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Quantum criticality in f-electron based heavy-fermion systems arises from the competition of the on-site Kondo with the inter-site exchange interaction. The essential question is how the heavy quasiparticles evolve if these materials are tuned from the paramagnetic into the antiferromagnetically ordered state. The traditional picture describes a spin-density-wave transition at which the quasiparticles retain their itinerant character. Unconventional quantum criticality, which qualitatively differs from the predictions of standard theory, may arise due to a destruction of Kondo screening. The latter may lead to a decomposition of the heavy quasiparticles into conduction electrons and local magnetic moments. I will report a comparative low-temperature study on different quantum critical heavy fermion metals with particular focus on YbRh2Si2.
Work in collaboration with M. Brando, G. Donath, T. Westerkamp, C. Krellner, Y. Tokiwa, S. Paschen, C. Geibel, F. Steglich, E. Abrahams and Q. Si. |
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