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TT: Fachverband Tiefe Temperaturen
TT 38: CE: Quantum-Critical Phenomena 2
TT 38.5: Vortrag
Freitag, 26. März 2010, 11:45–12:00, H18
High-temperature signatures of quantum criticality in heavy-fermion compounds and the relation to two-impurity Kondo systems — •Johann Kroha1, Laszlo Borda1, Markus Klein2, Friedrich Reinert2, Pascal Simon3, Oliver Stockert4, and Hilbert von Löhneysen5 — 1Universität Bonn — 2Universität Würzburg — 3Université Joseph Fourier, Grenoble — 4Max-Planck-Institut CPfS — 5Karlsruhe Institute of Technology
We propose a new criterion for distinguishing the Hertz-Millis (HM) and local quantum critical (LQC) scenarios of magnetic quantum phase transitions (QPT) in heavy-fermion systems from their high-temperature behavior [1]. The criterion is based on our finding that the complete screening of a single Kondo spin can be suppressed by the RKKY coupling to the surrounding magnetic ions even without magnetic ordering. As a consequence, the signature of Kondo breakdown can be observed in spectroscopic measurements above the lattice coherence and magnetic ordering temperatures, where fluctuations of the Fermi surface and quantum critical fluctuations do not play a role. We show that the predicted dependence of the screening scale TK on the RKKY coupling agrees in detail with recent scanning tunneling microscopy (STM) results on two-impurity Kondo systems. Applying the resulting high-temperature criterion to high-resolution photoemission measurements on CeCu6−xAux suggests that the QPT in this system is dominated by the LQC scenario.
[1] M. Klein et al., Phys. Rev. Lett. 101, 266404 (2008); Phys Rev. B 79, 075111 (2009).