Electron and Hole<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">g</mml:mi></mml:math>Factors and Exchange Interaction from Studies of the Exciton Fine Structure in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>In</mml:mi></mml:mrow><mml:mrow><mml:mn>0.60</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Ga</mml:mi></mml:mrow><mml:mrow><mml:mn>0.40</mml:mn></m

Bayer, М.; Kuther, A.; Forchel, A.; Gorbunov, A. V.; Timofeev, V. B.; Schäfer, F. P.; Reithmaier, J.P.; Reinecke, T. L.; Walck, Scott N.

doi:10.1103/physrevlett.82.1748

Cited by 392 publications

(294 citation statements)

References 27 publications

Supporting

Mentioning

271

Contrasting

Order By: Relevance

“…[7,8,9] As a consequence, angular momentum is no longer a good quantum number and the ± 1 excitons become mixed to linearly polarized eigenstates, resulting in an energy splitting δ 1 of the bright exciton doublet (see Fig. 1, upper panel right).…”

mentioning

confidence: 99%

“…As mentioned, studies of the exchange interaction induced splitting have been up to now reported by photoluminescence on single QDs [7,8] or by non-linear spectroscopy such as four-wave-mixing [12] or differential transmission [13] on ensembles. Here we use another non-linear technique to address this problem, namely pump-probe Faraday rotation [15], for which the laser was tuned to the energy of the ground state transition in the QDs and split into two trains: An electron spin polarization is induced by a circularly polarized pump beam and is tested by the rotation of the linear polarization of a probe beam.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Tailored quantum dots for entangled photon pair creation

et al. 2006

Self Cite

View full text Add to dashboard Cite

We compare the asymmetry-induced exchange splitting δ1 of the bright-exciton ground-state doublet in self-assembled (In,Ga)As/GaAs quantum dots, determined by Faraday rotation, with its homogeneous linewidth γ, obtained from the radiative decay in time-resolved photoluminescence. Post-growth thermal annealing of the dot structures leads to a considerable increase of the homogeneous linewidth, while a strong reduction of the exchange splitting is simultaneously observed. The annealing can be tailored such that δ1 and γ become comparable, whereupon the carriers are still well confined. This opens the possibility to observe polarization entangled photon pairs through the biexciton decay cascade.PACS numbers: 71.36.+c, 73.20.Dx, 78.47.+p, Entangled photon pairs are a key requirement for the implementation of quantum teleportation schemes.[1] Typically, such photon pairs are created by parametric down conversion of a strongly attenuated laser beam in a non-linear optical crystal, with limited efficiency. Recently, the decay of a biexciton complex confined in a quantum dot (QD) has been suggested as an efficient source for polarization entangled photon pairs.[2] This concept was based on the assumption of an idealistic QD structure for which the valence band ground state has pure heavy hole character with angular momentum projections J h,z = ±3/2 along the heterostructure growth direction. When an electron-hole pair is injected, the momenta of the carriers become coupled by the exchange interaction. If the dot has perfect D 2d -symmetry, angular momentum is a good quantum number: the optically active states with momenta M = ±1 are degenerate, and their decay leads to emission of σ ± -circularly polarized photons.If the dot ground states are occupied by two electrons and two holes, each with opposite spin orientations, a spin singlet biexciton X 2 is formed, for whose decay two channels exist, as shown in Fig. 1 (upper panel left). The first photon is emitted with either σ + or σ − -polarization, and then the second photon with opposite polarization, as long as no spin flip occurs after the first process. Unless a polarization measurement is performed, the two photon polarization state is therefore described by2, forming an entangled state. A key requirement is that the photons emitted at each stage of the cascade are quasi-degenerate within their homogeneous linewidth, such that they cannot be distinguished by an energy measurement.Experiments have failed up to now to demonstrate such an entanglement, as only classical correlations were observed.[3] While some of the idealizations of the original proposal are well fulfilled, for example, for strongly confined self-assembled (In,Ga)As/GaAs quantum dots (such as the long exciton spin relaxation time as com- pared to the radiative lifetime [4], or the almost pure heavy-hole character of the valence band ground state [6]), a fundamental problem arises from the broken D 2d symmetry, which is reduced to at least C 2v or even lower symmetry in realistic dot structures. [7,8,...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Tailored quantum dots for entangled photon pair creation

et al. 2006

Self Cite

View full text Add to dashboard Cite

show abstract

“…excitation above the bandgap energy of WL or GaAs barrier). In case of neutral excitons (X 0 ) in QDs, it has been shown both experimentally [5,22] and theoretically [23] that the eigenstates of the optically active bright exciton states in zero magnetic field generally are |X and |Y, split under influence of an anisotropic electron-hole exchange interaction (AEI) due to anisotropy of the QD originating from e.g. in-plane QD elongation and/or interface anisotropy.…”

Section: Origin Of the Qd Pl And Pl Polarizationmentioning

confidence: 99%

Effects of a longitudinal magnetic field on spin injection and detection in InAs/GaAs quantum dot structures

Beyer¹,

Wang²,

Buyanova³

et al. 2012

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Abstract. Effects of a longitudinal magnetic field on optical spin injection and detection in InAs/GaAs quantum dot (QD) structures are investigated by optical orientation spectroscopy. An increase in optical and spin polarization of the QDs is observed with increasing magnetic field in the range of 0-2 T, and is attributed to suppression of exciton spin depolarization within the QDs that is promoted by hyperfine interaction and anisotropic electron-hole exchange interaction. This leads to a corresponding enhancement in spin detection efficiency of the QDs by a factor of up to 2.5. At higher magnetic fields when these spin depolarization processes are quenched, electron spin polarization in anisotropic QD structures (such as double QDs that are preferably aligned along a specific crystallographic axis) still exhibits rather strong field dependence under non-resonant excitation. In contrast, such field dependence is practically absent in more "isotropic" QD structures (e.g. single QDs). We attribute the observed effect to stronger electron spin relaxation in the spin injectors (i.e. wetting layer and GaAs barriers) of the lower-symmetry QD structures, which also explains the lower spin injection efficiency observed in these structures.PACS numbers: 73.21. La, 78.67.Hc, 72.25.Fe, 72.25.Rb IntroductionSemiconductor quantum dot (QD) structures are currently under intense investigations in view of their potential applications in spin-based quantum information technology and nanospintronics, as the three-dimensional carrier confinement in these structures promises suppression of many spin relaxation mechanisms that are predominant in semiconductors of higher dimensionality [1]. In threeand two-dimensional structures, the most important spin relaxation mechanisms such as the D'yakonov-Perel and Elliott-Yafet mechanisms are promoted by the motion of carriers. For confined carriers in QDs, the lack of carrier motion efficiently deactivates these spin relaxation mechanisms. Furthermore, their atomic-like, discrete energy level structure restricts efficiency of phonon-induced inelastic scattering processes. Hyperfine interactions of confined carriers with nuclear spins of host lattice atoms within QDs [2,3] and carrier-carrier exchange interaction [4] become the dominant spin relaxation mechanisms at low temperatures. The expected extended carrier spin lifetimes have been confirmed experimentally [5][6][7][8], and efficient room-temperature spin detection has also recently been demonstrated [9], which is encouraging for proposals of QDs in applications of quantum computing

show abstract

“…Magnetic semiconductor quantum dots (QDs), where excitons (electron-hole pairs) can interact strongly with the magnetic atoms, hold particular promise as building blocks for such spin--based systems. In these low dimensional structures, the geometric factors that become more and more important with decreasing QD size (because of the quantum confinement) need to be considered with great care [6]. For instance, any in-plane asymmetry can introduce very strong effects in the case of small dots (energy shift of the quantum levels, induced linear polarization) as revealed by single dot optical spectroscopy [7,8].…”

Section: Introductionmentioning

confidence: 99%

Optical Properties of Manganese-Doped Individual CdTe Quantum Dots

et al. 2005

View full text Add to dashboard Cite

The magnetic state of a single magnetic ion (Mn 2+ ) embedded in an individual quantum dot is optically probed using microspectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn 2+ ion (S = 5/2) is analyzed in detail. The exciton-Mn 2+ exchange interaction shifts the energy of the exciton depending on the Mn 2+ spin component and six emission lines are observed at zero magnetic field. The emission spectra of individual quantum dots containing a single magnetic Mn atom differ strongly from dot to dot. The differences are explained by the influence of the system geometry, specifically the in-plane asymmetry of the quantum dot and the position of the Mn atom. Depending on both these parameters, one has different characteristic emission features which either reveal or hide the spin state of the magnetic atom. The observed behavior in both zero field and under magnetic field can be explained quantitatively by the interplay between the exciton-manganese exchange interaction (dependent on the Mn position) and the anisotropic part of the electron-hole exchange interaction (related to the asymmetry of the quantum dot).

show abstract

Electron and HolegFactors and Exchange Interaction from Studies of the Exciton Fine Structure inIn0.60Ga0.40

Cited by 392 publications

References 27 publications

Tailored quantum dots for entangled photon pair creation

Tailored quantum dots for entangled photon pair creation

Effects of a longitudinal magnetic field on spin injection and detection in InAs/GaAs quantum dot structures

Optical Properties of Manganese-Doped Individual CdTe Quantum Dots

Contact Info

Product

Resources

About