How Magnetic Field Enters Heat Current: Application to Fluctuation Nernst Effect

TL;DR

This paper develops a gauge-invariant microscopic approach to correctly define heat transfer in thermomagnetic phenomena, resolving longstanding issues and aligning theoretical predictions with physical principles like Onsager reciprocity.

Contribution

It introduces a gauge-invariant framework that accounts for electron-magnetic field interactions and surface currents, refining the understanding of thermomagnetic effects in strongly interacting systems.

Findings

Heat transfer includes electron-magnetic field interaction energy.

Surface currents transfer charge but not heat in the Nernst effect.

Thermomagnetic coefficients satisfy Onsager relations when using the new approach.

Abstract

A problem of the definition of the heat transported in thermomagnetic phenomena has been well realized in the late sixties, but not solved up to date. Ignoring this problem, numerous recent theories grossly overestimate the thermomagnetic coefficients in strongly interacting systems. Here we develop a gauge-invariant microscopic approach, which shows that the heat transfer should include the energy of the interaction between electrons and a magnetic field. We also demonstrate that the surface currents induced by the magnetic field transfer the charge in the Nernst effect, but do not transfer the heat in the Ettingshausen effect. Only with these two modifications of the theory, the physically measurable thermomagnetic coefficients satisfy the Onsager relation. We critically revised the Gaussian fluctuation model above the superconducting transition and show that the gauge invariance uniquely relates thermomagnetic phenomena in the Fermi liquid with the particle-hole asymmetry.