Microscopic theory of anisotropic organic cavity exciton polaritons

Zoubi, Hashem; Rocca, G. C. La

doi:10.1103/physrevb.71.235316

Cited by 48 publications

(63 citation statements)

References 25 publications

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“…10,11 The nature of polaritons in disordered organic MCs has been addressed from the theoretical point of view 12,13,14,15 , showing the coexistence of delocalized and partially localized polaritons. The possible interaction with molecular vibrations was discussed 16,17 , the effect of anisotropy in organic crystal was characterized 18 , as well as the possible occurrence of non-linear phenomena 19 for high density of polaritons.…”

Section: Introductionmentioning

confidence: 99%

Exciton-phonon scattering and photoexcitation dynamics inJ-aggregate microcavities

Michetti

Rocca

2009

Phys. Rev. B

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We have developed a model accounting for the photo-excitation dynamics and the photoluminescence of strongly coupled J-aggregate microcavities. Our model is based on a description of the J-aggregate film as a disordered Frenkel exciton system in which relaxation occurs due to the presence of a thermal bath of molecular vibrations. In a strongly coupled microcavity exciton-polaritons are formed, mixing superradiant excitons and cavity photons. The calculation of the microcavity steady-state photoluminescence, following a CW non resonant pumping, is carried out. The experimental photoluminescence intensity ratio between upper and lower polariton branches is accurately reproduced. In particular both thermal activation of the photoluminescence intensity ratio and its Rabi splitting dependence are a consequence of the bottleneck in the relaxation, occurring at the bottom of the excitonic reservoir. The effects due to radiative channels of decay of excitons and to the presence of a paritticular set of discrete optical molecular vibrations active in relaxation processes are investigared.

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Section: Introductionmentioning

confidence: 99%

Exciton-phonon scattering and photoexcitation dynamics inJ-aggregate microcavities

Michetti

Rocca

2009

Phys. Rev. B

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“…While the electronic excitations can transfer between atoms due to dipoledipole interactions, there is no direct electron exchange. A simplified model atomic Hamiltonian then reads [9]:where B α † i and B α i are the creation and annihilation operators of an excitation at atom (i, α), respectively. The summation i runs over the lattice sites, while α labels the two atoms at one site.…”

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confidence: 99%

“…While the electronic excitations can transfer between atoms due to dipoledipole interactions, there is no direct electron exchange. A simplified model atomic Hamiltonian then reads [9]:…”

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confidence: 99%

Bright and dark excitons in an atom-pair–filled optical lattice within a cavity

Zoubi

Ritsch

2008

Europhys. Lett.

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We study electronic excitations of a degenerate gas of atoms trapped in pairs in an optical lattice. Local dipole-dipole interactions produce a long lived antisymmetric and a short lived symmetric superposition of individual atomic excitations as the lowest internal on-site excitations. Due to the much larger dipole moment the symmetric states couple efficiently to neighbouring lattice sites and can be well represented by Frenkel excitons, while the antisymmetric dark states stay localized. Within a cavity only symmetric states couple to cavity photons inducing long range interactions to form polaritons. We calculate their dispersion curves as well as cavity transmission and reflection spectra to observe them. For a lattice with aspherical sites bright and dark states get mixed and their relative excitation energies depend on photon polarizations. The system should allow to study new types of solid state phenomena in atom filled optical lattices.PACS numbers: 71.36.+c, 71.35.Lk A dilute gas of bosonic atoms near T = 0 in an opticallattice has proved an ideal test-system to study important quantum phenomena of solid state physics with well controllable parameters [1,2]. A striking example is a reversible quantum phase transition from the superfluid into the Mott-insulator phase [3] simply by changing the optical potential depth. In the Mott insulator case each optical-lattice site is filled with a fixed number of atoms down to one or two atoms per site. For a deep enough lattice the atoms cannot move and form an artificial crystal. Naturally it is now interesting to study further complex solid state phenomena in this system, e.g. by exploiting the internal atomic level structure, which bears a strong analogy to excitonic dynamics of molecular crystals (Frenkel excitons) as predicted in Ref. [4]. By the help of an optical cavity these excitons get strongly coupled over large distances via photons and form polaritons. In the present paper we investigate a special interesting case of such excitons [5] and cavity polaritons [6] which can appear only for lattice filled with two atoms per site, which is a straight forward to prepare in optical lattices by the help of a Mott insulator state with filling factor 2.Let us start from a degenerate gas of effective two-level atoms trapped in a 2D optical lattice, located within a cavity with a single cavity mode close to resonance with an internal atomic transition. The lattice laser is tuned far off resonance to the atomic excitations and results in light shifts of the ground and excited states with periodicity of half the laser wave length. Here we assume the two optical-lattices for ground and excited states located at the same positions, which can be realized for Alkali or Alkaline atoms. At certain magic laser frequencies the excited state even experiences an equal shift as the ground state [2,7]. We believe that more general lattice configurations might imply new physics, but this goes beyond our aim here. At temperatures close to T = 0, the atomic center of mass mo...

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“…To conclude, we point out that a microcavity filled with molecular aggregates [39][40][41][42][43][44] in the strong coupling regime of excitons to cavity modes is another promising arrangement to realize an all-optical switch. 44 The recent observation of optical bistability in planar inorganic microcavities 45 and the prediction of the effect for hybrid organic-inorganic microcavities 46 in the strong coupling regime suggest that organic microcavities can exhibit a similar behavior.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

Intrinsic optical bistability of thin films of linear molecular aggregates: The two-exciton approximation

Klugkist

Малышев

Knoester

2008

The Journal of Chemical Physics

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We generalize our recent work on the optical bistability of thin films of molecular aggregates ͓J. A. Klugkist et al., J. Chem. Phys. 127, 164705 ͑2007͔͒ by accounting for the optical transitions from the one-exciton manifold to the two-exciton manifold as well as the exciton-exciton annihilation of the two-exciton states via a high-lying molecular vibronic term. We also include the relaxation from the vibronic level back to both the one-exciton manifold and the ground state. By selecting the dominant optical transitions between the ground state, the one-exciton manifold, and the two-exciton manifold, we reduce the problem to four levels, enabling us to describe the nonlinear optical response of the film. The one-and two-exciton states are obtained by diagonalizing a Frenkel Hamiltonian with an uncorrelated on-site ͑diagonal͒ disorder. The optical dynamics is described by means of the density matrix equations coupled to the electromagnetic field in the film. We show that the one-to two-exciton transitions followed by a fast exciton-exciton annihilation promote the occurrence of bistability and reduce the switching intensity. We provide estimates of pertinent parameters for actual materials and conclude that the effect can be realized.

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Microscopic theory of anisotropic organic cavity exciton polaritons

Cited by 48 publications

References 25 publications

Exciton-phonon scattering and photoexcitation dynamics inJ-aggregate microcavities

Exciton-phonon scattering and photoexcitation dynamics inJ-aggregate microcavities

Bright and dark excitons in an atom-pair–filled optical lattice within a cavity

Intrinsic optical bistability of thin films of linear molecular aggregates: The two-exciton approximation

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