Observable NMR signal from circulating current order in YBCO
  Assuming, as suggested by recent neutron scattering experiments, that a broken symmetry state with orbital current order occurs in the pseudo-gap phase of the cuprate superconductors, we show that there must be associated equilibrium magnetic fields at various atomic sites in the unit cell, which should be detectable by NMR experiments. 
Samuel Lederer and Steven A. Kivelson
cond-mat.supr-con cond-mat.str-el