title: Shrinking light to allow forbidden transitions on the atomic scale.
abstract: The diversity of light-matter interactions accessible to a system is limited by the small size of an atom relative to the wavelength of the light it emits, as well as by the small value of the fine-structure constant. We developed a general theory of light-matter interactions with two-dimensional systems supporting plasmons. These plasmons effectively make the fine-structure constant larger and bridge the size gap between atom and light. This theory reveals that conventionally forbidden light-matter interactions--such as extremely high-order multipolar transitions, two-plasmon spontaneous emission, and singlet-triplet phosphorescence processes--can occur on very short time scales comparable to those of conventionally fast transitions. Our findings may lead to new platforms for spectroscopy, sensing, and broadband light generation, a potential testing ground for quantum electrodynamics (QED) in the ultrastrong coupling regime, and the ability to take advantage of the full electronic spectrum of an emitter.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. nrivera@mit.edu.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Rivera
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Ido
authors.initials: I
authors.lastname: Kaminer
authors.affiliation: Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhen
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Joannopoulos
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Marin
authors.initials: M
authors.lastname: Soljačić