Nernst Effect: Evidence of Local Kondo Scattering in Heavy Fermions

A distinctly temperature-dependent Nernst coefficient, nu, which is strongly enhanced over that of LaCu2Si2, is observed between T = 2 and 300 K for CeCu2Si2 and Ce0.8La0.2Cu2Si2. 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 (approximate to 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.