Understanding resonant tunnel transport in non-identical and non-aligned clusters as applied to disordered carbon systems

Abstract

We study the conductance spectra and the corresponding current-voltage characteristics of a set of three impurity clusters of different sizes arranged in the form of a scalene triangle and compare with the transport of their horizontal and vertical configurations. The tuning capability of resonant tunnelling features in a quantum dot device made of these non-aligned impurity clusters is demonstrated by re-distributing their diameters and inter-cluster distances in a systematic manner. By manipulating the inter-cluster coupling for a scalene triangular configuration, the transition of current-voltage curves from a step-like feature to a negative differential resistance can be produced. This process also yields conductance features for triangular configurations, which can be compared to the quantum dot structures perfectly aligned to the direction of the propagating wavevector. The strength of inter-cluster coupling or order parameter for these configurations is analysed from the relative variation of the width and the energy difference of the sharp and broad peaks observed in the density of states spectra. Based on the relative change of the inter-cluster coupling with the cluster configurations, a transport model applicable to structurally inhomogeneous systems is proposed in order to explain the experimentally observed variation of the energy band gap with the disorder parameters.

Evaluation of highly entangled states in asymmetrically coupled three NV centers by quantum simulator

“…In general interaction with photons produces sub-radiance and super radiance states where the resonance peak can be tuned with the symmetry of a three-dot configuration. A strong resonance peak relative to nonresonance can be demonstrated by introducing inequalities in interdot couplings through a distribution of the size and distance [23,24]. In some irregular configurations a strong resonant tunnelling can be found from the strong entanglement or a right combination of states as observed by breaking the symmetry of a regular configuration.…”

“…Therefore, we extend the work beyond ordered configurations of NV centers by breaking the symmetry to produce strong luminescence (resonance) features. The coupling strength between any two NV center defects depends on the size of the quantum dots as well as the distance between them [23]. Like the resonance spectra of quantum dots the geometric configurations of the NV centers in relation to one another (such as vertical, horizontal or triangular) would affect the luminescence if the coupling between them are varied [24].…”