Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 2: Quantum-Critical Phenomena

TT 2.10: Talk

Monday, March 26, 2007, 12:00–12:15, H19

High-temperature echo of the quantum phase transition in CeCu_6−xAu_x — •M. Klein¹, A. Nuber¹, H. v. Löhneysen^2,3, and F. Reinert¹ — ¹Universität Würzburg, Experimentelle Physik II, Am Hubland, 97074 Würzburg — ²Universität Karlsruhe, Physikalisches Institut, D-76128 Karlsruhe — ³Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe

During the last years many experiments and theoretical investigations have been performed to explain the nature of quantum critical points (QCP) in heavy-fermion compounds. One important candidate of these compounds is CeCu_6−xAu_x which goes from a paramagnetic metal to an antiferromagnetic metal as x increases. The QCP appears when the critical value of x_c∼0.1 is reached.
We have performed high-resolution photoemission experiments(Δ E<5 meV) on single crystals with different gold concentrations at temperatures in the range from T=15 K to 60 K. Though these temperatures were much higher than the characteristic temperatures we see a significant jump in the spectral weight of the Kondo-resonance at x_c implying a sudden change in the correlation between localized 4f-electrons and conduction electrons. A comparison with NCA calculations allows a quantitative determination of the Kondo temperature and the crystal field energies. This finite temperature signatur is a further key to solve the question about the nature of the QCP in this system.