# Magnetically Activated Rotational Vacuum Friction

## TL;DR

This paper predicts a novel magnetic field-induced torque on neutral nanospheres due to time-reversal symmetry breaking, with implications for thermal and Casimir physics.

## Contribution

It introduces a quantum theoretical framework showing how static magnetic fields can induce vacuum torques on neutral particles with temperature differences.

## Key findings

- Nonzero torque on isotropic nanospheres under magnetic activation
- Spontaneous changes in particle rotation direction
- Exotic dynamics of temperature and rotation frequency

## Abstract

We predict the existence of a torque acting on an isotropic neutral nanosphere activated by a static magnetic field when the particle temperature differs from the surrounding vacuum. This phenomenon originates in time-reversal symmetry breaking of the particle interaction with the vacuum electromagnetic field. We present a rigorous quantum treatment of photons and particle excitations that leads to a nonzero torque even in a motionless particle. We also find that the dynamical evolution of the particle temperature and rotation frequency follow an exotic dynamics, including spontaneous changes in the rotation direction. Magnetically activated thermal vacuum torques open a unique avenue for the investigation of the effect of time-reversal symmetry-breaking in thermal and Casimir physics.