Singular Floquet scattering with atomic interactions

The shaping of physical systems by periodic driving is a powerful tool gaining increasing attention. However the modelling of periodically modulated nonperturbative effects is challenging due to the necessity of employing time dependent tools beyond perturbation theory, and often reduces to a time independent approximation with effective parameters. It is hence an important question to determine the extent of the validity of such effective descriptions, and possible directions going beyond it.

I will present a nonperturbative and time-dependent approach to Floquet two-body atomic interactions [1]. With it we find the existence of singular solutions that cannot be seen in a time independent approximation, where poles of the scattering S-matrix cross the real energy axis at a critical drive strength, making the S-matrix nonanalytic. The Floquet singular solutions have common properties with spectral singularities (or exceptional points) and mark an abrupt change of the system properties.

In particular, I will discuss the application to ultracold atoms and ion-atom hybrid systems [2,3].

[1] H. Landa, arXiv:1708.09828

[2] H. Landa, in preparation.

[3] A. Sykes, H. Landa, and D. Petrov, PRA 95, 062705 (2017).