Quantum effects in the radial thermal expansion of bundles of single-walled carbon nanotubes doped with 4He

TL;DR

This study investigates how 4He impurities affect the radial thermal expansion of single-walled carbon nanotube bundles at low temperatures, revealing quantum tunneling effects and impurity concentration dependence.

Contribution

It provides experimental evidence of quantum tunneling influencing thermal expansion in nanotube bundles doped with helium-4.

Findings

Negative thermal expansion observed between 2.1-3.7 K

Expansion magnitude decreases with lower 4He concentration

Quantum tunneling likely causes the enhanced negative expansion

Abstract

The radial thermal expansion (ar) of bundles of single-walled carbon nanotubes saturated with 4He impurities to the molar concentration 9.4% has been investigated in the interval 2.5-9.5 K using the dilatometric method. In the interval 2.1-3.7 K (ar) is negative and is several times higher than the negative (ar) for pure nanotube bundles. This most likely points to 4He atom tunneling between different positions in the nanotube bundle system. The excess expansion was reduced with decreasing 4He concentration.