The Nuclear Spin Nanomagnet

TL;DR

This paper demonstrates that optical pumping of a single quantum dot can induce near-complete nuclear spin polarization, creating a stable, tiny magnetic nanomagnet through the Overhauser effect.

Contribution

It reveals a novel method to achieve and sustain nuclear spin self-polarization in quantum dots, effectively turning them into nanomagnets.

Findings

Nuclear spin polarization reaches nearly 100%.

The nuclear polarization creates a stable effective magnetic field.

Quantum dots act as tiny ferromagnetic nanomagnets.

Abstract

Linearly polarized light tuned slightly below the optical transition of the negatively charged exciton (trion) in a single quantum dot causes the spontaneous nuclear spin polarization (self-polarization) at a level close to 100%. The effective magnetic field of spin-polarized nuclei brings the optical transition energy into resonance with photon energy. The resonantly enhanced Overhauser effect sustains the stability of the nuclear self-polarization even in the absence of spin polarization of the quantum dot electron. As a result the optically selected single quantum dot represents a tiny magnet with the ferromagnetic ordering of nuclear spins - the nuclear spin nanomagnet.