Convergence of energy-dependent incommensurate antiferromagnetic neutron scattering peaks to commensurate resonance in underdoped bilayer cuprates

Abstract

The recently discovered coexistence of incommensurate antiferromagnetic neutron scattering peaks and commensurate resonance in underdoped YBa${}_2$Cu${}_3$O${}_{6+x}$ is calling for an explanation. Within the t-J model, the doping and energy dependence of the spin dynamics of the underdoped bilayer cuprates in the normal state is studied based on the fermion-spin theory by considering the bilayer interactions. Incommensurate peaks are found at $[(1\pm \hat{I}´)\ddot{I}€,\ddot{I}€]$ and $[\ddot{I}€,(1\pm \hat{I}´)\ddot{I}€]$ at low energies with $\hat{I}´$ initially increasing with doping at low dopings and then saturating at higher dopings. These incommensurate peaks are suppressed, and the parameter $\hat{I}´$ is reduced with increasing energy. Eventually it converges to the $[\ddot{I}€,\ddot{I}€]$ resonance peak. Thus the recently observed coexistence is interpreted in terms of bilayer interactions.

15 pages, Revtex, five figures are included, accepted for publication in Phys. Rev. B