Abstract
<title>Abstract</title> <p>Photon-dressed states exhibit mixed light-matter character, offering new possibilities for tailoring the electronic structure of quantum materials not only through the matter itself, but also through the laser driving the system. In condensed matter systems, these non-equilibrium states enable new technological applications, including the light-induced anomalous Hall effect in graphene, time-reversal symmetry breaking in 2D materials, and light-induced superconductivity. A usual way to strengthen light-matter interaction, thereby favoring photon-dressed states, is to use ultrashort laser pulses with high peak electric fields. Here, we demonstrate a complementary approach, exploiting the extreme field enhancement naturally generated in picocavities to create steady Floquet states upon irradiation with low-power, continuous-wave lasers. The gap between the tip and sample of a scanning tunneling microscope naturally forms a size-tunable picocavity that hosts electronic gap states that coherently interact with the driving laser. We demonstrate that by tuning the polarization, power, and frequency of the drive, we exert exquisite control over the created hybrid light-matter states, allowing us to tune the electronic gap and spectral weights at will. Our results present a novel route for controlling quantum matter via its hybridization with light, opening the door to technological applications that demand permanent states rather than transient ones.</p>