Effect of paramagnon drag on thermoelectric transport properties: Linear response theory

TL;DR

This paper develops a microscopic linear response theory to quantify how paramagnon drag influences thermoelectric properties, especially the Seebeck coefficient, near ferromagnetic transition points in paramagnetic materials.

Contribution

It derives a general formula for the paramagnon drag contribution to the Seebeck coefficient and clarifies conditions for enhancement near ferromagnetic transitions.

Findings

Seebeck coefficient can be enhanced near the ferromagnetic transition.

Derived a general formula for paramagnon drag contribution.

Analyzed effects for different band structures and mixtures.

Abstract

It has been proposed that paramagnetic materials exhibit a unique thermoelectric effect near the ferromagnetic transition point due to spin fluctuations. This phenomenon is often referred to as paramagnon drag. We calculate the contribution of this paramagnon drag to the Seebeck coefficient microscopically on the basis of the linear response theory. This leed to a general formula for the contribution to the Seebeck coefficient due to the paramagnon drag, and we clarify the conditions in which the Seebeck coefficient enhances near the ferromagnetic transition point for a single-band and isotropic system. Moreover, we calculate the Seebeck coefficients for a band $\varepsilon \propto k^n$ and a mixture of free-electron-like and flat bands.