Excitons outperform light in quantum materials engineering
Researchers have achieved a breakthrough in Floquet engineering, revealing that excitons quasiparticles formed within semiconductors can alter material properties far more effectively than light alone. This discovery paves the way for on-demand creation of exotic quantum materials.
Scientists from the Okinawa Institute of Science and Technology (OIST) and Stanford University demonstrated that exciton-driven Floquet effects in monolayer semiconductors are two orders of magnitude stronger and longer-lasting than those produced by conventional light-based methods. The findings, published in Nature Physics on January 18, 2026, highlight a promising alternative to traditional approaches.
Floquet engineering typically relies on periodic external forces, such as intense laser light, to temporarily reshape a material's electronic structure and convert ordinary semiconductors into exotic quantum states. Yet, practical challenges persist: the high light intensities often risk damaging samples while yielding only modest results.
The new study introduces excitons as a superior driving force. When photons excite electrons in a semiconductor, they leave behind positively charged "holes," forming bound electron-hole pairs known as excitons. These quasiparticles oscillate at tunable frequencies and interact more strongly with surrounding electrons than photons do, thanks to potent Coulomb forces, especially in 2D materials.
Professor Keshav Dani from OIST's Femtosecond Spectroscopy Unit noted that excitons couple much more strongly to the material than photons. This opens a potential pathway to the exotic quantum devices and materials promised by Floquet engineering.
The team validated their approach using time- and angle-resolved photoemission spectroscopy (TR-ARPES). They first observed Floquet replicas from intense optical pumping, then reduced light intensity by over an order of magnitude and detected exciton-driven effects just 200 femtoseconds later.
Dr. Vivek Pareek, an OIST alumnus now at the California Institute of Technology, reported that capturing light-induced Floquet effects required dozens of hours of data acquisition, while exciton versions took only about two hours and produced far more pronounced signals. Measurements confirmed hybridization between exciton-dressed conduction bands and valence bands, aligning with first-principles calculations and linking to excitonic insulator physics.
The implications extend further, suggesting that other bosonic quasiparticles like phonons from acoustic vibrations, plasmons from free electrons, and magnons from magnetic fields could fuel Floquet engineering.
Dr. David Bacon, formerly at OIST and now at University College London, described the work as unlocking applied Floquet physics. With strong potential for directly creating and manipulating quantum materials, it provides the spectral signatures needed for practical first steps, even if the full recipe remains elusive.
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