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arXiv · 2408.07345

Missing spectral weight in a heavy-fermion system far above N\'eel temperature

Jingwen Li·Debankit Priyadarshi·Chia-Jung Yang·Ulli Pohl·Oliver Stockert·Hilbert von Löhneysen·Shovon Pal·Manfred Fiebig·Johann Kroha
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Abstract

The competition between the Kondo spin-screening effect and the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in heavy-fermion systems drives the quantum phase transition between the magnetically ordered and the heavy-Fermi-liquid ground states. Despite intensive investigations of heavy quasiparticles on the Kondo-screened side of the quantum phase transition and of their breakdown at the quantum critical point, the magnetically ordering side has not systematically been studied. Using terahertz time-domain spectroscopy, we report a suppression of the Kondo quasiparticle weight in CeCu$_{6-x}$Au$_x$ samples on the antiferromagnetic side of the quantum phase transition at temperatures as much as two orders of magnitude above the N\'{e}el temperature $T_\text{N}$. With our systematic investigations into the high-temperature, paramagnetic region on the antiferromagnetic side of the phase diagram of CeCu$_{6-x}$Au$_x$, i.e., with $x =$ 0.2, 0.3, and 0.5, we show that the suppression results from a quantum frustration effect induced by the temperature-independent RKKY interaction. Hence, our results emphasize that besides critical fluctuations, the RKKY interaction may play an important role in the quantum-critical scenario.

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Jingwen Li, Debankit Priyadarshi, Chia-Jung Yang, Ulli Pohl, Oliver Stockert, Hilbert von Löhneysen, Shovon Pal, Manfred Fiebig, Johann Kroha. 2024-08-14. Missing spectral weight in a heavy-fermion system far above N\'eel temperature. https://doi.org/10.1103/physrevb.111.035117

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