Tangential and quantum frictional forces on a neutral particle moving near a surface

TL;DR

This paper calculates tangential quantum and classical frictional forces on a neutral atom or nanoparticle moving near a surface, revealing conditions under which these forces are significant and providing numerical examples.

Contribution

It derives formulas for tangential forces in nonretarded regimes for arbitrary temperatures, including quantum friction at zero temperature and thermal effects for nanoparticles.

Findings

Quantum friction can reach about 1/3 of Casimir-Polder force at zero temperature.

Tangential forces are both frictional and accelerating at nonzero temperatures.

Numerical examples demonstrate forces for Na atoms and MgO nanoparticles near surfaces.

Abstract

We calculate tangential forces applied to a ground state atom (nanoparticle) moving with nonrelativistic velocity parallel to the surface of Drude -modelled or Lorentz -modelled half -space using the formalism of fluctuation electrodynamics.The obtained formulae assume the nonretarded regime and arbitrary temperatures of the particle and medium. The quantum frictional force is realized at zero temperature of the particle and medium and can reach about 1/3 of the static value of the Casimir -Polder force in the case of ground state atom. In the case of nanoparticles and nonzero temperature, the tangential forces appears to be both frictional and accelerating. Numerical examples are given for atoms of Na above the surface of Au and MgO nanoparticles above the surface of SiC.