Analysis of the Pairing Interaction in the Cuprates
Analysis of the Pairing Interaction in the Cuprates
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Cuprates配对相互作用分析
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
M. Holcomb
中科院分区：
文献类型：
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作者：
W. Little;M. Holcomb
大量超导铜酸盐的热差反射(TDR)谱使我们能够确定每个超导铜酸盐中配对相互作用的能量依赖性和强度。它们都表现出来自声子的强大贡献，以及来自1.7 eV附近电子跃迁的较小但显著的贡献。最近信噪比的改善表明，在所有情况下，电子激发都伴随着能量降低约0.5 eV的较弱伴星。没有发现其他贡献。我们将这些跃迁分别确定为铜离子在3D9和3D8态下的dz2到dx2-y2激发，并计算了它们所介导的耦合强度。计算值与观测强度在数量级上是一致的。我们发现，除了对应于类电声子项的直接电子耦合外，氧和铜轨道之间的重叠还导致了交换项。直接术语耦合只到S波的间隙，至于声子，而交换术语耦合到S波到d波，反之亦然。我们讨论了这一结果的后果。
Thermal difference reflectance (TDR) spectra taken on a large number of superconducting cuprates has enabled us to determine the energy dependence and strength of the pairing interaction in each. All show strong contributions from the phonons and a smaller, but significant contribution from an electronic transition near 1.7 eV. Recent improvements in the signal-to-noise ratio have revealed that the electronic excitation is accompanied in all cases by a weaker companion about 0.5 eV lower in energy. No other contributions are found. We identify these transitions as the dz2 to dx2–y2 excitations of the Cu ion in the 3d9 and 3d8 states, respectively, and have calculated the coupling strength mediated by each. The calculated values agree in order of magnitude with the observed strengths. We find that, in addition to the direct electronic coupling that corresponds to an electron–phonon-like term, the overlap between the oxygen and the copper orbitals leads to an exchange term. The direct term couples only to an s-wave gap, as for phonons, while the exchange term couples s-wave to d-wave, and vice versa. We discuss the consequences of this result.