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We demonstrate that two-dimensional (2D) arrays of coupled quantum dots (QDs)with six-fold degenerate p orbitals can display bistable states, suitable forapplication in high-density memory device with low power consumption. Due tothe inter-dot coupling of $p_x$ and $p_y$ orbitals in these QD arrays, twodimensional conduction bands can be formed in the x-y plane, while the $p_z$orbitals remain localized in the x-y plane such that the inter-dot couplingbetween them can be neglected. We model such systems by taking into account theon-site repulsive interactions between electrons in $p_z$ orbitals and thecoupling of the localized $p_z$ orbitals with the 2D conduction bands formed by$p_x$ and $p_y$ orbitals. The Green's function method within an extendedAnderson model is used to calculate the tunneling current through the QDs. Wefind that bistable tunneling current can exist for such systems due to theinterplay of the on-site Coulomb interactions (U) between the $p_z$ orbitalsand the delocalized nature of conduction band states derived from thehybridization of $p_x$ / $p_y$ orbitals. This bistable current is not sensitiveto the detailed band structure of the two dimensional band, but dependscritically on the strength of $U$ and the ratio of the left and right tunnelingrates. The behavior of the electrical bistability can be sustained when the 2DQD array reduces to a one-dimensional QD array, indicating the feasibility forhigh-density packing of these bistable nanoscale structures.

Bistable states of quantum dot array junctions for high-density memory