The increase of Binding Energy and Enhanced Binding in Non-Relativistic QED

We consider a Pauli-Fierz Hamiltonian for a particle coupled to a photon field. We discuss the effects of the increase of the binding energy and enhanced binding through coupling to a photon field, and prove that both effects are the results of the existence of the ground state of the self-energy operator with total momentum $P = 0$.Comment: 14 pages, Latex. Final version, accepted for publication in J. Math. Phy