Microscopic analysis of charge and spin photocurrents injected by circularly polarized one-color laser pulses in GaAs quantum wells

Duc, Huynh Thanh; Förstner, Jens; Meier, Torsten

doi:10.1103/physrevb.82.115316

Cited by 26 publications

(24 citation statements)

References 42 publications

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“…Without any additional electric or magnetic fields, injection currents do not exist in bulk GaAs, they are, however, present in GaAs quantum wells (QW) with lower symmetry. 10,19,20 Under the action of an optical field that induces interband transitions the electronic charge density in the noncentrosymmetric GaAs crystal is shifted in real space from the As atoms towards the neighboring Ga atoms and this process leads to the so-called shift current.…”

Section: Introductionmentioning

confidence: 99%

“…Previously we have developed a microscopic approach 20 in which we employed the commonly used 14-band k.p method to obtain the electron bandstructure and the Bloch functions for GaAs QWs and used the wave functions to formulate the multiband semiconductor Bloch equations (SBE). We solved the SBE to describe the optoelectronic response excited by ultrashort laser pulses.…”

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Ultrafast shift and rectification photocurrents in GaAs quantum wells: Excitation intensity dependence and the importance of band mixing

et al. 2016

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A microscopic approach that is based on the multisubband semiconductor Bloch equations formulated in the basis of a 14-band k · p model is employed to compute the temporal dynamics of photocurrents in GaAs quantum wells following the excitation with femtosecond laser pulses. This approach provides a transparent description of the interband, intersubband, and intraband excitations, fully includes all resonant as well as off-resonant excitations, and treats the light-matter interaction non-perturbatively. For linearly polarized excitations the photocurrents contain contributions from shift and rectification currents. We numerically compute and analyze these currents generated by the excitation with femtosecond laser pulses for [110]-and [111]-oriented GaAs quantum wells. It is shown that the often employed perturbative χ (2) -approach breaks down for peak fields larger than about 10 kV/cm and that non-perturbative effects lead to a reduction of the peak values of the shift and rectification currents and to temporal oscillations which originate from Rabi flopping. In particular, we find a complex oscillatory photon energy dependence of the magnitudes of the shift and rectification currents. Our simulations demonstrate that this dependence is the result of mixing between the heavy-and light-hole valence bands. This is a surprising finding since the bandmixing has an even larger influence on the strength of the photocurrents than the absorption coefficient. For [110]-oriented GaAs quantum wells the calculated photon energy dependence is compared to experimental results and a good agreement is obtained which validates our theoretical approach.

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Ultrafast shift and rectification photocurrents in GaAs quantum wells: Excitation intensity dependence and the importance of band mixing

et al. 2016

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“…As predicted in Ref. 27, charge oscillations may also occur along the y = [110] direction if the structure is excited with circularly (or even linearly) polarized light. Yet, for the experimental conditions, in particular the temperature, discussed in this paper, we could not observe any charge oscillations along the y direction, as shown by the THz traces plotted in Fig.…”

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confidence: 89%

“…Recently, a microscopic theory of injection currents launched by all-optical excitation of (110)-oriented GaAs QWs with circularly polarized light has been developed. 27 Injection currents result from an optically induced polar carrier distribution in momentum space which, in turn, arises from spin splitting of the subbands. As predicted in Ref.…”

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All-optical generation of coherent in-plane charge oscillations in GaAs quantum wells

et al. 2011

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We have induced ultrafast charge oscillations in the plane of an unbiased and undoped (110)-oriented GaAs quantum well by coherent optical excitation of heavy-hole and light-hole exciton transitions. The oscillations arise from an in-plane charge displacement between heavy-hole and light-hole states, which results from the periodic parts of the Bloch wave functions and the (110) orientation. The observations are evidence for the existence of a substantial far-infrared transition-dipole moment between heavy-and light-hole subbands for in-plane wave vectors, which we estimate to be ∼0.5 eÅ for the quantum well under study. Our findings might prove important for designs of far-infrared detectors and emitters.Excitation of semiconductors with ultrashort optical pulses leads to a polarization that coherently couples to the electric field of the excitation pulse. This coherent excitation is responsible for the initial, ultrafast nonlinear response of optically excited semiconductors and has been studied in great detail for both free-carrier and exciton excitations for two decades. 1 One of the fascinating phenomena linked to this coherent regime is the occurrence of quantum beats and the accompanying charge oscillations, the study of which has provided fundamental insight into ultrafast light-matter interactions. [2][3][4][5] Quantum beats occur in a three-level system in which two excited states are coupled via a common ground state. 2,3,6-8 If a transition-dipole moment exists between the two excited states, the quantum beats will be accompanied by charge oscillations with a frequency corresponding to the energy difference between the two excited levels. 4,5,9,10 Thus, in semiconductor heterostructures, a measurement of the simultaneously emitted electromagnetic radiation, whose frequency is usually within the THz range, is direct evidence of an intersubband transition-dipole moment which cannot be studied by all-optical techniques such as four-wave mixing and transmission measurements. 4,6 So far, charge oscillations have been measured in a coupled double or in a single asymmetric quantum well (QW) employing beating between two electron subbands 5,9 and in a single QW employing beating between heavy-and light-hole subbands. 4 Specifically, the charge oscillations studied in Refs. 4, 5, and 9 resulted from a displacement of the slowly varying envelope function along the growth direction of the QW.In this paper we report the observation of charge oscillations between heavy-and light-hole exciton states occurring in the plane of an undoped GaAs QW. We take advantage of the (110) orientation of the QW, in which optically excited heavyand light-hole states lead to oppositely oriented, macroscopic polarizations in the plane of the QW. 11,12 This in-plane charge displacement results from the periodic parts of the Bloch wave functions and, thus, is of a different physical nature than the one linked to previously observed out-ofplane oscillations. 4,5,9 Our observations prove the existence of a substantial transition-dipole ...

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“…For a (110)-oriented GaAs QW, where the QW itself is symmetric, the in-plane symmetry is reduced to C 2v point group compared to T d for bulk GaAs and D 2d for an undoped (001)-oriented GaAs QW. The reduced symmetry results in the different spin (angular momentum) states of the conduction (valence) bands being split in k-space along the [110] crystal axis while no splitting exists along the [001] crystal axis, 15,16 and, along with the k-linear terms of the transition dipole moment, contributes to the generation of spin currents.…”

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Anisotropic homogeneous linewidth of the heavy-hole exciton in (110)-oriented GaAs quantum wells

et al. 2013

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Microscopic analysis of charge and spin photocurrents injected by circularly polarized one-color laser pulses in GaAs quantum wells

Cited by 26 publications

References 42 publications

Ultrafast shift and rectification photocurrents in GaAs quantum wells: Excitation intensity dependence and the importance of band mixing

Ultrafast shift and rectification photocurrents in GaAs quantum wells: Excitation intensity dependence and the importance of band mixing

All-optical generation of coherent in-plane charge oscillations in GaAs quantum wells

Anisotropic homogeneous linewidth of the heavy-hole exciton in (110)-oriented GaAs quantum wells

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