Are room temperature superconductors theoretically possible, and through what mechanism?

Question

At the moment, the highest critical temperature superconductor known to science (or myself, at least) is mercury barium calcium copper oxide. With a $T_{c}$ of roughly 133 K, that's well above the boiling point of nitrogen, and even well above the boiling point of oxygen, though using liquid oxygen to cool down anything probably wouldn't be the brightest idea. However, it's nowhere near the type of temperature that can cheaply be maintained, and far further still from the temperatures found naturally.

Are room-temperature superconductors forbidden by any known theory? If not, is there any known theory stating a mechanism by which they could operate, and what is the mechanism?

Answer 1

Room-temperature superconductors are not forbidden by any known theory. However, discovery is difficult, while engineering is possible. One thing about superconductors is that they do not give off any heat. So cooling is just a function of fighting the insulation. With the discovery of super-insulators, the rest is just engineering!

Here's an interesting wikipedia article on the subject.

It should, however, be noted that these kinds of quantum states may be more common than non-quantum states. For instance, it is believed that neutron stars may be in a quantum state of some sort (perhaps super fluidity - I'm going from memory, so the details are a little hazy).

One thing that is clear is that with the application of extraordinary pressures, the transition temperature generally goes up. The highest pressures are supplied by diamond anvils, where the pressure chamber is formed between the points of two diamonds. Researchers generalise to other control parameters (Temperature, Pressure, Magnetic Field, ...), but generally speaking the control parameter is inimical to superconductivity (with pressure being the notable exception).

Answer 2

As mentioned here, metallic hydrogen may be a conventional superconductor up to about 290 K. This is then due to the low mass of the metal ions, this leads to a strong coupling of the electrons with the lattice vibrations.

Answer 3

The proton gas in the interiors of neutron stars$^1$ is likely to be both superfluid and superconducting at temperatures way above 300 K - with critical temperatures as high as $10^9$ K (e.g., Haskell & Sedrakian 2017).

This is because the behaviours of the "Cooper pairs" in this case are due to long range strong force interactions with a potential energy of $\sim$ MeV.

Thus there is nothing fundamental about low temperatures, they just need to be low enough that you can make the Cooper pairs with whatever long range interaction is being considered.

$^1$ There must be protons (and electrons) present in a neutron gas. The neutrons decay until the densities and hence Fermi energies of the protons and electrons are high enough to block further decay. Typically this means that $n_p/n_n$ is in the range 0.01-0.1.

Answer 4

Room temp superconductors are not forbidden fruit. It's simply finding right chemistry. Room temperature also implies they can exist in standard atmospheric pressures. So materials that can be used a RTDC don't require pressurization which in and of itself is energy intensive habit. Such a material would be revolutionary though would still require some modest amount of cooling to handle enormous energies transmitted thru it as a medium so as to reduce its resistance.

California is beginning massive program of burying major utility power lines underground because underground soil is ideal insulation and thermal sink for cables. More importantly cables invulnerable to heatwave, rain, snow, Wildfire, floods.