Manifestations of the hyperfine interaction between electron and nuclear spins in singly-charged (In,Ga)As/GaAs quantum dots

TL;DR

This study investigates how hyperfine interactions influence electron and nuclear spins in charged (In,Ga)As/GaAs quantum dots, revealing anisotropic nuclear spin fluctuations and limited dynamic nuclear polarization under optical excitation.

Contribution

It provides new insights into the anisotropic nature of nuclear spin fluctuations and the effects of optical excitation on dynamic nuclear polarization in quantum dots.

Findings

Nuclear spin fluctuations are about 30 mT at low power.

NSF distribution becomes anisotropic under strong circularly polarized light.

DNP is limited under intense, short photoexcitation.

Abstract

The nuclear spin fluctuations (NSF) as well as the dynamic nuclear polarization (DNP) and their effects on the electron spins in negatively charged (In,Ga)As/GaAs quantum dots have been studied by polarized pump-probe and photoluminescence spectroscopy techniques. The effective magnetic field of the NSF is about 30 mT at low excitation power. The NSF distribution becomes highly anisotropic at strong optical excitation by circularly polarized light with periodically alternating helicity. This phenomenon is attributed to a decrease of the nuclear spin entropy due to the hyperfine interaction with polarized electron spins. The DNP is limited to small values for intense, but short photoexcitation.