Fröhlich multipolarons

A study is made of the behavior of N nonrelativistic charged particles in a polarizable medium in which they form polarons. Through the exchange of phonons, the polarons attract each other, and a new bound state arises – the Fröhlich multipolaron. The energy and effective mass of the multipolaron depend strongly on the number $N$ of particles that form it, and this leads to an energy instability of the multipolaron. It is shown that systematic allowance for the mutual Coulomb repulsion of the particles forming the cluster restore its energy stability.