Evidence for the light hole in GaAs/AlGaAs quantum wells from optically-pumped NMR and Hanle curve measurements

Sesti, Erika L.; Worthoff, Wieland Alexander; Wheeler, Dustin D.; Suter, Dieter; Hayes, Sophia E.

doi:10.1016/j.jmr.2014.07.001

Cited by 5 publications

(3 citation statements)

References 42 publications

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“…The experimental procedures for OPNMR have been described previously with critical parameters noted: , The external magnetic field ( B 0 ) was 4.7 T. B 1 excitation strength was ∼20 kHz; σ + polarization and laser power were held constant at 100 mW. The sample was irradiated for a time period of τ L (90 s) after the saturation sequence; a short period of time (τ D ) was inserted where the laser was shuttered (∼1 s), and the NMR spectra were then acquired by a quadrupolar echo pulse sequence (using 55° pulses) while the laser was shuttered (Figure S2).…”

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confidence: 99%

Enhanced NMR with Optical Pumping Yields⁷⁵As Signals Selectively from a Buried GaAs Interface

et al. 2017

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We have measured the As signals arising from the interface region of single-crystal semi-insulating GaAs that has been coated and passivated with an aluminum oxide film deposited by atomic layer deposition (ALD) with optically pumped NMR (OPNMR). Using wavelength-selective optical pumping, the laser restricts the volume from which OPNMR signals are collected. Here, OPNMR signals were obtained from the interface region and distinguished from signals arising from the bulk. The interface region is highlighted by interactions that disrupt the cubic symmetry of the GaAs lattice, resulting in quadrupolar satellites for nuclear [Formula: see text] isotopes, whereas NMR of the "bulk" lattice is nominally unsplit. Quadrupolar splitting at the interface arises from strain based on lattice mismatch between the GaAs and ALD-deposited aluminum oxide due to their different coefficients of thermal expansion. Such spectroscopic evidence of strain can be useful for measuring lattice distortions at heterojunction boundaries and interfaces.

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Enhanced NMR with Optical Pumping Yields⁷⁵As Signals Selectively from a Buried GaAs Interface

et al. 2017

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“…electron spins was first demonstrated by Lampel in 1968 [3]. Since then, numerous investigations in II-VI [4,5], III-V [6][7][8][9][10][11][12][13][14][15][16], and Group IV [17] semiconductors have been conducted with the primary objective of creating and detecting nuclear spin orientation. Under the broad definition of "optically pumped NMR" (OPNMR) or "laser-enhanced NMR," many investigations have been done that study the dependence of nuclear spin polarization on a number of variables, including laser wavelength and polarization [18][19][20], sample temperature [12], and magnetic field strength [9,11,21].…”

Section: Dynamic Polarization Of Nuclei By Means Of Coupling To Opticmentioning

confidence: 99%

Modelling of OPNMR phenomena using photon energy-dependent 〈S〉 in GaAs and InP

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Sesti

et al. 2016

Journal of Magnetic Resonance

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We have modified the model for optically-pumped NMR (OPNMR) to incorporate a revised expression for the expectation value of the z-projection of the electron spin, 〈S〉 and apply this model to both bulk GaAs and a new material, InP. This expression includes the photon energy dependence of the electron polarization when optically pumping direct-gap semiconductors in excess of the bandgap energy, E. Rather than using a fixed value arising from coefficients (the matrix elements) for the optical transitions at the k=0 bandedge, we define a new parameter, S(E). Incorporating this revised element into the expression for 〈S〉, we have simulated the photon energy dependence of the OPNMR signals from bulk semi-insulating GaAs and semi-insulating InP. In earlier work, we matched calculations of electron spin polarization (alone) to features in a plot of OPNMR signal intensity versus photon energy for optical pumping (Ramaswamy et al., 2010). By incorporating an electron spin polarization which varies with pump wavelength into the penetration depth model of OPNMR signal, we are able to model features in both III-V semiconductors. The agreement between the OPNMR data and the corresponding model demonstrates that fluctuations in the OPNMR intensity have particular sensitivity to light hole-to-conduction band transitions in bulk systems. We provide detailed plots of the theoretical predictions for optical pumping transition probabilities with circularly-polarized light for both helicities of light, broken down into illustrative plots of optical magnetoabsorption and spin polarization, shown separately for heavy-hole and light-hole transitions. These plots serve as an effective roadmap of transitions, which are helpful to other researchers investigating optical pumping effects.

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“…[4]) has considerably progressed during recent years [5][6][7][8][9]. The application of modern optical techniques like Faraday rotation [10,11], spin noise [12,13] and time-resolved photoluminescence [6,7], combined with more traditional techniques of magneto-optical spectroscopy and nuclear magnetic resonance (NMR) [14,15], gave the opportunity to identify the basic mechanisms of spin and energy relaxation in the intertwined spin systems of nuclei and resident charge carriers [16].…”

Section: Introductionmentioning

confidence: 99%

Subsecond nuclear spin dynamics in n -GaAs

et al. 2019

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We use time-resolved detection of the Hanle effect and polarized photoluminescence with dark intervals to investigate the buildup and decay of the spin polarization of nuclei interacting with donor-bound electrons indoped GaAs. Strong hyperfine coupling defines the millisecond timescale of the spin dynamics of these nuclei, as distinct from the nuclei far from impurity centers, characterized by a thousand times longer spin-relaxation time. The dynamics of spin polarization and relaxation attributed to the nuclei inside the donor orbit is observed on the time scale from 200 to 425 ms.

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Evidence for the light hole in GaAs/AlGaAs quantum wells from optically-pumped NMR and Hanle curve measurements

Cited by 5 publications

References 42 publications

Enhanced NMR with Optical Pumping Yields⁷⁵As Signals Selectively from a Buried GaAs Interface

Enhanced NMR with Optical Pumping Yields⁷⁵As Signals Selectively from a Buried GaAs Interface

Modelling of OPNMR phenomena using photon energy-dependent 〈S〉 in GaAs and InP

Subsecond nuclear spin dynamics in n -GaAs

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Evidence for the light hole in GaAs/AlGaAs quantum wells from optically-pumped NMR and Hanle curve measurements

Cited by 5 publications

References 42 publications

Enhanced NMR with Optical Pumping Yields75As Signals Selectively from a Buried GaAs Interface

Enhanced NMR with Optical Pumping Yields75As Signals Selectively from a Buried GaAs Interface

Modelling of OPNMR phenomena using photon energy-dependent 〈S〉 in GaAs and InP

Subsecond nuclear spin dynamics in n -GaAs

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Enhanced NMR with Optical Pumping Yields⁷⁵As Signals Selectively from a Buried GaAs Interface

Enhanced NMR with Optical Pumping Yields⁷⁵As Signals Selectively from a Buried GaAs Interface