McElroy K, Simmonds R W, Hoffman J E, Lee D-H, Orenstein J, Eisaki H, Uchida S, Davis J C
Department of Physics, University of California, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Nature. 2003 Apr 10;422(6932):592-6. doi: 10.1038/nature01496.
The electronic structure of simple crystalline solids can be completely described in terms either of local quantum states in real space (r-space), or of wave-like states defined in momentum-space (k-space). However, in the copper oxide superconductors, neither of these descriptions alone may be sufficient. Indeed, comparisons between r-space and k-space studies of Bi2Sr2CaCu2O8+delta (Bi-2212) reveal numerous unexplained phenomena and apparent contradictions. Here, to explore these issues, we report Fourier transform studies of atomic-scale spatial modulations in the Bi-2212 density of states. When analysed as arising from quasiparticle interference, the modulations yield elements of the Fermi-surface and energy gap in agreement with photoemission experiments. The consistency of numerous sets of dispersing modulations with the quasiparticle interference model shows that no additional order parameter is required. We also explore the momentum-space structure of the unoccupied states that are inaccessible to photoemission, and find strong similarities to the structure of the occupied states. The copper oxide quasiparticles therefore apparently exhibit particle-hole mixing similar to that of conventional superconductors. Near the energy gap maximum, the modulations become intense, commensurate with the crystal, and bounded by nanometre-scale domains. Scattering of the antinodal quasiparticles is therefore strongly influenced by nanometre-scale disorder.
简单晶体固体的电子结构可以完全用实空间（r空间）中的局域量子态或动量空间（k空间）中定义的波状态来描述。然而，对于铜氧化物超导体，单独使用这两种描述可能都不够。事实上，对Bi2Sr2CaCu2O8+δ（Bi-2212）的r空间和k空间研究之间的比较揭示了许多无法解释的现象和明显的矛盾。在这里，为了探究这些问题，我们报告了对Bi-2212态密度中原子尺度空间调制的傅里叶变换研究。当将这些调制分析为准粒子干涉产生时，调制产生的费米面和能隙元素与光电子能谱实验结果一致。多组色散调制与准粒子干涉模型的一致性表明不需要额外的序参量。我们还探究了光电子能谱无法探测到的未占据态的动量空间结构，发现其与占据态的结构有很强的相似性。因此，铜氧化物准粒子显然表现出与传统超导体类似的粒子-空穴混合。在能隙最大值附近，调制变得强烈，与晶体呈共格，且由纳米尺度的畴界定。因此，反节点准粒子的散射受到纳米尺度无序的强烈影响。
