Dynamics of hole singlet triplet qubits with large g-factor differences

TL;DR

This study investigates how cubic Rashba spin-orbit interaction influences singlet-triplet oscillations in Ge hole double quantum dots, revealing complex magnetic field effects and emphasizing the importance of understanding the energy landscape for hole spin qubits.

Contribution

It provides new insights into the effects of cubic Rashba spin-orbit interaction on hole spin qubits and clarifies the relationship between avoided crossings and spin-orbit strength.

Findings

Magnetic field direction alters singlet-triplet oscillation patterns.

Large avoided crossings do not necessarily indicate strong spin-orbit interaction.

Landau-Zener sweeps help disentangle Zeeman and spin-orbit effects.

Abstract

The spin-orbit interaction is the key element for electrically tunable spin qubits. Here we probe the effect of cubic Rashba spin-orbit interaction on mixing of the spin states by investigating singlet-triplet oscillations in a planar Ge hole double quantum dot. By varying the magnetic field direction we find an intriguing transformation of the funnel into a butterfly-shaped pattern. Landau-Zener sweeps disentangle the Zeeman mixing effect from the spin-orbit induced coupling and show that large singlet-triplet avoided crossings do not imply a strong spin-orbit interaction. Our work emphasizes the need for a complete knowledge of the energy landscape when working with hole spin qubits.