Nernst Effect: Evidence of Local Kondo Scattering in Heavy Fermions

A distinctly temperature-dependent Nernst coefficient, ν, which is strongly enhanced over that of LaCu₂Si₂, is observed between $T=2$ and 300 K for CeCu₂Si₂ and Ce0.8La0.2Cu₂Si₂. The enhanced ν(T) is determined by the asymmetry of the on-site Kondo (conduction electron -4f electron) scattering rate. Taking into account the measured Hall mobility, μH, the highly unusual thermopower, S, of these systems can be semiquantitatively described by S(T)=-ν(T)/μH(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 (≈20 K for CeCu₂Si₂). Our results suggest that the Nernst effect can act as a proper probe of local charge-carrier scattering. This promises to impact on exploring the unconventional enhancement of the thermopower in correlated materials suited for potential applications.