Critical transport behavior in quantum dot solids

TL;DR

This paper models electron transport in quantum dot solids, revealing a complex metal-insulator transition phase diagram with a crossover between universality classes, which is crucial for advancing quantum dot solar cell technologies.

Contribution

The study introduces a new disorder-aware transport model for QD solids and maps the phase diagram of the metal-insulator transition, highlighting a crossover between universality classes.

Findings

Identified a broad parameter space with a distinct critical exponent from the Anderson transition.

Discovered a crossover from Anderson to Chiral Orthogonal universality class due to weak kinetic disorder.

Provided insights into the metal-insulator transition relevant for quantum dot solar cell development.

Abstract

Due to recent advances, silicon solar cells are rapidly approaching the Shockley-Queisser limit of 33% efficiency. Quantum Dot (QD) solar cells have the potential to surpass this limit and enable a new generation of photovoltaic technologies beyond the capabilities of any existing solar energy modalities. The creation of the first epitaxially-fused quantum dot solids showing broad phase coherence and metallicity necessary for solar implementation has not yet been achieved, and the metal-insulator transition in these materials needs to be explored. We have created a new model of electron transport through QD solids, informed by 3D-tomography of QD solid samples, which considers disorder in both the on-site and hopping terms of the commonly studied Anderson Hamiltonian. We used the transfer matrix method and finite-size scaling to create a dynamic metal-insulator transition phase diagram. For a surprisingly large portion of the parameter space, our model shows a critical exponent distinct from the expected value for the Anderson transition. We show the existence of a crossover region from the universality class of the Anderson transition (AI) to the Chiral Orthogonal class (BDI) due to the addition of weak kinetic (hopping) disorder.