Mapping of few-electron wave-functions in semiconductor nanocrystals - evidence of exchange interaction

TL;DR

This study investigates how electric fields influence the wave-functions of few-electron states in InAs nanocrystals, revealing state reordering and symmetry changes that are observable via wave-function mapping, with implications for understanding exchange interactions.

Contribution

It demonstrates the Stark-induced reordering of electron states and symmetry changes in InAs nanocrystals, linking electric field effects to observable wave-function characteristics.

Findings

Electric field causes reordering of 5-electron states.

Symmetry of local density of states changes with nanocrystal size.

State symmetry transitions from spherical to torus-like with increasing size.

Abstract

The influence of the tip-substrate bias induced electric field in a scanning-tunneling-spectroscopy experiment on charged InAs nanocrystals is studied. Calculating the ground and first excited many-particle state for five electrons occupying the quantum dot reveals a Stark-induced reordering of states by increasing the electric field strength. It is shown that this reordering of states is accompanied by a symmetry change of the local density of states (LDOS), which in principal is observable in a wave-function mapping experiment. Since in the usually performed experiments the electric field can not be directly controlled, we investigate the crystal size dependence of the 5-electron LDOS symmetry. It is found that the symmetry changes from spherical to torus-like by increasing the nanocrystal radius.