When the interaction between light and matter is strong enough, photon and matter excitations mix to create hybrid light/matter states called polaritons. Traditionally, their hybrid character has been used to achieve new functionalities in which polaritons are utilized as dressed photons. However, over the last ten years, it has become clear that the strong light-matter coupling regime can be used with an alternative purpose: to significantly modify material properties by dressing the matter excitations. Under strong coupling conditions, it has been shown that energy transport and harvesting in organic materials can be enhanced and that the energy landscape of the molecules can be altered in such a way that photochemical reactions and even ground-state chemical reactions can be modified. This new platform for creating quantum materials has triggered the search for achieving strong light-matter coupling conditions with other types of electronic excitations, such as those associated with excitons in van der Waals 2D materials and perovskite quantum dot solids, among others.

In this seminar I will present the main findings in this brand-new research field, but also our accompanying efforts in the last ten years to developing an accurate theoretical formalism, able to capture the complex and quantum nature of the electromagnetic fields associated with the nanophotonic structures in which polaritons emerge.