A long standing puzzle regarding the disparity of local and long range CuO₆ octahedral tilt correlations in the underdoped regime of La₂₋xBaxCuO₄ is addressed by utilizing complementary neutron powder diffraction and inelastic neutron scattering (INS) approaches. Long-range and static CuO₆ tilt order with orthogonally inequivalent Cu-O bonds in the CuO₂ planes in the low temperature tetragonal (LTT) phase is succeeded on warming through the low-temperature transition by one with orthogonally equivalent bonds in the low temperature orthorhombic (LTO) phase. In contrast, the signatures of LTT-type tilts in the instantaneous local atomic structure persist on heating throughout the LTO crystallographic phase on the nanoscale, although becoming weaker as temperature increases. Analysis of the INS spectra for the x = 1/8 composition reveals the dynamic nature of the LTT-like tilt fluctuations within the LTO phase and their 3D character. The doping dependence of relevant structural parameters indicates that the magnitude of the Cu-O bond anisotropy has a maximum at x = 1/8 doping where bulk superconductivity is most strongly suppressed, suggesting that the structural anisotropy might be influenced by electron-phonon coupling and the particular stability of the stripe-ordered phase at this composition. The bond-length modulation that pins stripe order is found to be remarkably subtle, with no anomalous bond length disorder at low temperature, placing an upper limit on any in-plane Cu-O bondlength anisotropy. The results further reveal that although appreciable octahedral tilts persist through the high-temperature transition and into the high temperature tetragonal (HTT) phase, there is no significant preference between different tilt directions in the HTT regime. As a result, this study also exemplifies the importance of a systematic approach using complementary techniques when investigating systems exhibiting a large degree of complexity and subtle structural responses.
Bozin, Emil S., et al. "Reconciliation of local and long-range tilt correlations in underdoped La<sub>2-x</sub>Ba<sub>x</sub>CuO<sub>4</sub>(0 ≤ x ≤ 0.155)." Physical Review. B, Condensed Matter and Materials Physics, vol. 91, no. 5, Feb. 2015. https://doi.org/10.1103/PhysRevB.91.054521
Bozin, Emil S., Zhong, Ruidan, Knox, Kevin R., Gu, Genda, Hill, John P., Tranquada, John M., & Billinge, Simon J. L. (2015). Reconciliation of local and long-range tilt correlations in underdoped La<sub>2-x</sub>Ba<sub>x</sub>CuO<sub>4</sub>(0 ≤ x ≤ 0.155). Physical Review. B, Condensed Matter and Materials Physics, 91(5). https://doi.org/10.1103/PhysRevB.91.054521
Bozin, Emil S., Zhong, Ruidan, Knox, Kevin R., et al., "Reconciliation of local and long-range tilt correlations in underdoped La<sub>2-x</sub>Ba<sub>x</sub>CuO<sub>4</sub>(0 ≤ x ≤ 0.155)," Physical Review. B, Condensed Matter and Materials Physics 91, no. 5 (2015), https://doi.org/10.1103/PhysRevB.91.054521
@article{osti_1182483,
author = {Bozin, Emil S. and Zhong, Ruidan and Knox, Kevin R. and Gu, Genda and Hill, John P. and Tranquada, John M. and Billinge, Simon J. L.},
title = {Reconciliation of local and long-range tilt correlations in underdoped La<sub>2-x</sub>Ba<sub>x</sub>CuO<sub>4</sub>(0 ≤ x ≤ 0.155)},
annote = {A long standing puzzle regarding the disparity of local and long range CuO₆ octahedral tilt correlations in the underdoped regime of La₂₋xBaxCuO₄ is addressed by utilizing complementary neutron powder diffraction and inelastic neutron scattering (INS) approaches. Long-range and static CuO₆ tilt order with orthogonally inequivalent Cu-O bonds in the CuO₂ planes in the low temperature tetragonal (LTT) phase is succeeded on warming through the low-temperature transition by one with orthogonally equivalent bonds in the low temperature orthorhombic (LTO) phase. In contrast, the signatures of LTT-type tilts in the instantaneous local atomic structure persist on heating throughout the LTO crystallographic phase on the nanoscale, although becoming weaker as temperature increases. Analysis of the INS spectra for the x = 1/8 composition reveals the dynamic nature of the LTT-like tilt fluctuations within the LTO phase and their 3D character. The doping dependence of relevant structural parameters indicates that the magnitude of the Cu-O bond anisotropy has a maximum at x = 1/8 doping where bulk superconductivity is most strongly suppressed, suggesting that the structural anisotropy might be influenced by electron-phonon coupling and the particular stability of the stripe-ordered phase at this composition. The bond-length modulation that pins stripe order is found to be remarkably subtle, with no anomalous bond length disorder at low temperature, placing an upper limit on any in-plane Cu-O bondlength anisotropy. The results further reveal that although appreciable octahedral tilts persist through the high-temperature transition and into the high temperature tetragonal (HTT) phase, there is no significant preference between different tilt directions in the HTT regime. As a result, this study also exemplifies the importance of a systematic approach using complementary techniques when investigating systems exhibiting a large degree of complexity and subtle structural responses.},
doi = {10.1103/PhysRevB.91.054521},
url = {https://www.osti.gov/biblio/1182483},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {ISSN PRBMDO},
number = {5},
volume = {91},
place = {United States},
publisher = {American Physical Society (APS)},
year = {2015},
month = {02}}
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 764https://doi.org/10.1016/j.nima.2014.07.029