Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 44: Correlated Electrons: Quantum-Critical Phenomena – Experiments

TT 44.2: Talk

Tuesday, March 17, 2015, 14:15–14:30, H 3005

Quantum Criticality in Yb(Rh_0.93Co_0.07)₂Si₂ — •Alexander Steppke¹, Luis Pedrero^1,2, Robert Borth¹, Michael Nicklas¹, Cornelius Krellner³, Christoph Geibel¹, Frank Steglich¹, and Manuel Brando¹ — ¹Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany — ²Technische Universität Dresden, 01062 Dresden, Germany — ³Johann Wolfgang Goethe-Universität, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany

The heavy-fermion compound YbRh₂Si₂ is a prototype system which allows us to study an unconventional quantum critical point. With slight isoelectronic substitution of Rh by 7% Co the AFM order is stabilized (T_N=0.4 K) and in thermodynamic (χ_ac(T)) and electrical transport measurements (ρ(T, H)) the Kondo-breakdown energy scale T^* detaches from the putative conventional spin-density wave QCP [1]. To investigate the existence of this quantum phase transition and the possible role of the additional energy scale we performed thermodynamic measurements at low temperatures. At a QCP the absence of characteristic energy scales other than the temperatures has been shown to lead to power-law scaling behavior in the Grüneisen ratio [2]. Combining results from specific heat, magnetization and thermal expansion we exclude a SDW QCP when the AFM order is suppressed by a magnetic field from the thermal and magnetic Grüneisen ratio. This is corroborated by measurements under hydrostatic pressure.

[1] S. Friedemann et al., Nat. Phys. 5 (2009) 465.

[2] L. Zhu et al., PRL 91 (2003) 066404.