Nuclear magnetic resonances in (In,Ga)As/GaAs quantum dots studied by resonant optical pumping

Abstract

The photoluminescence polarizations of (In,Ga)As/GaAs quantum dots annealed at different temperatures are studied as a function of external magnetic field (Hanle curves). In these dependencies, remarkable resonant features appear due to all-optical nuclear magnetic resonances (NMR) for optical excitation with modulated circular polarization. Application of an additional radio-frequency field synchronously with the polarization modulation strongly modifies the NMR features. The resonances can be related to transitions between different nuclear spin states split by the strain-induced gradient of the crystal field and by the externally applied magnetic field. A theoretical model is developed to simulate quadrupole and Zeeman splittings of the nuclear spins in a strained quantum dot. Comparison with the experiment allows us to uniquely identify the observed resonances. The large broadening of the NMR resonances is attributed to variations of the quadrupole splitting within the quantum dot volume, which is well described by the model.

Theory of spin inertia in singly charged quantum dots

“…In self-assembled QDs the strain usually leads to the quadrupole splitting of the nuclear spin sublevels [20,34,35], which induces nuclear spin dynamics. Indeed, the quadrupole splittings lead to random nuclear spin precession and changes of the Overhauser field orientation on the sub-microsecond timescale.…”

Spin phenomena in quantum dots revealed by trion photoluminescence

“…A model considering Zeeman splitting of nuclear states in presence of the quadrupole interaction is developed. It allows to identify all the resonances observed and to describe their broadening [12].…”

“…The number of such atoms is order of 10 5 usually and the highly coupled system of carrier spin interacting with the effective magnetic field of nuclear spins (Overhauser field) is the typical example of multi-degrees freedom system. Here the brief review of recent study results of such system [2][3][4][5][6][7][8][9][10][11][12] will be presented.…”

Cross calibration of deformation potentials and gradient-elastic tensors of GaAs using photoluminescence and nuclear magnetic resonance spectroscopy in GaAs/AlGaAs quantum dot structures

“…The relation between strain and EFG is described by a fourth rank "gradient-elastic" tensor S ijkl , which can be parameterized by two components S 11 and S 44 in case of cubic crystal symmetry. The need for accurate S ijkl values have reemerged recently in view of using NMR for non-destructive structural analysis of nanoscale semiconductor structures [21][22][23][24][25][26][27] as well as exploring the effect of nuclear quadrupolar interaction on coherent electron-nuclear spin dynamics in solid state qubits [28][29][30] .…”