Pulsed Nuclear Pumping and Spin Diffusion in a Single Charged Quantum Dot

TL;DR

This paper demonstrates a feedback mechanism in a single charged quantum dot where optical pulses induce nuclear spin polarization and diffusion, enabling dynamic control of electron spin precession.

Contribution

It introduces a novel feedback process between nuclear spins and electron spin in a quantum dot driven by pulsed optical excitation, supported by a simple numerical model.

Findings

Observation of hysteretic spin behavior due to feedback.

Identification of optical nuclear pumping and spin diffusion effects.

Potential for dynamic electron spin control via pulse timing.

Abstract

We report the observation of a feedback process between the nuclear spins in a single charged quantum dot and its trion transition, driven by a periodic sequence of optical pulses. The pulse sequence intersperses off-resonant ultrafast pulses for coherent electron-spin rotation and resonant narrow-band optical pumping. The feedback manifests as a hysteretic triangle-like pattern in the free-induction-decay of the single spin. We present a simple, quasi-analytic numerical model to describe this observation, indicating that the feedback process results from the countering effects of optical nuclear pumping and nuclear spin-diffusion inside the quantum dot. This effect allows dynamic tuning of the electron Larmor frequency to a value determined by the pulse timing, potentially allowing more complex coherent control operations.