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Single-charge Circuits

Working Group 2.42


Single-electron transport with
hybrid S-I-N-I-S Turnstiles

In the year 2008, a Finnish group around Prof.J. Pekola [1] demonstrated, for a simple transistor structure with only two ultrasmall S-I-N tunnel junctions and an rf-gate capacitively coupled to the middle island (Fig.1), a remarkable ability to transfer electron charges controllably one by one. Here, the abbreviation S-I-N denotes a tunnel junction between Superconductive and Normal metal leads separated by a thin Insulating barrier. Due to that as well as because of its operation principle - loading and unloading of electron charges in a cyclic way through the N-island, this circuit is used to be called "hybrid turnstile".  In our group, we investigate the physical mechanisms responsible for the transfer accuracy and develop experimental approaches (see, e.g., Ref. [2]) towards an application of the hybrid turnstile in current metrology.


Scanning electron microskope image showing the island and the very small tunnel junctions

Figure 1:
SEM Image of a hybrid turnstile with an on-chip resistor.


IV-characteristics showing constant-current steps

Figure 2:
Current plateaus for two types of devices, SNS und SNS with a Cr-resistor (R-SNS).


[1] J.P. Pekola, J.J. Vartiainen, M. Möttönen, O.-P.Saira, M.Meschke, and D.V. Averin, Hybrid single-electron transistor as a source of quantized electric current, Nature Phys. 4, 120 (2008).

[2] S. V. Lotkhov, A. Kemppinen, S. Kafanov, J. P. Pekola, and A. B. Zorin, Pumping properties of the hybrid single-electron transistor in dissipative environment, Appl. Phys. Lett. 95, 112507 (2009).