Negative Friction Coefficients in Superlubric Graphite-Hexagonal Boron Nitride Heterojunctions

TL;DR

This paper predicts negative friction coefficients in superlubric graphite-hexagonal boron nitride heterojunctions due to load-induced suppression of superstructure distortions, revealing a novel frictional mechanism in layered materials.

Contribution

It introduces a new understanding of friction behavior in layered heterojunctions, showing load and temperature effects on interfacial dynamics.

Findings

Negative friction coefficients predicted in heterojunctions

Load suppresses moiré superstructure distortions

Temperature increases friction via out-of-plane fluctuations

Abstract

Negative friction coefficients, where friction is reduced upon increasing normal load, are predicted for superlubric graphite-hexagonal boron nitride heterojunctions. The origin of this counterintuitive behavior lies in the load-induced suppression of the moir\'e superstructure out-of-plane distortions leading to a less dissipative interfacial dynamics. Thermally induced enhancement of the out-of-plane fluctuations leads to an unusual increase of friction with temperature. The highlighted frictional mechanism is of a general nature and is expected to appear in many layered material heterojunctions.