Excitation spectrum of two correlated electrons in a lateral quantum dot with negligible Zeeman splitting

TL;DR

This study combines tunneling spectroscopy and theoretical calculations to analyze the excitation spectrum of a two-electron quantum dot with negligible Zeeman splitting, revealing electron correlation effects and Wigner-molecular states.

Contribution

It provides new experimental and theoretical insights into the excitation spectrum of two-electron quantum dots with spatial anisotropy and negligible Zeeman splitting.

Findings

Splitting of the two lowest triplet states at zero magnetic field.

Identification of additional excited states at finite magnetic fields.

Good agreement between experimental spectra and exact diagonalization calculations.

Abstract

The excitation spectrum of a two-electron quantum dot is investigated by tunneling spectroscopy in conjuction with theoretical calculations. The dot made from a material with negligible Zeeman splitting has a moderate spatial anisotropy leading to a splitting of the two lowest triplet states at zero magnetic field. In addition to the well-known triplet excitation at zero magnetic field, two additional excited states are found at finite magnetic field. The lower one is identified as the second excited singlet state on the basis of an avoided crossing with the first excited singlet state at finite fields. The measured spectra are in remarkable agreement with exact diagonalization calculations. The results prove the significance of electron correlations and suggest the formation of a state with Wigner-molecular properties at low magnetic fields.