Spin flip from dark to bright states in InP quantum dots

Snoke, D. W.; Hübner, Jens; Rühle, W. W.; Zundel, M. K.

doi:10.1103/physrevb.70.115329

Cited by 16 publications

(16 citation statements)

References 25 publications

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“…). Recently, the dark to bright relaxation time has been measured by Snoke et al [15] for InP QDs, exp 200 τ = ps, which is in fair agreement with our estimate of 500 ps.…”

Section: Results and Conclusionsupporting

confidence: 88%

Exciton‐spin relaxation in weakly confining quantum dots due to spin–orbit interaction

Tsitsishvili

Kalt

Baltz

2006

Physica Status Solidi (b)

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In weakly confining quantum structures such as interfacial islands or quantum disks the exciton-spin relaxation is governed by two independent electron and hole spin flip processes between the optically active and dark states. A microscopic theory for these transitions is presented which is based on second order spin -orbit and carrier -phonon interaction processes. We found that the sequential relaxation between bright and dark states leads to much faster exciton-spin relaxation than for strongly confining ("small") quantum dots where the dominant process stems from electron -hole exchange interaction plus hole deformation potential coupling. In addition, the fast exciton spin relaxation implies that the (exciton-bound) electron spin flip time is also much shorter than for a single electron.

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“…). Recently, the dark to bright relaxation time has been measured by Snoke et al [15] for InP QDs, exp 200 τ = ps, which is in fair agreement with our estimate of 500 ps.…”

Section: Results and Conclusionsupporting

confidence: 88%

Exciton‐spin relaxation in weakly confining quantum dots due to spin–orbit interaction

Tsitsishvili

Kalt

Baltz

2006

Physica Status Solidi (b)

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“…The measured spin relaxation time ranges from 200 ps [23] to 167 ns [24]. The spin-relaxation time calculated from perturbation theory is approximately 2 ns in In(Ga)As/GaAs QDs at 4 K [26], which seems to be in good agreement with some experimental values [25].…”

Section: Introductionsupporting

confidence: 65%

“…Remarkably, we find that in the Hartree-Fork (HF) approximation, the transition from a bright to dark state is forbidden. Sophisticated configuration interaction (CI) [30] calculations suggest that the bright-to-dark exciton transition is approximately tens of μs in InAs/GaAs QDs, much longer than previous calculations [26] and early experimental values [23][24][25] but supported by more recent measurements [27].…”

Section: Introductionmentioning

confidence: 88%

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Slow exciton spin relaxation in single self-assembledIn1−xGaxAs/GaAsquantum dots

Wei

Guo

2014

Phys. Rev. B

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We calculate the acoustic phonon-assisted exciton spin relaxation via spin-orbit coupling in single selfassembled In 1−x Ga x As/GaAs quantum dots using an atomistic empirical pseudopotential method. We show that the transition rate from bright to dark exciton states is zero under Hartree-Fock approximation. The exciton spin relaxation time obtained from sophisticated configuration interaction calculations is approximately 15-55 μs in pure InAs/GaAs QDs and even longer in alloy dots. These results are more than three orders of magnitude longer than previous theoretical and experimental results (a few ns), but agree with more recent experiments which suggest that excitons have long spin-relaxation times (>1 μs).

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“…Among the possible mechanisms influencing R ͑exciton lifetime, pump rate, etc.͒ 20 and I X / ͑I X + I XX ͒, there are at least two temperature dependent ones: dark-to-bright exciton transitions 22,23 ͑D → B͒ and thermal excitation of holes. 19 The first one is expected to reduce R as D → B events produce bright excitons in addition to those formed by direct capture of an electron-hole pair ͑EHP͒ with proper angular momenta by the QD.…”

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confidence: 99%

Thermal effects in InP/(Ga,In)P quantum-dot single-photon emitters

et al. 2009

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We present second-order photon correlation measurements on single InP/͑Ga,In͒P quantum dots as a function of temperature. Low background emission allows to obtain antibunching minima g ͑2͒ ͑0͒ below 0.25 up to 45 K. The antibunching time R increases or decreases with temperature depending on the quantum-dot size. The two trends result from a competition between hole thermal excitation and dark-to-bright exciton transitions. The former prevails in smaller dots showing increasing R with temperature, while the latter dominates in larger quantum dots showing decreasing R with temperature. DOI: 10.1103/PhysRevB.80.161305 PACS number͑s͒: 78.67.Hc, 78.55.Cr, 42.50.Ar Semiconductor quantum dots ͑QDs͒ are among the most promising single-photon emitters ͑SPEs͒ for quantum information applications due to their versatility, scalability, and ease to handle as compared to atom or ion-based SPEs. [1][2][3][4] However, the use of semiconductor QDs as true "on demand" SPEs is conditioned by the presence of "background photons" ͑photons emitted outside the QD but at the QD energy͒ and decoherence. 5 One important source of decoherence in QDs is the random transition between bright exciton ͑BX͒ and dark exciton ͑DX͒ states ͑exciton states with total angular momentum 1 and 2, respectively͒. 6 Exciton energy splittings, as the dark-bright exciton splitting E DB and the fine-structure splitting ⌬ FS , which are large in QDs as compared to higher dimensional systems due to the increased electron-hole Coulomb interaction, are strongly sensitive to the QD size and shape. 7-9 InP QDs have received special attention for their potential use as SPEs in the visible range. [10][11][12][13][14][15][16] Photon correlation measurements for both continuous 9,11 and pulsed excitation 11,13,15 as well as under electrical injection 14 show clear antibunching dips in the second-order photon correlation function g ͑2͒ ͑ ͒ at zero delay ͑ =0͒. The standard form of the correlation function iswhere R is the characteristic ͑minimum͒ time needed for the emission of a second photon after the first one has been emitted by the QD and ␤ is generally determined by background photons. A value ␤ = 1 indicates perfect SPE. The low values of g ͑2͒ ͑0͒ found in InP QDs ͑between 0.1 and 0.2͒ ͑Refs. 10-15͒ is indicative of efficient single-photon emission. High-temperature operation of a SPE is beneficial for practical uses. Antibunching dips up to 200 K have been reported for GaN ͑Ref. 17͒ and CdSe ͑Ref. 18͒ QDs and up to 90 K in InGaAs/AlGaAs QDs. 19 In InP QDs an upper limit of 80 K has been reached using Al containing barriers. 13 Upon raising temperature the g ͑2͒ ͑0͒ value progressively increases due to the increasing background luminescence. Temperature also influences the antibunching width. Indeed R depends on several factors, as the pumping rate, the exciton lifetime 20 and the carrier relaxation time, some of them being temperature dependent. An increase in R with temperature has been reported in InGaAs/AlGaAs QDs. 19 In this Rapid Communication we pres...

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Spin flip from dark to bright states in InP quantum dots

Cited by 16 publications

References 25 publications

Exciton‐spin relaxation in weakly confining quantum dots due to spin–orbit interaction

Exciton‐spin relaxation in weakly confining quantum dots due to spin–orbit interaction

Slow exciton spin relaxation in single self-assembledIn1−xGaxAs/GaAsquantum dots

Thermal effects in InP/(Ga,In)P quantum-dot single-photon emitters

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