Optically detected nuclear magnetic resonance and Knight shift in AlxGa1−xAs/GaAs heterostructures

Krapf, M.; Denninger, G.; Pascher, H.; Weimann, G.; Schlapp, W.

doi:10.1016/0038-1098(91)90704-y

Cited by 39 publications

(23 citation statements)

References 13 publications

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“…To understand the origin of this hysteresis, we first note that the equilibration time constant is similar to previously measured nuclear relaxation times for Ga and As in quantum wells [24], indicating that the source of the hysteresis is the influence of the GaAs nuclear spins upon the 2DEG electron spin energies through the contact hyperfine interaction. The hyperfine Hamiltonian is:…”

Section: Experimental Results and Intepretationsupporting

confidence: 63%

Dynamic nuclear polarization at the edge of a two-dimensional electron gas

et al. 1997

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We have used gated GaAs/AlGaAs heterostructures to explore nonlinear transport between spin-resolved Landau level (LL) edge states over a submicron region of two-dimensional electron gas (2DEG). The current I flowing from one edge state to the other as a function of the voltage V between them shows diode-like behavior-a rapid increase in I above a well-defined threshold Vt under forward bias, and a slower increase in I under reverse bias. In these measurements, a pronounced influence of a current-induced nuclear spin polarization on the spin splitting is observed, and supported by a series of NMR experiments. We conclude that the hyperfine interaction plays an important role in determining the electronic properties at the edge of a 2DEG.

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Section: Experimental Results and Intepretationsupporting

confidence: 63%

Dynamic nuclear polarization at the edge of a two-dimensional electron gas

et al. 1997

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“…Using the proportionality of the Knight shift, it has been proposed to use it to map the excited-state electron wave function of a quantum well, [18][19][20] possibly with atomic resolution. 21 However, the relatively small electron-spin density and the small number of nuclear spins in quantumconfined heterostructures makes the measurement of Knight shifts a serious problem.…”

Section: Introductionmentioning

confidence: 99%

“…21 However, the relatively small electron-spin density and the small number of nuclear spins in quantumconfined heterostructures makes the measurement of Knight shifts a serious problem. 20 Some of the optically detected NMR techniques that have been used to overcome the sensitivity issues of NMR in individual heterostructures such as quantum wells and quantum dots cause severe broadending of the NMR transitions, 18,19 thereby obscuring the relatively small Knight shifts. These problems can be avoided with a more recently introduced experiment, 22 which uses optical pumping to increase the nuclear spin polarization as well as optical detection, but combines them with pulsed radiofrequency ͑rf͒ excitation of the nuclear spins to avoid power broadening: during detection, the nuclear spins precess freely, in the absence of an rf field.…”

Section: Introductionmentioning

confidence: 99%

Light-induced Knight shifts inGaAs∕AlxGa1−xAsquantum wells

2005

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The coupling between quantum-confined electron spins in semiconductor heterostructures and nuclear spins dominates the dephasing of spin qubits in III/V semiconductors. The interaction can be measured through the electron-spin dynamics or through its effect on the nuclear spin. Here, we discuss the resulting shift of the NMR frequency ͑the Knight shift͒ and measure its size as a function of the charge-carrier density for photoexcited charge carriers in a GaAs quantum well.

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“…The NMR spectrum is then recorded by saturating one nuclear spin species with a cw radiofrequency (rf) field, either by sweeping the frequency or the strength of the external magnetic field. This approach has made possible, e.g., measurements of the Knight-shift [8] and quadrupole splittings [9,10]. Such optically detected NMR (ODNMR) experiments provide sufficient sensitivity to measure spectra of individual quantum wells [11][12][13].…”

Section: Introductionmentioning

confidence: 99%