Topologically Protected Zero Modes in Twisted Bilayer Graphene

TL;DR

This paper demonstrates that twisted bilayer graphene exhibits unique topological zero-energy modes due to Dirac-point splitting, with potential implications for topological quantum states.

Contribution

The study provides a symmetry-based analysis and an effective Hamiltonian capturing the topological properties of twisted bilayer graphene, highlighting the robustness of zero modes.

Findings

Presence of degenerate zero-energy Landau levels

Zero modes are protected against strong magnetic fields

Effective Hamiltonian accurately describes topological features

Abstract

We show that the twisted graphene bilayer can reveal unusual topological properties at low energies, as a consequence of a Dirac-point splitting. These features rely on a symmetry analysis of the electron hopping between the two layers of graphene and we derive a simplified effective low-energy Hamiltonian which captures the essential topological properties of twisted bilayer graphene. The corresponding Landau levels peculiarly reveal a degenerate zero-energy mode which cannot be lifted by strong magnetic fields.