I wonder if the forced phase-change the confinement causes applies to other contexts? Could we use a similar trick to force superconductive materials into their low-temperature superconductive phase at higher temperatures?
(Repost of the same comment from the other thread about the same paper)
I'm by no means an expert, and I may be wrong, but I personally don't think that it's possible to achieve superconductivity at room temperature and normal pressure using this approach at the current state of the art.
If you take a look at the phase diagram of the water [1] you could notice that the pressure required to crystallize water at temperature near 105°C is something near p_freeze = 2.5⋅10^9 Pa. However, the water is inside of the nanotubes of radius r = 0.5⋅10^(-9) m (the article says about the tubes being of diameter 1.05 nm). Such small radius creates significant surface tension (the same force that allows soap bubbles to exist) which is expressed by equation [2] as Δp = γ/r. According to
[3] the surface tension coefficient for water at 105°C is γ = 58⋅10^(-3) N/m, so Δp ≈ 1.2⋅10^8 Pa. The required for crystallization and the actual pressures differ in just one order of magnitude.
But the reasoning above used the macroscopic physical laws, and of course one could expect deviations from them when thinking about diameters as small as 4 water molecule diameters. Of course there is still no theoretical model that describes this configuration and calculates exact values of p_freeze and Δp precisely for it. But such model don't have to change the orders of magnitude in the problem, just estimate factors of order of 1, and we could use rough intuition gained previously about the process even without such model.
So if you try to apply these intuitions to the superconductivity you immediately meet difficulties because all known superconductors are in solid state, not liquid. It could be overcome by putting it to the nanotubes in liquid state and then letting it crystallize. Let's assume that this is possible. Evidence [4] suggests that to get a superconductor at high temperatures it requires to have pressure of order 10^11-10^12 Pa. This pressure is two orders of magnitude higher than the one required to freeze water at 100°C. That means that surface tension coefficient in such material should be two orders of magnitude higher than in liquid H2O to create pressure of order of magnitude required for phase transition to superconducting state.
I wasn't able to find data about surface tension in superconducting materials like like H2S mentioned in [4], but I doubt that it is 100 larger than surface tension in water. And it is impossible to significantly increase pressure by decreasing radius of tubes because this radius is already of order of molecules size. So I don't think that it is possible to get high temperature superconductors at normal pressure and room temperature using nanotubes and already known superconducting materials.
