By harnessing internal quantum vibrations instead of powerful lasers, scientists are opening the door to designing entirely new materials with light-like precision but far less damage. Credit: SciTechDaily.com
Scientists have shown that it may be possible to transform materials simply by triggering internal quantum ripples rather than blasting them with intense light.
Imagine being able to change what a material is capable of simply by shining light on it.
That idea may sound like something out of science fiction, but it is exactly what physicists aim to achieve through a growing research area known as Floquet engineering. By exposing a material to a repeating external influence such as light, scientists can temporarily reshape how its electrons behave. This process allows materials to take on entirely new properties, including behaviors normally associated with exotic states of matter, like superconductivity.
The underlying theory behind Floquet physics has been studied for years, dating back to a bold proposal by Oka and Aoki in 2009. However, real-world demonstrations have been rare. Only a small number of experiments over the past decade have successfully shown clear Floquet effects. A major obstacle has been the reliance on intense light, which must be powerful enough to alter electronic behavior but often comes close to damaging or destroying the material itself while delivering limited results.
A 3D rendering of a pair of hands holding glowing bands of energy like a cat’s cradle. One of the bands fold inwards, reminiscent of the Mexican-hat-like momentum dispersion indicative of Floquet effects. The glowing orbs above the hands, one dark and the other light, represent the electron and hole that together form an exciton. Credit: Jack Featherstone
A New Approach Beyond High Intensity Light
Researchers have now uncovered a more efficient way forward. An international team co-led by the Okinawa Institute of Science and Technology (OIST) and Stanford University has demonstrated that particles known as excitons can drive Floquet effects far more effectively than light alone. Their findings were published in Nature Physics.
“Excitons couple much more strongly to the material than photons due to the strong Coulomb interaction, particularly in 2D materials,” says Professor Keshav Dani from the Femtosecond Spectroscopy Unit at OIST. “And they can thus achieve strong Floquet effects while avoiding the challenges posed by light. With this, we have a new potential pathway to the exotic future quantum devices and materials that Floquet engineering promises.”
This discovery offers a promising alternative to laser-driven methods, opening new possibilities for controlling quantum materials without extreme energy input.
Mexican Hat Dispersion Indicative of Hybridization
How Floquet Engineering Works in Quantum Materials
Floquet engineering has long been viewed as a potential route to creating quantum materials on demand using ordinary semiconductors. The basic idea comes from a simple physical principle. When a system experiences a repeating force, its overall behavior can become more complex than the repetition itself. A familiar example is a playground swing. Regular pushes can send the swing higher, even though the motion remains rhythmic.
In the quantum world, this principle takes on new meaning. Inside a crystal, electrons already experience a repeating structure in space because atoms are arranged in a precise lattice. This spatial repetition defines which energy levels, known as bands, electrons are allowed to occupy.
When light with a specific frequency shines on the crystal, it adds a second repeating influence, this time in time rather than space. As photons interact with electrons in a rhythmic pattern, the allowed energy bands shift. By carefully tuning the light’s frequency and intensity, researchers can create hybrid energy bands that alter how electrons move and interact. These changes temporarily give the material new properties, much like how two musical notes combine to create a new sound.
Once the light is turned off, the material returns to its original state. But while the drive is active, scientists can effectively dress materials in new quantum behaviors.
The time- and angle-resolved photoemission spectroscopy (TR-ARPES) setup at OIST, here with study co-first author Xing Zhu, PhD student in the Femtosecond Spectroscopy Unit. Featuring a proprietary, table-top extreme-UV source emitting bursts at femtosecond intervals (1fs = one millionth of one billionth of a second), this setup captured the first real images of excitons, helped sketch out the evolution of dark excitons, and has now proved the feasibility of excitonic Floquet engineering. Credit: Bogna Baliszewska (OIST)
Why Light Alone Has Not Been Enough
“Until now, Floquet engineering has been synonymous with light drives,” says Xing Zhu, PhD student at OIST. “But while these systems have been instrumental to proving the existence of Floquet effects, light couples weakly to matter, meaning that very high frequencies, often at the femtosecond scale, are required to achieve hybridization. Such high energy levels tend to vaporize the material, and the effects are very short-lived. By contrast, excitonic Floquet engineering requires much lower intensities.”
This limitation has kept Floquet engineering largely confined to laboratory demonstrations rather than practical applications.
What Makes Excitons So Effective
Excitons form inside semiconductors when electrons absorb energy and jump from their normal position in the valence band to a higher energy level known as the conduction band. This jump leaves behind a positively charged hole. The electron and hole remain bound together, forming a short-lived quasiparticle.
These excitons naturally carry oscillating energy from their initial excitation. That energy interacts with nearby electrons at adjustable frequencies. Because excitons are made from the material’s own electrons, they interact much more strongly with the surrounding structure than external light does.
“Excitons carry self-oscillating energy, imparted by the initial excitation, which impacts the surrounding electrons in the material at tunable frequencies. Because the excitons are created from the electrons of the material itself, they couple much more strongly with the material than light. And crucially, it takes significantly less light to create a population of excitons dense enough to serve as an effective periodic drive for hybridization, which is what we have now observed,” explains co-author Professor Gianluca Stefanucci of the University of Rome Tor Vergata.
Observing Excitonic Floquet Effects in Real Time
The breakthrough builds on years of exciton research at OIST and the development of a state-of-the-art TR-ARPES (time- and angle-resolved photoemission spectroscopy) system.
To separate the effects of light from those of excitons, the team studied an atomically thin semiconductor. They first applied a strong optical drive to directly observe changes in the electronic band structure, confirming traditional Floquet behavior. Next, they reduced the light intensity by more than an order of magnitude and examined the electronic response 200 femtoseconds later. This timing allowed them to isolate the effects driven by excitons rather than the light itself.
“The experiments spoke for themselves,” says Dr. Vivek Pareek, OIST graduate who is now a Presidential Postdoctoral Fellow at the California Institute of Technology. “It took us tens of hours of data acquisition to observe Floquet replicas with light, but only around two to achieve excitonic Floquet – and with a much stronger effect.”
Opening the Door to Practical Floquet Engineering
The results confirm that Floquet effects are not limited to light-based methods. They can also be reliably generated using other bosonic particles beyond photons. Excitonic Floquet engineering requires far less energy than optical approaches and points toward a broader toolkit for controlling quantum materials.
In theory, similar effects could be achieved using other excitations such as phonons (using acoustic vibration), plasmons (using free-floating electrons), or magnons (using magnetic fields). Together, these possibilities lay the groundwork for practical Floquet engineering and the controlled creation of advanced quantum materials and devices.
“We’ve opened the gates to applied Floquet physics,” concludes study co-first author Dr. David Bacon, former OIST researcher now at the University College London, “to a wide variety of bosons. This is very exciting, given its strong potential for creating and directly manipulating quantum materials. We don’t have the recipe for this just yet – but we now have the spectral signature necessary for the first, practical steps.”
Reference: “Driving Floquet physics with excitonic fields” by Vivek Pareek, David R. Bacon, Xing Zhu, Yang-Hao Chan, Fabio Bussolotti, Marcos G. Menezes, Nicholas S. Chan, Joel Pérez Urquizo, Kenji Watanabe, Takashi Taniguchi, Enrico Perfetto, Michael K. L. Man, Julien Madéo, Gianluca Stefanucci, Diana Y. Qiu, Kuan Eng Johnson Goh, Felipe H. da Jornada and Keshav M. Dani, 19 January 2026, Nature Physics.
DOI: 10.1038/s41567-025-03132-z
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