Pervasive symmetry-lowering nanoscale structural fluctuations in the cuprate La2−xSrxCuO4

R. J. Spieker; M. Spaić; I. Khayr; X. He; D. Zhai; Z. W. Anderson; N. Bielinski; F. Ye; Y. Liu; S. Chi; S. Sarker; M. J. Krogstad; R. Osborn; D. Pelc; M. Greven

doi:10.1103/dvg1-w33v

Pervasive symmetry-lowering nanoscale structural fluctuations in the cuprate La2−xSrxCuO4

R. J. Spieker, M. Spaić, I. Khayr, X. He, D. Zhai, Z. W. Anderson, N. Bielinski, F. Ye, Y. Liu, S. Chi, S. Sarker, M. J. Krogstad, R. Osborn, D. Pelc, M. Greven

DOI 10.1103/dvg1-w33v · Physical Review B

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Abstract

The cuprate superconductors are among the most widely studied quantum materials, yet there remain fundamental open questions regarding their electronic properties and the role of structural degrees of freedom. Recent neutron and x-ray scattering measurements uncovered exponential scaling with temperature of the strength of orthorhombic fluctuations in the tetragonal phase of La2−xSrxCuO4 and Tl2Ba2CuO6+δ, unusual behavior that closely resembles prior results for the emergence of superconducting fluctuations, and that points to a common origin rooted in inherent correlated structural inhomogeneity. Here we use neutron and x-ray diffuse scattering to provide further insight into structural fluctuations in La2−xSrxCuO4. We perform measurements up to temperatures that approach the melting point of the undoped parent compound, and we investigate the effects of in situ in-plane uniaxial elastic stress and plastic deformation. Our neutron scattering results for the parent compound La2CuO4 reveal that short-range orthorhombic fluctuations persist to the maximum experimental temperature of nearly 1000 K, i.e., to a significant fraction of the crystallization temperature. At this temperature, the spatial characteristic length extracted from the momentum-space data is still about three lattice constants. The neutron scattering experiment enables quasistatic discrimination and reveals that the response is increasingly dynamic at higher temperatures. We also find that neither compressive elastic stress along the tetragonal [110] direction nor irreversible plastic deformation activating the 〈100〉[001] slip system significantly alter the robust orthorhombic fluctuations. Overall, these results support the notion that these fluctuations couple to subtle, underlying inhomogeneity that underpins the cuprate phase diagram. Finally, in La1.8Sr0.2CuO4, we uncover low-energy structural fluctuations at a nominally forbidden reflection that are distinct from the orthorhombic distortions. While the origin of these fluctuations is not clear, they might be related to the presence of extended defects such as dislocations or stacking faults.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
La2-xSrxCuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	40	Pressure unresolved	unknown