Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 24: Quantum-Critical Phenomena

TT 24.8: Vortrag

Mittwoch, 7. September 2022, 16:45–17:00, H23

Electronuclear quantum criticality — Jacintha Banda¹, Daniel Hafner¹, Javier F. Landaeta¹, Elena Hassinger^1,2, Keisuke Mitsumoto³, Mauro Giovannini⁴, Julian Sereni⁵, Christoph Geibel¹, and •Manuel Brando¹ — ¹Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany — ²Technical University Munich, Physics department, 85748 Garching, Germany — ³Liberal Arts and Sciences, Toyama Prefectural University, Imizu, Toyama 939-0398, Japan — ⁴Department of Chemistry and Industrial Chemistry (DCCI), University of Genova, 16100 Genova, Italy — ⁵Department of Physics, CAB-CNEA, CONICET, 8400 San Carlos de Bariloche, Argentina

We present here a rare example of electronuclear quantum criticality in a metal. The compound YCu_4.6Au_0.4 is located at an unconventional quantum critical point (QCP). The relevant Kondo and RKKY exchange interactions are very weak, of the order of 1 K with a strong competition between antiferromagnetic and ferromagnetic correlations, possibly due to geometrical frustration within the fcc Yb sublattice. This causes strong spin fluctuations which prevent the system to order magnetically. Because of the very low Kondo temperature the Yb³⁺ 4f-electrons couple weakly with the conduction electrons allowing the coupling to the nuclear moments of the ¹⁷¹Yb and ¹⁷³Yb isotopes to become important. Thus, the quantum critical fluctuations observed at the QCP derive not from purely electronic states but from entangled ’electronuclear’ states. This is evidenced in the anomalous temperature and field dependence of the specific heat at very low temperatures.