Double island Coulomb blockade in (Ga,Mn)As-nanoconstrictions

TL;DR

This paper investigates Coulomb blockade phenomena in (Ga,Mn)As nanoconstrictions, revealing multiple transport regimes and proposing a double ferromagnetic island model to explain complex conductance behaviors.

Contribution

It introduces a novel double ferromagnetic island model to explain Coulomb blockade effects in (Ga,Mn)As nanostructures, supported by detailed transport analysis.

Findings

Observation of ohmic, SET, and insulating regimes with decreasing constriction size.

Complex Coulomb diamond patterns and conductance suppression near charge degeneracy.

Validation of a modified orthodox theory incorporating energy-dependent density of states.

Abstract

We report on a systematic study of the Coulomb blockade effects in nanofabricated narrow constrictions in thin (Ga,Mn)As films. Different low-temperature transport regimes have been observed for decreasing constriction sizes: the ohmic, the single electron tunnelling (SET) and a completely insulating regime. In the SET, complex stability diagrams with nested Coulomb diamonds and anomalous conductance suppression in the vicinity of charge degeneracy points have been observed. We rationalize these observations in the SET with a double ferromagnetic island model coupled to ferromagnetic leads. Its transport characteristics are analyzed in terms of a modified orthodox theory of Coulomb blockade which takes into account the energy dependence of the density of states in the metallic islands.