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

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Fractional Chern insulators (FCIs) are topological states of matter that exhibit exotic electronic properties.
• Stabilizing FCIs typically requires strong external magnetic fields, limiting their practical applications.
• Twisted bilayer systems offer a platform for realizing novel quantum phenomena, including topological phases.

Purpose of the Study:

• To introduce a new, magnetic-field-free method for stabilizing fractional Chern insulators.
• To investigate the role of nonlinear strain interactions in creating topological phases.
• To explore the potential of this method for 2D materials.

Main Methods:

• Utilizing a Dirac model with strain-induced nonlinearities to describe twisted bilayer systems.
• Employing lattice deformations to flatten bands and enhance electron correlations.
• Performing scanning tunneling microscopy (STM) to measure the correlation gap.

Main Results:

• Demonstrated stabilization of topological phases with Chern numbers C=1/3 and C=2/3.
• Observed a correlation gap (0.01-0.028 eV) that scales with interaction intensity, providing a testable signature.
• Showcased the efficacy of intrinsic strain as a field-free alternative to moiré-based techniques.

Conclusions:

• Nonlinear strain interactions provide a viable route to stabilize fractional Chern insulators without external magnetic fields.
• This field-free approach offers advantages over existing methods and is applicable to various 2D materials.
• The observed correlation gap serves as an experimental fingerprint for these topological states.