Molecular spintronics: Coherent spin transfer in coupled quantum dots

TL;DR

This paper models coherent electron spin transfer in coupled quantum dots using a transfer Hamiltonian, linking theoretical calculations with experimental Faraday rotation data to quantify spin transfer probabilities and exchange energies.

Contribution

It introduces a theoretical framework for analyzing Faraday rotation signals in coupled quantum dots, providing quantitative estimates of spin transfer matrix elements and probabilities.

Findings

Transfer matrix element ~0.08 eV

Spin transfer probability ~10%

Faraday rotation linked to spin transfer and exchange energy

Abstract

Time-resolved Faraday rotation has recently demonstrated coherent transfer of electron spin between quantum dots coupled by conjugated molecules. Using a transfer Hamiltonian ansatz for the coupled quantum dots, we calculate the Faraday rotation signal as a function of the probe frequency in a pump-probe setup using neutral quantum dots. Additionally, we study the signal of one spin-polarized excess electron in the coupled dots. We show that, in both cases, the Faraday rotation angle is determined by the spin transfer probabilities and the Heisenberg spin exchange energy. By comparison of our results with experimental data, we find that the transfer matrix element for electrons in the conduction band is of order 0.08 eV and the spin transfer probabilities are of order 10%.