Scale-free structural organization of oxygen interstitials in La2CuO4+y
Scale-free structural organization of oxygen interstitials in La2CuO4+y
复制标题
DOI：
10.1038/nature09260
复制
发表时间：
2010-08-12
期刊：
影响因子：
64.8
通讯作者：
Bianconi, Antonio
中科院分区：
文献类型：
--
作者：
Fratini, Michela;Poccia, Nicola;Bianconi, Antonio
众所周知，过渡金属氧化物（1-3），包括高过渡温度（高t -c）氧化铜超导体（4-7）的微观结构是复杂的。当有氧气间隙或空位时尤其如此，这会影响体积性质。例如，在Sr2O1+yCuO2（参考文献9）、YBa2Cu3O6+y（参考文献10）和La2CuO4+y（参考文献11-15）中，分隔超导CuO2平面的间隔层中的氧间隙发生了有序现象，导致转变温度升高，但空穴浓度没有变化。众所周知，复杂系统通常具有尺度不变的结构组织16，但迄今为止还没有在高t -c材料中发现。本文报道了La2CuO4+y高t -c超导体的La2O2+y间隔层中氧间隙的有序分布具有分形特征，其最大极限尺寸为400 μ m。有趣的是，这些掺杂剂的分形分布似乎增强了高温下的超导性。
It is well known that the microstructures of the transition-metal oxides(1-3), including the high-transition-temperature (high-T-c) copper oxide superconductors(4-7), are complex. This is particularly so when there are oxygen interstitials or vacancies 8, which influence the bulk properties. For example, the oxygen interstitials in the spacer layers separating the superconducting CuO2 planes undergo ordering phenomena in Sr2O1+yCuO2 (ref.9), YBa2Cu3O6+y (ref.10) and La2CuO4+y (refs 11-15) that induce enhancements in the transition temperatures with no changes in hole concentrations. It is also known that complex systems often have a scale-invariant structural organization 16, but hitherto none had been found in high-T-c materials. Here we report that the ordering of oxygen interstitials in the La2O2+y spacer layers of La2CuO4+y high-T-c superconductors is characterized by a fractal distribution up to a maximum limiting size of 400 mu m. Intriguingly, these fractal distributions of dopants seem to enhance superconductivity at high temperature.