Fermionic Casimir effect in case of Andreev reflection

– We describe the Fermionic Casimir effect in the case of two spherical superfluid scatterers immersed in a normal Fermi system. It is shown that due to the focusing property of Andreev reflection this new Casimir-like energy is significantly enhanced when compared to the case of normal scatterers with specular reflection. Introduction. – If two or more voids (or hard-wall scatterers) are formed in a normal uniform Fermi system, effective Casimir-like interactions between such voids appear [1,2]. For example, two spherical voids of radius a with distance between their centers R in a Fermi medium at zero temperature and with Fermi wave vector k F would interact with each other with the effective potential energy