Loading indirect excitons into an electrostatic trap formed in coupled GaAs quantum wells

Gärtner, A.; Schuh, Dieter; Holleitner, Alexander W.; Kotthaus, J. P.

doi:10.1016/j.physe.2007.10.042

Cited by 5 publications

(6 citation statements)

References 17 publications

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“…So far, trapping of excitons has been demonstrated in strained systems, [2]- [4] magnetic traps, [5] "natural traps" defined by interface roughness fluctuations, [6] and electrostatic traps. [7]- [13] As recently reported, [11]- [13] dipolar excitons can be very efficiently trapped in coupled quantum well (QW) heterostructures made of GaAs/AlGaAs with a lithographically structured SiO 2 -layer on top. There, dipolar excitons are trapped in the plane of the GaAs-QWs just below the perimeter of the SiO 2 -layers via the electrostatic influence of surface charges at the GaAs/SiO 2 interface.…”

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confidence: 84%

“…The thickness of the SiO 2 -layer is ~50 nm, and the titanium top gate has a thickness of ~5 nm. As recently reported, [12], [13] an electrostatic field ~10 µm beside the channel. [13] We thereby avoid heating effects and impurity-PL which are always present at the excitation spot.…”

mentioning

confidence: 90%

“…[14]- [16] The lateral expansion of excitons has been extensively studied in two dimensions (2D). [13], [15], [17]- [26] At high exciton densities, the interaction of the dipolar excitons leads to a fast, pressure-driven non-linear expansion in 2D. [17], [21], [25] At lower 2D densities, the exciton motion is diffusive, and the corresponding diffusion coefficient has a dependence on the QW width consistent with a universal power law.…”

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confidence: 97%

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Density Enhanced Diffusion of Dipolar Excitons within a One-Dimensional Channel

et al. 2009

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We experimentally investigate the lateral diffusion of dipolar excitons in coupled quantum wells in two (2D) and one (1D) dimensions. In 2D, the exciton expansion obeys nonlinear temporal dynamics due to the repulsive dipole pressure at a high exciton density, in accordance with recent reports. In contrast, the observed 1D expansion behaves linearly in time even at high exciton densities. The corresponding 1D diffusion coefficient exceeds the one in 2D by far and depends linearly on the exciton density. We attribute the findings to screening of quantum well disorder by the dipolar excitons.

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Density Enhanced Diffusion of Dipolar Excitons within a One-Dimensional Channel

et al. 2009

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“…Moreover, the dipole orientation of the excitons provides the possibility to control transport via patterned electrodes positioned adjacent to the CQWs [19][20][21]. Exciton transport has been studied in electrostatic traps [22][23][24][25][26], linear potential gradients [19,21] and stationary [27] and moving [28] lattices. The high degree of control led to demonstrations of devices such as excitonic optical transistors [29].…”

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confidence: 99%

Exciton effective mass enhancement in coupled quantum wells in electric and magnetic fields

Wilkes

Muljarov

2016

New J. Phys.

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We present a calculation of exciton states in semiconductor coupled quantum wells in the presence of electric and magnetic fields applied perpendicular to the QW plane. The exciton Schrödinger equation is solved in real space in three-dimensions to obtain the Landau levels of both direct and indirect excitons. Calculation of the exciton energy levels and oscillator strengths enables mapping of the electric and magnetic field dependence of the exciton absorption spectrum. For the ground state of the system, we evaluate the Bohr radius, optical lifetime, binding energy and dipole moment. The exciton mass renormalization due to the magnetic field is calculated using a perturbative approach. We predict a non-monotonous dependence of the exciton ground state effective mass on magnetic field. Such a trend is explained in a classical picture, in terms of the ground state tending from an indirect to a direct exciton with increasing magnetic field.

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“…Interwell excitons are characterized by a strong Stark shift in the presence of an electric field in the growth direction 8 . This allows electrostatic trapping methods [9][10][11] , as well as accumulation of interwell excitons at the interface of cold electron and hole gases; measurements in this type of system have suggested the appearance of coherence of dipolar excitons at low temperature (in the 100 mK range) [12][13][14] . In response to 12 , Semkat et al 15 have argued that under similar (but not identical) numerically simulated conditions, it is possible to observe comparable fringe visibility entirely due to the optics of the point-spread function of a tiny exciton cloud.…”

Section: Introductionmentioning

confidence: 99%

Darkening of interwell excitons in coupled quantum wells due to a stress-induced direct-to-indirect transition

et al. 2015

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In previous studies, an inhomogeneous strain field was used as a trapping mechanism for interwell excitons in coupled GaAs/Al0.45Ga0.55As quantum wells. Photoluminescence measurements in this system demonstrated the presence of a dark population of excitons at trap center in the low-temperature, high-stress, high-density regime. The dramatic appearance of this effect at low temperature and high density initially suggested that it may be indicative of a Bose-Einstein condensation (BEC) phase transition. Further experiments revealed that this effect appears more readily in wider quantum wells and occurs at strain values near the heavy-hole/light-hole crossover point. In this paper, it will be shown that this effect occurs in a regime where the heavy-hole valence band maximum shifts away from k || = 0, which is expected to strongly suppress the recombination rate at low temperatures. Simulations based on this assumption will be shown to match the experimentally observed behavior, without requiring the appearance of a Bose-Einstein condensate.

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Loading indirect excitons into an electrostatic trap formed in coupled GaAs quantum wells

Cited by 5 publications

References 17 publications

Density Enhanced Diffusion of Dipolar Excitons within a One-Dimensional Channel

Density Enhanced Diffusion of Dipolar Excitons within a One-Dimensional Channel

Exciton effective mass enhancement in coupled quantum wells in electric and magnetic fields

Darkening of interwell excitons in coupled quantum wells due to a stress-induced direct-to-indirect transition

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