arXiv subjects

J. Wiegand

Publications and source records attributed to J. Wiegand.

2 recordsLinked to original sources

arXiv2018

Spin and reoccupation noise in a single quantum dot beyond the fluctuation-dissipation theorem

We report on the nonequilibrium spin noise of a single InGaAs quantum dot charged by a single hole under strong driving by a linearly polarized probe light field. The spectral dependency of the spin noise power evidences a homogeneous broadening and negligible charge fluctuations in the environment of the unbiased quantum dot. Full analysis of the spin noise spectra beyond the fluctuation-dissipation theorem yields the heavy-hole spin dynamics as well as the trion spin dynamics. Moreover, the experiment reveals an additional much weaker noise contribution in the Kerr rotation noise spectra. This additional noise contribution has a maximum at the quantum dot resonance and shows a significantly longer correlation time. Magnetic-field-dependent measurements in combination with theoretical modeling prove that this additional noise contribution unveils a charge reoccupation noise which is intrinsic in naturally charged quantum dots.

cond-mat.mes-hall↗

arXiv2012

Measurement of heavy-hole spin dephasing in (InGa)As quantum dots

We measure the spin dephasing of holes localized in self-assembled (InGa)As quantum dots by spin noise spectroscopy. The localized holes show a distinct hyperfine interaction with the nuclear spin bath despite the p-type symmetry of the valence band states. The experiments reveal a short spin relaxation time τ_{fast}^{hh} of 27 ns and a second, long spin relaxation time τ_{slow}^{hh} which exceeds the latter by more than one order of magnitude. The two times are attributed to heavy hole spins aligned perpendicular and parallel to the stochastic nuclear magnetic field. Intensity dependent measurements and numerical simulations reveal that the long relaxation time is still obscured by light absorption, despite low laser intensity and large detuning. Off-resonant light absorption causes a suppression of the spin noise signal due to the creation of a second hole entailing a vanishing hole spin polarization.

cond-mat.mes-hall↗