Congratulations to Dr. Hrvoje Petek and his collaborators for publishing their study this week in Physical Review X! The article is titled "Observation of Nonadiabatic Landau-Zener Tunneling among Floquet States". Describing the study, Dr. Petek states, 

"In a joint Pittsburgh experiment and Swiss theory research, we have described the optical dressing of the surface bands of the Cu(111) surface under various light-fluence conditions. At low fluence, the time-periodic optical field induces four-photon photoemission (4PP) under three-photon resonant conditions from the Shockley surface state to the first image potential state. The field induces a Stark (Autler-Townes) shift of the surface-state bands as the delay between identical pump and probe pulses passes through zero during interferometric scanning with attosecond precision, where constructive interference increases the field strength and enhances electronic band dressing. At a high optical field, a new dominant signal penetrates between the Autler-Townes split bands. Theoretical modeling of the optical phase-resolved Rabi flopping shows that this is a consequence of non-adiabatic Landau-Zener-Stückelberg-Majorana tunneling between different-order Floquet states. The experiment shows how light can modify the electronic structure of matter with attosecond control of optical fields. Congratulations to Dr. Zehua Wang (experiment) and Dr. Yun Yen (theory) for publishing these results in Physical Review X! This research was the crowning item of their PhD theses."