# Fluctuation induced forces in the presence of mobile carrier drift

## TL;DR

This paper investigates how a flowing dc current in a medium modifies the Casimir-Lifshitz force on a nearby polarizable object, introducing a significant lateral force dependent on drift velocity and temperature differences.

## Contribution

It demonstrates that mobile carrier drift can alter the Casimir-Lifshitz force and induce a lateral force, revealing new effects of current flow on fluctuation-induced forces.

## Key findings

- The dc current significantly modifies the force on the particle.
- A lateral force appears due to carrier drift, non-monotonic with drift velocity.
- Temperature differences can cause the lateral force to act as drag or anti-drag.

## Abstract

A small polarizable object (an atom, molecule or nanoparticle), placed above a medium with flowing dc current in it, is considered. It is shown that the dc current can have a strong effect on the force exerted on the particle. The Casimir-Lifshitz force, well studied in the absence of current, gets modified due to drifting mobile carriers in the medium. Furthermore, a force in the lateral direction appears. This force is a non-monotonic function of the drift velocity and its maximal value is comparable with the Casimir-Lifshitz force. If the temperatures of the medium and the particle are different, this lateral force can be directed along the current (drag) or in the opposite direction (anti-drag).