NEMO-3D based atomistic simulation of a double quantum dot structure for spin-blockaded transport

摘要

This work combines an atomistic electronic structure calculation with many-body rate equations to simulate the current-voltage (Ⅰ-Ⅴ) characteristics of a weakly-coupled Double Quantum Dot (DQD) system in the spin-blockade regime. Here we performed a NEMO-3D based, atomistic simulation of the geometry of the DQD to obtain its single electron eigen-states, hopping parameters, and Coulomb integrals followed by the evaluation of Ⅰ-Ⅴ characteristics with the many-electron spectrum of the DQD system, derived from this single-electron parameter set. The many-electron spectra and wave-functions are evaluated by exact-diagonalization of the many-electron system. The Hamiltonian is constructed from single electron eigen-states, hopping parameters and Coulomb integrals derived from atomistic NEMO 3-D simulations. Calculated Ⅰ-Ⅴ characteristics exhibit multiple regions of prominent Negative Differential Resistances (NDRs) that resemble the experimental trends. Unlike resonant tunnelling devices, however, level crossings in DQDs are negligible, and the NDRs result from a delicate interplay of delocalization, orbital offset and Coulomb interaction.