Isospin Blockade in Transport through Vertical Double Quantum Dots

TL;DR

This paper investigates how magnetic fields and slight asymmetries influence charge polarization and transport in vertically coupled quantum dots, revealing an isospin blockade and negative differential conductance phenomena.

Contribution

It uncovers correlation-induced energy crossings and their transformation into anticrossings due to asymmetry, affecting transport properties in double quantum dots.

Findings

Charge polarization can be tuned by magnetic field.

Isospin blockade suppresses vertical transport.

Negative differential conductance appears during charge localization.

Abstract

We study the spectrum and the transport properties of two identical, vertically coupled quantum dots in a perpendicular magnetic field. We find correlation-induced energy crossings in a magnetic field sweep between states differing only in the vertical degree of freedom. Considering the influence of a slight asymmetry between the dots caused by the applied source-drain voltage in vertical transport experiments these crossings convert to anticrossings accompanied by the build-up of charge polarization which is tunable by the perpendicular magnetic field. The polarization strongly affects the vertical transport through the double quantum dot and is manifest in an isospin blockade and the appearance of negative differential conductances in the magnetic field range where the charge localization occurs.