Spin relaxation of excitons in zero-dimensional InGaAs quantum disks

Gotoh, Hideki; Ando, Hiroaki; Kamada, H.; Chavez‐Pirson, Arturo; Temmyo, Jiro

doi:10.1063/1.120988

Cited by 101 publications

(63 citation statements)

References 16 publications

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“…The emission from peak 1 was also linearly polarized. Since the degree of polarization of the emission depended strongly on the pump polarization angle, we believe that the effect is largely due to the selection rules for photon absorption and emission [20,21]. The polarization of a pump photon is transferred into the spin of an exciton, and if no spin relaxation occurs, the spin is transfered back to the emitted photon polarization.…”

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confidence: 99%

Triggered Single Photons from a Quantum Dot

et al. 2001

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We demonstrate a new method for generating triggered single photons. After a laser pulse generates excitons inside of a single quantum dot, electrostatic interactions between them and the resulting spectral shifts allow a single emitted photon to be isolated. Autocorrelation measurements show a reduction of the two-photon probability to 0.12 times the value for Poisson light. Strong antibunching persists when the emission is saturated. The emitted photons are also polarized.PACS numbers: 42.50. Dv, Photons from classical light sources, which usually consist of a macroscopic number of emitters, follow Poisson statistics or super-Poisson statistics [1]. With a single quantum emitter, however, one can hope to generate a regulated photon stream, containing one and only one photon in a given time interval. Such an "anti-bunched" source would be useful in the new field of quantum cryptography, where security from eavesdropping depends on the ability to produce no more than one photon at a time [2,3].Continuous streams of anti-bunched photons were first observed from single atoms and ions in traps [4,5]. More recently, experiments demonstrating triggered single photons have used single molecules as the emitters, excited optically either by laser pulses [6,7] or through adiabatic following [8].Solid-state sources have potential advantages. Most importantly, they may be conveniently integrated into larger structures, such as distributed-Bragg-reflector (DBR) microcavities [9,10] to make monolithic devices. In addition, most do not suffer from the photo-bleaching effect that severely limits the lifespan of many molecules. The first experimental effort towards a solid-state singlephoton source was based on electrostatic repulsion of single carriers in a semiconductor micropost p-i-n structure [11]. Milli-Kelvin temperatures were required, however, and sufficient collection efficiency to measure the photon autocorrelation function was not obtained. More recently, continuous anti-bunched fluorescence has been seen from color centers in a diamond crystal [12,13] and from CdSe quantum dots [14].Our method to generate triggered single photons involves pulsed optical excitation of a single quantum dot and spectral filtering to remove all but the last emitted photon. Optically active quantum dots confine electrons and holes to small regions so that their energy levels are quantized [15]. If several electrons or holes are placed in the dot at the same time, they will, to a first approximation, occupy single-particle states as allowed by the Pauli exclusion principle. However, electrostatic interactions between the particles cause perturbations in the eigenstates and energies. For example, if two electronhole pairs (excitons) are created (a "biexcitonic" state), the first pair to recombine emits at a slightly lower energy than the second pair, due to a net attractive interaction [16,17]. We exploit this effect to generate single photons not only through regulated absorption, as in the single-molecule experiments, but also through t...

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Triggered Single Photons from a Quantum Dot

et al. 2001

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“…These expectations have been reinforced by numerous experimental confirmations of long spin relaxation times reported for carriers in the ground state of a QD at low temperatures. 5,6 Unfortunately, experimental investigations of spin properties of QDs at room temperature ͑RT͒, relevant to practical device applications, still remain sparse. Reported values of RT electron spin polarization, by monitoring optical polarization in continuous-wave ͑cw͒ optical orientation or electrical injection experiments, have so far been largely limited to just a few percent.…”

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Strong room-temperature optical and spin polarization in InAs/GaAs quantum dot structures

Beyer

Buyanova

Suraprapapich

et al. 2011

Applied Physics Letters

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Room-temperature optical and spin polarization up to 35% is reported in InAs/GaAs quantum dots in zero magnetic field under optical spin injection using continuous-wave optical orientation spectroscopy. The observed strong spin polarization is suggested to be facilitated by a shortened trion lifetime, which constrains electron spin relaxation. Our finding provides experimental demonstration of the highly anticipated capability of semiconductor quantum dots as highly polarized spin/light sources and efficient spin detectors, with efficiency greater than 35% in the studied quantum dots.Original Publication:Jan Beyer, Irina A Buyanova, S. Suraprapapich, C. W. Tu and Weimin Chen, Strong room-temperature optical and spin polarization in InAs/GaAs quantum dot structures, 2011, Applied Physics Letters, (98), 20, 203110.http://dx.doi.org/10.1063/1.3592572Copyright: American Institute of Physicshttp://www.aip.org

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“…4,5,6,7 Recent studies of electron spin dynamics in neutral QDs 4,5,8 have revealed that the discrete energy levels in quantum dots arising from three-dimensional quantum confinement blocks the dominant spin relaxation channels present in higher dimensional bulk and quantum well systems, resulting in considerably longer spin relaxation times. Combined with the high optical luminescence efficiency observed in QDs, 9,10,11 these long spin relaxation times should lead to larger spin-dependent luminescence signatures in spin detection applications incorporating QDs as an optical marker.…”

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Efficient electron spin detection with positively charged quantum dots

Gündoğdu

Hall

Boggess

et al. 2004

Applied Physics Letters

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We report the application of time-and polarization-resolved photoluminescence up-conversion spectroscopy to the study of spin capture and energy relaxation in positively and negatively charged, as well as neutral, InAs self-assembled quantum dots. When compared to the neutral dots, we find that carrier capture and relaxation to the ground state is much faster in the highly charged dots, suggesting that electron-hole scattering dominates this process. The long spin lifetime, short capture time, and high radiative efficiency of the positively charged dots, indicates that these structures are superior to both quantum well and neutral quantum dot light-emitting diode (LED) spin detectors for spintronics applications.The efficient detection of spin-polarized carriers is a crucial issue for the design of semiconductor-based spintronic devices. 1 A light-emitting diode (LED) configuration employing a quantum well as an optical marker has proven to be an effective means of detecting spin polarized carriers. 2,3 In a spin LED, the degree of circular polarization of the quantum well luminescence provides a direct measure of the spin polarization of the carriers arriving at the spatial location of the quantum well.The application of semiconductor quantum dots (QDs) in such a spin detection scheme is expected to provide a substantial improvement in spin sensitivity over the use of a quantum well. 4,5,6,7 Recent studies of electron spin dynamics in neutral QDs 4,5,8 have revealed that the discrete energy levels in quantum dots arising from three-dimensional quantum confinement blocks the dominant spin relaxation channels present in higher dimensional bulk and quantum well systems, resulting in considerably longer spin relaxation times. Combined with the high optical luminescence efficiency observed in QDs, 9,10,11 these long spin relaxation times should lead to larger spin-dependent luminescence signatures in spin detection applications incorporating QDs as an optical marker. The first spin LED using neutral QDs was recently demonstrated. 6 Few experiments have examined electron spin dynamics in charged quantum dots. 12,13 Through a comparison of spin capture and relaxation dynamics in neutral, positively (+QDs) and negatively (-QDs) charged QDs, we demonstrate that +QDs act as a highly efficient detector for spin-polarized electrons. Our room temperature time-resolved measurements reveal that, following capture of spin-polarized electrons, the initial degree of circular polarization of the QD ground state luminescence is more than four times larger in +QDs compared to neutral QDs. The larger spin signature in +QDs originates from an increased rate of capture of spin polarized electrons through interaction with the built-in hole population, 14,15 as indicated by the early time dynamics of the QD photoluminescence. Rapid electron capture into +QDs reduces spin relaxation in the GaAs barriers prior to capture, resulting in a six-fold enhancement in the time-integrated spin detection efficiency with the incorporation of positiv...

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Spin relaxation of excitons in zero-dimensional InGaAs quantum disks

Cited by 101 publications

References 16 publications

Triggered Single Photons from a Quantum Dot

Triggered Single Photons from a Quantum Dot

Strong room-temperature optical and spin polarization in InAs/GaAs quantum dot structures

Efficient electron spin detection with positively charged quantum dots

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