Parallel spin stripes and their coexistence with superconducting ground states at optimal and high doping in La_{1.6−x}Nd_{0.4}Sr_{x}CuO_{4}

Abstract

Three-dimensional, commensurate long-range magnetic order in La_{2}CuO_{4} quickly evolves to quasi-two-dimensional, incommensurate correlations upon doping with mobile holes, and superconductivity follows for x as small as 0.05 in the La_{2−x}Sr_{x}/Ba_{x}CuO_{4} family of superconductors. The onset of superconductivity in these systems is known to be coincident with a remarkable rotation of the incommensurate spin order from “diagonal stripes” below x = 0.05 to “parallel stripes” above. However, little is known about the spin correlations at optimal and high doping levels, around and beyond the proposed quantum critical point for the pseudogap phase, p^{*}. Here, we present elastic and inelastic neutron scattering measurements on single crystals of La_{1.6−x}Nd_{0.4}Sr_{x}CuO_{4} with x = 0.125, 0.19, 0.24, and 0.26 and show that two-dimensional, quasistatic, parallel spin stripes have an onset at temperatures such that the parallel spin stripe phase extends beyond p^{*} and envelops the entirety of superconducting ground states in this system. We also show that the elastic order parameter for parallel spin stripes at optimum doping, x = 0.19, displays an inflection point at superconducting T_{c}, while the low-energy dynamic spectral weight of parallel stripe fluctuations grows with decreasing temperature and saturates below T_{c}.