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 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.

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.

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.