Optical manipulation of material properties could bring about new functions. For example, exciting electrons with strong light can lead to exotic quantum effects. The periodic perturbations from the strong light field cause electrons to have multiple evenly spaced energy states rather than just one fixed energy state. “The original energy state surrounds itself with several envelopes of light,” said Rupert Huber, professor at the Institute for Experimental and Applied Physics at the University of Regensburg. How long it takes the electrons to clothe themselves with light? It’s been a mystery until now.
The research team chose photoelectron spectroscopy to study the surface of a crystal, and the team made an unforeseen discovery. Their measurements went beyond the limit of what could be realized with spectroscopy to date in terms of time resolution in strong light fields. Surprisingly, Floquet bands form after a single optical cycle, a very short time. The work provides important new information on the evolution of Floquet bands. Dressing electrons with light is often difficult in solids because the energy introduced is quickly converted into heat. By demonstrating that such dressing happens after just a single optical cycle, we pave the way for changing solid-state properties very rapidly and very strongly with light. This opens up the path towards tailored quantum functions and ultrafast electronics.
