Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 25: Correlated Electrons: Quantum-Critical Phenomena 1

TT 25.11: Vortrag

Mittwoch, 28. März 2012, 12:15–12:30, H 3010

Influence of charge carrier doping on the T^∗-Scale in YbRh₂Si₂ — •Maik-Hendrik Schubert, Manuel Mchalwat, Elias Blumenröther, H. S. Jeevan, Yoshi Tokiwa, and Philipp Gegenwart — I. Physik. Institut, Georg-August Universität Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen, Germany

YbRh₂Si₂ is a prototype heavy-fermion metal which displays a magnetic field-induced antiferromagnetic (AF) quantum critical point (QCP). It has attracted much attention due to an additional low-energy scale T^⋆(B) merging at the QCP, whose origin is controversially discussed. Here, we report measurements of the electrical resistivity ρ(T,B) on different single crystalline samples of charge-carrier doped Yb(Rh_1−xT_x)₂Si₂ (T=Fe, Ni) at temperatures down to 15 mK and in magnetic fields up to 7 T. The partial substitution of Rh by either Fe or Ni introduces holes or electrons, respectively. The evolution of the single-ion Kondo scale is similar as for isoelectronic Co substitution and in accordance with the chemical pressure effect. However, while chemical pressure has little influence on T^⋆(B), we observe a drastic reduction or increase of B^⋆(T=0) by Fe- or Ni-doping, respectively. Most interestingly, B^⋆(T=0) is always pinned at the field-induced AF QCP, in contrast to chemical pressure results. As AF order is completely suppressed by Fe-doping, a heavy Fermi liquid ground (without T^⋆(B) anomaly) is observed.

Work supported by the DFG through the research unit 960 (Quantum phase transitions).