New approach to the thermal Casimir force between real metals

TL;DR

This paper introduces a new theoretical approach to calculating the thermal Casimir force between real metals, using a plasma-like dielectric permittivity that aligns with physical principles and experimental data.

Contribution

It proposes a plasma-like dielectric permittivity model that accurately describes the thermal Casimir force and resolves inconsistencies of previous models like the Drude function.

Findings

The new model satisfies the Kramers-Kronig relations.

Casimir entropy is positive and vanishes at zero temperature.

The approach aligns with all existing experimental measurements.

Abstract

The new approach to the theoretical description of the thermal Casimir force between real metals is presented. It uses the plasma-like dielectric permittivity that takes into account the interband transitions of core electrons. This permittivity precisely satisfies the Kramers-Kronig relations. The respective Casimir entropy is positive and vanishes at zero temperature in accordance with the Nernst heat theorem. The physical reasons why the Drude dielectric function, when substituted in the Lifshitz formula, is inconsistent with electrodynamics are elucidated. The proposed approach is the single one consistent with all measurements of the Casimir force performed up to date. The application of this approach to metal-type semiconductors is considered.