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Register a new userRayleigh scattering in coupled microcavities: Experiment
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Added by
Zolt\\'an V\\\"or\\\"os
Publication date
2014
fields
Physics
and research's language is
English
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We experimentally analyze Rayleigh scattering in coupled planar microcavities. We show that the correlations of the disorder in the two cavities lead to inter-branch scattering of polaritons, that would otherwise be forbidden by symmetry. These longitudinal correlations can be inferred from the strength of the inter-branch scattering.
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In this paper we theoretically study how structural disorder in coupled semiconductor heterostructures influences single-particle scattering events that would otherwise be forbidden by symmetry. We extend the model of V. Savona to describe Rayleigh scattering in coupled planar microcavity structures, and answer the question, whether effective filter theories can be ruled out. They can.
We calculate the intensity of the polariton mediated inelastic light scattering in semiconductor microcavities. We treat the exciton-photon coupling nonperturbatively and incorporate lifetime effects in both excitons and photons, and a coupling of the photons to the electron-hole continuum. Taking the matrix elements as fitting parameters, the results are in excellent agreement with measured Raman intensities due to optical phonons resonant with the upper polariton branches in II-VI microcavities with embedded CdTe quantum wells.
We investigate the scattering of an electron by phonons in a small structure between two one-dimensional tight-binding leads. This model mimics the quantum electron transport through atomic wires or molecular junctions coupled to metallic leads. The electron-phonon coupled structure is represented by the Holstein model. We observe permanent energy transfer from the electron to the phonon system (dissipation), transient self-trapping of the electron in the electron-phonon coupled structure (due to polaron formation and multiple reflections at the structure edges), and transmission resonances that depend strongly on the strength of the electron-phonon coupling and the adiabaticity ratio. A recently developed TEBD algorithm, optimized for bosonic degrees of freedom, is used to simulate the quantum dynamics of a wave packet launched against the electron-phonon coupled structure. Exact results are calculated for a single electron-phonon site using scattering theory and analytical approximations are obtained for limiting cases.
We present calculations of the intensity of polariton-mediated inelastic light scattering in semiconductor microcavities within a Greens function framework. In addition to reproducing the strong coupling of light and matter, this method also enables the inclusion of damping mechanisms in a consistent way. Our results show excellent agreement with recent Raman scattering experiments.
The attenuation of long-wavelength phonons (waves) by glassy disorder plays a central role in various glass anomalies, yet it is neither fully characterized, nor fully understood. Of particular importance is the scaling of the attenuation rate $Gamma(k)$ with small wavenumbers $k!to!0$ in the thermodynamic limit of macroscopic glasses. Here we use a combination of theory and extensive computer simulations to show that the macroscopic low-frequency behavior emerges at intermediate frequencies in finite-size glasses, above a recently identified crossover wavenumber $k_dagger$, where phonons are no longer quantized into bands. For $k!<!k_dagger$, finite-size effects dominate $Gamma(k)$, which is quantitatively described by a theory of disordered phonon bands. For $k!>!k_dagger$, we find that $Gamma(k)$ is affected by the number of quasilocalized nonphononic excitations, a generic signature of glasses that feature a universal density of states. In particular, we show that in a frequency range in which this number is small, $Gamma(k)$ follows a Rayleigh scattering scaling $sim!k^{d+1}$ ($d$ is the spatial dimension), and that in a frequency range in which this number is sufficiently large, the recently observed generalized-Rayleigh scaling of the form $sim!k^{d+1}log!{(k_0/k)}$ emerges ($k_0!>k_dagger$ is a characteristic wavenumber). Our results suggest that macroscopic glasses --- and, in particular, glasses generated by conventional laboratory quenches that are known to strongly suppress quasilocalized nonphononic excitations --- exhibit Rayleigh scaling at the lowest wavenumbers $k$ and a crossover to generalized-Rayleigh scaling at higher $k$. Some supporting experimental evidence from recent literature is presented.
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