Imaging asymmetric Coulomb blockade phenomena across metallic nanoislands

TL;DR

This study uses scanning tunneling spectroscopy to analyze how junction-specific electrostatics influence asymmetric Coulomb blockade phenomena in indium nanoislands on black phosphorus, revealing the impact of work function differences.

Contribution

It provides a quantitative link between junction parameters and Coulomb blockade spectra, highlighting the role of electrostatics in nanoscale charge transport.

Findings

Observed spatially dispersive charging resonances with asymmetric bias shifts.

Demonstrated that work function differences cause the observed asymmetries.

Validated experimental results with orthodox theory calculations.

Abstract

Coulomb blockade (CB) arises in nanoscale systems with ultra-small capacitance, where discrete charging effects dictate electron transport, enabling wide-ranging applications based on single-electron transistors. Despite established electrostatic control of charge states in quantum dots and nanoislands, a rigorous quantitative link between junction parameters and the CB spectrum remains elusive. Here, using scanning tunneling spectroscopy, we investigate the spatial variation of CB in indium nanoislands on semiconducting black phosphorus. We observe spatially dispersive charging resonances whose trajectories exhibit a finite shift of the symmetry axis in bias as well as a pronounced asymmetric curvature. By comparing the experimental results with calculations based on orthodox theory, we show that these features originate from work function differences in the junctions, underscoring the importance of junction-specific electrostatics in nanoscale charge transport.