A spin dephasing mechanism mediated by the interplay between the spin-orbit coupling and the asymmetrical confining potential in semiconductor quantum dot

TL;DR

This paper reveals a spin dephasing mechanism in semiconductor quantum dots caused by charge noise, mediated by spin-orbit coupling and potential asymmetry, with implications for spin qubit coherence times.

Contribution

It introduces a new spin dephasing mechanism linked to charge noise and quantum dot asymmetry, quantifying its impact on different materials and well-height parameters.

Findings

Dephasing times vary significantly across materials like InSb, InAs, and GaAs.

Lowering the well-height increases spin dephasing.

Dephasing times can reach milliseconds in GaAs quantum dots.

Abstract

Understanding the spin dephasing mechanism is of fundamental importance in all potential applications of the spin qubit. Here we demonstrate a spin dephasing mechanism in semiconductor quantum dot due to the $1/f$ charge noise. The spin-charge interaction is mediated by the interplay between the spin-orbit coupling and the asymmetrical quantum dot confining potential. The dephasing rate is proportional to both the strength of the spin-orbit coupling and the degree of the asymmetry of the confining potential. For parameters typical of the InSb, InAs, and GaAs quantum dots with a moderate well-height $V_{0}=10$ meV, we find the spin dephasing times are ${\rm T}^{*}_{2}=7$ $\mu$s, $275$ $\mu$s, and $55$ ms, respectively. In particular, the spin dephasing can be enhanced by lowering the well-height. When the well-height is as small as $V_{0}=5$ meV, the spin depahsing times in the InSb, InAs, and GaAs quantum dots are decreased to ${\rm T}^{*}_{2}=0.38$ $\mu$s, $18$ $\mu$s, and $9$ ms, respectively.