# Designing Flat Band by Strain

## TL;DR

This paper investigates how heterostrain influences moiré band structures in twisted bilayer graphene and TMDs, revealing significant band separation changes and tunable flat bands, which help explain experimental observations.

## Contribution

It demonstrates that heterostrain can significantly modify moiré bands in bilayer systems, providing new insights into band engineering and experimental phenomena.

## Key findings

- Heterostrain increases band separation in bilayer graphene.
- Heterostrain enables tunable flat bands in bilayer TMDs.
- Resolves puzzles in spectroscopy and quantum oscillation experiments.

## Abstract

We study the effects of heterostrain on moir\'e bands in twisted bilayer graphene and bilayer transition metal dichalcogenide (TMD) systems. For bilayer graphene with twist angle near $1^\circ$, we show that heterostrain significantly increases the energy separation between conduction and valence bands as well as the Dirac velocity at charge neutrality, which resolves several puzzles in scanning tunneling spectroscopy and quantum oscillation experiments at once. For bilayer TMD, we show that applying small heterostrain generally leads to flat moir\'e bands that are highly tunable.