CNR-SPIN, Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy.
Science. 2012 Aug 17;337(6096):821-5. doi: 10.1126/science.1223532. Epub 2012 Jul 12.
The concept that superconductivity competes with other orders in cuprate superconductors has become increasingly apparent, but obtaining direct evidence with bulk-sensitive probes is challenging. We have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations with an incommensurate periodicity of ~3.2 lattice units in the copper-oxide planes of the superconductors (Y,Nd)Ba(2)Cu(3)O(6+)(x), with hole concentrations of 0.09 to 0.13 per planar Cu ion. The intensity and correlation length of the fluctuation signal increase strongly upon cooling down to the superconducting transition temperature (T(c)); further cooling below T(c) abruptly reverses the divergence of the charge correlations. In combination with earlier observations of a large gap in the spin excitation spectrum, these data indicate an incipient charge density wave instability that competes with superconductivity.
超导电性与铜酸盐超导体中其他序竞争的概念变得越来越明显，但使用体敏感探针获得直接证据具有挑战性。我们使用共振软 X 射线散射，在超导（Y，Nd）Ba（2）Cu（3）O（6+）（x）的铜氧化物平面中，以约 3.2 个晶格单位的非调谐周期性，识别出二维电荷涨落，其中每个平面 Cu 离子的空穴浓度为 0.09 至 0.13。在冷却到超导转变温度（T（c））时，涨落信号的强度和相关长度强烈增加；在 T（c）以下进一步冷却会突然逆转电荷相关性的发散。与自旋激发谱中存在大能隙的早期观测结果相结合，这些数据表明存在与超导竞争的初始电荷密度波不稳定性。
