Superconducting characteristics of 4-A carbon nanotube-zeolite composite.
We have fabricated nanocomposites consisting of 4-A carbon nanotubes embedded in the 0.7-nm pores of aluminophosphate-five (AFI) zeolite that display a superconducting specific heat transition at 15 K. MicroRaman spectra of the samples show strong and spatially uniform radial breathing mode (RBM) signals at 510 cm(-1) and 550 cm(-1), characteristic of the (4, 2) and (5, 0) nanotubes, respectively. The specific heat transition is suppressed at >2 T, with a temperature dependence characteristic of finite-size effects. Comparison with theory shows the behavior to be consistent with that of a type II BCS superconductor, characterized by a coherence length of 14 +/- 2 nm and a magnetic penetration length of 1.5 +/- 0.7 mum. Four probe and differential resistance measurements have also indicated a superconducting transition initiating at 15 K, but the magnetoresistance data indicate the superconducting network to be inhomogeneous, with a component being susceptible to magnetic fields below 3 T and other parts capable of withstanding a magnetic field of 5 T or beyond.
Department of Physics and William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Rolf
R
Lortz
Qiucen
Q
Zhang
Wu
W
Shi
Jian Ting
JT
Ye
Jiang Ting
JT
Ye
Chunyin
C
Qiu
Zhe
Z
Wang
Hongtao
H
He
Ping
P
Sheng
Tiezheng
T
Qian
Zikang
Z
Tang
Ning
N
Wang
Xixiang
X
Zhang
Jiannong
J
Wang
Che Ting
CT
Chan