FLEET seminar. Engineering order-disorder transition at the surface of topological insulators to manipulate electronic properties

Abdulhakim Bake, PhD candidate, University of Wollongong, Institute for Superconducting and Electronic Materials (ISEM).

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Topological insulators (TIs) are a special type of materials that have unique properties: They are insulators on the inside but conduct electricity very well on their surface. The surface states of TIs enable the transport of charges with no backscattering due to spin-momentum locking, resulting in less generation of heat compared to ordinary conductors. This unique behaviour of the surface electrons in topological insulators has many potential applications in low-energy electronics, as it could allow for more efficient and faster electronic devices that generate less heat.

The main focus of this seminar will be on a novel method of engineering topological surface and edge states based on controlling the topological phase transition of Sb₂Te₃ with a focused ion-beam. Sb₂Te₃ is a 3D strong topological insulator and is a layered chalcogenide material. One discovery of this work is that Sb₂Te₃ is sensitive to ion beam damage and can easily be amorphized with a certain fluence of ion-beam. The seminar will also discuss the ways of fabricating FIB-assisted devices and also discusses the strategy of minimizing ion-beam-induced microstructural damage to characterizing Sb₂Te₃ samples at the atomic resolution scale.

With robust experimental and theoretical evidence, we will conclude that Sb₂Te₃ topological states collapse upon amorphization, and highly conducting surface and edge states emerge at the boundary of crystalline and amorphous Sb₂Te₃. This provides a viable avenue for engineering surface and edge states by controlling the phase transition of Sb₂Te₃.

Finally, the seminar will conclude by summarizing the main findings and highlighting avenues for future work.

ISEM seeks to stimulate the technological and commercial development to advance technologies including batteries for electric vehicles and energy storage; applied superconductivity for electrical and medical devices; energy conversion and transmission; spintronic and electronic materials for applications; terahertz science; and nano-structured materials.