A suggested 4 x 4 structure in underdoped cuprate superconductors: a   Wigner supersolid
  A wave function is proposed for the "$4\times 4$" inhomogeneous structures observed on cuprate superconductors. It is based on the Gutzwiller-RVB technique proposed in recent papers, and consists of a Wigner solid of hole pairs embedded in a sea of d-wave spin singlet pairs. Arguments are given that the nodal quasiparticles may remain unscattered and even superconducting on such a structure. 
P. W. Anderson