Large Nernst Effect in a layered metallic antiferromagnet EuAl$_2$Si$_2$

TL;DR

This study reports a giant Nernst effect in EuAl$_2$Si$_2$, a layered antiferromagnet, driven by band compensation and high mobility, with potential applications in thermoelectric devices at low temperatures.

Contribution

It demonstrates a record large Nernst signal in EuAl$_2$Si$_2$, highlighting the role of band structure and topological features in enhancing thermoelectric effects.

Findings

Nernst signal reaches 130 μV/K at 8 K and 13 T.

Large Nernst effect is two orders of magnitude greater than the Seebeck effect.

High mobility electron and hole carriers are identified.

Abstract

The large Nernst effect is advantageous for developing transverse Nernst thermoelectric generators or Ettingshausen coolers within a single component, avoiding the complexity of electron- and hole-modules in longitudinal Seebeck thermoelectric devices. We report a large Nernst signal reaching 130 uV/K at 8 K and 13 T in the layered metallic antiferromagnet EuAl$_2$Si$_2$. Notably, this large transverse Nernst thermopower is two orders of magnitude greater than its longitudinal counterpart. The Nernst coefficient peaks around 4 K and 8 K at 3 T and 13 T, respectively. At similar temperatures, both the Hall coefficient and the Seebeck signal change sign. Additionally, nearly compensated electron- and hole-like carriers with high mobility ($\sim$ 4000 cm$^2$/Vs at 4 K) are revealed from the magnetoconductivity. These findings suggest that the large Nernst effect and vanishing Seebeck thermopower in EuAl$_2$Si$_2$ are due to the compensated electron- and hole-like bands, along with the high mobility of the Weyl band near the Fermi level. Our results underscore the importance of band compensation and topological fermiology in achieving large Nernst thermopower and exploring potential Nernst thermoelectric applications at low temperatures.