Microscopic theory of phonon-induced effects on semiconductor quantum dot decay dynamics in cavity QED

Abstract

We investigate the influence of the electron-phonon interaction on the decay dynamics of a quantum dot coupled to an optical microcavity. We show that the electron-phonon interaction has important consequences on the dynamics, especially when the quantum dot and cavity are tuned out of resonance, in which case the phonons may add or remove energy leading to an effective nonresonant coupling between quantum dot and cavity. The system is investigated using two different theoretical approaches: (i) a second-order expansion in the bare phonon coupling constant, and (ii) an expansion in a polaron-photon coupling constant, arising from the polaron transformation which allows an accurate description at high temperatures. In the low temperature regime we find excellent agreement between the two approaches. An extensive study of the quantum dot decay dynamics is performed, where important parameter dependencies are covered. We find that in general the electron-phonon interaction gives rise to a greatly increased bandwidth of the coupling between quantum dot and cavity. At low temperature an asymmetry in the quantum dot decay rate is observed, leading to a faster decay when the quantum dot has a larger energy than to the cavity. We explain this as due to the absence of phonon absorption processes. Furthermore, we derive approximate analytical expressions for the quantum dot decay rate, applicable when the cavity can be adiabatically eliminated. The expressions lead to a clear interpretation of the physics and emphasizes the important role played by the effective phonon density, describing the availability of phonons for scattering, in quantum dot decay dynamics. Based on the analytical expressions we present the parameter regimes where phonon effects are expected to be important. Also, we include all technical developments in appendices.

Decoherence in semiconductor cavity QED systems due to phonon couplings

“…We model the QD-cavity system coupled to longitudinal acoustical (LA) phonons using a standard Hamiltonian [6,[11][12][13][16][17][18]39], employing the following Hilbert space for the QD-cavity system: {|1 = |e,n = 0 , |2 = FIG. 2.…”

“…The importance of phonons in semiconductor cQED is by now well established, both experimentally [5][6][7][8][9] and theoret-* per.kaer@gmail.com ically [10][11][12][13][14][15][16]. However, theoretical studies of the degree of indistinguishability of photons emitted from a cQED system interacting with a non-Markovian phonon reservoir only appeared recently [17,18].…”

Influence of phonons on solid-state cavity-QED investigated using nonequilibrium Green's functions

“…Secondorder perturbation theory within the time convolutionless (TCL) approach has been used to investigate nonMarkovian effects for various regimes 19,21,33,34 . Yet, an exact diagonalization approach reported at 0K…”

The role of phonons for exciton and biexciton generation in an optically driven quantum dot

“…In the case of strong light-matter coupling there is a strong interplay between exciton-phonon and light-matter interaction, which for example can be seen in the line-width broadening in the Mollow-Triplet [180,102]. The combined exciton-photon and exciton-phonon interaction in the strong coupling regime has been subject to many theoretical works [181,58,87,90,95,88,89,128,182,91]. A detailed discussion of the phenomena related to the interplay between these coupling mechanisms is beyond the scope of this review.…”

“…Also for dots in cavities phonons can play a decisive role, e.g., for the dephasing [87,88,89,90,91], the photon statistics [92,58,93,94], the indistinguishability of photons [95] as well as for providing a dot-cavity coupling in the case of non-resonant QD and cavity modes where phenomena like off-resonant cavity feeding have been found [96,82,97,98,99,100,101,102]. Although such systems are not at the focus of the present review, we note in passing that in this case, additional relaxation mechanisms, in particular cavity losses, may become of importance.…”