Superconductivity, Topology and Correlated Insulators in Magic Angle Graphene Superlattices – How Much Magic is Needed?

Monday, October 25, 2021

Join us for the Physics Condensed Matter Seminar at 10:00 am

Title: Superconductivity, Topology and Correlated Insulators in Magic Angle
Graphene Superlattices – How Much Magic is Needed?

Twisted bilayer graphene (TBG) with a rotational misalignment close to the magic-angle value of 1.1 degrees features isolated flat electronic bands that host several distinct correlated phases. In this talk, I will present our transport and scanning tunneling microscopy (STM) experiments that explore the rich phase diagram of TBG and the stability of various phases to twist angle deviation from the magic value. First, we will discuss transport measurements showing that while correlated insulators, ferromagnetic and topological phases are bound to appear only in the immediate vicinity of the magic angle, superconductivity alongside more subtle signatures of strong correlations can be seen in a much broader angle range. In the second part, we will discuss STM experiments that reveal how strong electronic interactions and superlattice moire potential conspire to modify, i.e., flatten, the TBG band structure and thus significantly amplify the local density of states. Near the magic angle, this interaction-driven band flattening gives rise to various spectroscopic gaps that correspond to correlated insulating and topological Chern phases at zero and finite magnetic fields as well as affirm unconventional nature of superconductivity in this system.

https://berkeley.zoom.us/j/97545820986

Location: 
virtual (zoom)
Affiliation: 
Caltech