DEPARTMENT OF PHYSICS DISSERTATION DEFENSE: Steven Tran

Ph.D. Candidate:  Steven Tran

Research Advisor:   David Goldhaber-Gordon

Public zoom link:  https://stanford.zoom.us/j/99306574745?pwd=P2zDPpLMwxCtu2BJCXdoStKja6GR2f.1

Title:    Mapping Twisted Bilayer Graphene: Toward Reproducible Structure and Controlled Electronic Properties

Abstract:  Van der Waals (vdW) moiré superlattices are a popular platform to study flat electronic bands which host highly correlated and topological phases. Generated by controlling the relative lattice orientations between vdW layers, vdW moiré superlattices offer a way to engineer novel electronic phases with a simple rotation (twist) between materials. However, researchers currently have poor control over twist, meaning the range of electronic phases is not completely known. In this talk, I will present developments which can help refine processes for improving twist angle control and provide complementary moiré structural information to electrical transport. I will introduce torsional force microscopy (TFM), an imaging technique capable of visualizing moiré superlattices (and, surprisingly, atomic lattices) in real space under ambient conditions. I will then discuss the nuances of extracting structural information from TFM images. Finally, I will present a study of electrical transport through twisted bilayer graphene where regions of the electrical device were characterized using TFM.