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

TL;DR

This paper demonstrates that 2D arrays of coupled quantum dots with specific orbital interactions can exhibit bistable states suitable for high-density, low-power memory devices, with the bistability arising from Coulomb interactions and orbital hybridization.

Contribution

The study introduces a model showing how coupled quantum dot arrays with p orbitals can produce bistable tunneling currents for memory applications, highlighting the role of Coulomb interactions and orbital hybridization.

Findings

Bistable tunneling current exists due to Coulomb interactions and orbital hybridization.

Bistability is robust against detailed band structure variations.

Feasibility for high-density nanoscale memory devices is demonstrated.

Abstract

We demonstrate that two-dimensional (2D) arrays of coupled quantum dots (QDs) with six-fold degenerate p orbitals can display bistable states, suitable for application in high-density memory device with low power consumption. Due to the inter-dot coupling of $p_x$ and $p_y$ orbitals in these QD arrays, two dimensional 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 coupling between them can be neglected. We model such systems by taking into account the on-site repulsive interactions between electrons in $p_z$ orbitals and the coupling 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 extended Anderson model is used to calculate the tunneling current through the QDs. We find that bistable tunneling current can exist for such systems due to the interplay of the on-site Coulomb interactions (U) between the $p_z$ orbitals and the delocalized nature of conduction band states derived from the hybridization of $p_x$ / $p_y$ orbitals. This bistable current is not sensitive to the detailed band structure of the two dimensional band, but depends critically on the strength of $U$ and the ratio of the left and right tunneling rates. The behavior of the electrical bistability can be sustained when the 2D QD array reduces to a one-dimensional QD array, indicating the feasibility for high-density packing of these bistable nanoscale structures.