Exciton oscillator strength in magnetic-field-induced spin superlattices CdTe/(Cd,Mn)Te

Ivchenko, E. L.; Kavokin, A. V.; Кочерешко, В. П.; Posina, G. R.; Uraltsev, I. N.; Yakovlev, D. R.; Bicknell-Tassius, R.N.; Waag, A.; Landwehr, G.

doi:10.1103/physrevb.46.7713

Cited by 107 publications

(53 citation statements)

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“…Optical value of ε ∞ = 7.25 is inferred from the low-energy value of the refraction index of CdTe [12] and used as a background when describing exciton effects. However, experimental reflection spectra at exciton lines in CdTe/CdMnTe superlattices have been found to require the background dielectric constant as high as 9.95 [5]. Exact data on the complex dielectric constant of bulk crystals in a broad spectral range are needed both for the substrate and optical device applications.…”

Section: Introductionmentioning

confidence: 99%

“…The promises of this interaction include optical isolators on the giant Faraday effect [2], spintronics [3], lasers [4], and other device applications of tunable bands and lines observed in bulk crystals, magnetic quantum wells [5][6][7], and dots [8,9]. Device operation at the fundamental absorption edge is of special interest because of the most pronounced dependence of the material optical parameters on the interacting photon energy.…”

Section: Introductionmentioning

confidence: 99%

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Complex dielectric constant of Cd_0.8SMn_0.2Te crystals near the fundamental absorption edge

Safonova¹,

Brazis²,

Narkowicz³

2004

Lith. J. Phys.

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The complex dielectric constant of Cd0.8Mn0.2Te single crystals is determined from reflection measurements in the photon energy range from 1.75 to 2 eV at the lattice temperature T = 2 K. The light reflection model includes exciton absorption and dispersive background dielectric constant contribution. The same model is found to be efficient in describing the band of nonreciprocal reflection arising in nonzero magnetic field in the Voigt geometry.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Complex dielectric constant of Cd_0.8SMn_0.2Te crystals near the fundamental absorption edge

Safonova¹,

Brazis²,

Narkowicz³

2004

Lith. J. Phys.

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“…The strength of the magnetoreflectivity signal is determined by the density of unoccupied states and hence the density of holes in the Landau levels. The absorption coefficient is directly related to dispersion in the refractive index through the KramersKronig relation and it has been shown theoretically that the magnitude of the excursion of the reflectivity around the transition energy is proportional to the absorption coefficient [11]. The direct reflectivity spectra measured at 14.5T are shown as an example of this analysis in the lower part of Fig.1.…”

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confidence: 99%

Measurements of composite fermion masses from the spin polarization of two-dimensional electrons in the region 1<ν<2

et al. 2002

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Measurements of the reflectivity of a 2-D electron gas are used to deduce the polarization of the Composite Fermion hole system formed for Landau level occupancies in the regime 1 < ν < 2. The measurements are consistent with the formation of a mixed spin CF system and allow the density of states or 'polarization' effective mass of the CF holes to be determined. The mass values at ν = 3/2 are found to be ∼ 1.9me for electron densities of 4.4 × 10 11 cm −2 , which is significantly larger than those found from measurements of the energy gaps at finite values of effective magnetic field.The fractional quantum Hall effect has been very successfully described in terms of the picture of Composite Fermions [1] [2], however considerable uncertainties exist about both the Composite Fermion masses and the role of spin and the formation of partially polarized states [3][4][5][6][7]. In particular Park and Jain [3] have pointed out that the CF mass measured from activation measurements of the energy gap may be substantially smaller than the thermodynamic or "polarization" mass which determines the equilibrium spin populations of the carriers, an idea which has received some recent experimental support [6]. In this paper we describe a direct measurment of the polarization of the 2D Composite Fermion (CF) gas and deduce values for the polarization mass.In the Composite Fermion model 2D electrons at filling factor ν = 1/2 form a new collective state with quasiparticle excitations, known as Composite Fermions, and zero effective magnetic field. If the Zeeman energy is small compared to the equivalent Fermi energy in the Composite Fermion system the spin polarization of the 2D electrons around ν = 1/2 deviates from 100% even at zero temperature. Cyclotron-like quantization of the energy spectra of the Composite Fermions away from ν = 1/2 causes oscillations in the spin polarization of the 2D electrons at integer filling factors for Composite Fermions. Simultaneously, transport properties of the 2DEG become controllable by the ratio of the cyclotron energy for the Composite Fermions to the Zeeman energy [4] [8]. In spite of this evidence for partial polarization of the CF system direct measurements of the CF Fermi wavevector suggest that the system is close to fully polarized both at ν = 1/2 [9] and at ν = 3/2 [10].In this work we report direct measurements of the properties of Composite Fermion holes in the region of level occupancy 1 < ν < 2. For small values of the Zeeman energy a very convenient way to treat the unoccupied states in the zeroth Landau level in the region 1 < ν < 2 is as "holes" [4] with an effective filling factor given by ν h = 2 − ν e relative to completely filled electron sublevels of both spins. The properties of such holes in the region 1 < ν e < 2 are equivalent to the properties of electrons in the region 0 < ν e < 1 if the energy scale for the Coulomb interaction is much less than the cyclotron energy. Thus a new Composite Fermion system is generated around filling factor ν h = 1/2 which corresponds to...

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“…8 are extended to the case of randomly inhomogeneous 2D ensembles of QDs with homogeneous line broadening. In the strong confinement regime, 8 the effective permittivity of a QD is written as a Lorentzian function [17][18][19] with a single resonance frequency ͑eigenfrequency͒ 0…”

Section: Modelmentioning

confidence: 99%

Anomalous exciton lifetime by electromagnetic coupling of self-assembled InAs/GaAs quantum dots

Bogaart

Haverkort

2010

Journal of Applied Physics

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We report on the experimental observation of a hitherto ignored long-range electromagnetic coupling between self-assembled InAs/GaAs quantum dots ͑QDs͒. A 12 times enhancement of the QD exciton lifetime is observed by means of time-resolved differential reflection spectroscopy. The enhancement is due to local field effects within the QD ensemble. The electromagnetic coupling of the QDs results in a collective polarizability, and is observed as a suppression of the emission rate. Our results reveal that the mutual coupling strength can be optically tuned by varying the pump excitation density. This enables us to optically tune the exciton lifetime.

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Exciton oscillator strength in magnetic-field-induced spin superlattices CdTe/(Cd,Mn)Te

Cited by 107 publications

References 20 publications

Complex dielectric constant of Cd_0.8SMn_0.2Te crystals near the fundamental absorption edge

Complex dielectric constant of Cd_0.8SMn_0.2Te crystals near the fundamental absorption edge

Measurements of composite fermion masses from the spin polarization of two-dimensional electrons in the region 1<ν<2

Anomalous exciton lifetime by electromagnetic coupling of self-assembled InAs/GaAs quantum dots

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Exciton oscillator strength in magnetic-field-induced spin superlattices CdTe/(Cd,Mn)Te

Cited by 107 publications

References 20 publications

Complex dielectric constant of Cd0.8SMn0.2Te crystals near the fundamental absorption edge

Complex dielectric constant of Cd0.8SMn0.2Te crystals near the fundamental absorption edge

Measurements of composite fermion masses from the spin polarization of two-dimensional electrons in the region 1<ν<2

Anomalous exciton lifetime by electromagnetic coupling of self-assembled InAs/GaAs quantum dots

Contact Info

Product

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Complex dielectric constant of Cd_0.8SMn_0.2Te crystals near the fundamental absorption edge

Complex dielectric constant of Cd_0.8SMn_0.2Te crystals near the fundamental absorption edge