The project MMUSCLES – Modification of Molecular Structure Under Strong Coupling to Confined Light Modes – is focused on what we now call polaritonic chemistry and/or molecular polaritonics, i.e. the modification and manipulation of molecular properties due to their interaction with light modes in nanophotonic cavities. Light, or electromagnetic waves, are one of the best tools we have for manipulating matter, for example by using lasers. However, the presence of nanophotonic structures allows to change the properties of light so fundamentally that this change is noticeable to the molecules even when there is no external light at all, and only the field generated by the molecules themselves is present. In this regime of “strong coupling”, the molecular quantum states are mixed with the states of light and it becomes impossible to treat them separately. Instead, the system is described by hybrid light-matter states, so-called polaritons, that share and combine aspects of both their constituents. In the last years, it has become clear that these changes also affect the internal structure of the molecules and their dynamics, which paves the way towards using this effect to change material properties and even chemical reactions. For example, this could provide a completely novel way of catalysing reactions, in particular photochemical reactions for which very few conventional catalysts exist, but which are of paramount importance for, e.g. harvesting light energy with organic solar cells. MMUSCLES is focused on developing theoretical methods capable of treating these fundamentally quantum effects and using them to explain and develop this new way of doing chemistry and manipulating materials.
Importantly, the coupling strengths available in these systems are so large that important quantum effects are expected and observed even at room temperature, also opening the route towards possible room-temperature quantum devices.
The main conclusions of the project have been that molecular polaritonics do indeed provide a range of novel strategies to manipulate molecular properties and obtain novel functionalities, not just in photochemistry, but in a wide range of additional aspects, such as light absorption and emission characteristics, energy transport over long distances and/or different molecular species. The field has grown and evolved over the last years, new design principles have been developed, and several active efforts exist to develop competitive devices (such as organic light emitting diodes) going beyond the state of the art.
