Electron transport through multilevel quantum dot

TL;DR

This paper investigates electron transport through multilevel quantum dots using Green's function techniques, revealing how energy levels, coupling, Fermi energy, and surface disorder influence conductance, current-voltage characteristics, and noise, including a novel disorder effect.

Contribution

It provides a detailed analysis of quantum transport in multilevel quantum dots, highlighting the impact of surface disorder and finite size effects, which are less explored in prior studies.

Findings

Conductance peaks are sharp in weak coupling and broaden in strong coupling.

Surface disorder can increase current amplitude in strong disorder regimes.

Current amplitude depends strongly on system size, indicating quantum size effects.

Abstract

Quantum transport properties through some multilevel quantum dots sandwiched between two metallic contacts are investigated by the use of Green's function technique. Here we do parametric calculations, based on the tight-binding model, to study the transport properties through such bridge systems. The electron transport properties are significantly influenced by (a) number of quantized energy levels in the dots, (b) dot-to-electrode coupling strength, (c) location of the equilibrium Fermi energy $E_F$ and (d) surface disorder. In the limit of weak-coupling, the conductance ($g$) shows sharp resonant peaks associated with the quantized energy levels in the dots, while, they get substantial broadening in the strong-coupling limit. The behavior of the electron transfer through these systems becomes much more clearly visible from our study of current-voltage ($I$-$V$) characteristics. In this context we also describe the noise power of current fluctuations ($S$) and determine the Fano factor ($F$) which provides an important information about the electron correlation among the charge carriers. Finally, we explore a novel transport phenomenon by studying the surface disorder effect in which the current amplitude increases with the increase of the surface disorder strength in the strong disorder regime, while, the amplitude decreases in the limit of weak disorder. Such an anomalous behavior is completely opposite to that of bulk disordered system where the current amplitude always decreases with the disorder strength. It is also observed that the current amplitude strongly depends on the system size which reveals the finite quantum size effect.