Cristel Chandre will present a seminar entitled “Trapped by the light: Nonlinear dynamics of the Kramers-Henneberger atom”

Can an intense, linearly polarized laser field trap an electron in a stable, laser-dressed state? For years, the existence of this so-called Kramers-Henneberger (KH) atom has been debated. The conventional theoretical framework relies on the emergence of a double-well in the KH potential, derived by averaging electron motion over one laser cycle. Yet, because this averaging approximation is largely invalid right where the double-well structure appears, the fundamental conditions for the KH state have remained questionable. 

Here, we present a nonperturbative method that moves beyond cycle-averaging to establish rigorous conditions for the KH atom’s existence. We will show that across a wide range of laser parameters, the KH atom is governed by an asymmetric periodic orbit that shares the laser’s period. Through quantum simulations, we will highlight the clear structural imprints this orbit leaves on the wavefunction and define the specific parameter regime—characterized by an elliptic periodic orbit—where the KH atom transitions from a theoretical artifact to a physical reality.