A fleeting photoinduced electronic state and the subsequent formation of a photoinduced hidden state in a metal – organic framework were captured in just 30 femtoseconds by researchers at Science Tokyo, Tohoku University, and Nagoya Institute of Technology, Japan. By combining ultrafast laser spectroscopy with theoretical analysis, the researchers found that a transient electronic state plays a key role in this process. The findings provide new insights into controlling material properties with light for future applications.
When materials absorb light, they can enter unusual states with properties that differ from their normal behavior. These photoinduced states offer scientists a way to control material properties beyond what can be achieved through heating or cooling. Understanding how such states emerge on ultrafast timescales is essential for designing future photoresponsive materials and advanced optical technologies.
However, the earliest stages of the photoinduced state formation can occur on the femtosecond (fs) timescale (a millionth of a billionth of a second), making it extremely difficult to observe and understand the process. To overcome this, a research team led by Assistant Professor Tadahiko Ishikawa from the Department of Chemistry, School of Science, Institute of Science Tokyo (Science Tokyo), Japan, along with then doctoral student Samiran Banu (currently a Special Postdoctoral Researcher at RIKEN), conducted a study in collaboration with researchers from Tohoku University and Nagoya Institute of Technology, Japan. They investigated how a photoinduced hidden state forms in a metal–organic framework (MOF), which is made by linking metal ions with organic molecules. Their findings were published in the journal Physical Review Letters on July 22, 2026.
“We found that the photoinduced hidden state forms within 30 fs through a previously unknown intermediate electronic state,” says Ishikawa.
To capture these ultrafast changes, the researchers used time-resolved reflectance spectroscopy with ultrashort laser pulses lasting only six fs. This technique tracks how a material’s reflected light changes immediately after it absorbs a laser pulse. Using ultrashort laser pulses, they tracked the MOF’s electronic behavior with precise time resolution. The results revealed that within 30 fs, the reflectance spectrum changed rapidly, showing features associated with the formation of a new optical absorption band. This signified that a photoinduced hidden state had formed.
To understand why these changes occurred, the team further used theoretical calculations along with their experiments. The analysis revealed that immediately after the material absorbed light, it briefly entered a transient electronic state in which the electronic bonding between neighboring sites became stronger and weaker in a repeating pattern. This state is known as a bond-order wave state. This short-lived state was then followed by small shifts in the positions of atoms within the material, ultimately leading to the photoinduced hidden state.
Theoretical calculations revealed that the resulting photoinduced state may be polar, meaning that positive and negative electrical charges become unevenly distributed across the material. These photoinduced polar states could inspire new ways to control a material’s electronic properties using light.
"By revealing intermediate states, our method could help design materials that can be efficiently controlled using light," explains Ishikawa.
Beyond revealing how photoinduced states emerge, the findings provide a promising strategy for controlling the properties of materials using ultrashort light pulses. The ability to create and manipulate these temporary states may pave the way for the development of new photoresponsive materials for high-speed electronics, optoelectronic devices, and other technologies that rely on precise control of material properties. Future studies could apply the same approach to a wider range of materials, bringing us one step closer to designing novel light-controlled materials.
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About Institute of Science Tokyo (Science Tokyo)
Institute of Science Tokyo (Science Tokyo) was established on October 1, 2024, following the merger between Tokyo Medical and Dental University (TMDU) and Tokyo Institute of Technology (Tokyo Tech), with the mission of “Advancing science and human wellbeing to create value for and with society.”
Reference
DOI: https://doi.org/10.1103/x43y-61c1
Physical Review Letters
Experimental study
Not applicable
Ultrafast formation of a photoinduced hidden state driven by a bond-order wave in a metal–organic framework
22-Jul-2026
The authors declare that they have no conflict of interest.