Molecular states in a one-electron double quantum dot

TL;DR

This paper investigates the energy states of a strongly coupled one-electron double quantum dot in GaAs/AlGaAs, identifying symmetric and antisymmetric states through conductance measurements and exploring magnetic field effects on tunnel coupling.

Contribution

It provides the first clear experimental identification of symmetric and antisymmetric states in a strongly tunnel-coupled double quantum dot using differential conductance.

Findings

Identification of symmetric and antisymmetric states via conductance

Magnetic field reduces tunnel coupling and modulates orbital energies

Observation of a larger tunnel splitting at excited state anticrossing

Abstract

The transport spectrum of a strongly tunnel-coupled one-electron double quantum dot electrostatically defined in a GaAs/AlGaAs heterostructure is studied. At finite source-drain-voltage we demonstrate the unambiguous identification of the symmetric ground state and the antisymmetric excited state of the double well potential by means of differential conductance measurements. A sizable magnetic field, perpendicular to the two-dimensional electron gas, reduces the extent of the electronic wave-function and thereby decreases the tunnel coupling. A perpendicular magnetic field also modulates the orbital excitation energies in each individual dot. By additionally tuning the asymmetry of the double well potential we can align the chemical potentials of an excited state of one of the quantum dots and the ground state of the other quantum dot. This results in a second anticrossing with a much larger tunnel splitting than the anticrossing involving the two electronic ground states.