot with a charging energy of approximately 4.5 meV. We show the evolution of Coulomb resonances as a function of perpendicular magnetic field, which provides indications of the formation of the graphene specific 0th Landau level. Finally, we demonstrate that the complex pattern superimposing the quantum dot energy spectra is due to the formation of additional localized states with increasing magnetic field.

No MeSH data available.


Related in: MedlinePlus