Two-dimensional geometry of spin excitations in the high-transition-temperature superconductor YBa2Cu3O6+x

• Published in: Nature (London) Vol. 430; no. 7000; pp. 650 - 654
• Main Authors: Hinkov, V, Pailhès, S, Bourges, P, Sidis, Y, Ivanov, A, Kulakov, A, Lin, C T, Chen, D P, Bernhard, C, Keimer, B
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 05-08-2004
• Subjects: Condensed Matter; Crystals; Geometry; High temperature superconductors; Physics; Strongly Correlated Electrons; Superconductivity
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature02774

The fundamental building block of the copper oxide superconductors is a Cu4O4 square plaquette. The plaquettes in most of these materials are slightly distorted to form a rectangular lattice, for which an influential theory predicts that high-transition-temperature (high-T(c)) superconductivity is nucleated in 'stripes' aligned along one of the axes. This theory received strong support from experiments that indicated a one-dimensional character for the magnetic excitations in the high-T(c) material YBa2Cu3O6.6 (ref. 4). Here we report neutron scattering data on 'untwinned' YBa2Cu3O6+x crystals, in which the orientation of the rectangular lattice is maintained throughout the entire volume. Contrary to the earlier claim, we demonstrate that the geometry of the magnetic fluctuations is two-dimensional. Rigid stripe arrays therefore appear to be ruled out over a wide range of doping levels in YBa2Cu3O6+x, but the data may be consistent with liquid-crystalline stripe order. The debate about stripes has therefore been reopened.