2-DIMENSIONAL AND 3-DIMENSIONAL POLARONS WITH EXTENDED COHERENT STATES

The properties of two- and three-dimensional polarons are investigated with the use of extended coherent states. In the weak-coupling limit, the obtained expansions for the ground-state energy and effective mas s to the second order in the coupling constant alpha are the same as t he previous exact ones. Moreover, in the intermediate-coupling regime, the numerical results for the ground-state energy and effective mass agree with the results by the Feynman path-integral method, and perhap s closer to the exact results than the Feynman ones. It is suggested t hat the present approach should be an effective one in polaron physics .