On the strongly correlated quantum matter paradigm : magnetism–superconductivity redux

The principal dilemma of real-space pairing versus pairing of electron–lattice (or other) origin can, in our view, be addressed properly for strongly correlated systems by explaining an overall phase diagram involving different magnetic and superconducting phases within a single consistent framework. In this comment, particular emphasis is put on the connection/coexistence with antiferromagnetism, as well as on the existence of the upper critical concentration for the disappearance of superconductivity in high-temperature superconductors. The analysis provides clear evidence for the kinetic exchange as being a natural origin of both phenomena, in conjunction with the strongly correlated motion (hopping) of the carriers. A subtle difference between the exchange- and the paramagnon-induced pairing is also noted. An analogical scenario is advocated briefly for heavy fermion systems. Some further tests are proposed in order to provide a convincing proof of the magnetic origin, combined with the strongly correlated nature of carriers, of this unconventional superconductivity and its universality in strongly correlated systems, solid-state or otherwise. The role of strong correlations among the fermions composing Cooper pairs is emphasized