  By drilling periodic thru-holes in a suspended film, the phonon system can be
modified. Being motivated by the BCS theory, the technique, so-called phonon
engineering, was applied to a niobium sheet. The newly emergent high-$T_{c}$
superconductivity, however, cannot be accounted for by the BCS theory. Rather,
its exposed configuration, namely a square-lattice oxygen network, is
reminiscent of the copper-oxygen plane in cuprate high-$T_c$ superconductors.
It turns out that its magnetic result is consistent with the principle of giant
atom, which was developed by another heroes of superconductivity, Fritz London
and John Slater, in the 1930s, several decades earlier than the propagation of
BCS theory. The superconducting transition feature is discussed on the basis of
a comprehensive theory of the giant atom -- the theory of hole
superconductivity.
