Collective single mode precession of electron spins in a quantum dot ensemble

TL;DR

This paper demonstrates that electron spins in a quantum dot ensemble can be synchronized into a single precession mode using periodic optical pulses, resulting in a coherent, dephasing-free macroscopic magnetic moment.

Contribution

It introduces a method to achieve collective single mode precession of electron spins in quantum dots through nuclei-induced frequency focusing and optical pulse synchronization.

Findings

All electron spins can be driven into a single precession mode.

The synchronized spin ensemble precesses without dephasing.

Nuclei-induced frequency focusing enables this collective behavior.

Abstract

We show that the spins of all electrons, each confined in a quantum dot of an (In,Ga)As/GaAs dot ensemble, can be driven into a single mode of precession about a magnetic field. This regime is achieved by allowing only a single mode within the electron spin precession spectrum of the ensemble to be synchronized with a train of periodic optical excitation pulses. Under this condition a nuclei induced frequency focusing leads to a shift of all spin precession frequencies into the synchronized mode. The macroscopic magnetic moment of the electron spins that is created in this regime precesses without dephasing.