Molecular states observed in a single pair of strongly coupled self-assembled InAs quantum dots

TL;DR

This study investigates molecular states in a single pair of strongly coupled InAs quantum dots using a single electron transistor, revealing electron occupation in symmetric and anti-symmetric states with smaller Coulomb diamonds than previously reported.

Contribution

It provides experimental evidence of molecular states in a single pair of coupled InAs quantum dots and confirms the findings with numerical calculations.

Findings

Observation of Coulomb diamonds with charging energy < 5 meV

Electrons occupy symmetric and anti-symmetric molecular states

Results agree with exact diagonalization calculations

Abstract

Molecular states in a SINGLE PAIR of strongly coupled self-assembled InAs quantum dots are investigated using a sub-micron sized single electron transistor containing just a few pairs of coupled InAs dots embedded in a GaAs matrix. We observe a series of well-formed Coulomb diamonds with charging energy of less than 5 meV, which are much smaller than those reported previously. This is because electrons are occupied in molecular states, which are spread over both dots and occupy a large volume. In the measurement of ground and excited state single electron transport spectra with magnetic field, we find that the electrons are sequentially trapped in symmetric and anti-symmetric states. This result is well-explained by numerical calculation using an exact diagonalization method.