Parallel spin stripes and their coexistence with superconducting ground states at optimal and high doping in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>La</mml:mi><mml:mrow><mml:mn>1.6</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Nd</mml:mi><mml:mrow><mml:mn>0.4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mi>Sr</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>CuO</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>
Qianli Ma, Kirrily C. Rule, Zachary W. Cronkwright, Mirela Dragomir, Gabrielle Mitchell, Evan M. Smith, Songxue Chi, Alexander I. Kolesnikov, Matthew B. Stone, Bruce D. Gaulin
Abstract
Three-dimensional, commensurate long-range magnetic order in La 2 CuO 4 quickly evolves to quasi-twodimensional, 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 lowenergy dynamic spectral weight of parallel stripe fluctuations grows with decreasing temperature and saturates below T c .