Hard Materials Seminar - "Characterizing Structural Reconstruction in Twisted Bismuth Selenide Using Electron Ptychography and 4D-STEM for Tunable Quantum Materials"

Understanding materials with topological electronic properties is critical to realizing topological quantum computing and helicity-controlled 2D optoelectronics. Bismuth selenide (Bi2Se3) is a known intrinsic topological insulator; however, in its traditional bulk crystal fabrication, it is challenging to tune its quantum properties.

Twisting is a well-established fabrication method for 2D materials that has resulted in non-trivial quantum geometry; however, twisted 2D materials such as magic angle graphene require careful tuning of twist angle to sub-degree accuracy to achieve desirable properties.

In contrast, twisted topological insulators, such as twisted Bi2Se3, have been predicted to host nontrivial quantum geometry across a wide range of twist angles. In this work, we employ electron ptychography and 4D-STEM to characterize complex, 3D structure of mm-scale twisted Bi2Se3 membranes and how they evolve with twist and strain.