Giant thermopower changes related to the resistivity maximum and colossal magnetoresistance in EuCd2P2

TL;DR

This paper reports giant, field-dependent thermopower anomalies in EuCd2P2, linked to resistivity peaks, with potential implications for enhancing thermoelectric effects through electronic property gradients.

Contribution

It introduces a simple drift-diffusion model explaining large thermopower changes caused by resistivity gradients in EuCd2P2, highlighting a new mechanism for giant thermopower.

Findings

Thermopower exceeds 4000 μV/K in a narrow temperature range.

Giant thermopower anomalies are suppressed by small magnetic fields.

The observed behavior is explained by a resistivity gradient-driven model.

Abstract

We present the thermopower of EuCd2P2, a material which exhibits a large resistivity peak with significant magnetic field dependence in the temperature range of 10-25 K. In the same region we observe a highly unusual behavior of the thermopower with two sign changes and giant extrema. The overall variation of the thermopower exceeds 4 000 muV/K and takes place in an extremely narrow temperature region of less than 5 K. The anomaly is suppressed completely in a small magnetic field of 0.5 T. We discuss this observation using a simple drift-diffusion picture and taking into account that the temperature gradient inducing the thermopower voltage is accompanied by a gradient of the electrical resistivity. Our simple estimation yields the correct magnitude, shape, and field dependence of the thermopower anomaly observed in EuCd2P2. These results open a new route to giant thermopower values via gradients of electronic properties.