A POLARON-TYPE OF TREATMENT FOR HE-3 IN SUPERFLUID HE-4

A polaron-type model is proposed to describe the deformation in the su perfluid He-4 ground state, due to the presence of a (3)Ke atom. The i nteraction matrix element of the model is expressed in terms of the st ructure factor of the superfluid on the basis of the hypernetted chain approximation. Both the use of an intermediate polaron coupling theor y (rather than perturbation theory) and the determination of the preci se interaction matrix elements are crucial ingredients to obtain an ad equate theoretical description based on a polaron-type model. A genera lization of Feynman's path-integral technique is used for the treatmen t of intermediate coupling. The present work solves i.a. an outstandin g problem regarding the He-3 effective mass in superfluid He-4. The th eoretical result (an effective mass of 23123m(3) as compared to the ex perimental value of 2.3m(,) where m(3) is the bare He-3 mass) confirms that our formalism accurately describes the deformation cloud around the He-3 atom. Also the difference between the specific heat of the mi xture and the specific heat of pure superfluid He-4, and the diffusion of He-3 in the superfluid, are accurately explained as the result of the interaction of He-3 with the excitations of the superfluid.