标题： 多层铜氧化物中外层金属屏蔽增强超导相干性 显示英文标题

标题： Superconducting coherence boosted by outer-layer metallic screening in multilayered cuprates

摘要： 在每单元晶胞含有三个或更多CuO2层的多层高温超导铜氧化物中，内部的CuO2平面（IPs）在空间上与掺杂层分离，因此比外部平面（OPs）更清洁。 虽然层间耦合和清洁IPs的存在已被提出作为增强超conductivity的关键因素，但它们各自的作用难以区分，因为IPs和OPs通常同时成为超导体。 在这里，我们使用ARPES研究了五层结构的(Cu,C)Ba2Ca4Cu5Oy（Cu1245），其Tc为78 K，以及三层结构的Ba2Ca2Cu3O6(F,O)2（F0223），其Tc为100 K，并揭示了一种前所未有的情况，即只有IPs成为超导体，而OPs在低温下仍保持金属态。 模型计算表明，超过95%的OP波函数局限于OP本身，与来自超导IPs的杂化作用最小。 特别是，我们实验实现了理想的配置：一个超导的CuO2层被重掺杂的金属外层夹在中间，这些外层屏蔽了来自掺杂层的无序。 引人注目的是，这个干净的CuO2层在所有已知的铜氧化物中超导能隙最大，并且相干的Bogoliubov峰扩展超过了反铁磁区边界——这一直被认为是超导相干性消失的边界，在严重欠掺杂的铜氧化物中如此。 此外，在布里渊区边缘出现了一个广泛延伸的相干平带，克服了赝能隙阻尼效应。 我们的结果引入了一个新的物理参数——屏蔽程度，用于研究超导性和赝能隙之间的竞争，可能为理解其起源提供新的视角。 几乎无无序的超导CuO2层为连接无序的实际材料和通常忽略无序效应的理想理论模型提供了一个模型平台。 显示英文摘要

摘要： In multilayered high-Tc cuprates with three or more CuO2 layers per unit cell, the inner CuO2 planes (IPs) are spatially separated from the dopant layers and thus remain cleaner than the outer planes (OPs). While both interlayer coupling and the presence of clean IPs have been proposed as key factors enhancing superconductivity, their individual roles have been difficult to disentangle, as IPs and OPs typically become superconducting simultaneously. Here we investigate five-layer (Cu,C)Ba2Ca4Cu5Oy (Cu1245) with Tc = 78 K and three-layer Ba2Ca2Cu3O6(F,O)2 (F0223) with Tc = 100 K using ARPES, and uncover an unprecedented situation, in which only the IPs become superconducting while the OPs remain metallic at low temperatures. Model calculations indicate that more than 95% of the OP wavefunction remains confined to OP itself, with minimal hybridization from the superconducting IPs. In particular, we experimentally realize an ideal configuration: a single superconducting CuO2 layer sandwiched between heavily overdoped metallic outer layers, which screen disorder originating from the dopant layers. Strikingly, this clean CuO2 layer exhibits the largest superconducting gap among all known cuprates and coherent Bogoliubov peaks extending beyond the antiferromagnetic zone boundary -- long regarded as the boundary beyond which coherence vanishes in heavily underdoped cuprates. Furthermore, a widely extended coherent flat band emerges at the Brillouin zone edge, overcoming the pseudogap damping effect. Our results introduce a new physical parameter, the degree of screening, to investigate the competition between superconductivity and the pseudogap, potentially shedding new light on its origin. The nearly disorder-free superconducting CuO2 layers offer a model platform for bridging the gap between disordered real materials and idealized theoretical models, which generally neglect disorder effects.