Giant enhancement of polariton relaxation in semiconductor microcavities by polariton-free carrier interaction: Experimental evidence and theory

Tartakovskii, A. I.; Krizhanovskii, D. N.; Malpuech, G.; Emam-Ismail, M.; Chernenko, A. V.; Kavokin, Alexey; Kulakovskiĭ, V. D.; Skolnick, M. S.; Roberts, J.S.

doi:10.1103/physrevb.67.165302

Cited by 38 publications

(19 citation statements)

References 22 publications

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“…There are also indications recently that a large population of free electrons, however, may assist the energy relaxation of excitons (25)(26)(27)(28). Dark J ϭ 2 excitons, which are created by spin flip from the light-generated J ϭ 1 excitons with a time constant of Ϸ100 ps (29), also may play a role.…”

Section: Experimental Principlesmentioning

confidence: 99%

Polariton lasing vs. photon lasing in a semiconductor microcavity

Deng

Weihs

Snoke

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

400

368

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Nearly one decade after the first observation of Bose-Einstein condensation in atom vapors and realization of matter-wave (atom) lasers, similar concepts have been demonstrated recently for polaritons: half-matter, half-light quasiparticles in semiconductor microcavities. The half-light nature of polaritons makes polariton lasers promising as a new source of coherent and nonclassical light with extremely low threshold energy. The half-matter nature makes polariton lasers a unique test bed for many-body theories and cavity quantum electrodynamics. In this article, we present a series of experimental studies of a polariton laser, exploring its properties as a relatively dense degenerate Bose gas and comparing it to a photon laser achieved in the same structure. The polaritons have an effective mass that is twice the cavity photon effective mass, yet seven orders of magnitude less than the hydrogen atom mass; hence, they can potentially condense at temperatures seven orders of magnitude higher than those required for atom Bose-Einstein condensations. Accompanying the phase transition, a polariton laser emits coherent light but at a threshold carrier density two orders of magnitude lower than that needed for a normal photon laser in a same structure. It also is shown that, beyond threshold, the polariton population splits to a thermal equilibrium Bose-Einstein distribution at in-plane wave number k ʈ > 0 and a nonequilibrium condensate at kʈ ϳ 0, with a chemical potential approaching to zero. The spatial distributions and polarization characteristics of polaritons also are discussed as unique signatures of a polariton laser. E xperimentally realized macroscopic degenerate boson systems, such as lasers, superfluid He 3 and He 4 , the Bardeen-CooperSchreiffer state in superconductors, and Bose-Einstein condensation (BEC) of atomic vapors, have deepened our fundamental understanding of macroscopic quantum orders and led to novel research tools as well as applications. A missing member from the family has been a macroscopically ordered state of weakly interacting bosons in condensed matter systems. Exciton and polariton BECs are the most promising candidates in this category. Since they were first proposed in the 1960s (1-3), tremendous efforts have been engaged in the search (4-13). Exciton and polariton BECs are attractive yet elusive because of the complications inherent to solid-state systems with strong Coulomb interactions. It is a formidable task to describe the excitations in solids in full detail. The common approach is to treat the stable ground state of an isolated system as a quasivacuum and to introduce quasiparticles as units of elementary excitation, which only weakly interact with each other. An exciton is a typical example of such a quasiparticle. As a result of optical excitation from the crystal ground state, an exciton consists of a bound pair of an electron and hole whose Coulomb interaction serves as the binding energy. Excitons have integral total spin, thus they behave like bosons, weakly interac...

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Section: Experimental Principlesmentioning

confidence: 99%

Polariton lasing vs. photon lasing in a semiconductor microcavity

Deng

Weihs

Snoke

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

400

368

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“…Our results are in better agreement with the experimental results shown in Refs. 12,16 . Allowing the el-pol scattering, the bottleneck is shifted towards lower momenta, changing the population in an asymmetric way compared with the pnonon-polariton relaxation.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…However, in semiconductor microcavities, under non-resonant excitation, acoustic phonons provide an effective channel for polaritons relaxation 14,15 . Moreover, recent experiments 1,16 have shown the importance of electron-polariton scattering at densities where the electron-electron interaction are insufficiently effective due to the their fast relaxation. This two relaxation mechanisms could be the most relevant to relax the huge population at the bottleneck.…”

Section: Introductionmentioning

confidence: 99%

Time resolved scattering relaxation mechanisms of microcavity polaritons

Chaves¹,

Rodríguez²

2005

Solid State Communications

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We study the polariton relaxation dynamics for different scattering mechanisms as: Phonon and electron scattering procesess. The relaxation polariton is obtained at very short times by solving the Boltzman equation. Instead of the well-known relaxation process by phonons, we show that the bottleneck effect relaxes to the ground state more efficiently at low pump power intensity when the electron relaxation process is included. In this way, we clearly demonstrate that different relaxation times exist, for which any of these two mechanism is more efficient to relax the polariton population to the ground state.

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“…These systems were recently the objects of theoretical and experimental research [1][2][3][4][5][6][7][8][9]. The interaction of two-dimensional excitons (direct and indirect) with photons and possible polariton formation is of particular interest.…”

Section: Introductionmentioning

confidence: 99%

“…The interaction of two-dimensional excitons (direct and indirect) with photons and possible polariton formation is of particular interest. Polaritons in microcavities essentially change radiation characteristics of QW in microcavities [5][6][7][8][9] and the spectrum of light scattering in the region of the exciton-polariton Rabi splitting [1][2][3][4]9].…”

Section: Introductionmentioning

confidence: 99%