Quantum thermodynamics of overdamped modes in local and spatially dispersive materials

TL;DR

This paper explores the quantum thermodynamics of overdamped electromagnetic modes in materials, focusing on entropy behavior at low temperatures and how spatial dispersion influences the properties of eddy modes in the context of the magnetic Casimir-Polder interaction.

Contribution

It provides a detailed analysis of how spatial dispersion affects the entropy and thermodynamic properties of overdamped modes, revealing the limitations of local models and the regularizing effect of nonlocal responses.

Findings

Spatial dispersion leads to more regular entropy behavior at low temperatures.

The local (Drude) model exhibits an entropy defect under certain conditions.

The study connects quantum thermodynamics with classical phenomena like magnetohydrodynamics and superconductivity.

Abstract

The quantum thermodynamical properties of (quasi-normal) overdamped electromagnetic modes (eddy currents) are investigated in the context of the magnetic Casimir-Polder interaction. The role of the material response in terms of spatially local and nonlocal material models is discussed. In particular, the focus is set on the system's entropy in the limit of low temperatures. In specific circumstances the spatially local (Drude) model reveals an "entropy defect", while spatial dispersion leads to a more regular behavior. We present a detailed description of this phenomenon and of the different mechanisms at work in the system with regard to the eddy modes' properties. Extensively discussing classical and quantum features, we relate our results to the wide range of literature and draw intriguing connections to seemingly distant fields as, e.g., the theory of magnetohydrodynamics and superconductivity.