Grueneisen Ratio Divergence at the Quantum Critical Point in CeCu_{6-x}Ag_x

Abstract

The heavy fermion system CeCu${}_{6-x}$Ag${}_x$ is studied at its antiferromagnetic quantum critical point, $x_c=0.2$, by low temperature ($T\ge 50$ mK) specific heat, $C(T)$, and volume thermal expansion, $\beta (T)$, measurements. Whereas $C/T\propto \log (T_0/T)$ would be compatible with the predictions of the itinerant spin-density-wave (SDW) theory for two-dimensional critical spin fluctuations, $\beta (T)/T$ and the Grüneisen ratio, $\Gamma (T)\propto \beta /C$, diverge much weaker than expected, in strong contrast to this model. Both $C$ and $\beta$, plotted as a function of the reduced temperature $t=T/T_0$ with $T_0=4.6$ K are similar to what was observed for YbRh${}_2$(Si${}_{0.95}$Ge${}_{0.05}$)${}_2$ ($T_0=23.3$ K) indicating a striking discrepancy to the SDW prediction in both systems.

arXiv commentPhysical Review Letters, to be published

References in corpus (8)

• Locally critical quantum phase transitions in strongly correlated metals
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• How do Fermi liquids get heavy and die?
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• Two-dimensional fluctuations at the quantum-critical point of CeCu_{6-x}Au_x
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