Fermion bound states from Yukawa coupling with periodic bosonic background

The Yukawa coupling of fermions with a periodic bosonic background is shown to give rise to several bound states to the fermionic spectrum, with some bound states gluing together around specific energy eingenvalues as the Yukawa coupling increases. This effect induces the presence of degenerate energy states inside the fermionic gap and may be of current interest.
Comment: to appear in EPJ C as a letter