【摘要】 铜氧化物高温超导体的超导机理是近30年凝聚态物理学悬而未决的重大科学难题之一.为了彻底解决这一科学难题,最有效的办法是直接测量铜氧化物中的超导层-Cu O₂的性质.在本研究中,我们首次利用分子束外延技术在Bi₂Sr₂CaCu₂O_8+δ衬底表上制备出了单层的CuO₂薄膜.原位低温扫描隧道显微镜研究表明,取决于衬底电荷转移情况,单层Cu O₂薄膜会呈现"U"和"V"两种不同形状的能隙结构.我们发现,"V"形状能隙对应于铜氧化物中BiO层的赝能隙,和超导的形成没有必然的联系;"U"形状无节点的能隙为超导能隙,它不受非磁性杂质（K,Cs和Ag）散射的影响.我们的研究说明铜氧化物高温超导体具有s波电子配对对称性.根据这些结果,我们提出了调制掺杂诱导的、基于刚性能带（rigid-band）的二维空穴液体模型,利用这个模型我们可以解释复杂的高温超导相图.更多还原

【Abstract】 The pairing mechanism of high-temperature superconductivity in cuprates remains the biggest unresolved mystery in condensed matter physics. To solve the problem, one of the most effective approaches is to investigate directly the superconducting Cu O₂ layers. Here,by growing Cu O₂ monolayer films on Bi₂Sr₂ Ca Cu₂O_8+δd substrates, we identify two distinct and spatially separated energy gaps centered at the Fermi energy, a smaller U-like gap and a larger V-like gap on the films, and study their interactions with alien atoms by low-temperature scanning tunneling microscopy. The newly discovered U-like gap exhibits strong phase coherence and is immune to scattering by K, Cs and Ag atoms, suggesting its nature as a nodeless superconducting gap in the Cu O₂ layers, whereas the V-like gap agrees with the well-known pseudogap state in the underdoped regime. Our results support an s-wave superconductivity in Bi₂Sr₂ Ca Cu₂O_8+δd, which, we propose, originates from the modulation-doping resultant twodimensional hole liquid confined in the Cu O₂ layers.更多还原