Molekylions

Molekylions are a proposed class of quasiparticles that arise in certain molecular solids and synthetic polymers. They are defined as localized, charge-carrying excitations that couple electronic states to molecular vibrations, behaving as particle-like entities within a lattice. The concept positions molekylions between electronic excitations and vibrational dynamics, offering a framework to describe transport and energy localization at the molecular scale.

The term molekylion blends the ideas of a molecule and an ion, reflecting their dual character as both charge carriers and vibrationally active excitations. The concept emerged in discussions of strong electron-phonon coupling in organic crystals and polymeric systems, where discrete, mobile energy packets can traverse a material without dispersing into conventional charge carriers.

Structurally, a molekylion is envisaged as a bound state comprising a localized electronic excitation and an associated lattice distortion. It carries a net charge and exhibits a quantized energy spectrum. Its effective mass and mobility depend on the strength of coupling to molecular vibrations and the dimensionality of the host lattice, which can enable either diffusive or soliton-like transport in one-dimensional chains.

Formation and stability require conditions that balance electronic localization with lattice response, such as specific doping levels, photoexcitation, or high molecular order. Molekylions are typically studied in organized molecular crystals, nanotubular assemblies, and well-defined polymeric wires.

Experimental evidence relies on spectroscopic signatures of coupled excitations, time-resolved measurements of carrier dynamics, and transport studies showing discrete, channel-like conduction properties. The field is evolving, with ongoing debate about interpretation and the precise regimes where molekylions dominate transport.

See also quasiparticle, polaron, exciton, molecular electronics, soliton.