Pb(2)-phosphate is a crystalline compound. They are creating a 2D film of it using vapor deposition, then doping it with copper ions. This is a standard process in semiconductor manufacturing. There are room temperature ambient pressure materials doped to create quantum wells in production right now. They are not super conductors, because the quantum wells are merely impurities that reduce the resistance of the material. I believe this paper is claiming a crystal so saturated with quantum wells that it conducts primarily through quantum wells with almost no resistance.