Bond-centered, bond-ordered stripes in doped antiferromagnets

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Motivated by recent inelastic neutron scattering experiments on cuprates, we discuss the formation of bond order in the stripe phase. We suggest that the spin Peierls order emerges in hole-rich domain walls (DWs) formed between hole-poor regions in which long-range antiferromagnetic (AF) correlations exist. On the example of a single stripe we analyze the stability of such structures. The motion of a hole inside the DW which takes the form of a bond ordered ladder is in principle unrestricted. The hole hopping in domains is to some extent obscured by the fact that a moving hole spoils AF correlations. The propagation of a hole along the stripe which takes the form of the ladder-like domain wall that separates antiphase AF domains is a combination of these two types of motion occurring in two different environments. By analyzing the energy dispersion of a quasiparticle propagating along the bond-centered, bond-ordered stripe and of a quasiparticle propagating along the site-centered stripe we deduce that bond ordered stripes are stable at the total doping level 1/8 and the linear stripe-filling level 1/2. This conclusion seems to be relevant to the nature of the stripe phase in La₁.875 Ba₀.125 Cu O₄.