Berlin 2012 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

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 Steglich² — ¹1. 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.