Wrap up

Wrap up
  
In a very short wrap up discussion, it was agreed that one common link between many different families of unconventional superconductors is that they appear in a dome-shape region around the extrapolated quantum critical point of another phase that appears at higher temperature. In that case, the mechanism for superconductivity is likely to be the exchange of collective modes associated with the phase that would disappear at this quantum critical point in the absence of superconductivity. Materials falling into this type of explanation include Bechgaard salts, many pnictides, heavy fermions, MnP, SrTiO3. Electron-doped cuprates may fall into this category, but this is still disputed. The most commonly encountered quantum critical point in the previous examples is antiferromagnetic, but it is not the only possibility. The case of hole-doped cuprates is still the most controversial: does the dome surround a quantum critical point, and if it does, what is its nature? Participants agreed that we must look closely at symmetry sensitive experiments and recent ARPES from China that may be sufficiently detailed and accurate to give indications of the mechanism.