"
“Carbon Nanotube Superconductivity: An Update”
  

ØSpeaker :Prof. Ping Sheng (HKUST, Clear Water Bay, Kowloon, Hong Kong)
ØPlace : #512, Hogil Kim Memorial Bldg., POSTECH
ØDate & Time : July 6 (Mon), 15:00 - 16:00

  
ØAbstract
Superconductivity in carbon nanotubes is a topic of intriguing interest.먹튀 토토While the small-diameter nanotubes
Are먹튀 토토predicted먹튀 토토to먹튀 토토have먹튀 토토enhanced먹튀 토토electron-phonon먹튀 토토coupling—a먹튀 토토key먹튀 토토element responsible먹튀 토토for먹튀 토토nanotube
superconductivitythe associated increase in fluctuation effects is unfavorable to the먹튀 토토manifestation먹튀 토토of먹튀 토토a
superconducting transition.먹튀 토토The possibility of a Peierls transition in thin nanotubes is a further먹튀 토토deterrent먹튀 토토to
superconductivity.먹튀 토토It먹튀 토토follows that the existence of coupling먹튀 토토between먹튀 토토the먹튀 토토nanotubes먹튀 토토is먹튀 토토important먹튀 토토to먹튀 토토the
realization of its superconducting behavior, since the transverse coherence can suppress먹튀 토토fluctuations먹튀 토토and
lower the Peierls transition temperature, thereby making the먹튀 토토appearance먹튀 토토of먹튀 토토a먹튀 토토superconducting먹튀 토토transition
possible.먹튀 토토 Owing to먹튀 토토its먹튀 토토ordered먹튀 토토and먹튀 토토closely-spaced먹튀 토토pore먹튀 토토structure (with먹튀 토토a먹튀 토토13.6먹튀 토토Å먹튀 토토center-to-center
separation between the 0.7 nm diameter pores), the AFI zeolite (composition: Al12P12O48) with embedded
4-Å carbon nanotubes constitutes an ideal material먹튀 토토for먹튀 토토the먹튀 토토observation먹튀 토토of먹튀 토토nanotube먹튀 토토superconductivity.
  
In this talk먹튀 토토I먹튀 토토will먹튀 토토describe먹튀 토토the먹튀 토토eight-year effort먹튀 토토that먹튀 토토resulted먹튀 토토in먹튀 토토the먹튀 토토two먹튀 토토new먹튀 토토developments먹튀 토토in먹튀 토토2007
(on improved sample fabrication) and먹튀 토토2008 (on making electrical contacts),먹튀 토토leading먹튀 토토to먹튀 토토reasonably먹튀 토토easy
observation of nanotube먹튀 토토superconductivity with high reliability먹튀 토토and먹튀 토토repeatability.먹튀 토토I n particular,먹튀 토토we먹튀 토토have
measured the specific heat signal for the superconducting transition as well as the resistive superconducting
transition.먹튀 토토The coupled carbon nanotube arrays can yield both nearly 1D superconducting behavior as well
as the Josephson array behavior, with their attendant magnetic characteristics.먹튀 토토The overall physical picture
that emerges is that of a coupled Josephson array consisting of aligned nanotubes crossing over from먹튀 토토an
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 the먹튀 토토c-axis먹튀 토토of먹튀 토토the
nanotubes.먹튀 토토The attainment of global coherence is seen at 5K and below, accompanied by the appearance
of a well-defined supercurrent gap at 2K.먹튀 토토While the existence of the superconducting transition in nanotube
arrays is now beyond reasonable doubt, there are still many aspects먹튀 토토of먹튀 토토the먹튀 토토data먹튀 토토which먹튀 토토have먹튀 토토yet먹튀 토토to먹튀 토토be
theoretically understood.먹튀 토토I will present some important lessons learned from the eight-year effort and what
they tell us about the mesoscopic electronic states in most carbon nanotubes.먹튀 토토In particular, these lessons
may shed light on why nanotube superconductivity was not observed and/or confirmed earlier.
  
                   Contact Person : Prof. Wokyung Sung(054-279-2061, wsung@postech.ac.kr)"