Negative exchange interactions in coupled few-electron quantum dots

Abstract

It has been experimentally shown that negative exchange interactions can arise in a linear three-dot system when a two-electron double quantum dot is exchange coupled to a larger quantum dot containing on the order of one hundred electrons. The origin of this negative exchange can be traced to the larger quantum dot exhibiting a spin triplet-like rather than singlet-like ground state. Here, we show using a microscopic model based on the configuration interaction (CI) method that both triplet-like and singlet-like ground states are realized depending on the number of electrons. In the case of only four electrons, a full CI calculation reveals that triplet-like ground states occur for sufficiently large dots. These results hold for symmetric and asymmetric quantum dots in both Si and GaAs, showing that negative exchange interactions are robust in few-electron double quantum dots and do not require large numbers of electrons.

8 pages, 3 figures

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Cited by in corpus (13)

• Semiconductor Spin Qubits
• Coherent spin control of s-, p-, d- and f-electrons in a silicon quantum dot
• Fast spin exchange between two distant quantum dots
• Interplay of exchange and superexchange in triple quantum dots
• Interacting holes in Si and Ge double quantum dots: from a multiband approach to an effective-spin picture
• Extended Hubbard model describing small multi-dot arrays in bilayer graphene
• Robust entangling gate for capacitively coupled few-electron singlet-triplet qubits
• Singlet-triplet transition in double quantum dots in two-dimensional topological insulators
• Microscopic theory on magnetic-field-tuned sweet spot of exchange interactions in multielectron quantum-dot systems
• Theory on electron-phonon spin dehphasing in GaAs multi-electron double quantum dots
• Sign-switching of superexchange mediated by few electrons under non-uniform magnetic field
• Exploring Entanglement Spectrum and Phase Diagram in multi-electron Quantum Dot Chains
• Negative exchange interaction in Si quantum dot arrays via valley-phase induced ${\mathbb{Z}}_2$ gauge field