The Polariton is a quasi-particle in condensed matter systems, where it describes the superposition of an excitation—typically an exciton (itself the quasi-particle that arises from binding a solid-state electron with a valence hole)[1]—with a photon.
The concept was first proposed theoretically, and christened so, by John Hopfield[2], and its most fruitful implementation, in 2D, was discovered experimentally during a sabbatical stay in Arakawa's group in Tokyo by Claude Weisbuch,[3] who referred to it as his «Japanese effect.»[4] Weisbuch did not initially recognized it as a Hopfield polariton, or "bulk polariton", for which the photon is delocalized in the full 3D crystal, but as a cavity QED effect (Weisbuch was in fact already a polariton expert, having reported its first resonant observation 15 years earlier[5]). The situation was quickly settled during the July (1993) Erice Summer School on "Confined Electrons and Photons: New Physics and Applications" which featured «heated sessions (involving in particular the two Elis, Eli Burstein and Eli Yablonovitch) on the nature of these excitations» according to Weisbuch himself.[6] The name of "Cavity-Polariton" was then agreed to well describe Hopfield's counterpart in reduced dimensionality, and be more suitable than Weisbuch's initial choice for merly Rabi splitting:
The term "vacuum field Rabi splitting" has so far been used for semiconductor microcavities in analogy to atomic physics where this effect was first observed. From a solid state physics point of view, where dispersion has to be considered, the term "cavity-polariton" is more appropriate.
The first appearance of the "cavity polariton" term was in Ref. [7], where the idea of the underlying dispersion was being formed. The breakthrough came in Ref. [8] where the now famous polariton dispersion was provided for the first time:
It seems that the theorists who should have predicted cavity-polaritons are C. Andreani et al.,[9] who narrowly missed it by overlooking the dimensionality mismatch could be fixed with a cavity. He seems, however, to have readily understood (and explained) it[10] to R. Houdré et al. as they were shaping the field.[4]
Historical overviews includes Refs. [11][4], etc.
Important concepts (I'm particularly interested in) include:
A historical review of the polariton concept, from Hopfield's lone-warrior paper[2] that gets all the credit despite fairly serious variations with the finally adopted results (including in its operational definition, involving four operators), along with other contributions.[12][13]