With the developments of spectroscopic techniques and light sources, in recent years, it has become possible to not just subject a material to an intense light pulse but also to prepare it long enough in a non-equilibrium state, which then has linear response properties of its own. Such changed properties arise either transiently while the system slowly regains its equilibrium after an excitation or, perhaps more strikingly, while the light is acting on it. In the latter case the material and the light form a combined quantum state, a so called dressed state, which can have physical properties that dramatically differ from the ones of the isolated crystal. 

Light dressing is the overarching concept tying together two fields of research laying at opposite ends of the spectrum of the possible field intensities [1]: Floquet engineering and cavity QED.

In the field of Floquet engineering [2] strong lasers are employed to transiently alter materials properties while in cavity QED [3] even the low energy properties of a system, i.e. its ground state, can be affected by the strong coupling to a single cavity photon.

In this talk I will illustrate the interplay between the two fields, their shortcomings and advantages, and how they complement each other with particular emphasis on the challenges associated with the manipulation and observation of the predicted topological properties of the dressed system.

[1] H. Hübener, UDG et al., Nat. Mater 20, 438 (2021)
[2] T. Oka and S. Kitamura, Annu. Rev. Condens. Matter Phys. 10, 387 (2018)
[3] M. Ruggenthaler, et al., Nat. Rev. Chem. 2, 0118 (2018)