Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 34: Correlated Electrons: f-Electron Systems and Heavy Fermions 1

TT 34.9: Vortrag

Mittwoch, 18. März 2020, 11:45–12:00, HSZ 204

Valence effect in the thermopower of Eu systems — •Ulrike Stockert1, Silvia Seiro2,1, Nubia Caroca-Canales1, Elena Hassinger1, and Christoph Geibel11MPI for Chemical Physics of Solids, Dresden — 2Institute for Solid State Research, IFW, Dresden

EuIr2Si2 and EuNi2P2 have been classified as valence-fluctuating (VF) materials with a strongly temperature-dependent Eu valence. At low temperature T the effective charge carrier masses are significantly enhanced due to hybridization between the Eu 4f and the conduction electron states. The relative importance of hybridization and valence fluctuations in Eu-based VF systems is not yet clear and a topic of current interest.

We present thermal conductivity and thermopower data for EuIr2Si2 and EuNi2P2 in the temperature range beween 2 K and 300 K. The thermal conductivities of both materials are conventional with differences arising due to different crystal quality. By contrast, the thermopowers of EuIr2Si2 and EuNi2P2 exhibit large values and a characteristic T dependence that cannot be explained satisfactorily by simple hybridization models. Instead, we may describe the thermopower by taking into account the temperature-dependence of the Eu valence, which leads to additional thermopower contributions due to variations in the chemical potential. These findings corroborate the relevance of the valence fluctuations for understanding the properties of EuIr2Si2 and EuNi2P2 at intermediate temperatures.

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