Pohang Accelerator Laboratory announced on the 4th that Dr. Cheon Se-hwan's research team has identified a hidden ultrafast phase transition pathway in the smart material vanadium dioxide film, overturning conventional wisdom for the first time in the world.
Smart materials are adaptive materials that respond to changes in the external environment to beneficially alter their physical properties. They are attracting attention as a core technology of future industries, with applications in various industries such as medical and life sciences, electronics, energy storage technology, architecture, and the environment.
Vanadium dioxide is a smart material that exhibits an electrical phase transition from an insulator to a conductor near room temperature. Although active research is ongoing, there has been a decades-long debate over whether the electrical phase transition occurs at the same temperature as the structural phase transition, and whether it is due to purely electronic factors or changes in crystal structure.
Using advanced experimental devices at the Pohang Accelerator Laboratory, including the X-ray Free Electron Laser (PAL-XFEL) and the 3rd generation synchrotron radiation accelerator (PLS-II), the research team precisely studied the light-induced structural and electrical phase transitions in vanadium dioxide films subjected to tensile strain. They discovered that two phase transitions occurred at different time intervals of hundreds of femtoseconds.
As a result, the research team revealed a quantum phenomenon (quantum mechanical Mott insulator-conductor transition) in which the electrical properties of a material suddenly change from a state where electricity does not flow to a state where it does flow, solely based on the behavior of electrons. They also presented the possibility of controlling the onset of such electrical changes induced by light by applying tensile strain to the sample.
This research indicates that the results can be applied not only to vanadium dioxide but also to similar Mott insulator-conductor transition quantum materials. The utilization of these materials in ultrafast light-induced smart material control technology is expected.
Dr. Cheon Se-hwan stated, "This research was made possible by the organic integration of advanced experimental devices at the Pohang Accelerator Laboratory." He emphasized that when combining Korea's strengths in semiconductor and smart material technology with cutting-edge experimental and measurement technology, leading research that can lead the world through synergy is possible.
This research was supported by the Ministry of Science and ICT's synchrotron accelerator joint research support project, accelerator personnel training and utilization support project, and basic research project. It also received support from the Pohang University of Science and Technology (POSTECH) - Max Planck Institute and POSTECH Photon Science Center's research project on the quantum properties and spatiotemporal characteristics of phase quantum materials. The research results were published online in the internationally renowned academic journal 'Advanced Materials.' The vanadium dioxide film samples used in the research were provided by Professor Lee Shin-bum of the Daegu Gyeongbuk Institute of Science and Technology (DGIST).