Disorder in Topological Systems: Friend or Foe?*

Topological semimetals (TSMs) present new opportunities for controlling electron charge and spin transport, making them of interest for spintronic applications. Our current understanding of electron behavior in TSMs is largely derived from extensive theoretical work on idealized materials and experiments on bulk crystals, which tend to exhibit minimal disorder. However, their use in devices will likely require fabrication in thin film form, which will undoubtedly introduce a greater array of defects and other inhomogeneities. Understanding the role of disorder is crucial for directing spin-dependent phenomena and designing future spintronic devices, especially because it is unclear if and when predicted materials properties, including topological protection, ultrahigh electron mobilities, and large magnetoresistance, will remain relevant in real thin films. In this talk, I will discuss our work to understand the interplay between epitaxial synthesis, various forms of disorder, and the resulting electron behavior in Cd₃As₂ and TaAs [1-4]. While some forms of disorder are detrimental to electron transport (e.g. dislocations), others can be used as tools for tuning electron transport and spin behavior (e.g. point defects, impurities and interfaces). Prospects and challenges for controlling and utilizing disorder in TSMs will also be discussed.

 

[1] A. D. Rice, et al., Defects in Cd3As2 epilayers via molecular beam epitaxy and strategies for  

      reducing them, PR Materials 3, 121201 (2019) 

[2] A. D. Rice, et al., Epitaxial Dirac semimetal vertical heterostructures for advanced device    

      architectures, Adv. Func. Mater. 2111470 (2022) 

[3] J. N. Nelson, et al., Direct link between disorder and magnetoresistance in topological  

      semimetals, PRB 107, L220206 (2023)  

[4] J. N. Nelson, et al., Thin-film TaAs: Developing a platform for Weyl semimetal devices, Matter 6,  

      1 (2023)