Fermi Volume Evolution and Crystal-Field Excitations in Heavy-Fermion Compounds Probed by Time-Domain Terahertz Spectroscopy (C4)

S. Pal, C. Wetli, F. Zamani, O. Stockert, H. v Löhneysen, M. Fiebig, and J. Kroha:

Phys. Rev. Lett., 122, 096401 (2019)

🔓 arXiv:1810.07412 (2018)

We measure the quasiparticle weight in the heavy-fermion compound CeCu6−xAux (x=0, 0.1) by time-resolved terahertz spectroscopy for temperatures from 2 up to 300 K. This method distinguishes contributions from the heavy Kondo band and from the crystal-electric-field satellite bands by different terahertz response delay times. We find that the formation of heavy bands is controlled by an exponentially enhanced, high-energy Kondo scale once the crystal-electric-field states become thermally occupied. We corroborate these observations by temperature-dependent dynamical mean-field calculations for the multiorbital Anderson lattice model and discuss consequences for quantum-critical scenarios.