Controlling the Interaction of Electron and Nuclear Spins in a Tunnel-Coupled Quantum Dot

TL;DR

This paper introduces a method to control nuclear and electron spins in a tunnel-coupled quantum dot, enabling precise manipulation of emission polarization and nuclear spin states through optical excitation.

Contribution

It demonstrates a novel technique for manipulating nuclear and electron spins in a quantum dot via resonant optical excitation and tunnel coupling, revealing bistability and continuous control of nuclear polarization.

Findings

Observation of bistability in emission polarization and nuclear spin polarization.

Demonstration of continuous nuclear spin control by tuning laser wavelength.

Identification of a natural cycle of electron spin creation in the system.

Abstract

We present a technique for manipulating the nuclear spins and the emission polarization from a single optically active quantum dot. When the quantum dot is tunnel coupled to a Fermi sea, we have discovered a natural cycle in which an electron spin is repeatedly created with resonant optical excitation. The spontaneous emission polarization and the nuclear spin polarization exhibit a bistability. For a sigma(+) pump, the emission switches from sigma(+) to sigma(-) at a particular detuning of the laser. Simultaneously, the nuclear spin polarization switches from positive to negative. Away from the bistability, the nuclear spin polarization can be changed continuously from negative to positive, allowing precise control via the laser wavelength.