Field-free fractional Chern insulators in twisted bilayers via nonlinear strain

We provide a new method for exploiting nonlinear strain interactions to stabilize fractional Chern insulators in twisted bilayer systems in the absence of external magnetic fields. A Dirac model with strain-induced nonlinearities reveals topological phases with Chern numbersC=1/3and2/3, driven by lattice deformations that flatten bands and boost correlations. Using scanning tunneling microscopy, the correlation gapΔgapscales with interaction intensity, offering a testable signature (0.01-0.028 eV). By using intrinsic strain, this field-free method outperforms moiré-based techniques and may be used to 2D materials such as graphene and transition-metal dichalcogenides.