Dephasing of excited‐state excitons in InGaAs quantum dots

Borri, Paola; Langbein, Wolfgang Werner; Muljarov, Egor A.; Zimmermann, R.

doi:10.1002/pssb.200671516

Cited by 7 publications

(9 citation statements)

References 12 publications

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“…4 (d) could be significantly less affected by acoustic phonon scattering, allowing excitons to dephase at their zero-phonon dephasing rate or both levels are affected similarly and quantum oscillations between both dephasing components in two different levels sharing the same ground state are observed. The inhomogeneous broadening would damp the beating amplitude depending on the degree of correlation 30,31 . Coherent LO phonons can certainly generate oscillation when the time delay T is scanned which can affect the dephasing rate τ according to the oscillation period along T, but should not generate beating in τ 14 .…”

Section: Resultsmentioning

confidence: 99%

Quantum beats due to excitonic ground-state splitting in colloidal quantum dots

et al. 2012

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The dephasing of PbS quantum dots has been carefully measured using three pulse four-wave mixing and two-dimensional nonlinear optical spectroscopy. The temperature dependence of the homogeneous linewidth obtained from the two-dimensional spectra indicates significant scattering by acoustic phonons, whereas the excitation density dependence shows negligible excitation induced broadening in agreement with previous results. The rapid dephasing is attributed to elastic scattering by acoustic phonons. However, two dephasing components emerge, the short component that dominates the decay and a weaker longer decay, likely due to 'zero-phonon' dephasing. Quantum beats originating from two separate states can be observed, possibly revealing a ∼23.6 meV splitting of the excitonic ground state. Finally, the emergence of biexcitonic effects enhanced by the high quantum confinement is discussed.

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Section: Resultsmentioning

confidence: 99%

Quantum beats due to excitonic ground-state splitting in colloidal quantum dots

et al. 2012

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“…This picture is valid at very low temperatures. In an ordinary vacuum, this corresponds to the situation where the dynamics of quantum dots and their polarization decay is "radiatively limited" [29,32,33]. In a PBG material, where radiative processes can be suspended on timescales much longer than in ordinary vacuum, it is important to consider additional channels for phonon-mediated decay of the photon-atom bound state.…”

Section: A Undamped Acoustic Phononsmentioning

confidence: 99%

“…Experimental studies [29][30][31] in strongly confined quantum dots at low temperatures have clearly demonstrated that the polarization decay has a non-Lorentzian homogenous line shape with a very narrow zero-phonon line superimposed on a broad acoustic-phonon spectrum. These In x Ga x−1 As/GaAs quantum dot excitons have lifetimes as long as T 1 = 900 ps in an unstructured electromagnetic vacuum with dephasing times T 2 = 630 ps at cryogenic temperatures [32][33][34]. Since the dephasing times are almost as large as the decay times, dephasing in these materials is radiatively limited.…”

Section: Introductionmentioning

confidence: 99%

Microscopic theory of multiple-phonon-mediated dephasing and relaxation of quantum dots near a photonic band gap

Roy

John

2010

Phys. Rev. A

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We derive a quantum theory of the role of acoustic and optical phonons in modifying the optical absorption line shape, polarization dynamics, and population dynamics of a two-level atom (quantum dot) in the "colored" electromagnetic vacuum of a photonic band-gap (PBG) material. This is based on a microscopic Hamiltonian describing both radiative and vibrational processes quantum mechanically. We elucidate the extent to which phonon-assisted decay limits the lifetime of a single photon-atom bound state and derive the modified spontaneous emission dynamics due to coupling to various phonon baths. We demonstrate that coherent interaction with undamped phonons can lead to an enhanced lifetime of a photon-atom bound state in a PBG. This results in reduction of the steady-state atomic polarization but an increase in the fractionalized upper state population in the photon-atom bound state. We demonstrate, on the other hand, that the lifetime of the photon-atom bound state in a PBG is limited by the lifetime of phonons due to lattice anharmonicities (breakup of phonons into lower energy phonons) and purely nonradiative decay. We also derive the modified polarization decay and dephasing rates in the presence of such damping. This leads to a microscopic, quantum theory of the optical absorption line shapes. Our model and formalism provide a starting point for describing dephasing and relaxation in the presence of external coherent fields and multiple quantum dot interactions in electromagnetic reservoirs with radiative memory effects.

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“…In these InGaAs/GaAs quantum dots, exciton lifetimes in free space were measured to be as long as T 1 ¼ 900 ps with dephasing times T 2 ¼ 630 ps. In In 0.6 Ga 0.4 As/GaAs self-assembled quantum dots the dephasing times were measured to be as long as the decay times [24][25][26][27][28][29]. The exciton lifetime can be further extended by placing these quantum dots inside the structured reservoir of the photonic crystal, as a radiative recombination of the electrons and the holes is suppressed if the energy of the emitted photon is deep inside the photonic band gap.…”

Section: Introductionmentioning

confidence: 99%

Quantum dynamics of two quantum dots in the vicinity of a photonic band edge: role of structured reservoirs and phonons

Roy

2010

Journal of Modern Optics

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We study the population and disentanglement dynamics of two identical quantum dots placed inside the structured electromagnetic reservoir of a photonic crystal and coupled to an independent bath of thermal phonons. A formalism based on the method of generalized-Laplace transforms is developed to study the population and disentanglement dynamics. The effect of resonant dipole dipole interaction between the two quantum dots on the population dynamics in the presence of phonons and shows that the two two-level atoms can have a residual population at long times in the structured reservoir of a photonic crystal due to the formation of a photon-atom bound state. The disentanglement dynamics of the two quantum dots (assumed to be initially entangled) is studied using concurrence as a measure and is computed from the reduced two two-level system density matrix using the method of generalized-Laplace transforms. We show that partial disentanglement results from the interaction of the two quantum dots with the electromagnetic and phonon reservoirs. However, substantial entanglement is preserved in the fractionalized steady state formed if the transition frequency of two the quantum dots lies in the vicinity of the photonic band edge. We also discuss in detail the role of acoustic phonons on the population and disentanglement dynamics and the long time residual entanglement.

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Dephasing of excited‐state excitons in InGaAs quantum dots

Cited by 7 publications

References 12 publications

Quantum beats due to excitonic ground-state splitting in colloidal quantum dots

Quantum beats due to excitonic ground-state splitting in colloidal quantum dots

Microscopic theory of multiple-phonon-mediated dephasing and relaxation of quantum dots near a photonic band gap

Quantum dynamics of two quantum dots in the vicinity of a photonic band edge: role of structured reservoirs and phonons

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