Fermi surface reconstruction from bilayer charge ordering in the   underdoped high temperature superconductor YBa2Cu3O6+x
  We show that the distribution of quantum oscillation frequencies observed over a broad range of magnetic field can be reconciled with the wavevectors of charge modulations found in nuclear magnetic resonance and resonant x-ray spectroscopy experiments in underdoped YBa2Cu3O6+x within a model of biaxial charge ordering occurring in a bilayer CuO2 planar system. Bilayer coupling introduces the possibility of different period modulations and quantum oscillation frequencies corresponding to each of the bonding and antibonding bands, which can be reconciled with recent experimental observations 
N. Harrison, S. E. Sebastian
cond-mat.supr-con cond-mat.str-el