Phonon-drag effect in FeGa3

TL;DR

This study reveals pronounced low-temperature peaks in thermal conductivity and thermopower in FeGa3, attributed to phonon-drag effects, supported by experimental data and theoretical calculations excluding strong electronic correlations.

Contribution

The paper provides the first systematic investigation of phonon-drag effects in FeGa3, combining experimental measurements with density functional theory calculations to clarify the origin of low-temperature thermopower peaks.

Findings

Pronounced peaks in thermal conductivity and thermopower below 20 K.

Peaks attributed to phonon-drag effect, not electronic correlations.

Weak anisotropy in transport properties.

Abstract

The thermoelectric properties of single- and polycrystalline FeGa3 are systematically investigated over a wide temperature range. At low temperatures, below 20 K, previously not known pronounced peaks in the thermal conductivity (400-800 W K^-1m-1) with corresponding maxima in the thermopower (in the order of -16000 microV/K) were found in single crystalline samples. Measurements in single crystals along [100] and [001] directions indicate only a slight anisotropy in both the electrical and thermal transport. From susceptibility and heat capacity measurements, a structural or magnetic phase transition was excluded. Using density functional theory-based calculations, we have revisited the electronic structure of FeGa3 and compared the magnetic (including correlations) and non-magnetic electronic density of states. Thermopower at fixed carrier concentrations are calculated using semi-classical Boltzmann transport theory, and the calculated results match fairly with our experimental data and exclude the possibility of strong electronic correlations as an explanation for the low temperature enhancement. Eventually, after a careful review, we assign the peaks in the thermopower as a manifestation of the phonon-drag effect, which is supported by thermopower measurements in a magnetic field.