Abstract
Three-dimensional, commensurate long-range magnetic order in La2CuO4 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 La2−xSrx/BaxCuO4 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 La1.6−xNd0.4SrxCuO4 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 Tc, while the low-energy dynamic spectral weight of parallel stripe fluctuations grows with decreasing temperature and saturates below Tc.3 MoreReceived 2 September 2020Revised 12 March 2021Accepted 29 April 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.023151Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasSuperconductivityPhysical SystemsCupratesHigh-temperature superconductorsTechniquesNeutron scatteringCondensed Matter, Materials & Applied Physics
Highlights
The microscopic mechanism underlying high-temperature superconductivity in copper oxide materials has been hotly debated since its original discovery in 1986 [1,2], through to the present day [3,4,5,6,7,8,9,10,11,12,13,14,15,16]
On the basis of these measurements we propose a phase diagram for parallel spin stripes in Nd-LSCO that uncouples the connection between static magnetism and the pseudogap phase
Recent nuclear magnetic resonance (NMR) and ultrasound experiments at high magnetic field in LSCO have reported glassy antiferromagnetism existing to higher doping levels than previously believed, up to ∼0.19 [59]
Summary
The microscopic mechanism underlying high-temperature superconductivity in copper oxide materials has been hotly debated since its original discovery in 1986 [1,2], through to the present day [3,4,5,6,7,8,9,10,11,12,13,14,15,16]. The x = 0.26 doping level is close to the end of superconductivity in Nd-LSCO [44], while the x = 0.24 sample is close to the proposed quantum critical point, p∗ = 0.23 ± 0.005, associated with the pseudogap phase in Nd-LSCO [45] These measurements show welldefined, but non-resolution-limited magnetic Bragg peaks to appear at low temperatures in all of these samples, significantly extending the range of concentrations over which static, parallel spin stripes have been observed in Nd-LSCO and challenging the notion that static magnetism ends at or before p∗ [39]. We report that the effective Cu ordered moment within the spin stripe structure at low temperatures drops off monotonically and steeply from x = 0.125 to higher dopings, with a concomitant decrease in the in-plane correlation length This provides a reasonable explanation for why this signal has been so difficult to observe until now. We conclude that this parallel spin stripe state, in contrast with the parallel charge stripe state, does not compete with superconductivity in Nd-LSCO, but is a prerequisite for it
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