Response: Magnon-Exchange Pairing and Superconductivity

Abstract

A recent suggestion by G. Chen and W. A. Goddard (1) for electron pairing in high temperature superconducting oxides reintroduced the concept of magnon exchange as a replacement for the standard Bardeen-Cooper-Schrieffer (BCS) phonon exchange (2). This suggestion received considerable attention because [on the basis of microscopic calculations (1, 3) for small clusters] it provided precise estimates of the various superconducting transition temperatures T_c in the cuprate ceramics and calculated an upper bound T^(max)_c = 232 K. We show that, within the Chen-Goddard mechanism, the estimates of T_c are incorrect because Chen and Goddard use an equation for T_c appropriate only for weak coupling and that their T^(max)_c is spurious, as there is no upper bound when the correct expression is used.