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arXiv 2404.10046cond-mat.supr-concond-mat.str-el
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库珀对密度调制态的观测

Observation of Cooper-pair density modulation state

Lingyuan Kong, Michał Papaj, Hyunjin Kim, Yiran Zhang, Eli Baum, Hui Li, Kenji Watanabe, Takashi Taniguchi, Genda Gu, Patrick A. Lee, Stevan Nadj-Perge

AI总结:

本研究提出晶胞内对称性破缺引发的对密度调制(PDM)新概念,首次在FeTe₀.₅₅Se₀.₄₅剥离薄片中观测到该态,揭示其源于亚晶格能隙差异,由亚晶格对称破缺与向列畸变共同驱动,为强关联体系交织序研究开辟新方向。

摘要:

打破基底晶体空间群对称性的超导态可表现出序参量的非平凡空间调制。此前,这类特殊态与平移对称性破缺密切相关,会产生波长跨越若干个晶胞的密度波序。然而,一个相关的基础概念长期被忽视:当仅空间群的晶胞内对称性被打破时,超导态可呈现出一种独特的非平凡调制,同时保留长程晶格平移性。在此,我们将这一新概念称为对密度调制(PDM),并报道在铁基超导体FeTe$_{0.55}$Se$_{0.45}$的剥离薄片中首次观测到PDM态。利用扫描隧道显微镜,我们发现了稳定的超导能隙调制,其波长对应晶格周期,且振幅超过能隙平均值的30%。重要的是,我们发现观测到的调制源于两个名义上等价的铁亚晶格上超导能隙的巨大差异。实验结果得到模型计算的支持,表明与密度波序不同,PDM态由亚晶格对称性破缺与薄片特有的特殊向列畸变的共同作用驱动。我们的研究结果为探索强关联电子系统中的交织序开辟了新前沿,也为铁基超导体研究翻开了新篇章。

英文摘要:

Superconducting states that break space-group symmetries of the underlying crystal can exhibit nontrivial spatial modulation of the order parameter. Previously, such remarkable states were intimately associated with the breaking of translational symmetry, giving rise to the density-wave orders, with wavelengths spanning several unit cells. However, a related basic concept has been long overlooked: when only intra-unit-cell symmetries of the space group are broken, the superconducting states can display a distinct type of nontrivial modulation preserving long-range lattice translation. Here, we refer to this new concept as the pair density modulation (PDM), and report the first observation of a PDM state in exfoliated thin flakes of iron-based superconductor FeTe$_{\text{0.55}}$Se$_{\text{0.45}}$. Using scanning tunneling microscopy, we discover robust superconducting gap modulation with the wavelength corresponding to the lattice periodicity and the amplitude exceeding 30% of the gap average. Importantly, we find that the observed modulation originates from the large difference in superconducting gaps on the two nominally equivalent iron sublattices. The experimental findings, backed up by model calculations, suggest that in contrast to the density-wave orders, the PDM state is driven by the interplay of sublattice symmetry breaking and a peculiar nematic distortion specific to the thin flakes. Our results establish new frontiers for exploring the intertwined orders in strong-correlated electronic systems and open a new chapter for iron-based superconductors.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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