# Particular type of gap in the spectrum of multiband superconductors

## TL;DR

This paper demonstrates that in multiband superconductors with hybridized orbitals, a unique spectral gap appears away from the Fermi energy, affecting optical conductivity and dependent on both hybridization and superconductivity.

## Contribution

It reveals a novel spectral gap in multiband superconductors caused by hybridization, distinct from the standard BCS model, with implications for optical properties.

## Key findings

- A specific gap appears away from the Fermi level in certain multiband superconductors.
- The gap's existence depends on both hybridization and superconductivity.
- Spectral weight convergence in optical conductivity is slower due to this gap.

## 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.