Spin noise of electrons and holes in (In,Ga)As quantum dots: Experiment and theory

Abstract

The spin fluctuations of electron and hole doped self-assembled quantum dot ensembles are measured optically in the low-intensity limit of a probe laser in absence and presence of longitudinal or transverse static magnetic fields. The experimental results are modeled by two complementary approaches based either on semiclassical or quantum mechanical descriptions. This allows us to characterize the hyperfine interaction of electron and hole spins with the surrounding bath of nuclei on time scales covering several orders of magnitude. Our results demonstrate (i) the intrinsic precession of the electron spin fluctuations around the effective nuclear Overhauser field caused by the host lattice nuclear spins, (ii) the comparably long time scales for electron and hole spin decoherence, as well as (iii) the dramatic enhancement of the spin lifetimes induced by a longitudinal magnetic field due to the decoupling of nuclear and charge carrier spins.

Nonequilibrium nuclear spin distribution function in quantum dots subject to periodic pulses

“…It has been shown, that the accuracy of the FOA approximation [5] increases with increasing magnetic field [9,11,17]. Only in the theory of higher order correlation functions additional processes have to be included in order to make connection to the experiment [32].…”

“…Our approach is based on the observation that the Overhauser field generated by the large number of nuclei spin behaves as a classical variable in leading order [5,[9][10][11], particularly in a large external magnetic field. Chen at al.…”

Detection and amplification of spin noise using scattered laser light in a quantum-dot microcavity

“…As the peak width is constant in the measured range of fields, we can set ∆g = 0, and determine the ∆B N = /(τ s gµ B ) = 4.8 mT, in accord with the value taken from QDs without DBR structure, see Ref. [27]. Note that to achieve a weakly perturbative regime of probing, the probe power for measuring the spin noise of the QDs in the DBR structure is reduced by two orders of magnitude as compared to that in a bare QD ensemble.…”

“…The noise signal consists of a double Lorentzian-peak structure, with a peak centered around zero frequency and a second peak, moving proportionally to the magnetic field (Larmor peak) [8,27]. Here, we only concentrate on the magnetic-field dependent Larmor peak, which allows us to extract basic parameters of the system.…”

“…2(c), we extrapolate Γ HWHM to zero power from which we obtain the intrinsic width Γ 0 = 36 MHz, which corresponds to τ s = 4.4 ns. Further, it is known that τ s is given by the spread of g-factors ∆g and the fluctuating nuclear fields in the electron surrounding, ∆B N [8,27,30]…”