Electron spin and charge switching in a coupled quantum dot quantum ring system

TL;DR

This study investigates electron spin and charge dynamics in a coupled quantum dot and quantum ring system under magnetic fields, revealing electron transfer transitions and unique Aharonov-Bohm oscillation behaviors.

Contribution

It provides a detailed analysis of electron distribution and spin states in a coupled dot-ring system, highlighting effects of magnetic field and confinement on electron transitions and oscillations.

Findings

Electron transfer between dot and ring depends on confinement strength, gate voltage, and magnetic field.

Transitions cause changes in Aharonov-Bohm oscillation periodicity.

Singlet-triplet splitting shows piecewise linear dependence on magnetic field due to Aharonov-Bohm effect.

Abstract

Few-electron systems confined in a quantum dot laterally coupled to a surrounding quantum ring in the presence of an external magnetic field are studied by exact diagonalization. The distribution of electrons between the dot and the ring is influenced by the relative strength of the dot and ring confinement, the gate voltage and the magnetic field which induces transitions of electrons between the two parts of the system. These transitions are accompanied by changes in the periodicity of the Aharonov-Bohm oscillations of the ground-state angular momentum. The singlet-triplet splitting for a two electron system with one electron confined in the dot and the other in the ring exhibits piecewise linear dependence on the external field due to the Aharonov-Bohm effect for the ring-confined electron, in contrast to smooth oscillatory dependence of the exchange energy for laterally coupled dots in the side-by-side geometry.