Magnesium becomes a possible superconductor near the 2D limit or ultra-thin films

Amazing stuff!

"... challenging the textbook paradigm that states only certain elements in the periodic table can be superconductors. ... have shown that the phenomenon of quantum confinement can turn non-superconducting elements into superconductors. ...

Here by quantum confinement I mean the phenomenon in which the energy of a quantum particle, such as an electron, can greatly increase when it's spatially confined, an effect that is ultimately due to the Heisenberg uncertainty principle—the more you constrain the spatial position of a quantum particle, the larger its energy fluctuations become. ...

Surprisingly, in this case, the critical temperature that can be reached by miniaturizing magnesium nano-sheets of about half nanometer thickness is as high as 10 Kelvin. This is an important consideration because it means that liquid helium can be used to cool the material down to achieve superconductivity instead of using much more expensive cooling technologies. ..."

From the abstract:

"It is known that noble metals such as gold, silver and copper are not superconductors; this is also true for magnesium. This is due to the weakness of the electron–phonon interaction, which makes them excellent conductors but not superconductors.

As has recently been shown for gold, silver and copper, and even for magnesium, it is possible that in very particular situations, superconductivity may occur. Quantum confinement in thin films has been consistently shown to induce a significant enhancement of the superconducting critical temperature in several superconductors.

It is therefore an important fundamental question whether ultra-thin film confinement may induce observable superconductivity in non-superconducting metals such as magnesium.

We study this problem using a generalization, in the Eliashberg framework, of a BCS theory of superconductivity in good metals under thin-film confinement. By numerically solving these new Eliashberg-type equations, we find the dependence of the superconducting critical temperature on the film thickness, L.

This parameter-free theory predicts superconductivity in very thin magnesium films. We demonstrate that this is a fine-tuning problem where the thickness must assume a very precise value, close to half a nanometer."

Magnesium becomes a possible superconductor near the 2D limit

Possible Superconductivity in Very Thin Magnesium Films (open access)