Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 3: Correlated Electrons: Quantum-Critical Phenomena

TT 3.2: Talk

Monday, March 27, 2006, 09:45–10:00, HSZ 301

Hidden Quantum Critical Point in CeCoIn_5−xSn_x Studied by Thermal Expansion and Grüneisen Ratio Divergence — •G. Donath¹, R. Küchler¹, P. Gegenwart¹, E.D. Bauer², J.L. Sarrao², and F. Steglich¹ — ¹Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany — ²Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 USA

The heavy fermion superconductor CeCoIn_5−xSn_x has attracted much interest because of a magnetic field-induced quantum critical point at H_QCP that coincides with the upper critical field H_c2 for unconventional superconductivity. Most remarkably, it is not possible to separate both phenomena from each other. By contrast, H_QCP is pinned to H_c2 if superconductivity is weakened by Sn substitution [1].
We present low-temperature thermal expansion measurements, α(T,B), for the various concentrations, x=0, 0.03, 0.06, 0.09, 0.12, 0.18, and compare them with the predictions of the spin-density-wave theory for an antiferromagnetic quantum critical point.
Furthermore, the effect of Sn subsitution on the Grüneisen ratio Γ(T)∝α/C (C: specific heat) is discussed.

[1] E.D. Bauer et al., Phys. Rev. Lett. 94, 047001 (2005)