Carbon nanotube Josephson junctions

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We have succeeded in making reproducible superconducting contacts to gated single-walled carbon nanotubes (SWCNTs). Devices with two types of superconducting trilayer electrodes are fabricated; Ti/Al/Ti and Ti/Nb/Ti. We have devices both in the high transparency regime (Fabry-Perot regime), and in the intermediate transparency regime (Kondo regime).
In the Fabry-Perot regime we observe peaks in the differential conductance at +-2Delta/e due to the onset of quasi particle tunneling, and features at +-Delta/e and +-2Delta/3e due to multiple Andreev reflections (MARs). An excess current is observed and extracted at several different gate voltages. The dependence of the excess current on the normal state conductance is presented and fitted to SNS-theory with good agreement.
In the Kondo regime we report on devices with four period shell filling structures together with features due to quasi particle tunneling and MARs. A narrow peak in differential conductance around zero bias is interpreted as a noise smeared supercurrent. We examine its temperature dependence in resonance, and its interplay with Kondo resonances.

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Journal: TechConnect Briefs
Volume: 1, Technical Proceedings of the 2006 NSTI Nanotechnology Conference and Trade Show, Volume 1
Published: May 7, 2006
Pages: 174 - 177
Industry sector: Advanced Materials & Manufacturing
Topic: Carbon Nano Structures & Devices
ISBN: 0-9767985-6-5