Signatures of correlations in intensity-dependent excitonic absorption changes

Meier, Torsten; Koch, S. W.; Brick, P.; Ell, C.; Khitrova, G.; Gibbs, H. M.

doi:10.1103/physrevb.62.4218

Cited by 47 publications

(29 citation statements)

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“…Yet, neither Pauli blocking nor firstorder Coulomb-induced nonlinearity are expected to lead to a coupling among the subspaces of different exciton spin state, thus, the observed correlations evidence high-order Coulomb correlations between excitons. 19 Their strength makes the observation of biexciton bound states likely 20 and we associate the induced absorption that shows up about 4 meV below the exciton line to bound biexcitons. 21 Since bound biexciton states can be formed within an electron gas, we can now determine if, similarly to unbound biexciton states, they may take part into coherent processes.…”

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confidence: 99%

Dressed excitons within an incoherent electron gas: Observation of a Mollow triplet and an Autler-Townes doublet

2008

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We demonstrate that the interaction between excitons and a sea of incoherent electrons does not preclude excitons dressing by light. We investigate if exciton-electron scattering plays some inhibiting role in the coherent light-exciton coupling by measuring the dynamical absorption spectrum of a modulation-doped CdTe quantum well that shows clear evidence for significant electron scattering of the excitonic states. We show the occurrence of dressed and correlated excitons by detecting quantum coherent interferences through excitonic Autler-Townes doublet and ac Stark splitting that evolves into a Mollow triplet with gain. We also evidence the partial inhibition of the electron-exciton scattering by exciton-light coupling. DOI: 10.1103/PhysRevB.77.121301 PACS number͑s͒: 78.67.De, 71.35.Cc, 71.35.Ee, 78.47.Ϫp The absorption spectrum of semiconductor quantum wells is dominated by a strong exciton resonance. Excitons are bound, conduction electron valence-hole pairs and are quite often compared to a two level system as a hydrogen atom. The role of many body interactions and exciton correlations in the exciton dynamical absorption spectrum has attracted much interest for several decades. The response of the exciton absorption to an incoherent and thermalized electronhole population obtained through nonresonant pumping in the continuum corresponds mainly to a broadening of the exciton resonance that is dominated by collision broadening ͑excitation-induced dephasing͒ rather than by a bleaching due to the saturation of the oscillator strength caused by phase space filling.1 The effect increases with electron-hole concentration. In the regime of coherent pumping at the exciton resonance, the light-field dresses the electron-hole gas and dynamical Stark splitting has been clearly observed in GaAs quantum wells embedded 2 or not 3,4 in a microcavity. Actually, in this coherent regime, the excitation-induced dephasing is found to be reduced as a result of the significant decrease of the Coulomb collision rates.5 As a consequence, the light-induced exciton dressing renders this many-body excitonic system comparable to a noninteracting atom system. 6 This issue is very important if one tries to extend coherent manipulations as those performed in atomic systems 7 to semiconductors in view of possible applications. In modulation-doped semiconductor quantum wells, excess carriers coalesce with excitons to form charged excitons ͑trions͒. The absorption spectrum is then modified: a trion resonance appears below the exciton resonance.8 However, many-body interactions also tend to become more complex. Electrons, for instance, are known to strongly screen the exciton oscillator strength 8,9 and to modify their linewidth and binding energy through exchange interactions.10 Thus, the shape of the exciton line, as well as that of the trion line, depends strongly on the strength of electron scattering with excitons and trions. Indeed, we have observed, as others before us, that a high-energy tail develops at both exciton and trion res...

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Dressed excitons within an incoherent electron gas: Observation of a Mollow triplet and an Autler-Townes doublet

2008

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“…Instead, we consider that the observed FWM signals at 1.550 eV manifest themselves as the results of many-body correlation among the carriers in bÀZnP 2 . The many-body correlation effects, such as LFR, PSF and EID, are taken into account in the analysis of nonlinear optical response of semiconductors by using the semiconductor Bloch [7][8][9][10][11][12][13][14][15], the extended OBE for the multi-level scheme [18,19,34], and the theoretical approach on a microscopic basis [22,[35][36][37]. These theoretical calculations can explain the FWM signals observed for negative time delay in exciton and biexciton system.…”

Section: Resultsmentioning

confidence: 93%

“…Instead, numerical calculations up to fifth order can be performed as in Ref. [37] where in the pump-probe experiments the fifth order contributions to the differential absorption spectra were shown to be essentially the negative of the third order contributions for the resonant excitation. Therefore, we infer that the fifth order FWM signals of the exciton, corresponding to the second term in Eq.…”

Section: Resultsmentioning

confidence: 99%

Slow dephasing and local field effects of exciton–biexciton transition in detected by femtosecond degenerate four-wave mixing

Nakanishi

Itoh

Miyagawa

et al. 2007

Journal of Luminescence

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“…In certain cases, these resonances seem to have no important qualitative influence on the nonlinear optical response, see e.g. [10,11]. Here, we extend the analysis of [14] and investigate triexciton resonances in semiconductor nanorings.…”

Section: Signatures Of Triexciton Resonances In Small Nanoringsmentioning

confidence: 93%

“…One can see that fifth-order contributions appear in Eq. (1) which are given by products of B's and p's [10,11] and also terms containing the three-exciton resonance W [7].…”

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Signatures of biexcitons and triexcitons in coherent non‐degenerate semiconductor optics

Meier

Sieh

Finger

et al. 2003

Physica Status Solidi (b)

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PACS 71.35. Ày, 73.21.Fg, 78.67.De Signatures of exciton and two-exciton states in semiconductor systems are investigated experimentally and theoretically. A set of quantum well samples with different well widths is studied using coherent excitation spectroscopy. The experimental results are analyzed using a microscopic model demonstrating the importance of biexciton correlations and disorder effects. Additional numerical investigations of absorption changes in small nanorings are employed to analyze optical transitions from two-exciton to three-exciton resonances.1 Introduction During the last decade significant progress has been made in understanding effects arising from many-body Coulomb correlations in coherent semiconductor optics, see e.g. [1][2][3]. Of particular importance in many studies has been the analysis of biexciton-induced contributions which strongly influence the dependence of low-intensity four-wave-mixing (FWM) and pump-probe (PP) signals on the polarization directions of the incident pulses.After briefly outlining the theoretical approach in Sect. 2, we discuss two examples to show that a detailed knowledge on biexciton-and also triexciton-induced resonances can be obtained using coherent non-degenerate nonlinear semiconductor optics. In Sect. 3 experimental results obtained via coherent excitation spectroscopy (CES) on a set of quantum wells with different well widths are presented. The observations are analyzed on the basis of microscopic model calculations. Numerical investigations of absorption changes in small nanorings using a two-color pump-probe (TCPP) set-up are presented in Sect. 4. This scheme is useful to analyze optical transitions between individual two-exciton and three-exciton resonances.

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Signatures of correlations in intensity-dependent excitonic absorption changes

Cited by 47 publications

References 16 publications

Dressed excitons within an incoherent electron gas: Observation of a Mollow triplet and an Autler-Townes doublet

Dressed excitons within an incoherent electron gas: Observation of a Mollow triplet and an Autler-Townes doublet

Slow dephasing and local field effects of exciton–biexciton transition in detected by femtosecond degenerate four-wave mixing

Signatures of biexcitons and triexcitons in coherent non‐degenerate semiconductor optics

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