Tunable g-Factors of Hybridized Orbitals in a Quantum Dot Molecule

Abstract

The ability to control the $g$-factors of orbital spin states in optically active quantum dot molecules (QDMs) is a prerequisite for the high-fidelity generation of multi-photonic cluster states with higher-dimensional entanglement structure. Protocols that rely on two coupled spins require knowledge of the $g$-factor and its dependence on external control parameters. Mismatches in the $g$-factor between tunnel-coupled dots introduce unwanted dephasing of coupled spin-states, making precise characterization and voltage control essential. Here, we measure the gate voltage dependence of the electron and hole $g$-factors of negatively charged trions $X^{-}$ in a single InGaAs QDM using polarization-resolved magneto-photoluminescence spectroscopy. The electron $g$-factor exhibits a pronounced step-like change at the tunneling resonance, shifting from $g_\mathrm{e} = -0.336\pm 0.008$ to $g_\mathrm{e} = -0.389\pm 0.003$, providing a direct spectroscopic fingerprint of molecular orbital formation and a shift of the wavefunction localization from the lower to the upper dot. In contrast, the hole $g$-factor remains nearly constant at $g_\mathrm{h} \approx 0.094 \pm 0.007$, exhibiting a weak modulation near the anticrossing voltages attributed to Coulomb-mediated deformation of the wavefunction by the tunneling electron. Our results are quantitatively reproduced by an eight-band $\mathbf{k}{\cdot}\mathbf{p}$ model, establishing electric-field control of the trion $g$-factors as a practical tool for independently tuning the Zeeman splitting of individual dots and opening new pathways towards the deterministic generation of two-dimensional photonic cluster states.