ALEXANDROV, A.S. and BEERE, W.H., 1995. Collective excitations and screening properties of a condensed charged Bose gas. Physical Review B, 51 (9), pp. 5887-5891
The Bogoliubov–de Gennes (BdG) type equations are derived for the Coulomb Bose gas describing the electrodynamics of charged bosons. The gauge invariant dielectric response function and collective excitations of a charged Bose gas at T=0 are found. We find a plasmon branch which is the same as the single-particle Bogoliubov spectrum in agreement with the textbook result. The superconducting properties of the charged Bose gas are verified. A gauge-invariant formalism for calculating the response of the supracondensate particles is proposed.