| Abstract | We present a theory of electronic properties of a quadruple quantum dot molecule (QQD) which focuses on geometry, chirality, and electron-electron interactions. The QQD is described by the extended Hubbard model solved using exact diagonalization method in real and Fourier space. The energy spectrum of a QQD is analysed as a function of the number of electrons Ne, for ring, linear, or star geometry. We discuss the interplay of chirality, topology, and Fermi statistics for a half-filled ring QQD charged with either additional electron or hole. We show that the chirality leads to the appearance of a topological phase and an effective gauge field stabilizing the spin polarised state. The spin polarised state with extra electron (hole) and spin unpolarised state at half-filling lead to spin blockade in transport through the ring-like QQD but not through a linear nor star QQD molecule. We demonstrate that the ground state can be tuned between a total spin S=1/2 and S=3/2 by changing the strength of on-site interactions or tuning the tunnelling matrix element. © 2013 Elsevier Ltd. All rights reserved. |
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