  Single-walled carbon nanotubes (SWNTs) have many interesting properties; they
may be metallic or semiconducting depending on their diameter and helicity of
the graphene sheet. Hydrostatic or quasi-hydrostatic high pressures can probe
many electronic features. Resistance - temperature measurements in SWNTs from
normal condition and under 0.4 GPa of quasi-hydrostatic pressures reveal a
semiconducting-like behavior. From 0.5 to about 2.0 GPa the resistance changes
to a Kondo-like feature due to magnetic impurities used to catalyse the
nanotube formation. Above 2.0 GPa, they become metallic and at about 2.4 GPa
the resistance decreases dramatically around 3 K suggesting a superconducting
transition.
