Reviewed by Frances BriggsFeb 6 2026
A novel terahertz microscope compresses light to even smaller dimensions – in the nanoscale.
An artist’s depiction of a superfluid wave propagating through a layered superconductor. Image Credit: Sampson Wilcox and Emily Theobald
The type of light that is shone on a material can reveal a lot about it. Optical light reveals its surface, X-rays expose its interior structures, and infrared captures the heat it emits.
According to a study published in the journal Nature, the Massachusetts Institute of Technology researchers have now employed terahertz light to show previously undetectable quantum oscillations in a superconducting material.
Terahertz light is a form of energy that lies between microwaves and infrared radiation on the electromagnetic spectrum. It oscillates more than a trillion times per second, which is precisely the rate at which atoms and electrons naturally vibrate within materials. This makes terahertz light an ideal instrument for probing these motions.
However, while the frequency is correct, the wavelength – the span over which the wave repeats in space – is wrong.
Terahertz waves have wavelengths of hundreds of microns. Terahertz beams cannot be tightly contained because the smallest point that any type of light may be focused onto is determined by its wavelength. As a result, a concentrated terahertz beam is physically too big to interact effectively with microscopic materials, instead washing over them without exposing fine detail.
This pinpoint of terahertz light can reveal quantum features in materials that were previously inaccessible.
The researchers used the new microscope to direct terahertz light into a sample of bismuth strontium calcium copper oxide, or BSCCO (pronounced "BIS-co"), a material that superconducts at high temperatures.
Using the terahertz instrument, the researchers discovered a frictionless "superfluid" of superconducting electrons jiggling back and forth at terahertz frequencies within the BSCCO material.
This new microscope now allows us to see a new mode of superconducting electrons that nobody has ever seen before.
Nuh Gedik, Donner Professor, Physics, Massachusetts Institute of Technology
By probing BSCCO and other superconductors with terahertz light, scientists can acquire a deeper understanding of the features that could lead to the long-awaited room-temperature superconductor.
The new microscope can also assist in detecting materials that generate and absorb terahertz radiation. Such materials might serve as the foundation for future wireless, terahertz-based communications, which have the ability to carry more data at quicker speeds than microwave-based communications.
There’s a huge push to take Wi-Fi or telecommunications to the next level, to terahertz frequencies. If you have a terahertz microscope, you could study how terahertz light interacts with microscopically small devices that could serve as future antennas or receivers.
Alexander von Hoegen, Study Lead Author and Postdoctoral Researcher, Materials Research Laboratory, Massachusetts Institute of Technology
Hitting a Limit
One interesting but still mostly unexplored imaging technique is terahertz light. It resides in a special spectral "sweet spot": Terahertz radiation is safe for usage in people and biological tissues because, like microwaves, radio waves, and visible light, it is nonionizing and does not contain enough energy to produce dangerous radiation effects.
Terahertz waves could also pass through a variety of materials, such as fabric, wood, cardboard, plastic, ceramics, and even thin brick walls, much like X-rays.
Terahertz light is being extensively investigated for applications in wireless communications, medical imaging, and security screening due to its unique properties.
The application of terahertz radiation to microscopy and the lighting of microscopic phenomena, on the other hand, has received significantly less attention. The diffraction limit, which limits spatial resolution to about the wavelength of the radiation employed, is the main cause. This basic constraint is shared by all forms of light.
Atoms, molecules, and many other small structures are far smaller than terahertz radiation, which has wavelengths on the order of hundreds of microns. Its capacity to directly resolve microscale characteristics is thus severely limited.
Our main motivation is this problem that, you might have a 10-micron sample, but your terahertz light has a 100-micron wavelength, so what you would mostly be measuring is air, or the vacuum around your sample. You would be missing all these quantum phases that have characteristic fingerprints in the terahertz regime.
Alexander von Hoegen, Study Lead Author and Postdoctoral Researcher, Materials Research Laboratory, Massachusetts Institute of Technology
Zooming In
The researchers overcame the terahertz diffraction barrier by using spintronic emitters, a new technique that generates short terahertz pulses. Spintronic emitters are constructed from many ultrathin metallic layers. When a laser illuminates the multilayered structure, it triggers a cascade of effects in the electrons within each layer, leading the structure to emit a pulse of energy at terahertz frequencies.
By holding a sample close to the emitter, the team was able to capture the terahertz light before it could propagate, thereby compressing it into an area far smaller than its wavelength. In this domain, light can overcome the diffraction limit and resolve details that were previously too small to discern.
The MIT team used this technique to study small, quantum-scale phenomena. For their latest study, the researchers created a terahertz microscope containing spintronic emitters and a Bragg mirror. This multilayered arrangement of reflective films successively filters out some unwanted wavelengths of light while allowing others through, shielding the sample from the "harmful" laser that causes terahertz emissions.
The researchers demonstrated the novel microscope by imaging a small, atomically thin sample of BSCCO. They placed the sample extremely close to the terahertz source and scanned it at temperatures near absolute zero, low enough for the material to become a superconductor. To produce the image, they scanned the laser beam, passing terahertz light through the sample and searching for the unique characteristics left by superconducting electrons.
“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,” von Hoegen added.
Following further study, the researchers determined that the terahertz microscope was observing the natural, collective terahertz oscillations of superconducting electrons within the material.
“It is this superconducting gel that we’re sort of seeing jiggle,” von Hoegen further added.
This jiggling superfluid was predicted, but never directly visualized until now. The team is currently using the microscope on additional two-dimensional materials, hoping to record more terahertz occurrences.
von Hoegen concluded, “There are a lot of fundamental excitations, like lattice vibrations and magnetic processes, and all these collective modes that happen at terahertz frequencies. We can now resonantly zoom in on these interesting physics with our terahertz microscope.”
The study was supported, in part, by the US Department of Energy and by the Gordon and Betty Moore Foundation.
Journal Reference
von Hoegen, A., et.al. (2026) Imaging a terahertz superfluid plasmon in a two-dimensional superconductor. Nature. DOI: 10.1038/s41586-025-10082-2.