Optically controlled excitonic transistor

Andreakou, P.; Poltavtsev, S. V.; Leonard, J. R.; Calman, E. V.; Remeika, Mikas; Kuznetsova, Y. Y.; Butov, L. V.; Wilkes, Joe; Hanson, M.; Gossard, A. C.

doi:10.1063/1.4866855

Cited by 64 publications

(59 citation statements)

References 25 publications

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“…Figures 4(c), 4(e), and 4(f) show the IX drift velocity, diffusion coefficient, and mobility, respectively. Their values are comparable to those for IX transport in devices where no electrode perforation is involved, 7,8,14,24 indicating that the perforations do not cause additional substantial obstacles for IX transport. Fig.…”

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confidence: 62%

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Indirect excitons in a potential energy landscape created by a perforated electrode

Dorow

Kuznetsova

Leonard

et al. 2016

Conference on Lasers and Electro-Optics

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We report on the principle and realization of an excitonic device: a ramp that directs the transport of indirect excitons down a potential energy gradient created by a perforated electrode at a constant voltage. The device provides an experimental proof of principle for controlling exciton transport with electrode density gradients. We observed that the exciton transport distance along the ramp increases with increasing exciton density. This effect is explained in terms of disorder screening by repulsive exciton-exciton interactions. V C 2016 AIP Publishing LLC. 1-12 Due to the spatial separation, the IXs also acquire a built-in dipole moment ed, where d is the approximate distance between the QW centers. The dipole moment can be explored to control the IX energy: an electric field F z applied perpendicular to the QW plane shifts the IX energy by E ¼ ÀedF z .13 These properties are advantageous for creating excitonic devices and studying the transport of IXs in electrostatic in-plane potential landscapes Eðx; yÞ ¼ ÀedF z ðx; yÞ.IX transport has been studied in various potential landscapes that were created by laterally modulated voltage V(x, y). These potential landscapes include ramps, 1,6,14 An alternative method for creating potential landscapes for IXs was proposed in Ref. 34, which is based on the lateral modulation of the electrode density rather than voltage. Divergence of the electric field around the periphery of an electrode reduces the normal component F z . This enables one to control F z , and thereby the potential energy landscape for IXs, by adjusting only the electrode density while keeping the entire device at a constant, uniform voltage. This method is beneficial compared to the voltage modulation method because it does not require an energy dissipating voltage gradient. One instance of this method based on varying the electrode width-the shaped electrode methodhas been used to create confining potentials for IXs in traps 18 and ramps. 14,24 In this work, we present an excitonic device based on the electrode density modulation in which a potential energy gradient is created by a perforated electrode at a constant

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confidence: 62%

“…One instance of this method based on varying the electrode width-the shaped electrode methodhas been used to create confining potentials for IXs in traps 18 and ramps. 14,24 In this work, we present an excitonic device based on the electrode density modulation in which a potential energy gradient is created by a perforated electrode at a constant …”

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confidence: 99%

Indirect excitons in a potential energy landscape created by a perforated electrode

Dorow

Kuznetsova

Leonard

et al. 2016

Conference on Lasers and Electro-Optics

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“…For example, a polariton spin flux optical router should be possible in a cross shaped ridge utilizing a similar scheme to the successful optical routing of exciton flux in coupled quantum wells. 41 We acknowledge financial support from the Greek GSRT ARISTEIA program Apollo and Spanish, MINECO Project Nos. MAT2011-22997 and MAT2014-53119-C2-1-R. C.A.…”

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confidence: 99%

Spin selective filtering of polariton condensate flow

Gao

Antón

Liew

et al. 2015

Applied Physics Letters

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Spin-selective spatial filtering of propagating polariton condensates, using a controllable spin-dependent gating barrier, in a one-dimensional semiconductor microcavity ridge waveguide is reported. A nonresonant laser beam provides the source of propagating polaritons, while a second circularly polarized weak beam imprints a spin dependent potential barrier, which gates the polariton flow and generates polariton spin currents. A complete spin-based control over the blocked and transmitted polaritons is obtained by varying the gate polarization. The generation of spin currents from the passage of electrons through ferromagnets is an important building-block for spintronic devices. For example, magnetic random access memory has developed from the spin valve concept, in which the current through a pair of ferromagnets is strongly attenuated when the magnets have opposite orientations. 1 This principle has a striking analogy in optics, where the attenuation of light passing through crossed polarizes also leads to information processing devices such as spatial light modulators based on liquid crystals. 2 Indeed analogies between spintronics and optics led to the emerging field of spinoptronics, 3 aiming to exploit a hybridization of the different fields.This hybridization is well illustrated by semiconductor microcavities in the strong coupling regime, which have become a promising basis for all-optical devices and circuits. [4][5][6][7][8] The strong coupling regime gives rise to excitonpolaritons (for simplicity, polaritons), whose light mass and integer spin facilitates condensation at elevated temperatures. 9,10 The excitonic fraction leads to strong carrier-carrier interactions 11 and sensitivity to gating electromagnetic fields. 12 At the same time, the photonic fraction allows the spin state of the polariton to be directly imprinted onto the polarization of the emitted light. An advantage over conventional spintronic devices is that, being neutral particles, polaritons do not experience strong dephasing due to Coulomb scattering and the coherent propagation of spin currents can be achieved over hundreds of microns. 13 Optically controlled carrier-carrier interactions in strongly coupled semiconductor microcavities have been shown to be a highly effective tool in the engineering of polaritons' energy landscapes, 14 for both the study of polariton condensate phenomena [15][16][17][18] and the realization of nascent polariton devices. [19][20][21][22][23][24] The interaction strength is spin dependent; 25-27 excitons with parallel spins experience a repulsive force, while the interaction between excitons with anti-parallel spin is weaker and can be attractive in nature. 28 In this work, we show that these anisotropic interactions allow the construction of a photonic analogue of current spin polarization as in a ferromagnet. Namely, we demonstrate spin polarization control of a polariton condensate signal using an optical gate in a high-finesse microcavity ridge. A schematic of the device is shown in Fig. 1(a)

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“…Lifetimes of IXs can exceed lifetimes of regular direct excitons by orders of magnitude [2-4, 6, 7]. Their long lifetimes allow IXs to travel over large distances before recombination, providing the opportunity to study exciton transport by optical imaging [9][10][11][12][13][14][15] and explore excitonic circuit devices based on exciton transport, see [16] and references therein.…”

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confidence: 99%

“…IXs were realized in wide single quantum wells (WSQW) [1][2][3][4] and in coupled quantum wells (CQW) [5][6][7][8] [2-4, 6, 7]. Their long lifetimes allow IXs to travel over large distances before recombination, providing the opportunity to study exciton transport by optical imaging [9][10][11][12][13][14][15] and explore excitonic circuit devices based on exciton transport, see [16] and references therein.Materials with a high IX binding energy allow extending the operation of the excitonic devices to high temperatures [17][18][19]. Furthermore, such materials can allow the realization of high-temperature coherent states of IXs [19].…”

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confidence: 99%

Transport of indirect excitons in ZnO quantum wells

et al. 2015

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We report on spatially-and time-resolved emission measurements and observation of transport of indirect excitons in ZnO/MgZnO wide single quantum wells.An indirect exciton (IX) in a semiconductor quantum well (QW) structure is composed of an electron and a hole confined to spatially separated QW layers. IXs were realized in wide single quantum wells (WSQW) [1][2][3][4] and in coupled quantum wells (CQW) [5][6][7][8] [2-4, 6, 7]. Their long lifetimes allow IXs to travel over large distances before recombination, providing the opportunity to study exciton transport by optical imaging [9][10][11][12][13][14][15] and explore excitonic circuit devices based on exciton transport, see [16] and references therein.Materials with a high IX binding energy allow extending the operation of the excitonic devices to high temperatures [17][18][19]. Furthermore, such materials can allow the realization of high-temperature coherent states of IXs [19]. These properties make materials with robust IXs particularly interesting. However, so far, studies of IX transport mainly concerned GaAs-based CQW. In this paper, we probe transport of IXs in ZnO/MgZnO WSQW structures. IXs in these structures are much more robust than in GaAs structures: their binding energy ∼ 30 meV [4] is considerably higher than that in GaAs/AlGaAs and GaAs/AlAs CQW (∼ 4 and ∼ 10 meV, respectively [7,20]). The binding energy of IXs is smaller than that of excitons in bulk ZnO (∼ 60 meV), however it is large enough to make the IXs stable at room temperature. At the same time, the measurements reported in this work show that transport lengths of IXs in WSQW ZnO structures reach ∼ 4 µm. In comparison, for excitons in bulk ZnO and direct excitons in ZnO structures, transport lengths are within ∼ 0.2 µm [21,22].In this work, we study polar and semipolar ZnO/MgZnO QW structures. The samples were grown by molecular beam epitaxy as in Refs. [4,23] Fig. 1a. The charges on the interfaces between ZnO and MgZnO result in a built-in electric field in the structure, which is stronger for polar samples [4,23]. The built-in electric field pulls the electron and the hole toward opposite borders of the QW, resulting in the spatial separation required for an IX.

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Optically controlled excitonic transistor

Cited by 64 publications

References 25 publications

Indirect excitons in a potential energy landscape created by a perforated electrode

Indirect excitons in a potential energy landscape created by a perforated electrode

Spin selective filtering of polariton condensate flow

Transport of indirect excitons in ZnO quantum wells

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