PHYSICS DISSERTATION DEFENSE: Joe Finney
Ph.D. Candidate: Joe Finney
Research Advisor: David Goldhaber-Gordon
Date: August 10, 2023
Time: 2 PM
Location: Shriram 108
Zoom Link: https://stanford.zoom.us/j/94391618798
Zoom Password: email nickswan [at] stanford.edu (nickswan[at]stanford[dot]edu) for password.
Title: Uniaxial heterostrain in twisted bilayer graphene above the magic angle
Abstract: Twisted bilayer graphene is an experimentally rich platform, hosting a variety of exotic states of matter with an unprecedented degree of tunability. I present measurements of a twisted bilayer graphene device twisted to 1.4 degrees, well above the magic angle at which correlations dominate. Despite the lack of correlated states, the device shows several unexpected behaviors in magnetotransport: regions in density of large quadratic magnetoresistance concurrent with an apparently non-Diophantine Landau fan diagram. I show that uniaxial heterostrain of only a few tenths of a percent neatly explains these unusual magnetotransport measurements. It is presently difficult to control such small amounts of strain in experiments. If we can control it, then heterostrain becomes a powerful tuning knob to control the band structure of twisted bilayer graphene, much like twist angle.