Regensburg 2016 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 8: Correlated Electrons: Quantum Impurities, Kondo Physics
TT 8.10: Vortrag
Montag, 7. März 2016, 12:45–13:00, H21
Terahertz Spectroscopy of Kondo-Lattice Systems — •Christoph Wetli1, Johann Kroha2, Cornelius Krellner3, Kristin Kliemt3, Oliver Stockert4, Hilbert v. Loehneysen5, and Manfred Fiebig1 — 1Department of Materials, ETH Zurich — 2Institute of Physics, Bonn University — 3Institute of Physics, Goethe University Frankfurt — 4MPI for Chemical Physics of Solids, Dresden — 5Institute of Solid State Physics, KIT
Quantum phase transitions are boosting the interest in the field of Kondo-lattice systems. Experimental insights have been mainly obtained by measuring the specific heat or the magnetic susceptibility and relating them to the increase of the quasiparticle effective mass. Lately, it has been demonstrated that ARPES experiments allow direct access to the electrons contributing to the Kondo-lattice effect. We show that THz radiation is a powerful and highly accurate alternative for investigating the approach to the coherent Kondo state of heavy-fermion systems. Photons in the THz range directly couple to the electronic heavy quasiparticles arising from the Kondo effect. This technique allows to study Kondo-lattice dynamics on the picosecond time scale. We report lifetime measurements of excited Kondo singlets for two crystalline rare earth heavy-fermion systems CeCu6 and YbRh2Si2 and find that the lifetimes scale inversely with the Kondo temperature. THz spectroscopy thus gives a very different perspective towards the Kondo-lattice effect, with the unique ability to combine temporal resolution and possible measurements in magnetic field.