Interplay of spin-orbit and hyperfine interactions in dynamical nuclear polarization in semiconductor quantum dots

TL;DR

This paper theoretically examines how spin-orbit and hyperfine interactions affect dynamical nuclear polarization in semiconductor quantum dots, revealing that strong spin-orbit coupling can hinder improvements in qubit coherence times.

Contribution

It provides a detailed analysis of the interplay between spin-orbit and hyperfine interactions in nuclear polarization transfer, highlighting their impact on qubit decoherence.

Findings

Spin-orbit interaction can polarize nuclear spins opposite to hyperfine effects.

Strong spin-orbit coupling prevents significant increase in qubit coherence time.

The study quantifies the influence of spin-orbit interactions on nuclear polarization dynamics.

Abstract

We theoretically study the interplay of spin-orbit and hyperfine interactions in dynamical nuclear polarization in two-electron semiconductor double quantum dots near the singlet $(S)$ - triplet $(T_+)$ anticrossing. The goal of the scheme under study is to extend the singlet $(S)$ - triplet $(T_0)$ qubit decoherence time $T_2^{*}$ by dynamically transferring the polarization from the electron spins to the nuclear spins. This polarization transfer is achieved by cycling the electron spins over the $S-T_+$ anticrossing. Here, we investigate, both quantitatively and qualitatively, how this hyperfine mediated dynamical polarization transfer is influenced by the Rashba and Dresselhaus spin-orbit interaction. In addition to $T_2^*$, we determine the singlet return probability $P_s$, a quantity that can be measured in experiments. Our results suggest that the spin-orbit interaction establishes a mechanism that can polarize the nuclear spins in the opposite direction compared to hyperfine mediated nuclear spin polarization. In materials with relatively strong spin-orbit coupling, this interplay of spin-orbit and hyperfine mediated nuclear spin polarizations prevents any notable increase of the $S-T_0$ qubit decoherence time $T_2^{*}$.