Electric backaction on moiré mechanics

Abstract

A lattice mismatch between Van der Waals layers produces a moiré pattern and a subsequent electron band reconstruction. When the bilayer is charged, the sliding motion of one layer with respect to the other produces electric pumping. Here I discuss the reciprocal process: that a voltage bias produces a layer-shear mechanical force. The effect is deduced from the lowest-order correction to the mechanical action by the coupling with electrons in an external field. In twisted bilayer graphene the new mechanical force is shown to be perpendicular to the applied field (due to C${}_2$ symmetries exchanging the layers) and proportional to the charge density measured from neutrality. This is strictly true when the chemical potential is within a gap opened by the moiré potential due to a topological quantization, and approximately true when the chemical potential crosses the flat bands in a model including the self-consistent Hartree interaction. In a mechanical device the effect should be manifested as an apparent enhancement of the friction between layers when the system is charged. Depinning fields for the sliding motion of the layers are estimated in the order of ${\mathcal{E}}_c\sim$ kV/cm around the magic angle.

8 pages + appendices + references, 4 figures

References in corpus (11)

• Flat Bands in Slightly Twisted Bilayer Graphene
• Finite temperature lattice properties of graphene beyond the quasiharmonic approximation
• Sliding charge density wave in manganites
• Topological charge pumping in twisted bilayer graphene
• Topological charge pumping by sliding moiré pattern
• Degradation of phonons in disordered moiré superlattices
• Symmetry Origin of Lattice Vibration Modes in Twisted Multilayer Graphene: Phasons vs Moiré Phonons
• Topological Sliding Moiré Heterostructure
• Depinning of the Charge-Density Waves in Quasi-2D 1T-TaS2 Devices Operating at Room Temperature
• Moiré edge states in twisted bilayer graphene and their topological relation to quantum pumping
• Moiré phonons and impact of electronic symmetry breaking in twisted trilayer graphene

Cited by in corpus (1)

• Charged moiré phonons in twisted bilayer graphene