Nuclear spin effects in singly negatively charged InP quantum dots

TL;DR

This study investigates nuclear spin effects on electron spin polarization in singly negatively charged InP quantum dots, revealing nuclear spin precession times, the influence of dynamic nuclear polarization, and the magnitude of nuclear spin fluctuations.

Contribution

It provides experimental measurements of nuclear spin dynamics and their impact on electron spin polarization in InP quantum dots, highlighting the relationship with excitation power and magnetic fields.

Findings

Nuclear spin precession period T_N is ~1 μs at 5 K.

Overhauser field increases linearly with excitation power.

Frozen nuclear spin fluctuations produce an effective magnetic field of 15 mT.

Abstract

Experimental investigation of nuclear spin effects on the electron spin polarization in singly negatively charged InP quantum dots is reported. Pump-probe photoluminescence measurements of electron spin relaxation in the microsecond timescale are used to estimate the time-period $T_{N}$ of the Larmor precession of nuclear spins in the hyperfine field of electrons. We find $T_{N}$ to be $\sim 1$ $\mu$s at $T \approx 5$ K, under the vanishing external magnetic field. From the time-integrated measurements of electron spin polarization as a function of a longitudinally applied magnetic field at $T \approx 5$ K, we find that the Overhauser field appearing due to the dynamic nuclear polarization increases linearly with the excitation power, though its magnitude remains smaller than 10 mT up to the highest excitation power (50 mW) used in these experiments. The effective magnetic field of the frozen fluctuations of nuclear spins is found to be 15 mT, independent of the excitation power.