Molecular formations and spectra due to electron correlations in three-electron hybrid double-well qubits

We show that systematic full configuration-interaction (FCI) calculations enable prediction of the energy spectra and intrinsic spatial spin structures many-body wave functions as a function detuning parameter for case three-electron hybrid qubits based on GaAs asymmetric double quantum dots. Specifically, in comparison with weak interactions treating entire double-dot qubit an integral unit, it is shown predicted spectroscopic patterns, originating from strong electron correlations, manifest formation Wigner molecules (WMs). Signatures WM include: (1) suppression gaps relative to noninteracting-electron modeling, (2) appearance pair avoided crossings arising between states associated two-electron occupancies left right wells. The molecule physical entity localization within each well, cannot be captured by previously employed independent-particle or two-site-Hubbard theoretical modeling qubits. emergence WMs investigated depth through concerted use FCI-adapted diagnostic tools like charge densities, well conditional probability distributions. Furthermore, spectrum strength Coulomb repulsion (at constant detuning) calculated order complement thorough analysis factors contributing emergence. report remarkable agreement recent experimental measurements. present FCI methodology multiwell dots can straightforwardly extended treat valleytronic two-band Si/SiGe qubits, where central role was confirmed recently. Such could also adapted simulations Si-based two-qubit logical gates made two interacting double-quantum-dot confining total $N\ensuremath{\le}6$ electrons.