Dephasing of two-spin states by electron-phonon interaction in semiconductor nanostructures: Spin-boson model with a dissipative reservoir

TL;DR

This paper models how electron-phonon interactions cause decoherence in two-electron spin states within semiconductor quantum dots, analyzing the dynamics and dependence on material and structural parameters.

Contribution

It introduces a spin-boson model to quantify dephasing of two-spin states due to electron-phonon interactions in semiconductor nanostructures.

Findings

Electron-phonon interaction causes initial Gaussian decay of coherence.

Long-term exponential decay is due to phonon relaxation.

Dephasing depends on quantum dot size, separation, and material.

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). We find that electron-phonon interaction causes an initial Gaussian decay of the off-diagonal density matrix element in the singlet-triplet Hilbert space, and a long-time exponential decay originating from phonon relaxation.