Observation of the Meissner state in superconducting arrays of 4-Å carbon nanotubes

We report clear observations of themagnetic Meissner effect in arrays of superconducting 4-angstrom carbon nanotubes grown in the linear channels of AlPO4-5 (AFI) zeolite single crystals. Both bulk magnetization and magnetic torque experiments show a pronounced signature of the lower critical IIc1 transition, a difference in zero-field cooled and field cooled branches during temperature sweeps below 6 K, and signatures of one-dimensional superconducting fluctuations below similar to 15-18 K. These experiments extend the magnetic phase diagram we obtained previously by resistive experiments [Z. Wang et al., Phys. Rev. B 81, 174530 (2010)] towards low magnetic fields and within the range of zero resistance.