Magnetic-Field-Induced Spin-Conserving and Spin-Flip Intersubband Transitions in InAs Quantum Wells

Gauer, C.; Wixforth, Achim; Kotthaus, J. P.; Kubisa, M.; Zawadzki, W.; Brar, B.; Kroemer, H.

doi:10.1103/physrevlett.74.2772

Cited by 18 publications

(10 citation statements)

References 19 publications

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“…The experimental situation is more comfortable for the case of low temperature light scattering, because the energy difference between spin density and charge density excitations can be used for the determination of the direct Coulomb interaction terms [9]. This technique cannot be applied to the FIR absorption, since spin flip excitations are not allowed, except for systems with strongly nonparabolic bands, which complicate the evaluation of collective effects [10]. The only FIR based method which, to our knowledge, seems to give the undressed intersubband energy is the study of the coupled intersubband Landau level transitions in the limit of high in-plane magnetic fields [11].…”

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confidence: 99%

Direct Observation of Depolarization Shift of the Intersubband Resonance

et al. 2000

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We have studied the intersubband resonance of GaAs/AlGaAs multi-quantum-well systems by comparing photon drag and absorption spectra obtained by in-plane photocurrent and photoconduction measurements. The peak absorption at room temperature is found to be blueshifted from the photon drag resonance by as much as 33 cm(-1). We argue that this difference gives directly the depolarization shift, since the resonant photon drag current is driven by the Doppler effect, which is a k-vector dependent single particle process.

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confidence: 99%

Direct Observation of Depolarization Shift of the Intersubband Resonance

et al. 2000

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“…For instance, in a system with a highly nonparabolic energy dispersion, the single-particle transition energy is a strong function of wave vector k, being smaller at the Fermi wave vector k f than at k 0. The single-particle spectrum is then broad, yet the ISR is a sharp peak [5][6][7]. The collective effects condense all the available oscillator strength into a single mode.…”

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confidence: 99%

Influence of Collective Effects on the Linewidth of Intersubband Resonance

et al. 1998

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We have measured the intersubband resonances of an InAs͞AlSb quantum well with two occupied subbands from cryogenic temperatures to well above room temperature. The higher energy mode is very robust with increasing temperature; the lower energy mode, however, broadens above 200 K. We explain the results in terms of Landau damping and argue generally that the collective nature of the intersubband resonance is crucial for an understanding of the scattering mechanisms that determine the intersubband resonance linewidth. [S0031-9007(98)05471-4] PACS numbers: 73.20.Dx, 73.20.Mf, 78.66.Fd Intersubband resonance (ISR) is a fundamental excitation of a low-dimensional semiconductor system. In a single-particle picture, the resonance corresponds to the transition between two quantized states. However, ISR is not a single-particle process [1,2]. Instead, ISR is a collective phenomenon better described as a plasmon, or charge-density excitation. The most obvious consequence of the collective effects is a shift of the ISR away from the energy separating the single-particle states. This shift tends to be only a small proportion of the resonance energy as the direct electron-electron interaction (depolarization field) and the exchange-correlation interaction (exciton effects) cause blueshifts and redshifts, respectively, and tend to cancel [3,4].Recently, the collective effects have been dramatically revealed by studying systems with a broad single-particle density of states. Nevertheless, for large densities the ISR is a single, narrow line. For instance, in a system with a highly nonparabolic energy dispersion, the single-particle transition energy is a strong function of wave vector k, being smaller at the Fermi wave vector k f than at k 0. The single-particle spectrum is then broad, yet the ISR is a sharp peak [5][6][7]. The collective effects condense all the available oscillator strength into a single mode. A similar effect also occurs in weakly coupled quantum wells which have a broad and complicated single-particle spectrum yet a narrow ISR can be observed [8,9]. In the nonlinear regime where ISR is excited with a very intense source, optical pumping of carriers induces a redshift as the collective effects weaken [10].These experiments show very convincingly that ISR is indeed a collective phenomenon. It has been argued that in the best samples the resonance is homogeneously broadened [11,12], in which case one can pose the question: What are the scattering mechanisms which destroy the coherence of the plasma oscillation? Surprisingly perhaps, a microscopic theory to answer this question does not seem to exist. In fact, the ISR linewidth is usually described with the single-particle scattering rates [11,12], ignoring the collective nature of the resonance. Calculations of the ISR width at low temperature in Si͞SiO 2 from charged ion scattering [13] suggest that this approach is likely to be misleading. Generally, it appears to be unclear how the prevalent single-particle picture of electron scattering, particularly w...

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“…We chose the Voigt geometry [13,14] or the multiple reflection path geometry [3] as our experimental configurations with a magnetic field oriented parallel to the layer of the 2DEG. At finite magnetic fields we observe both spin-conserving and combined spin-flip intersubband transitions simultaneously [15]. Here, the in-plane magnetic field couples the motion perpendicular and parallel to the interface and thus breaks the polarization selection rule for the spin-conserving IST.…”

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confidence: 78%

“…This excitation mechanism is independent of the underlying bandstructure and has also been demonstrated for the GaAs-system [24]. For detector structures the magnetic field-induced intersubband resonance is a highly accurate method for the determination of intersubband matrix elements [24,25]. Other than in conventional experimental configurations [3] the magnitude of the perpendicular electric field component is well defined in this geometry and thus one source of inaccuracies can be eliminated.…”

Section: Sm Article 718mentioning

confidence: 87%

“…Taking this value we find reasonable agreement with the experimental splitting of E:17 meV for k k $ while the calculated spin-splitting decreases rapidly as k-90. This, however, is to be expected since the oscillator strength of the spin-flip resonance is strongly k-dependent and only states near k kFermi contribute to the optical matrix elements [15]. We can also calculate from the oscillator strength of the spin-flip transitions given by the parameter G:3h \/2m…”

Section: Sm Article 718mentioning

confidence: 99%

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