  Zero-point quantum fluctuations of the electromagnetic vacuum create the
widely known London-van der Waals attractive force between two atoms. Recently,
there was a revived interest in the interaction of rotating matter with the
quantum vacuum. Here, we consider a rotating pair of atoms maintained by London
van der Waals forces and calculate the frictional torque they experience due to
zero-point radiation. Using a semi-classical framework derived from the
Fluctuation Dissipation Theorem, we take into account the full electrostatic
coupling between induced dipoles. Considering the case of zero temperature
only, we find a braking torque proportional to the angular velocity and to the
third power of the fine structure constant. Although very small compared to
London van der Waals attraction, the torque is strong enough to induce the
formation of dimers in binary collisions. This new friction phenomenon at the
atomic level should induce a paradigm change in the explanation of
irreversibility.
