Direct link between disorder, mobility and magnetoresistance in topological semimetals

TL;DR

This study systematically controls disorder in a topological Dirac semimetal, revealing how defect levels affect electron mobility and magnetoresistance, and providing new insights into the origins of linear magnetoresistance.

Contribution

It demonstrates precise control of point defects in Cd3As2 and links disorder levels to transport properties and magnetoresistance behavior, advancing understanding of disorder effects in topological semimetals.

Findings

Reducing arsenic vacancies increases mobility from 5,000 to 18,000 cm²/Vs.

Magnetoresistance increases from 200% to 1000% with fewer vacancies.

Linear magnetoresistance inversely correlates with disorder measures.

Abstract

The extent to which disorder influences the properties of topological semimetals remains an open question and is relevant to both the understanding of topological states and the use of topological materials in practical applications. Here, we achieve unmatched and systematic control of point defect concentrations in the prototypical Dirac semimetal Cd$_3$As$_2$ to gain important insight into the role of disorder on electron transport behavior. We find that arsenic vacancies introduce localized states near the Fermi level and strongly influence the electron mobility. Reducing arsenic vacancies by changing the As/Cd flux ratio used during deposition results in an increase in the magnetoresistance from 200%-1000% and an increase in mobility from 5000-18,000 cm$^2$/Vs. However, the degree of linear magnetoresistance, which has previously been linked to disorder, is found here to correlate inversely with measures of disorder, including disorder potential and disorder correlation lengths. This finding yields important new information in the quest to identify the origin of linear magnetoresistance in a wider range of materials.