The superconducting gap sets the basic energy scale that allows electricity to flow without resistance in a superconductor. In high‑temperature cuprates, the paired electrons (Cooper pairs) are mostly confined to thin copper–oxygen layers.
Terahertz spectroscopy has helped scientists study how the superfluid moves across these layers. But within the layers themselves, the superfluid shows up as charge oscillations at much higher energies than the gap, and these signals are hidden by strong energy loss.
MIT physicists built a specialized terahertz microscope that squeezes terahertz light into tiny spots, enabling them to see quantum vibrations in superconductors for the first time. When they tested it on a material called a sample of bismuth strontium calcium copper oxide, or BSCCO (pronounced “BIS-co”), they discovered a frictionless superfluid of electrons moving together and vibrating at terahertz speeds inside the material.
Nuh Gedik, the Donner Professor of Physics at MIT, said, “This new microscope now allows us to see a new mode of superconducting electrons that nobody has ever seen before.”
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Terahertz light is a type of energy that sits between microwaves and infrared on the spectrum. It vibrates more than a trillion times each second, just the right speed to match how atoms and electrons move inside materials. That makes it an ideal tool for studying these tiny motions.
Using terahertz light, the team hopes to uncover clues that could one day make room‑temperature superconductors possible. Their new microscope can also detect materials that emit or absorb terahertz radiation, paving the way for future wireless systems that send more data faster than today’s microwave networks.
Scientists haven’t used terahertz radiation much for microscopy because of a basic limit called diffraction. Light can only see details as small as its wavelength, and terahertz waves are hundreds of microns long, much bigger than atoms or molecules. That makes it hard for terahertz radiation to show tiny features directly.
The team solved the usual problem with terahertz light by using spintronic emitters, tiny stacks of metals that give off sharp terahertz pulses when hit by a laser. By putting the sample very close to the emitter, they caught the light before it spread out, squeezing it into a space smaller than its wavelength. This clever method lets terahertz light show details that used to be too small to see.
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Scientists adapted his idea and developed a new microscope that uses spintronic emitters and a Bragg mirror to filter light safely. This setup lets them study quantum‑scale details without damaging the sample.
To show how it works, they imaged an atom‑thin piece of BSCCO, a high‑temperature superconductor, cooled to near absolute zero. By scanning the laser and sending terahertz light through the sample, they captured the unique signals from the superconducting electrons.
Alexander von Hoegen, a postdoc in MIT’s Materials Research Laboratory and lead author of the study, said, “We see the terahertz field gets dramatically distorted, with little oscillations following the main pulse. That tells us that something in the sample is emitting terahertz light, after it got kicked by our initial terahertz pulse.”
The scientists discovered that their terahertz microscope was actually watching superconducting electrons move together in natural terahertz vibrations. As von Hoegen stated, “it’s like seeing a ‘superconducting gel’ jiggle”.
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Despite its earlier predictions, this behaviour was not observed before till now. Scientists are now planning to use this microscope to other two-dimensional materials, hoping to uncover even more hidden terahertz behaviors.
Journal Reference:
- von Hoegen, A., Tai, T., Allington, C.J. et al. Imaging a terahertz superfluid plasmon in a two-dimensional superconductor. Nature (2026). DOI: 10.1038/s41586-025-10082-2
