On the spatial dependence of Casimir friction in graphene

TL;DR

This paper investigates how Casimir friction between an atom and graphene depends on spatial parameters, revealing a threshold velocity related to the Fermi velocity for fermion pair production.

Contribution

It introduces a detailed analysis of the spatial dependence of Casimir friction in graphene, including the effects of atom-EM field coupling and the velocity threshold for fermion emission.

Findings

Fermion pair production occurs only above a certain velocity threshold.

The angular dependence of fermion emission probability is characterized.

Casimir friction exhibits a clear velocity threshold related to the Fermi velocity.

Abstract

We study the spatial properties of the Casimir friction phenomenon for an atom moving at a non-relativistic constant velocity parallel to a planar graphene sheet. The coupling of the atom to the vacuum electromagnetic (EM) field is implemented by an electric dipole term, plus a R\"ontgen term. We study the fermion pair production, evaluating the angular dependence of the fermion emission probability. The phenomenon exhibits a threshold: it only exists when the speed of the sliding motion is larger than the Fermi velocity of the medium.