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arXiv · 0905.2106

Thermal expansion and Grueneisen parameter in quantum Griffiths phases

Thomas Vojta
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Abstract

We consider the behavior of the Grüneisen parameter, the ratio between thermal expansion and specific heat, at pressure-tuned infinite-randomness quantum-critical points and in the associated quantum Griffiths phases. We find that the Grüneisen parameter diverges as $\ln(T_0/T)$ with vanishing temperature $T$ in the quantum Griffiths phases. At the infinite-randomness critical point itself, the Grüneisen parameter behaves as $[\ln(T_0/T)]^{1+1/(νψ)}$ where $ν$ and $ψ$ are the correlation length and tunneling exponents. Analogous results hold for the magnetocaloric effect at magnetic-field tuned transitions. We contrast clean and dirty systems, we discuss subtle differences between Ising and Heisenberg symmetries, and we relate our findings to recent experiments on CePd$_{1-x}$Rh$_x$.

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Thomas Vojta. 2009-07-16. Thermal expansion and Grueneisen parameter in quantum Griffiths phases. https://doi.org/10.1103/physrevb.80.041101

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