Phonon-induced dephasing of singlet-triplet superpositions in double quantum dots without spin-orbit coupling

TL;DR

This paper demonstrates that phonon-induced pure dephasing of singlet-triplet superpositions in double quantum dots occurs independently of spin-orbit coupling, driven by elastic phonon scattering, with potential microsecond coherence times at low temperatures.

Contribution

It reveals a new dephasing mechanism in double quantum dots that does not depend on spin-orbit or hyperfine interactions, emphasizing the role of elastic phonon scattering.

Findings

Dephasing times of microseconds at sub-Kelvin temperatures

Dephasing mechanism relies solely on tunnel coupling and Pauli exclusion

Dephasing persists at low temperatures due to elastic phonon scattering

Abstract

We show that singlet-triplet superpositions of two-electron spin states in a double quantum dot undergo a phonon-induced pure dephasing which relies only on the tunnel coupling between the dots and on the Pauli exclusion principle. As such, this dephasing process is independent of spin-orbit coupling or hyperfine interactions. The physical mechanism behind the dephasing is elastic phonon scattering, which persists to much lower temperatures than real phonon-induced transitions. Quantitative calculations performed for a lateral GaAs/AlGaAs gate-defined double quantum dot yield micro-second dephasing times at sub-Kelvin temperatures, which is consistent with experimental observations.