Bending Stiffness Collapse, Buckling, Topological Bands of Freestanding Twisted Bilayer Graphene

Abstract

The freestanding twisted bilayer graphene (TBG) is unstable, below a critical twist angle θ_c~3.7 degrees, against a moire (2 \times 1) buckling distortion at T=0. Realistic simulations reveal the concurrent unexpected collapse of the bending rigidity, an unrelated macroscopic mechanical parameter. An analytical model connects bending and buckling anomalies at T=0, but as temperature rises the former fades, while buckling persists further. The (2 \times 1) electronic properties are also surprising. The magic twist angle narrow bands, now eight in number, fail to show zone boundary splittings despite the new periodicity. Symmetry shows how this is dictated by an effective single valley physics. These structural, critical, and electronic predictions promise to make the freestanding state of TBG especially interesting.

References in corpus (4)

• 2D materials and van der Waals heterostructures
• Estimation of Young's Modulus of Graphene by Raman Spectroscopy
• Local Kekulé distortion turns twisted bilayer graphene into topological Mott insulators and superconductors
• Sliding nanomechanical resonators

Cited by in corpus (5)

• Universal Moiré Buckling of Freestanding 2D Bilayers
• Analytical solution for the relaxed atomic configuration of twisted bilayer graphene including heterostrain
• Emerging chirality and moiré dynamics in twisted layered material heterostructures
• A survey of interlayer interaction models for graphene and other 2D materials
• Buckling and flat bands in twisted bilayer graphene