Quasiparticle interference and superconducting gap in Ca2-xNaxCuO2Cl2
Quasiparticle interference and superconducting gap in Ca2-xNaxCuO2Cl2
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DOI：
10.1038/nphys753
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发表时间：
2007-12-01
期刊：
影响因子：
19.6
通讯作者：
Takagi, H.
中科院分区：
文献类型：
--
作者：
Hanaguri, T.;Kohsaka, Y.;Takagi, H.
高转变温度（高 T-c）超导性在含 CuO2 平面的铜酸盐中普遍存在，但每种铜酸盐都有自己的特性。 d 波超导能隙 (SG) 材料依赖性的研究应该为高温超导机制提供重要的见解。然而，由于“赝能隙”现象，人们常常不清楚光谱技术观察到的能隙是否真正代表了SG。在这里，我们使用扫描隧道光谱对 T-c=25-28 K 的近乎最佳掺杂的 Ca2-xNaxCuO2Cl2(Na-CCOC) 进行成像。它使我们能够观察该材料中的准粒子干涉效应，从而获得有关 SG 的明确信息。我们对 Na-CCOC 中准粒子干扰的分析表明，尽管 Bi2212 的 T-c 比 Na-CCOC 高三倍，但在相同掺杂水平下，间隙节点附近的 SG 色散几乎与 Bi2Sr2CaCu2Oy (Bi2212) 相同。我们还发现 Na-CCOC 中的 SG 被限制在比 Bi2212 更窄的能量和动量范围内，这至少部分解释了 T-c 的显着材料依赖性。
High-transition-temperature (high-T-c) superconductivity is ubiquitous in the cuprates containing CuO2 planes, but each cuprate has its own character. The study of the material dependence of the d-wave superconducting gap (SG) should provide important insights into the mechanism of high-T-c superconductivity. However, because of the 'pseudogap' phenomenon, it is often unclear whether the energy gaps observed by spectroscopic techniques really represent the SG. Here, we use scanning tunnelling spectroscopy to image nearly optimally doped Ca2-xNaxCuO2Cl2(Na-CCOC) with T-c=25-28 K. It enables us to observe the quasiparticle interference effect in this material, through which we obtain unambiguous information on the SG. Our analysis of quasiparticle interference in Na-CCOC reveals that the SG dispersion near the gap node is almost identical to that of Bi2Sr2CaCu2Oy (Bi2212) at the same doping level, despite the T-c of Bi2212 being three times higher than that of Na-CCOC. We also find that the SG in Na-CCOC is confined in narrower energy and momentum ranges than Bi2212, which explains-at least in part-the remarkable material dependence of T-c.