Multiple Andreev Reflections in a Carbon Nanotube Quantum Dot

Abstract

We report resonant multiple Andreev reflections in a multiwall carbon nanotube quantum dot coupled to superconducting leads. The position and magnitude of the subharmonic gap structure is found to depend strongly on the level positions of the single-electron states which are adjusted with a gate electrode. We discuss a theoretical model of the device and compare the calculated differential conductance with the experimental data.

Conductance properties of nanotubes coupled to superconducting leads: signatures of Andreev states dynamics

“…The observed subharmonic gap structure is discussed in more detail in Ref. [7]. The superconducting gap energy of ∆ = 0.1 meV is slightly less than the expected 0.18 meV for bulk aluminum which we attribute to the intermediate Au layer (necessary to obtain good electrical contact to the MWNT).…”

“…[11] numerical results were presented for the S-QD-S system neglecting electron correlation effects. This approach has also been used by Buitelaar et al [7] for analyzing the experimental results for the subgap structure of Ref. [6].…”

“…In particular Buitelaar et al [6] have achieved a physical realization of a S-QD-S system using carbon nanotubes coupled to Al/Au leads. Their results, showing an enhancement of the conductance in the Kondo regime with respect to the normal case, have attracted considerable theoretical attention [7,8,9].…”

Superconducting proximity effect in single-walled carbon nanotubes between NbN electrodes

“…However, because this unique electronic structure gives weak electronic coupling at the Fermi surface of metal electrodes, high contact resistance is usually observed between metal electrodes and SWNTs [6]. Recently, the superconducting proximity effect, Andreev reflection and even supercurrent have been observed in S/carbon nanotubes/S junctions by a few groups [7][8][9]. Because a high transparency contact is difficult to obtain, but it is very important for observing Andreev reflection and supercurrent, in S/SWNTs/S junctions.…”

Multiple Andreev Reflection and Enhanced Quantum Interferences in NbN/Network-Like Carbon Nanotubes/NbN SNS Junctions

“…Carbon nanotubes (CNTs) with a diameter of only a few nm as normal conductors are one of the best candidates for studying quasi one-dimensional (1D) proximity effect and AR. Though some experiments and theories have demonstrated 1D Tomonaga-Luttinger liquid behavior in single-wall carbon nantube (SWNT) or even multi-wall CNT (MWNT) (Bockrath et al,1999), some experiments have shown AR (Morpurgo et al,1999), MAR (Jarillo-Herrero et al,2006;Buitelaar et al,2003;Jorgensen et al,2006), Andreev bound states (Pillet et al,2010) and supercurrent in CNTs (Jarillo-Herrero et al,2006;Kasumov et al,1999), 25 www.intechopen.com and even superconducting quantum interference device made with CNTs (Cleuziou et al,2006). The superconducting proximity effect in the network-like structure with quasi-1D CNT will be discussed in the chapter.…”