Stripe Correlations of Spins and Holes in Cuprate Superconductors

It is argued that the stripe order of spins and holes found in La2−xSrxNiO4+δ is a useful model for spin and charge correlations in La2−xSrxCuO4. A direct connection with the cuprates is now established by neutron diffraction evidence for stripe order in La1.6−xNd0.4SrxCuO4 withx=0.12. The experimental work has stimulated new theoretical ideas.