Superfluid density as a guide to optimal superconductivity in doped low   dimensional antiferromagnets
  Following the direct observation of abrupt changes in the superconducting ground state in doped low dimensional antiferromagnets, we have identified a phase transition where superconductivity is optimal. The experiments indicate the presence of a putative quantum critical point associated with the emergence of a glassy state. This mechanism is argued to be an intrinsic property and as such largely independent of material quality and the level of disorder. 
Christos Panagopoulos