Quadrupolar effect on nuclear spin depolarization in single self-assembled quantum dots

Abstract

We investigate the nuclear spin polarization in single self-assembled InAlAs quantum dots under magnetic fields that are sufficiently weak to make the impacts of the quadrupole interaction apparent. The nuclear spin depolarization rate decreases as the magnitude of the applied longitudinal magnetic field increases. This trend can be explained by the dissolution of quadrupolar mixing that is coupled to the temporal fluctuations of the hyperfine interaction. In addition, the optically injected electron spin generates a considerable Overhauser field under a wide range of experimental conditions. These findings are important for nuclear spin engineering and electron spin manipulation in self-assembled III–V semiconductor quantum dots.

Influence of a Longitudinal Field on the Large In‐Plane Nuclear Field Formation in Single Quantum Dots

“…The fitting results were ms, ps, and mT, where , , and are the time fraction when the unpaired electron occupies the QD, the relaxation time of NSP, and the correlation time of HFI, respectively.) The obtained B z is comparable with the strength of NQI (the reduced quadrupolar field as ≈280 mT) estimated from an independent experiment …”

“…In the Hanle‐effect measurements, we observed the DCP and OHS under a transverse magnetic field up to ≈1.2 T. In this region, the OHS is less than (or comparable with) the linewidth of PL spectra, and thus, the separate detection of σ + and σ − PL components is essential for the precise evaluations of DCP and OHS. To reduce the measurement errors, a setup for the simultaneous acquisition of the orthogonal polarization components was developed as shown in Figure b . The excitation helicity was changed by the combination of a linear polarizer, a quarter‐wave plate (QWP), and a half‐wave plate (HWP), where the HWP was used to correct the phase distortion of the circular polarization due to the optics in the excitation beam path.…”

Systematic investigations of transient response of nuclear spins in the presence of polarized electrons

“…Thus, an effective field which can keep the nuclear-spin polarization even at B ap = 0 should be present, and we assumed a constant stray field for such an effective field. Another possible origin of the effective field is the Knight field which acts on nuclear spins from polarized electron spins [13]. Further study, however, is necessary to clarify the origin for the effective field.…”

“…This interaction dramatically increases the signal intensity available for detection of the nuclear-spin states compared with pick-up-coil detection. Several methods to create and detect nuclear spins through the hyperfine interaction have been demonstrated by using optically- [1][2][3][4][5][6][7][8][9][10][11][12][13] or electrically [14][15][16][17][18][19][20][21][22][23][24][25]-created electron spins.…”

Experimental studies on nuclear field generated orthogonal to electron spin in single self-assembled nanostructures

“…(Color online) Experimental setup for the Hanle effect measurement (LP: linear polarizer, HWP: half-wave plate, QWP: quarter-wave plate, SC-magnet: superconducting magnet). The simultaneous acquisition apparatus of the s + and spolarized PL components is inserted in the detection path.The detail of the setup is seen in our previous work 25).…”