Self-generated electronic heterogeneity and quantum glassiness in the   high temperature superconductors
  We present a systematic study of the spin and charge dynamics of copper oxide superconductors as a function of carrier concentration $x$. Our results portray a coherent physical picture, which reveals a quantum critical point at optimum doping ($x=x_{opt}$), and the formation of an inhomogeneous glassy state at $x < x_{opt}$. This mechanism is argued to arise as an intrinsic property of doped Mott insulators, and therefore to be largely independent of material quality and level of disorder. 
C. Panagopoulos and V. Dobrosavljevic