Theory of electron spin decoherence by interacting nuclear spins in a quantum dot

TL;DR

This paper develops a quantum theoretical model for electron spin decoherence in quantum dots, considering various nuclear interactions and their effects on spin coherence times under different experimental conditions.

Contribution

It introduces a nuclear pair-correlation method that accounts for hyperfine and nuclear interactions, highlighting the importance of hyperfine-mediated effects in spin decoherence.

Findings

Hyperfine interactions significantly influence electron spin decoherence.

Spin echo techniques reduce decoherence caused by intrinsic nuclear interactions.

Decoherence times differ notably between free-induction decay and spin echo measurements.

Abstract

We present a quantum solution to the electron spin decoherence by a nuclear pair-correlation method for the electron-nuclear spin dynamics under a strong magnetic field and a temperature high for the nuclear spins but low for the electron. The theory incorporates the hyperfine interaction, the intrinsic (both direct and indirect) nuclear interactions, and the extrinsic nuclear coupling mediated by the hyperfine interaction with the single electron in question. The last is shown to be important in free-induction decay (FID) of the single electron spin coherence. The spin echo eliminates the hyperfine-mediated decoherence but only reduces the decoherence by the intrinsic nuclear interactions. Thus, the decoherence times for single spin FID and ensemble spin echo are significantly different. The decoherence is explained in terms of quantum entanglement, which involves more than the spectral diffusion.