Disentangling Orbital and Confinement Contributions to <i>g</i>-Factor in Ge/SiGe Hole Quantum Dots.

Sommer, L; Seidler, I; Schupp, F J; Paredes, S; Hendrickx, N W; Massai, L; Tsoukalas, K; Orekhov, A et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Spin qubits are typically operated in the lowest orbital of a quantum dot to minimize interference from nearby states. In valence-band hole systems, strong spin-orbit coupling links spin and orbital degrees of freedom, strongly influencing the hole <i>g</i>-factor, a key parameter for qubit control. We investigate the out-of-plane <i>g</i>-factor in Ge quantum dots using excitation (single-particle) and addition (many-body) spectra. Excitation spectra allow us to distinguish the pure Zeeman <i>g</i>-factor from orbital contributions to the magnetic field splitting of states despite the strong spin-orbit coupling. This distinction clarifies discrepancies between <i>g</i>-factors extracted with the two methods, for different orbital states and different hole numbers. Furthermore, we find gate-tunability of <i>g</i>-factors at the level of 15%, highlighting its relevance for all-electric qubit manipulation.