Bound polarons in semiconductor nanostructures

Woggon, U.; Miller, David A. B.; Kalina, F.; Gerlach, B.; Kayser, D.; Leonardi, K.; Hommel, D.

doi:10.1103/physrevb.67.045204

Cited by 18 publications

(10 citation statements)

References 26 publications

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“…Experimental evidence of the enhanced phonon-assisted absorption due to effects of non-adiabaticity has been provided by the multi-phonon photoluminescence (PL) spectra observed under selective excitation in self-assembled InAs/GaAs quantum dots (García-Cristóbal et al, 1999) and by the photoluminescence excitation (PLE) measurements on single self-assembled InAs/GaAs (Lemaître et al, 2001) and InGaAs/GaAs (Zrenner et al, 2001) quantum dots. The polaron concept was also invoked for the explanation of the PLE measurements on self-organised In x Ga 1−x As/GaAs (Heitz et al, 2001) and CdSe/ZnSe (Woggon et al, 2003) quantum dots.…”

Section: Current Status Of Polarons and Open Problemsmentioning

confidence: 99%

Fröhlich polaron and bipolaron: recent developments

2009

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It is remarkable how the Fröhlich polaron, one of the simplest examples of a Quantum Field Theoretical problem, as it basically consists of a single fermion interacting with a scalar Bose field of ion displacements, has resisted full analytical or numerical solution at all coupling since ∼ 1950, when its Hamiltonian was first written. The field has been a testing ground for analytical, semi-analytical, and numerical techniques, such as path integrals, strong-coupling perturbation expansion, advanced variational, exact diagonalisation (ED), and quantum Monte Carlo (QMC) techniques. This article reviews recent developments in the field of continuum and discrete (lattice) Fröhlich (bi)polarons starting with the basics and covering a number of active directions of research. * Electronic address: jozef.devreese@ua.ac.be † Electronic address: a.s.alexandrov@lboro.ac.uk

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Section: Current Status Of Polarons and Open Problemsmentioning

confidence: 99%

Fröhlich polaron and bipolaron: recent developments

2009

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“…The most efficient mechanism of relaxation is scattering on LO phonons. Moreover, if in the same dot two exciton levels are separated by an integral multiple of the phonon energy, a bound polaron can be formed [9]. This is the case of the strong exciton-phonon coupling.…”

Section: Discussionmentioning

confidence: 96%

Energy relaxation in CdSe/ZnSe quantum dots under the strong exciton‐phonon coupling regime

Platonov

Kießling

Astakhov

et al. 2006

Phys. Status Solidi (c)

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Resonant photoluminescence and photoluminescence excitation spectroscopy have been applied to CdSe/ZnSe quantum dots where separation between the quantized levels is close to the optical phonon energy. A strong relaxation enhancement induced by the optical phonon is observed. The fine structure of the phonon replicas is resolved. It is attributed to the optical phonons with large wave vectors from the symmetrical points of the Brillouin zone.Introduction Quantum dots (QDs) are interesting objects to study the coupling of optical phonons with carriers or excitons, due to the controllable strength of coupling arising from the discrete (i.e., atomlike) energy levels in a QD. The strong coupling regime is obtained when the energy separation between the electron levels in a QD matches the longitudinal optical (LO) phonon energy [1,2]. QDs based on II-VI compounds are of particular interest for studying phonon assisted relaxation by means of optical spectroscopy, due to the efficient exciton-phonon interaction (Fröhlich interaction [3]) and large exciton oscillator strength [4]. On the other hand, fabrication of QD-based devices, light sources or converters [5], requires knowledge of the mechanisms of the carrier relaxation within the QD states. Therefore, electronor exciton-phonon scattering, being in charge for the relaxation, is also important for the applications.In this paper, we study the energy relaxation process of CdSe self-assembled QDs embedded in ZnSe. We used QDs of a small size with the energy level of the exciton ground state relatively close to the ZnSe barrier band gap, being just 200 meV below. In the samples selected for the study the energy splitting between the exciton ground state and excited states is nearly equal to an integral multiple of the longitudinal phonon energy in ZnSe, which allows analysis of the exciton-phonon coupling under double resonance condition, i.e. in the strong coupling regime. It is shown in the following, that this leads to a dramatic reconstruction of the photoluminescence profile. Moreover, under the strong coupling regime we are able to detect optical phonons out of the Γ-point of the phonon branch.

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“…In contrast, for CdTe dots (significantly smaller than the CdSe dots) the exciton-LO phonon coupling increases strongly for QDs with higher emission energy (smaller size). Finally, we show for annealed CdTe QDs that, the exciton-LO phonon interaction again becomes independent of emission energy, consistent with the larger dot sizes created by the annealing.1 Introduction Resonantly excited PL spectroscopy has been widely used to study the exciton-LO phonon coupling in semiconductor quantum dots (QDs) [1][2][3][4][5]. This interaction in QDs may be either in the strong [1,2] or weak [3][4][5] regime.…”

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confidence: 83%

“…This interaction in QDs may be either in the strong [1,2] or weak [3][4][5] regime. In the first case, when the energy between ground and excited state in QDs is comparable to the LO phonon frequency, a new quasi-particle, the polaron, is formed that can be observed in PL excitation experiments [2]. In the weak coupling regime the exciton-LO phonon complex is formed which appears as a broad emission line spaced by multiple LO phonon energies from the laser [3][4][5].…”

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confidence: 98%

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Exciton‐LO phonon interaction in II–VI self‐assembled quantum dots

Nguyen

Maćkowski

Jackson

et al. 2004

phys. stat. sol. (c)

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We study the exciton-LO phonon interaction in CdTe/ZnTe and CdSe/ZnSe self-assembled quantum dots (QDs) by means of resonantly excited PL spectroscopy. We find that in the case of large (~8-10 nm in diameter) CdSe QDs the strength of the exciton-LO phonon coupling is nearly independent of the dot size (e.g. emission energy). In contrast, for CdTe dots (significantly smaller than the CdSe dots) the exciton-LO phonon coupling increases strongly for QDs with higher emission energy (smaller size). Finally, we show for annealed CdTe QDs that, the exciton-LO phonon interaction again becomes independent of emission energy, consistent with the larger dot sizes created by the annealing.1 Introduction Resonantly excited PL spectroscopy has been widely used to study the exciton-LO phonon coupling in semiconductor quantum dots (QDs) [1][2][3][4][5]. This interaction in QDs may be either in the strong [1,2] or weak [3][4][5] regime. In the first case, when the energy between ground and excited state in QDs is comparable to the LO phonon frequency, a new quasi-particle, the polaron, is formed that can be observed in PL excitation experiments [2]. In the weak coupling regime the exciton-LO phonon complex is formed which appears as a broad emission line spaced by multiple LO phonon energies from the laser [3][4][5]. In all cases, however, the intensity of LO phonon replica reflects the shape of the nonresonantly excited PL spectrum [3,5]. This has been interpreted as all the QDs probed interact with phonons with the same strength [3].In this work, we study the exciton-LO phonon coupling in two II-VI self-assembled QD systems which are in different QD size regimes. In the first system, 3 nm diameter CdTe QDs are smaller than the exciton Bohr radius in bulk CdTe (10 nm) [6], while in the second system, 9 nm diameter CdSe QDs are larger than the bulk exciton Bohr radius [7]. The results of resonantly excited PL spectroscopy for the larger CdSe QDs show no dependence of the exciton-LO phonon coupling on the QD emission energy. In contrast, CdTe QDs exhibit resonant PL spectra which indicate that the exciton-LO phonon coupling is strongly enhanced for QDs emitting at higher energies, i.e. those with smaller sizes. However, by increasing the average CdTe QD size in the same sample by post-growth annealing [8], the exciton-LO phonon coupling becomes insensitive to the QD emission energy (similar to what is observed for CdSe dots). We ascribe the increase of the coupling for smaller QDs to confinement-induced changes of the QD exciton wave-function [9].

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Bound polarons in semiconductor nanostructures

Cited by 18 publications

References 26 publications

Fröhlich polaron and bipolaron: recent developments

Fröhlich polaron and bipolaron: recent developments

Energy relaxation in CdSe/ZnSe quantum dots under the strong exciton‐phonon coupling regime

Exciton‐LO phonon interaction in II–VI self‐assembled quantum dots

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