Are graphene and carbon nanotubes superconductors under atmospheric pressure? What are their critical temperature and current density for superconductivity?
No graphones and carbon nanotubes require temperatures near absolute zero to become superconductive.
last I checked there has been a research published in Nature magazine last October that has found a material, combination of The hydrogen, carbon, and sulfur compound that operates as a superconductor at up to 59 degrees Fahrenheit.
The catch: It does this under extreme pressures difficult to produce.
here is a link
You ask about pressure without regard to temperature. With superconductivity, temperature is all important. A bit of searching on the web shows that some researchers observed superconductivity in nanotubes at temperatures close to 20K. Looking at the article, there is no mention of pressure. It won't be atmospheric pressure because nitrogen and oxygen condense around 80K.
If you want to see room temperature, atmospheric pressure superconductors, graphene or otherwise, you will have a long wait.