Demonstration of an Unusual Thermal Effect in the Casimir Force from Graphene

TL;DR

This study experimentally demonstrates a significant thermal effect in the Casimir force involving graphene, showing that the effect is governed by the Fermi velocity rather than the speed of light, which is a novel finding.

Contribution

First experimental verification of a large thermal Casimir effect in graphene, confirming theoretical predictions that differ from conventional materials.

Findings

Good agreement between experiment and theory without fitting parameters

Thermal effect in graphene's Casimir force is unusually large below 1 micron

Effective temperature in graphene is determined by Fermi velocity

Abstract

We report precision measurements of the gradient of the Casimir force between an Au-coated sphere and graphene sheet deposited on a silica plate. The measurement data are compared with exact theory using the polarization tensor found in the framework of the Dirac model including effects of the nonzero chemical potential and energy gap of the graphene sample with no fitting parameters. The very good agreement between experiment and theory demonstrates the unusually big thermal effect at separations below 1 mum which has never been observed for conventional 3D materials. Thus, it is confirmed experimentally that for graphene the effective temperature is determined by the Fermi velocity rather than by the speed of light.