# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1902.08067