Electron spin synchronization induced by optical nuclear magnetic resonance feedback

TL;DR

This paper predicts a new physical mechanism where optical nuclear magnetic resonance feedback causes electron spin precession frequency focusing in quantum dots, involving Knight field oscillations and nuclear spin projections.

Contribution

It introduces a novel mechanism explaining electron spin frequency focusing via optical NMR feedback in quantum dots, not previously described.

Findings

Electron spin precession frequency is focused due to nuclear spin dynamics.

Knight field oscillates at nuclear resonance frequency, influencing electron spins.

Nuclear spin projection aligns to make electron precession a multiple of pulse repetition.

Abstract

We predict a new physical mechanism explaining the electron spin precession frequency focusing effect observed recently in singly charged quantum dots exposed to a periodic train of resonant circularly polarized short optical pulses [A. Greilich et al, Science 317, 1896 (2007), Ref. 1]. We show that electron spin precession in an external magnetic field and a field of nuclei creates a Knight field oscillating at the frequency of nuclear spin resonance. This field drives the projection of the nuclear spin onto magnetic field to the value that makes the electron spin precession frequency a multiple of the train cyclic repetition frequency, which is the condition at which the Knight field vanishes.