Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 4: CE: Quantum-Critical Phenomena 1

TT 4.9: Vortrag

Montag, 14. März 2011, 12:45–13:00, HSZ 201

Anomalous effect of hole-doping on YbRh₂Si₂ — •Yoshi Tokiwa, Hirale S. Jeevan, Maik Schubert, and Philipp Gegenwart — I. Physik. Institut, Georg-August Universität Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen, Germany

Substituting Fe at the Rh site in YbRh₂Si₂ causes both chemical pressure and hole doping. We have investigated single crystals of Yb(Rh_1−xFe_x)₂Si₂ with x=0.05 by specific heat, magnetization, resistivity and magnetocaloric effect measurements down to ∼20 mK. The observed shift of the broad maximum in ρ(T) from 140 to 115 K and the reduction of the Kondo temperature from 25 to 15 K could be ascribed to the effect of an effective chemical pressure of ∼0.8 GPa. Without charge carrier doping, such pressure enhances T_N from 0.07 to about 0.3 K. However, no magnetic order is found in Yb(Rh_0.95Fe_0.05)₂Si₂ which might be due to the hole-doping effect. The energy scale T^⋆(H) that for undoped YbRh₂Si₂ collapses at a critical field of 0.05 T is moderately shifted and terminates at a slightly smaller field H^⋆(T→ 0)=0.03 T. Divergent behavior of the Sommerfeld coefficient, γ∝(H−H_c)^G_r, and the magnetic Grüneisen ratio, Γ_H=−G_r/(H−H_c) with G_r=−0.18 and H_c=0.03 T, is found in the field-induced Landau Fermi liquid state at H>H_c and suggests a quantum critical point in the absence of antiferromagnetic ordering in this system. Work supported by the DFG through research unit 960 (Quantum phase transitions).