Title: Particular type of gap in the spectrum of multiband superconductors,
Abstract: We show, that in contrast to the free electron model (standard BCS model), a
particular gap in the spectrum of multiband superconductors opens at some
distance from the Fermi energy, if conduction band is composed of hybridized
atomic orbitals of different symmetries. This gap has composite
superconducting-hybridization origin, because it exists only if both the
superconductivity and the hybridization between different kinds of orbitals are
present. So for many classes of superconductors with multiorbital structure
such spectrum changes should take place. These particular changes in the
spectrum at some distance from the Fermi level result in slow convergence of
the spectral weight of the optical conductivity even in quite conventional
superconductors with isotropic s-wave pairing mechanism.