Abstract

In this talk, I will discuss our recent research on the emergence of topological flat bands in 2D materials under periodic strain. I will begin by introducing the concept of quadratic band crossing points and how periodic strain can act as a director potential with angular momentum. I will then discuss the emergence of "magic" values of strain field strengths that give rise to exact flat bands with Chern number C=±1 at the charge neutrality point, similar to those observed in twisted bilayer graphene. These flat bands have the ideal quantum geometry for fractional Chern insulators and have fragile topology. Additionally, I will explore the doubling of the number of flat bands for certain point groups and the exact solvability of the interacting Hamiltonian at integer fillings. I will also discuss the stability of these flat bands against deviations from the chiral limit and their possible realization in 2D materials. Finally, I will discuss topological flat bands in both strained monolayer and bilayer graphene, and the connection to the Jackiw-Rebbi zero modes. Our work suggests periodic strain as a promising route for realizing topological flat bands, which set the stage for the emergence of correlated quantum states.

References:
X. H. Wan, S. Sarkar, S. -Z. Lin and K. Sun, arXiv:2211.11618
X. H. Wan, S. Sarkar, K. Sun and S. -Z. Lin, arXiv:2302.07199