Coherent excitations in the Stark ladder: Excitonic Bloch oscillations

Dignam, Marc M.; Sipe, J. E.; Shah, Jagdeep

doi:10.1103/physrevb.49.10502

Cited by 76 publications

(62 citation statements)

References 13 publications

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“…6 Additionally, the amplitude of optically excited BO's depends on the exciting laser pulse width and energy that determine the initial conditions of the wave packets. 7 Pathbreaking investigations on BO's have been performed in four-wave-mixing, 8,9 THz emission, 10 and resonant transmittive electro-optic sampling ͑TEOS͒ experiments. 11 In recent years, the experimental determination of the spatial amplitude of the oscillating electronic wave packets has become an objective of the studies.…”

Section: Blochmentioning

confidence: 99%

Midbandgap electro-optic detection of Bloch oscillations

et al. 2000

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Bloch oscillations excited in a biased GaAs/Al x Ga 1Ϫx As superlattice are investigated in a time-resolved two-color electro-optic detection scheme. The detection of resonantly excited Bloch oscillations is based on the Pockels effect probed at a wavelength in the center of the band gap. The observed birefringence is induced by the macroscopic polarization of the electronic wave packets relative to the localized holes. The off-resonant detection away from optical transitions directly monitors the spatial dynamics of the electrons in amplitude and phase. The dependence of the amplitudes of the Bloch oscillating electrons on the applied electric fields are in good agreement with the electron-hole dipole lengths calculated by a quantum-mechanical model. Bloch1 and Zener 2 have proposed in their theoretical studies on the dynamics of electronic wave packets in periodic potentials a temporal and spatial oscillation of the carriers in the presence of a static electric field. The frequency and the spatial amplitude L of these Bloch oscillations ͑BO's͒ are ϭeFd/h and Lϭ⌬/eF, ͑1͒respectively, where F is the applied electric field, d the potential period, h Planck's constant, and ⌬ the electronic bandwidth. As proposed by Esaki and Tsu, this intriguing phenomenon can be realized in a biased semiconductor superlattice ͑SL͒.3 Here, BO's are excited by the coherent superposition of several electronic Wannier-Stark ͑WS͒ states 4,5 with a common hole state by short laser pulses. The localization lengths of the electronic wave packets deviate from the semiclassical picture of BO's ͓Eq. ͑1͔͒ if a fully quantum-mechanical calculation of the wave functions in the artificial semiconductor structure is used.6 Additionally, the amplitude of optically excited BO's depends on the exciting laser pulse width and energy that determine the initial conditions of the wave packets. Pathbreaking investigations on BO's have been performed in four-wave-mixing, 8,9 THz emission, 10 and resonant transmittive electro-optic sampling ͑TEOS͒ experiments.11 In recent years, the experimental determination of the spatial amplitude of the oscillating electronic wave packets has become an objective of the studies. The amplitude determination of BO's in a SL has been reported in a THz emission experiment.12 The amplitudes were calculated from the detected THz radiation power by applying a superradiance theory. Subsequently, the BO amplitude has been carefully determined in spectrally and time-resolved four-wave mixing experiments.13 Using this technique, the dependence of the amplitudes on the spectral position of the exciting laser pulses was investigated.14 Resonant TEOS experiments performed with optical detection spectrally integrated over WS transitions can only provide a qualitative analysis of the electronic dynamics due to nonlinearities of the electro-optic effect at the interband resonances.In this paper, we present the off-resonant electro-optic detection of Bloch oscillations in a GaAs/Al x Ga 1Ϫx As SL. BO's are excited resonantly, but detecte...

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Section: Blochmentioning

confidence: 99%

Midbandgap electro-optic detection of Bloch oscillations

et al. 2000

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“…As a consequence, electrons oscillate back and forth with a characteristic period given by B ϭ2 ប/(eFd), d being the spatial period of the SL. 4 For sufficiently large electric fields, electron wave functions in periodic SLs are no longer extended but localized ͑Stark-Wannier localization͒. This localization is due to the loss of quantum coherence arising from the misalignment of levels of neighboring quantum-wells.…”

Section: Introductionmentioning

confidence: 99%

Extended states and dynamical localization in semiconductor superlattices

Domı́nguez-Adame

Sánchez

Díez

1997

Journal of Applied Physics

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We study the quantum dynamics of electronic wave packets in quantum-well based semiconductor superlattices subject to an applied electric field. Using a high-accuracy numerical method, we analyze the dynamical behavior of electronic wave packets in periodic, random and random dimer superlattices. The spatial extent of electronic states is characterized by means of the time-dependent inverse participation ratio. We show that the delocalized states recently found in random dimer superlattices become spatially localized under the action of the applied field ͑dynamical localization͒ but wavepackets are much less localized than in purely random superlattices at moderate field. We conclude that the resonant tunneling effects causing delocalization in dimer superlattices play an important role even in the presence of moderate electric field. © 1997 American Institute of Physics. ͓S0021-8979͑97͒07801-8͔

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“…The one dimensional JDOS ρ is negligible in the range of terahertz radiation of experimental interest [14,15]. Thirdly, one also can regard the in-plane continuum as the source of the inhomogeneous broadening which was proposed by Thomas and von Plessen [16].…”

Section: Model and Numerical Resultsmentioning

confidence: 97%

Absorption and wave packets in optically excited semiconductor superlattices driven by direct-current-alternating-current (dc-ac) fields

Yan

Claro

Zeng

et al. 2001

J. Phys.: Condens. Matter

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Within the one-dimensional tight-binding minibands and on-site Coloumbic interaction approximation, the absorption spectrum and coherent wavepacket time evolution in an optically excited semiconductor superlattice driven by dc-ac electric fields are investigated using the semiconductor Bloch equations.The dominating roles of the ratios of dc-Stark to external ac frequency, as well as ac-Stark to external ac frequency, is emphasized. If the former is an integer N , then also N harmonics are present within one Stark frequency, while the fractional case leads to the formation of excitonic fractional ladders. The later ratio determines the size and profile of the wavepacket. In the absence of excitonic interaction it controls the maximum size wavepackets reach within one cycle, while the interaction produces a strong anisotropy and tends to palliate the dynamic wavepacket localization.

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Coherent excitations in the Stark ladder: Excitonic Bloch oscillations

Cited by 76 publications

References 13 publications

Midbandgap electro-optic detection of Bloch oscillations

Midbandgap electro-optic detection of Bloch oscillations

Extended states and dynamical localization in semiconductor superlattices

Absorption and wave packets in optically excited semiconductor superlattices driven by direct-current-alternating-current (dc-ac) fields

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