Exciton-polariton trapping and potential landscape engineering

Abstract

Exciton-polaritons in semiconductor microcavities have become a model system for the studies of dynamical Bose-Einstein condensation, macroscopic coherence, many-body effects, nonclassical states of light and matter, and possibly quantum phase transitions in a solid state. These low-mass bosonic quasiparticles can condense at comparatively high temperatures up to 300 K, and preserve the fundamental properties of the condensate, such as coherence in space and time domain, even when they are out of equilibrium with the environment. Although the presence of a confining potential is not strictly necessary in order to observe Bose-Einstein condensation, engineering of the polariton confinement is a key to controlling, shaping, and directing the flow of polaritons. Prototype polariton-based optoelectronic devices rely on ultrafast photon-like velocities and strong nonlinearities exhibited by polaritons, as well as on their tailored confinement. Nanotechnology provides several pathways to achieving polariton confinement, and the specific features and advantages of different methods are discussed in this review. Being hybrid exciton-photon quasiparticles, polaritons can be trapped via their excitonic as well as photonic component, which leads to a wide choice of highly complementary trapping techniques. Here, we highlight the almost free choice of the confinement strengths and trapping geometries that provide powerful means for control and manipulation of the polariton systems both in the semi-classical and quantum regimes. Furthermore, the possibilities to observe effects of the polariton blockade, Mott insulator physics, and population of higher-order energy bands in sophisticated lattice potentials are discussed. Observation of such effects could lead to realization of novel polaritonic non-classical light sources and quantum simulators.

Conical intersections for light and matter waves

“…However, in systems such as exciton-polariton condensates where the energy resolution is typically a limiting factor, accidental degeneracies may be superior to tight binding limit conical intersections in certain applications (recall that the energy bandwidth vanishes as the tight binding limit is approached). Thus this is an avenue that deserves further attention in the context of recent advances in generating structured potentials for exciton-polaritons [85]. Perhaps because of this bandwidth limitation, a "bosonic" conical intersection has not yet been realized for exciton-polariton condensates.…”

Evolution of Temporal Coherence in Confined Exciton-Polariton Condensates

“…Spatial confinement has previously been used to enhance condensation processes in trap structures and micropillars [19][20][21][22]; in our case, spatial confinement in 6 to 12-µm diameter etched micropillars allows us to form polariton condensates for which g (2) (0) above threshold reaches a plateau with values larger than unity. This g (2) (0) plateau value decreases with tightened optical confinement, reflecting the enhancement of coherence in such structures.…”

Polariton condensation in S- and P-flatbands in a two-dimensional Lieb lattice

“…Creating artificial lattices in order to emulate and simulate complex many-body systems with additional degrees of freedom has attracted considerable scientific interest [17][18][19]. Exciton-polariton gases in periodic lattice potential landscapes have emerged as a very promising solid state system to emulate many-body physics [20,21]. Polaritons are eigenstates resulting of strong coupling between a quantum well exciton and a photonic cavity mode.…”