From the Cover: Superconducting characteristics of 4-A carbon nanotube-zeolite composite
Abstract
We have fabricated nanocomposites consisting of 4-å 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 μm. 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.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- May 2009
- DOI:
- 10.1073/pnas.0813162106
- Bibcode:
- 2009PNAS..106.7299L
- Keywords:
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- resistance transition;
- specific heat;
- superconductivity;
- Physical Sciences:Applied Physical Sciences