Entropy-Based Theory of Thermomagnetic Phenomena: Poynting Vector, Vorticity, and Advanced Sensing

TL;DR

This paper develops an entropy-based theoretical framework for thermomagnetic phenomena, clarifying the role of entropy in coupling thermal and electric effects, and analyzing quantum and fluctuation contributions in superconductors.

Contribution

It introduces a novel entropy-centric approach to thermomagnetic effects, generalizes the Kubo formalism for entropy transfer, and explains high sensitivity and vortex entropy in superconductors.

Findings

Entropy couples thermal and electric phenomena in linear response.

Quantum currents do not transfer entropy, serving as ideal quantum connectors.

Vortex transport entropy in 2D superconductors exceeds vortex core entropy.

Abstract

We show that in the linear response approximation only entropy provides coupling between thermal and electric phenomena. The dissipationless quantum currents -- magnetization, superconducting, persistent and topological edge currents -- do not produce and transfer entropy and may be excluded from final formulas for thermomagnetic coefficients. The magnetization energy flux, eM X E, in crossed electric and magnetic fields strongly modifies the Poynting vector in magnetic materials and metamaterials, but do not contribute to the heat current. Calculating entropy fluxes of fluctuating Cooper pairs, we find the fluctuation Nernst coefficient in pure superconductors. To account electron scattering, we generalize the gauge-invariant Kubo formalism developed for the Hall effect to thermomagnetic entropy transfer. We also introduce the thermomagnetic entropy per unit charge and derive the Nernst coefficient proportional to the difference of the thermoelectric and thermomagnetic entropies. This explains the Sondheimer cancellation and high sensitivity of thermomagnetic phenomena to correlations. In 2D superconductors, the transport entropy transferred by a vortex moving through the background formed by vortex-antivortex pairs is the configuration entropy of kB ln 2, which strongly exceeds the intrinsic entropy of vortex core. Beyond the linear response, the non-entropic forces can lead to phenomena unexpected from thermodynamics, such as vortex attraction to the moving hot spot. Quantum currents do not transfer entropy and may be used as ideal connectors to quantum nanodetectors.