A promising—and powerful—new engineering breakthrough could soon enable researchers to alter the properties of materials by exciting electrons to higher-than-normal energy levels.
In physics, Floquet engineering involves changes in the properties of a quantum material induced by a driving force, such as high-powered light. The resulting effect causes the material’s behavior to change, introducing novel quantum states with properties that do not occur under normal conditions.
Given its promising applications, Floquet engineering has remained of interest to researchers for many years. Now, a team of scientists from the Okinawa Institute of Science and Technology (OIST) and Stanford University says they have developed a new method for achieving Floquet physics that is more efficient than past methods that rely on light.
21st Century Alchemy?
Professor Keshav Dani, a researcher with OIST’s Femtosecond Spectroscopy Unit, said in a statement announcing the breakthrough that the team’s new approach leverages what are known as excitons, which have proven far more powerful in coupling with quantum materials than existing methods “due to the strong Coulomb interaction, particularly in 2D materials.”
Because of this, Dani says, excitons “can thus achieve strong Floquet effects while avoiding the challenges posed by light.” The team says this offers a novel means of exploring various applications, which include “exotic future quantum devices and materials that Floquet engineering promises.”
Such unique phenomena could enable material science applications that are almost akin to alchemy, in that the concept of creating new materials simply by shining light on them sounds more like science fiction than even the most advanced 21st-century engineering.
Floquet Engineering
In the past, Floquet effects have remained elusive in the lab, although investigations over the years have demonstrated their promise, provided they can be achieved under practical conditions. However, a major limiting factor has been reliance on intense light as the primary driving force, which can also lead to damage or even vaporization of the materials, thereby limiting useful results.
Normally, Floquet engineering focuses on achieving such effects under quantum conditions that challenge our usual expectations of time and space. When researchers employ semiconductors or similar crystalline materials as a medium, electrons behave in accordance with what one of these dimensions—space—will allow. This is because of the distribution of atoms, which confines electron movement and thereby limits their energy levels.
Such conditions represent just one “periodic” condition that electrons are subjected to. However, if a powerful light is shone on the crystal at a certain frequency, it represents an additional periodic drive, albeit now in the dimension of time. The resulting rhythmic interaction between light (i.e., photons) and electrons leads to additional changes in their energy.
By controlling the frequency and intensity of the light used as this secondary periodic force, electrons can be made to exhibit unique behaviors, which also cause changes in the material they inhabit for the time during which they remain excited.
Hellbound and Down 