1D goes 2D: A Kosterlitz Thouless transition in superconducting arrays of 4-Angstrom carbon nanotubes

TL;DR

This paper reports the observation of a Kosterlitz-Thouless transition in superconducting arrays of 4-Angstrom carbon nanotubes embedded in zeolite, revealing a layered transition from 2D to 3D superconducting order with specific temperature and magnetic field dependencies.

Contribution

It provides experimental evidence of a KT transition in nanotube arrays, demonstrating a layered superconducting transition in a quasi-1D system embedded in a 3D matrix.

Findings

KT transition observed at 15K with a sharp resistance drop

Global superconductivity established below 5K

Anisotropic magnetic field dependence of the transition

Abstract

We report superconducting resistive transition characteristics for array(s) of coupled 4-Angstrom single wall carbon nanotubes embedded in aluminophosphate-five (AFI) zeolite. The transition was observed to initiate at 15K with a slow resistance decrease switching to a sharp, order of magnitude drop between 7.5-6.0K. The transition has strong (anisotropic) magnetic field dependence. Differential resistance versus current (voltage) measurements indicate that the establishment of coherence proceeds in stages as the temperature is lowered below 15K. In particular, the sharp resistance drop and its attendant nonlinear IV characteristics are consistent with the manifestations of a Kosterlitz-Thouless (KT) transition that establishes quasi long range order in the plane transverse to the c-axis of the nanotubes, leading to an inhomogeneous system comprising 3D superconducting regions connected by weak links. Global coherence is established at below 5K with the appearance of a well-defined supercurrent gap at 2K.