The article linked here is rubbish, CrSBr is not a meta material and also not a superconductor. It is a layered semiconductor. However, the Nature article they link to is quite interesting. The background is in cavity engineering, which is where one tries to modify intrinsic material properties by coupling to light "strongly". This is usually done by creating a cavity (think two opposing mirrors around the material) and have light bounce back and forth.

Here instead they don't need to use mirrors, but the refractive index is different enough to trap light in the material, and the electronic properties seem to be quite sensitive to the light because the magnetic phase is sensitive to magnetic fields and the different magnetic phases have quite different electronic properties. So all in all they find a strong light-matter coupling but only below 132K (the critical temperature of the magnetic phase).