Electrons don't like each other
Extended version of the talk given at the March Meeting in 2021
Abstract of the talk: We model the effects of Coulomb repulsion in doubly-occupied anisotropic quantum dots. Indeed, Coulomb interactions strongly influence the spectrum and the wave functions of a few electrons/holes confined in a quantum dot. When the confinement potential is not too strong, the Coulomb repulsion triggers the formation of a correlated state, the Wigner molecule, where the particles tend to split apart. We show that the anisotropy of the confinement potential strongly enhances the molecularization process. We support this conclusion with a simple harmonic potential model as well as full configuration-interaction calculations in realistic qubit devices. We highlight the exponential suppression of the singlet-triplet gap with increasing anisotropy and discuss how molecularization effects specifically hamper Pauli spin blockade readout and reduce the exchange interactions in two-qubit gates. We compare trends in different semiconductor materials and show that the molecularization effects are much stronger in silicon than in germanium, due to the heavier effective masses.
Related to the publication Phys. Rev. B 104, 195305 (2021).