Concept

Exciton-polariton

Summary
In physics the Exciton–polariton is a type of polariton; a hybrid light and matter quasiparticle arising from the strong coupling of the electromagnetic dipolar oscillations of excitons (either in bulk or quantum wells) and photons. Because light excitations are observed classically as photons, which are massless particles, they do not therefore have mass, like a physical particle. This property makes them a quasiparticle. The coupling of the two oscillators, photons modes in the semiconductor optical microcavity and excitons of the quantum wells, results in the energy anticrossing of the bare oscillators, giving rise to the two new normal modes for the system, known as the upper and lower polariton resonances (or branches). The energy shift is proportional to the coupling strength (dependent, e.g., on the field and polarization overlaps). The higher energy or upper mode (UPB, upper polariton branch) is characterized by the photonic and exciton fields oscillating in-phase, while the LPB (lower polariton branch) mode is characterized by them oscillating with phase-opposition. Microcavity exciton–polaritons inherit some properties from both of their roots, such as a light effective mass (from the photons) and a capacity to interact with each other (from the strong exciton nonlinearities) and with the environment (including the internal phonons, which provide thermalization, and the outcoupling by radiative losses). In most cases the interactions are repulsive, at least between polariton quasi-particles of the same spin type (intra-spin interactions) and the nonlinearity term is positive (increase of total energy, or blueshift, upon increasing density). Researchers also studied the long-range transport in organic materials linked to optical microcavities and demonstrated that exciton-polaritons propagate over several microns. This was done in order to prove that exciton-polaritons propagate over several microns and that the interplay between the molecular disorder and long-range correlations induced by coherent mixing with light leads to a mobility transition between diffusive and ballistic transport.
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Related lectures (6)
Excitons, Luminescence and LEDs
Explores excitons, luminescence, and LEDs, including their formation, impact on carrier density, and working principles.
Quantum Metrology
Covers topics like Ramsey interferometer, spin ensembles, and quantum Fisher information.
Spin Ensembles: Collective Effects and Quantum Metrology
Explores spin ensembles' collective effects and quantum metrology applications, covering Dicke states, polaritons, coherent spin states, and angular momentum properties.
Show more
Related publications (83)

Heralded Spectroscopy: a new single-particle probe for nanocrystal photophysics

Edoardo Charbon, Claudio Bruschini, Ivan Michel Antolovic, Samuel Burri, Arin Can Ülkü

Semiconductor nanocrystals feature multiply-excited states that display intriguing physics and significantly impact nanocrystal-based technologies. Fluorescence supplies a natural probe to investigate these states. Still, direct observation of multiexciton ...
SPIE-INT SOC OPTICAL ENGINEERING2023

Interaction of Confined Polaritons in Microcavity Structures

Morteza Navadeh Toupchi

A polariton is a quasiparticle formed from the coupling of a confined photon in a cavity to electronic excitation, like exciton in a semiconductor. This dissertation reports on series of experiments in confined polariton interaction by design, fabrication, ...
EPFL2021

Direct measurement of key exciton properties: Energy, dynamics, and spatial distribution of the wave function

Michele Puppin, Martin Wolf

Excitons, Coulomb-bound electron-hole pairs, are the fundamental excitations governing the optoelectronic properties of semiconductors. Although optical signatures of excitons have been studied extensively, experimental access to the excitonic wave functio ...
Hoboken2021
Show more
Related concepts (1)
Quasiparticle
In physics, quasiparticles and collective excitations are closely related phenomena arising when a microscopically complicated system such as a solid behaves as if it contained different weakly interacting particles in vacuum. For example, as an electron travels through a semiconductor, its motion is disturbed in a complex way by its interactions with other electrons and with atomic nuclei. The electron behaves as though it has a different effective mass travelling unperturbed in vacuum.