Two-spin dephasing by electron-phonon interaction in semiconductor double quantum dots

TL;DR

This paper investigates how electron-phonon interactions cause decoherence between two-electron spin states in semiconductor double quantum dots, analyzing the dynamics and dependence on system parameters.

Contribution

It provides a detailed analysis of two-spin dephasing mechanisms due to electron-phonon interactions in double quantum dots, including effects of dot parameters and material types.

Findings

Initial Gaussian decay of coherence at short times

Long-time exponential decay dominates due to phonon relaxation

Differences in decoherence between symmetric and biased quantum dots

Abstract

We study electron-phonon interaction induced decoherence between two-electron singlet and triplet states in a semiconductor double quantum dot using a spin-boson model. We investigate the onset and time evolution of this dephasing, and study its dependence on quantum dot parameters such as dot size and double dot separations, as well as the host materials (GaAs and Si). At the short time limit, electron-phonon interaction only causes an incomplete initial Gaussian decay of the off-diagonal density matrix element in the singlet-triplet Hilbert space. A complete long-time exponential decay due to phonon relaxation would eventually dominate over two-spin decoherence. We analyze two-spin decoherence in both symmetric and biased double quantum dots, identifying their difference in electron-phonon coupling and the relevant consequences.