Dynamic Valley Polarization in Moire Quantum Dots

TL;DR

This paper investigates how unpolarized light can induce significant valley polarization in moire quantum dots through exciton level crossing and nuclear spin interactions, even under weak magnetic fields.

Contribution

It reveals a novel mechanism of dynamic valley polarization driven by unpolarized light and nuclear spin fluctuations in moire quantum dots.

Findings

Unpolarized light can create significant valley polarization.

Valley polarization can reach complete in n-type moire quantum dots.

Nuclear spin fluctuations transfer angular momentum to excitons.

Abstract

We describe the effects of the crossing of the exciton levels in moire quantum dots in external magnetic field. We demonstrate that the unpolarized light can create significant dynamic valley polarization of interlayer excitons in the conditions where the Zeeman energy is much smaller than the thermal energy. The angular momentum is gained by the excitons from the nuclear spin fluctuations. In the $n$-type moire quantum dots for the typical experimental parameters, the unpolarized light can lead to the complete valley polarization of the resident electrons.