  The effect of a quantum phase transition associated with the appearance of
the fermion condensate in an electron liquid on the properties of
superconductors is considered. It is shown that the electron system in both
superconducting and normal states exhibits characteristic features of a quantum
protectorate after the point of this fermion-condensation quantum phase
transition. The single-particle spectrum of a superconductor can be represented
by two straight lines corresponding to two effective masses $M^*_{FC}$ and
$M^*_{L}$. The $M^*_{FC}$ mass characterizes the spectrum up to the binding
energy $E_0$ and $M^*_L$ determines the spectrum at higher binding energies.
Both effective masses are retained in the normal state. These results are used
to explain the lineshape of single-particle excitations and other properties of
high-$T_c$ superconductors and are in a good agreement with recent experimental
data.
