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Local structure of Sr 2 CuO 3.3 , a 95 K cuprate superconductor without CuO 2 planes

Abstract : The local structure of the highly "overdoped" 95 K superconductor Sr 2 CuO 3.3 determined by Cu K X-ray absorption fine structure (XAFS) at 62 K in magnetically oriented samples shows that: 1) the magnetization is perpendicular to the c axis; 2) at these levels of precision the Cu sublattice is tetragonal in agreement with the crystal structure; the O sublattice has: 3) continuous-Cu-O-chains that orient perpendicular to an applied magnetic field; 4) approximately half-filled-Cu-O-chains that orient parallel to this field; 5) a substantial number of apical O vacancies; 6) O ions at some apical positions with expanded Cu-O distances; and 7) interstitial positions that imply highly displaced Sr ions. These results contradict the universally accepted features of cuprates that require intact CuO 2 planes, magnetization along the c axis, and a termination of the superconductivity when the excess charge on the CuO 2 Cu ions exceeds 0.27. These radical differences in charge and structure demonstrate that this compound constitutes a separate class of Cu-O-based superconductors in which the superconductivity originates in a different , more complicated structural unit than CuO 2 planes while retaining exceptionally high transition temperatures.
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Contributor : Gianguido Baldinozzi <>
Submitted on : Tuesday, May 26, 2020 - 12:14:28 AM
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Steven Conradson, Theodore Geballe, Changqing Jin, Lipeng Cao, Gianguido Baldinozzi, et al.. Local structure of Sr 2 CuO 3.3 , a 95 K cuprate superconductor without CuO 2 planes. Proceedings of the National Academy of Sciences of the United States of America , National Academy of Sciences, 2020, pp.4565-4570. ⟨10.1073/pnas.1918890117⟩. ⟨hal-02484590⟩



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