Electrically TunablegFactors in Quantum Dot Molecular Spin States

We present a magnetophotoluminescence study of individual vertically stacked $\mathrm{InAs}/\mathrm{GaAs}$ quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the $g$ factors of different spin states that have molecular wave functions distributed over both quantum dots. We propose a phenomenological model for the change in $g$ factor based on resonant changes in the amplitude of the wave function in the barrier due to the formation of bonding and antibonding orbitals.