# Negative spin exchange in a multielectron quantum dot

## TL;DR

This study investigates the spin properties of a multielectron quantum dot, revealing a tunable sign reversal in exchange interactions that impacts quantum information processing.

## Contribution

It demonstrates the controllable sign reversal of exchange energy in a multielectron quantum dot, highlighting complex spin exchange correlations.

## Key findings

- Groundstate transitions from spin-1/2-like to singlet and triplet states.
- Exchange energy sign reversal persists at zero magnetic field.
- Gate voltages and magnetic fields tune exchange strength.

## Abstract

By operating a one-electron quantum dot (fabricated between a multielectron dot and a one-electron reference dot) as a spectroscopic probe, we study the spin properties of a gate-controlled multielectron GaAs quantum dot at the transition between odd and even occupation number. We observe that the multielectron groundstate transitions from spin-1/2-like to singlet-like to triplet-like as we increase the detuning towards the next higher charge state. The sign reversal in the inferred exchange energy persists at zero magnetic field, and the exchange strength is tunable by gate voltages and in-plane magnetic fields. Complementing spin leakage spectroscopy data, the inspection of coherent multielectron spin exchange oscillations provides further evidence for the sign reversal and, inferentially, for the importance of non-trivial multielectron spin exchange correlations.