Nernst Effect as a Probe of Local Kondo Scattering in Heavy Fermions

TL;DR

This study demonstrates that the Nernst effect effectively probes local Kondo scattering in heavy fermion materials, revealing temperature-dependent behavior and its relation to thermopower, with implications for understanding correlated electron systems.

Contribution

It introduces the Nernst effect as a new probe for local Kondo scattering in heavy fermions, linking it to thermopower over a wide temperature range.

Findings

Large, temperature-dependent Nernst coefficient observed in CeCu$_2$Si$_2$.

Thermopower can be described by Nernst coefficient and Hall mobility.

Nernst effect serves as a probe for local charge-carrier scattering.

Abstract

A large, strongly temperature-dependent Nernst coefficient, $\nu$, is observed between $T$ = 2 K and 300 K for CeCu$_2$Si$_2$ and Ce$_{0.8}$La$_{0.2}$Cu$_2$Si$_2$. The enhanced $\nu(T)$ is determined by the asymmetry of the on-site Kondo (conduction electron$-4f$ electron) scattering rate. Taking into account the measured Hall mobility, $\mu_H$, the highly unusual thermopower, $S$, of these systems can be semiquantitatively described by $S(T)$ $=$ $-$$\nu(T)/\mu_H(T)$, which explicitly demonstrates that the thermopower originates from the local Kondo scattering process over a wide temperature range from far above to well below the coherence temperature ($\approx$ 20 K for CeCu$_2$Si$_2$). Our results suggest that the Nernst effect can act as a proper probe of local charge-carrier scattering. This promises an impact on exploring the unconventional enhancement of the thermopower in correlated materials suited for potential applications.