Semiconductor charge qubit relaxation due to two-phonon processes

TL;DR

This paper theoretically investigates how two-phonon processes contribute to the relaxation of electron states in double quantum dots, highlighting their significance at room temperature compared to one-phonon processes.

Contribution

It provides a detailed analysis of two-phonon relaxation mechanisms and their dependence on system parameters, which was not thoroughly explored before.

Findings

Two-phonon processes are negligible at 1 K but become comparable to one-phonon processes at room temperature.

Relaxation rates depend strongly on inter-dot distance, confinement strength, and temperature.

Two-phonon processes can dominate electron relaxation at higher temperatures.

Abstract

We theoretically study the relaxation of electron orbital states of a double quantum dot system due to two-phonon processes. In particular, we calculate how the relaxation rates depend on the separation distance between the quantum dots, the strength of quantum dot confinement, and the lattice temperature. Enhancement of the rates by specific inter-dot distances and lattice temperatures, and the relative strength of different scattering channels are discussed. Our results show that although at low temperatures ($T \sim 1$ K) two-phonon processes are almost four orders of magnitude weaker compared to one-phonon processes in relaxing electron orbital states, at room temperature they are as important as one-phonon processes.