Recent discoveries of the formation of epitaxially connected quasi-two-dimensional quantum dot superlattices have opened new horizons to create novel materials with properties by design. Calculations of such 2D quantum dot solids forecast a rich electronic structure with features such as Dirac cones and topological edge states. However, to date, experimental validation of the properties emerging from the delocalization electrons in these systems is still lacking. A key scientific challenge is to understand the nature of charge localization in the best possible quantum dot superlattices that can be made today.
Kevin’s paper integrates structural analysis (in collaboration with the Kourkoutis Group, AEP), transport measurements and electronic band-structure calculation (in collaboration with the Wise group, AEP) to examine charge delocalization in atomically coherent quantum dot solids. We fabricate superlattices with the quantum dots registered to within a single atomic bond length. Although the structure of the quantum dot solid looks nearly perfect to the human eye, to an electron trying to form a Bloch wave the tolerance for disorder is much lower. Calculations of the electronic structure that include the remaining disorder, which we directly extract from experimental data, account for the electron localization inferred from transport measurements. The calculations show that improvement of the epitaxial connections will lead to completely delocalized electrons and thereby enable observation of the remarkable properties predicted for these materials. The results presented in this paper chart a course for future research to realize the exciting predicted properties.
Check out the full paper here: http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4576.html