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TT: Fachverband Tiefe Temperaturen

TT 34: Correlated Electrons: f-Electron Systems and Heavy Fermions 1

TT 34.13: Vortrag

Mittwoch, 18. März 2020, 12:45–13:00, HSZ 204

Visualizing the Kondo lattice crossover in an Yb-based heavy fermion system with Compton scattering — •Monika Güttler¹, Kurt Kummer², Akihisa Koizumi³, Kristin Kliemt⁴, Cornelius Krellner⁴, Clemens Laubschat¹, and Denis Vyalikh^5,6 — ¹IFMP, TU Dresden, Germany — ²ESRF, Grenoble, France — ³Graduate School of Material Science, University of Hyogo, Japan — ⁴Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt, Germany — ⁵DIPC, San Sebastian, Spain — ⁶IKERBASQUE, Bilbao, Spain

With the breakdown of coherent Kondo scattering with rising temperature, the Fermi surface (FS) in rare earth Kondo lattices is expected to transition from the large FS counting the 4f moments, which form entangled quasiparticles with huge masses with the conduction states, to the small FS with decoupled and localized 4f moments. A direct observation of this transition with temperature has however remained elusive because conventional probes of the FS in Kondo lattices require high magnetic fields which might reconstruct the FS or cannot work reliably at elevated temperatures. Using high-resolution Compton scattering we overcome these limitations and show that the FS topology in the prototypical Kondo lattice YbRh₂Si₂ undergoes pronounced changes between 14 K and 300 K in zero magnetic field. We present clear evidence for a largely restored small FS at room temperature which could not be observed before. Our results set an upper bound for the relevant energy scale of the complex Kondo crossover phenomenon in YbRh₂Si₂.