laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Séminaire, 16 Juin 2014 (SALLE D5)

Ping Sheng (Department of Physics, HKUST, Hong Kong, China)
Superconductivity in Arrays of 4-Angstrom Carbon Nanotubes Embedded in AFI Zeolite—An Update

Superconductivity in 4-Angstrom carbon nanotubes has been a decade-long
effort in my group. In this talk I would like to share some of the
observations and challenges. It is shown that by improving the sample
quality and devising strategy to make surface electrical contacts to the
samples that are separated by only 100 nm, observations of the
superconducting resistive transition can be obtained on samples comprising
4-Angstrom carbon nanotubes embedded in AFI zeolite pores. The picture
which emerges is that of a coupled Josephson array consisting of aligned
nanotubes crossing over from an individually fluctuating 1D system to a
coherent 3D superconductor, mediated by a Kosterlitz-Thouless (KT)
transition which establishes quasi long range order in the lateral plane
perpendicular to the c-axis of the nanotubes. Such a physical picture is
indeed supported by numerical simulations. The attainment of overall
coherence across the measuring electrodes is seen at 5K and below,
evidenced by the appearance of a well-defined supercurrent gap at 2K.
Magnetic torque measurements, showing evidence of Hc1 as well as
differences in the field-cooled and zero-field cooled data, are consistent
with the above interpretation. I will also describe the challenges that
are still to be addressed, the most crucial being the improvement in
sample quality.