Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 38: f-Electron Systems and Heavy Fermions

TT 38.7: Vortrag

Mittwoch, 3. April 2019, 11:30–11:45, H23

Exploring quantum criticality in strain-tuned heavy fermion thin films by THz spectroscopy — •C.-J. Yang¹, S. Pal¹, F. Zamani², M. Trassin¹, H. v. Loehneysen³, J. Kroha², and M. Fiebig¹ — ¹ETH Zurich, Switzerland. — ²Bonn University, Germany. — ³KIT, Germany.

Quantum phase transition (QPT) refers to a second-order phase transition between the ground states of a many-body system occurring around T = 0 K, governed by critical fluctuations. In heavy fermion compounds, CeCu_6−xAu_x, Cu-substitution by Au expands the lattice thereby inducing a QPT from a paramagnetic Fermi-liquid state to an antiferromagnetically ordered ground state at x = 0.1. In this contribution, we take a novel approach, replacing the role of Au by strain-tuning in CeCu₆ epitaxial thin films. Films of various thicknesses are sputtered from a pure CeCu₆ target onto single-crystal substrates. The crystallinity and orientation of the thin films are investigated by X-ray diffraction. To understand the dynamic evolution of Kondo quasiparticle weight and of optical properties, we perform time-resolved THz measurements as function of temperature. For the sample of a 30 nm thick CeCu₆ film, our results show similar temperature-dependent Kondo response as observed in bulk samples [1]. We find a logarithmic onset of the Kondo spectral weight at 100 K. This behavior is further corroborated by the temperature-dependent mass enhancement ratio and the inverse scattering rate. We also observe a non-linear temperature-dependence of the optical resistivity.
C. Wetli, S. Pal et al., Nat. Phys. 14, 1103 (2018)