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TT: Fachverband Tiefe Temperaturen

TT 25: Correlated Electrons: Quantum-Critical Phenomena 1

TT 25.12: Vortrag

Mittwoch, 28. März 2012, 12:30–12:45, H 3010

Electron spin resonance on YbRh2Si2 at mK temperatures close to the quantum critical point — •Marc Scheffler1, Conrad Clauß1, Martin Dressel1, Jörg Sichelschmidt2, Cornelius Krellner2, Christoph Geibel2, and Frank Steglich211. Physikalisches Institut, Universität Stuttgart, Germany — 2Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany

YbRh2Si2 is a prototypical heavy-fermion material close to a quantum critical point: the antiferromagnetic order can be suppressed by a small external magnetic field of 60mT. Above this quantum critical point, a broad region of the phase diagram displays signatures of quantum criticality. Furthermore, a Landau Fermi-liquid regime is found for magnetic fields higher than the quantum critical point. Previous electron spin resonance (ESR) measurements on YbRh2Si2 demonstrated that the ESR response of this Kondo lattice system is characterized by the properties of local Yb moments. So far, ESR studies on YbRh2Si2 were limited to temperatures above 500mK and could not access the quantum critical regime close to the QCP nor the antiferromagnetic phase.

Here we present ESR measurements on YbRh2Si2 single crystals performed in a dilution refrigerator down to temperatures below 100mK. With ESR frequencies of a few GHz, we can cover temperature and field regimes close to the quantum critical point. We present the temperature and field dependences of the ESR parameters, in particular the ESR g-factor, and discuss them in the context of recent theoretical models.

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DPG-Physik > DPG-Verhandlungen > 2012 > Berlin