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Tuning inter-dot tunnel coupling of an etched graphene double quantum dot by adjacent metal gates.

Wei D, Li HO, Cao G, Luo G, Zheng ZX, Tu T, Xiao M, Guo GC, Jiang HW, Guo GP - Sci Rep (2013)

Bottom Line: We find that tC can be controlled continuously about a factor of four by employing a single gate.Furthermore, tC, can be changed monotonically about another factor of four as electrons are gate-pumped into the dot one by one.The results suggest that the strength of tunnel coupling in etched graphene DQDs can be varied in a rather broad range and in a controllable manner, which improves the outlook to use graphene as a base material for qubit applications.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Quantum Information, Department of Optics and Optical Engineering, University of Science and Technology of China, Chinese Academy of Science, Hefei 230026, China.

ABSTRACT
Graphene double quantum dots (DQDs) open to use charge or spin degrees of freedom for storing and manipulating quantum information in this new electronic material. However, impurities and edge disorders in etched graphene nano-structures hinder the ability to control the inter-dot tunnel coupling, tC, the most important property of the artificial molecule. Here we report measurements of tC in an all-metal-side-gated graphene DQD. We find that tC can be controlled continuously about a factor of four by employing a single gate. Furthermore, tC, can be changed monotonically about another factor of four as electrons are gate-pumped into the dot one by one. The results suggest that the strength of tunnel coupling in etched graphene DQDs can be varied in a rather broad range and in a controllable manner, which improves the outlook to use graphene as a base material for qubit applications.

No MeSH data available.


Sample characterizaion.(a). Scanning electron micrograph in false color of the device.Dark regions are the graphene base structure consisting of a double quantum dot (100 nm*100 nm for each dot, 35 nm*100 nm for each ribbon) and an integrated QPC channel serving as in situ charge detector. Grey area is the etched-away region that shows the SiO2 substrate surface. The yellow regions are the metal gates used for control and as source/drain electrodes. (b). A typical QPC charge sensor stability diagram of the double quantum dot: differential charge sensor current dIQPC/dVLP as a function of two gate voltages VLP and VRP. The structure shows a well-defined double quantum dot with characteristic honeycomb patterns. Charge state is defined by (M, N), where M and N are the electron number in the left and right dot, respectively (The charging energy and regularity are the same throughout the samples tested. The difference in the honeycomb size between Fig. 1b and the else in the article stems from doped and undoped sample substrates).
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f1: Sample characterizaion.(a). Scanning electron micrograph in false color of the device.Dark regions are the graphene base structure consisting of a double quantum dot (100 nm*100 nm for each dot, 35 nm*100 nm for each ribbon) and an integrated QPC channel serving as in situ charge detector. Grey area is the etched-away region that shows the SiO2 substrate surface. The yellow regions are the metal gates used for control and as source/drain electrodes. (b). A typical QPC charge sensor stability diagram of the double quantum dot: differential charge sensor current dIQPC/dVLP as a function of two gate voltages VLP and VRP. The structure shows a well-defined double quantum dot with characteristic honeycomb patterns. Charge state is defined by (M, N), where M and N are the electron number in the left and right dot, respectively (The charging energy and regularity are the same throughout the samples tested. The difference in the honeycomb size between Fig. 1b and the else in the article stems from doped and undoped sample substrates).

Mentions: The device used for the experiment is a double quantum dot with an integrated charge state sensor. The base graphene structures of the DQD along with the adjacent detection channel are defined by plasma etching of a large flake. The electrostatic control is facilitated by incorporating additional metallic gates, as shown in the SEM picture, in Fig. 1a. We have studied over ten identical devices. For consistency, the bulk of the data presented in this paper is from one sample.


Tuning inter-dot tunnel coupling of an etched graphene double quantum dot by adjacent metal gates.

Wei D, Li HO, Cao G, Luo G, Zheng ZX, Tu T, Xiao M, Guo GC, Jiang HW, Guo GP - Sci Rep (2013)

Sample characterizaion.(a). Scanning electron micrograph in false color of the device.Dark regions are the graphene base structure consisting of a double quantum dot (100 nm*100 nm for each dot, 35 nm*100 nm for each ribbon) and an integrated QPC channel serving as in situ charge detector. Grey area is the etched-away region that shows the SiO2 substrate surface. The yellow regions are the metal gates used for control and as source/drain electrodes. (b). A typical QPC charge sensor stability diagram of the double quantum dot: differential charge sensor current dIQPC/dVLP as a function of two gate voltages VLP and VRP. The structure shows a well-defined double quantum dot with characteristic honeycomb patterns. Charge state is defined by (M, N), where M and N are the electron number in the left and right dot, respectively (The charging energy and regularity are the same throughout the samples tested. The difference in the honeycomb size between Fig. 1b and the else in the article stems from doped and undoped sample substrates).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3822378&req=5

f1: Sample characterizaion.(a). Scanning electron micrograph in false color of the device.Dark regions are the graphene base structure consisting of a double quantum dot (100 nm*100 nm for each dot, 35 nm*100 nm for each ribbon) and an integrated QPC channel serving as in situ charge detector. Grey area is the etched-away region that shows the SiO2 substrate surface. The yellow regions are the metal gates used for control and as source/drain electrodes. (b). A typical QPC charge sensor stability diagram of the double quantum dot: differential charge sensor current dIQPC/dVLP as a function of two gate voltages VLP and VRP. The structure shows a well-defined double quantum dot with characteristic honeycomb patterns. Charge state is defined by (M, N), where M and N are the electron number in the left and right dot, respectively (The charging energy and regularity are the same throughout the samples tested. The difference in the honeycomb size between Fig. 1b and the else in the article stems from doped and undoped sample substrates).
Mentions: The device used for the experiment is a double quantum dot with an integrated charge state sensor. The base graphene structures of the DQD along with the adjacent detection channel are defined by plasma etching of a large flake. The electrostatic control is facilitated by incorporating additional metallic gates, as shown in the SEM picture, in Fig. 1a. We have studied over ten identical devices. For consistency, the bulk of the data presented in this paper is from one sample.

Bottom Line: We find that tC can be controlled continuously about a factor of four by employing a single gate.Furthermore, tC, can be changed monotonically about another factor of four as electrons are gate-pumped into the dot one by one.The results suggest that the strength of tunnel coupling in etched graphene DQDs can be varied in a rather broad range and in a controllable manner, which improves the outlook to use graphene as a base material for qubit applications.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Quantum Information, Department of Optics and Optical Engineering, University of Science and Technology of China, Chinese Academy of Science, Hefei 230026, China.

ABSTRACT
Graphene double quantum dots (DQDs) open to use charge or spin degrees of freedom for storing and manipulating quantum information in this new electronic material. However, impurities and edge disorders in etched graphene nano-structures hinder the ability to control the inter-dot tunnel coupling, tC, the most important property of the artificial molecule. Here we report measurements of tC in an all-metal-side-gated graphene DQD. We find that tC can be controlled continuously about a factor of four by employing a single gate. Furthermore, tC, can be changed monotonically about another factor of four as electrons are gate-pumped into the dot one by one. The results suggest that the strength of tunnel coupling in etched graphene DQDs can be varied in a rather broad range and in a controllable manner, which improves the outlook to use graphene as a base material for qubit applications.

No MeSH data available.