Manipulating matter by strong coupling to vacuum fields

Laser technology is a familiar example of how confining light between two mirrors can tune its properties. Quantum mechanics also dictates that even without extraneous light, matter confined in a cavity resonant with its electronic or vibrational transitions can couple with vacuum electromagnetic field fluctuations. Garcia-Vidal et al. review the remarkable and still somewhat mysterious implications of this “strong-coupling” regime, with manifestations ranging from enhanced charge transport to site-selective chemical reactivity across a range of molecular and solid-state materials. Science , abd0336, this issue p. eabd0336 A Review describes chemical and physical manifestations of strong coupling in cavities tuned to electronic or vibrational resonances. Over the past decade, there has been a surge of interest in the ability of hybrid light-matter states to control the properties of matter and chemical reactivity. Such hybrid states can be generated by simply placing a material in the spatially confined electromagnetic field of an optical resonator, such as that provided by two parallel mirrors. This occurs even in the dark because it is electromagnetic fluctuations of the cavity (the vacuum field) that strongly couple with the material. Experimental and theoretical studies have shown that the mere presence of these hybrid states can enhance properties such as transport, magnetism, and superconductivity and modify (bio)chemical reactivity. This emerging field is highly multidisciplinary, and much of its potential has yet to be explored.