Uncovering the Spin-Valley Order of Correlated Phases in Magic-Angle Graphene

Uncovering the Spin-Valley Order of Correlated Phases in Magic-Angle Graphene
August 31, 2022

Monday, September 12, 2022
Join us for the Physics Condensed Matter Seminar at 2:30 - 3:30 pm

Title: Uncovering the spin-valley order of correlated phases in magic-angle graphene

Abstract: The twist angle between adjacent two-dimensional layers provides a powerful tuning knob to tailor electronic properties. One archetypal example is magic-angle twisted bilayer graphene (MATBG), whose flat low-energy bands host a variety of broken-symmetry ground states. However, despite intensive effort, the spin and valley order of these phases and their low-energy excitations remain poorly understood. In this talk, I will describe local electronic compressibility measurements that enable us to map out the flavor phase diagram and correlated Hofstadter spectrum in MATBG. We identify intervalley-coherent insulators and spin skyrmion excitations at low magnetic fields and deduce the spin polarization of Chern insulators at high field. I will discuss the implications of these findings and how microscopic parameters affect the delicate competition between distinct correlated ground states.

Bio: Ben Feldman is an Assistant Professor of Physics at Stanford University. He started at Stanford in 2018 following a Dicke postdoctoral fellowship at Princeton University in the lab of Ali Yazdani and Ph.D. work at Harvard University with Amir Yacoby. Research in the Feldman lab is focused on emergent strongly correlated and topological states, especially in 2D quantum materials. We use a mixture of cryogenic electronic transport, scanned probe microscopy, and capacitive sensing to realize, study, and control these novel phases.

Website: https://feldmanlab.stanford.edu/

Join Zoom Meeting if not unable to attend in person:
https://berkeley.zoom.us/j/91441096077

Location: 325 Physics South
Speaker: Ben Feldman
Affiliation: Stanford University