超伝導電子の量子運動を可視化するテラヘルツ顕微鏡を開発（Terahertz microscope reveals motion of superconducting electrons）

2026-02-04 マサチューセッツ工科大学（MIT）

＜関連情報＞

• https://news.mit.edu/2026/terahertz-microscope-reveals-motion-superconducting-electrons-0204
• https://www.nature.com/articles/s41586-025-10082-2

2次元超伝導体におけるテラヘルツ超流動プラズモンの画像化 Imaging a terahertz superfluid plasmon in a two-dimensional superconductor

A. von Hoegen,T. Tai,C. J. Allington,M. Yeung,J. Pettine,M. H. Michael,E. Viñas Boström,X. Cui,K. Torres,A. E. Kossak,B. Lee,G. S. D. Beach,G. D. Gu,A. Rubio,P. Kim & N. Gedik
Nature  Published:04 February 2026
DOI:https://doi.org/10.1038/s41586-025-10082-2

Abstract

The superconducting gap defines the fundamental energy scale for the emergence of dissipationless transport and collective phenomena in a superconductor^1,2,3. In layered high-temperature cuprate superconductors, in which the Cooper pairs are confined to weakly coupled two-dimensional (2D) copper–oxygen (CuO₂) planes^4,5, terahertz (THz) spectroscopy at subgap millielectronvolt (meV) energies has provided crucial insights into the collective superfluid response perpendicular to the superconducting layers^6,7,8,9. However, within the CuO₂ planes, the collective superfluid response manifests as plasmonic charge oscillations at energies far exceeding the superconducting gap, obscured by strong dissipation^2,6,9,10. Here we present spectroscopic evidence of a below-gap, 2D superfluid plasmon in few-layer Bi₂Sr₂CaCu₂O_8+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.