Synopsis: Two is better than one for a smooth ride

The friction on a sharp tip sliding along a double layer of graphene is half that of a single layer. The source of the contrast may be the difference in electron-phonon coupling in the two systems.
Synopsis figure

Friction is a measure of how much of the kinetic energy in two surfaces sliding against each other is converted into heat. Sliding friction depends on numerous factors—the roughness and compressibility of the surfaces in contact, their atomic structure, as well as the inelastic scattering of electrons and phonons in either surface—but separating all of these contributions is difficult.

Graphene—atomically thin layers of carbon—is perhaps the ideal material in which to study friction since it can be produced with atomic precision and with few defects. Moreover, graphite (many layers of graphene) is a well-known solid lubricant. In a paper appearing in Physical Review Letters, Tobin Filleter and colleagues at McGill University in Canada and collaborators in the US and Germany have measured the frictional force on an atomic force microscope tip as it slides across single and double layers of graphene. Even though the absolute magnitude of the frictional force varies for different tips, they always find that friction on a single graphene layer is twice that of a double layer.

Filleter et al. argue that the contrast comes from intrinsic differences in how energy is dissipated in the two graphene structures. With angle-resolved photoemission, they show that electron-phonon coupling is much stronger in single-layer graphene. The result is that vibrations excited by a sliding tip tend to excite electrons and are much more quickly damped, increasing frictional losses. – Jessica Thomas


More Features »

Subject Areas


Next Synopsis

Semiconductor Physics

A topological metal in one dimension

Read More »

Related Articles

Synopsis: Protons in the Fast Lane
Energy Research

Synopsis: Protons in the Fast Lane

A proposed graphene-based material could offer speedy transport of protons without the need for water. Read More »

Synopsis: Nonmetallic Tin Behaves Like 3D Graphene

Synopsis: Nonmetallic Tin Behaves Like 3D Graphene

By applying strain to a form of tin, researchers make it behave like a 3D analog of graphene. Read More »

Synopsis: Dirac Cones in Boron’s Version of Graphene
Materials Science

Synopsis: Dirac Cones in Boron’s Version of Graphene

A one-atom-thick sheet of boron atoms exhibits Dirac cones, marking the first time this electronic property has been found in a material lacking a graphene-like crystal structure.  Read More »

More Articles