近日，美国麻省理工学院Gedik, N.团队报道了在二维超导体中成像太赫兹超流体等离子体。该研究于2026年2月4日发表在《自然》杂志上。

超导能隙定义了超导体中无耗散输运与集体现象出现的基本能量尺度。在层状高温铜氧化物超导体中，库珀对被限制在弱耦合的二维铜氧（CuO₂）平面内。利用太赫兹光谱技术，可在亚能隙毫电子伏特能量尺度上获得垂直于超导层的集体超流响应关键信息。然而在CuO₂平面内，集体超流响应表现为能量远高于超导能隙的等离激元电荷振荡，这种现象通常被强耗散效应所掩盖。

研究组展示了几层Bi₂Sr₂CaCu₂O_8+x中存在低于能隙的二维超流等离激元的谱学证据，并实现了对其深度亚衍射太赫兹电动力学的空间分辨。通过将超导体置于自旋电子太赫兹发射器的近场区域，研究组揭示了这种块体样品中不存在、仅出现于超导相的特有共振现象，并通过几何各向异性与色散关系的系统测绘确定了其等离激元本质。关键的是，这些测量结果为二维体系中动量依赖与频率依赖的超导相变提供了直接观测窗口。

附：英文原文

Title: Imaging a terahertz superfluid plasmon in a two-dimensional superconductor

Author: von Hoegen, A., Tai, T., Allington, C. J., Yeung, M., Pettine, J., Michael, M. H., Vias Bostrm, E., Cui, X., Torres, K., Kossak, A. E., Lee, B., Beach, G. S. D., Gu, G. D., Rubio, A., Kim, P., Gedik, N.

Issue&Volume: 2026-02-04

Abstract: The superconducting gap defines the fundamental energy scale for the emergence of dissipationless transport and collective phenomena in a superconductor1,2,3. In layered high-temperature cuprate superconductors, in which the Cooper pairs are confined to weakly coupled two-dimensional (2D) copper–oxygen (CuO2) planes4,5, terahertz (THz) spectroscopy at subgap millielectronvolt (meV) energies has provided crucial insights into the collective superfluid response perpendicular to the superconducting layers6,7,8,9. However, within the CuO2 planes, the collective superfluid response manifests as plasmonic charge oscillations at energies far exceeding the superconducting gap, obscured by strong dissipation2,6,9,10. Here we present spectroscopic evidence of a below-gap, 2D superfluid plasmon in few-layer Bi2Sr2CaCu2O8+x and spatially resolve its deeply subdiffractive THz electrodynamics. By placing the superconductor in the near field of a spintronic THz emitter, we reveal this distinct resonance—absent in bulk samples and observed only in the superconducting phase—and determine its plasmonic nature by mapping the geometric anisotropy and dispersion. Crucially, these measurements offer a direct view of the momentum-dependent and frequency-dependent superconducting transition in two dimensions.

DOI: 10.1038/s41586-025-10082-2

Source: https://www.nature.com/articles/s41586-025-10082-2