Gaetano Campi, Alessandro Ricci, Nicola Poccia, Luisa Barba, G. Arrighetti, Manfred Burghammer, Alessandra-Stella Caporale, Antonio Bianconi
Oxygen chain fragments are known to appear at the insulator-to-superconductor transition in YBa2Cu3O6+y. However the self organization and the size distribution of oxygen chain fragments is not known. Here we contribute to fill this gap, using scanning micro-X-ray diffraction a novel non invasive imaging method based on advances in focusing synchrotron radiation beam. This novel approach allows us to probe both real-space and k-space of high-quality YBa2Cu3O6.33 single crystals with Tc=7K. We report compelling evidence for a nematic phase of nanoscale striped puddles with Ortho-II structure made of chain fragments in the basal Cu(1) plane with local oxygen concentration y larger than 0.5. The size of the Ortho-II puddles span a range between 2 and 9 nanometers. The real space imaging with micron resolution of the granular network of Ortho-II puddles shows that superconductivity at low hole doping in this system occurs in an inhomogeneous network of nanoscale oxygen ordered patches interspersed with oxygen depleted regions. The manipulation by thermal treatments of the Ortho-II puddles has been investigated focusing on their formation and evolution at the order-to-disorder phase transition at T=350 K.
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http://arxiv.org/abs/1212.2742
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