Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 38: f-Electron Systems and Heavy Fermions
TT 38.6: Vortrag
Mittwoch, 3. April 2019, 11:15–11:30, H23
Probing Fermi-surface evolution and crystal-field excitations in heavy-fermion systems by THz time-domain spectroscopy — •Shovon Pal1, Christoph Wetli1, Farzaneh Zamani2, Oliver Stockert3, Hilbert v. Loehneysen4, Manfred Fiebig1, and Johann Kroha2 — 1ETH Zurich, Switzerland. — 2Bonn University, Germany. — 3MPI-CPFS Dresden, Germany. — 4KIT, Germany.
An enlarged Fermi volume ratifies the existence of heavy quasiparticles (QPs) in heavy-fermion (HF) compounds. The energy scale for the heavy QP formation is believed to be the Kondo lattice temperature. However, recent observations of large Fermi volume at temperatures much higher than the Kondo lattice temperature raised controversies on the validity of this long-known scale. We measure the QP weight in the HF compound CeCu6−xAux (x = 0, 0.1) by time-resolved THz spectroscopy for temperatures from 2 K to 300 K. This method distinguishes contributions from the heavy Kondo band and from the crystal-electric-field (CEF) split satellite bands by different THz response delay times [1]. We find that an exponentially enhanced, high-energy Kondo scale controls the formation of heavy bands, once the CEF states become thermally occupied [2]. We corroborate these observations by temperature-dependent, high-resolution dynamical mean-field calculations for the multi-orbital Anderson lattice model and discuss its relevance for quantum critical scenarios.
C. Wetli, S. Pal et al., Nat. Phys. 14, 1103 (2018)
S. Pal et al., arXiv:1810.07412 (2018)