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Divergence of the Grueneisen Ratio at Quantum Critical Points in Heavy Fermion Metals

R. Kuechler·N. Oeschler·P. Gegenwart·T. Cichorek·K. Neumaier·O. Tegus·C. Geibel·J. A. Mydosh·F. Steglich·Lijun Zhu·Qimiao Si
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Abstract

We present low-temperature volume thermal expansion, $β$, and specific heat, $C$, measurements on high-quality single crystals of CeNi2Ge2 and YbRh2(Si$_{0.95}$Ge$_{0.05}$)$_2$ which are located very near to quantum critical points. For both systems, $β$ shows a more singular temperature dependence than $C$, and thus the Grueneisen ratio ${Γ\propto β/C}$ diverges as T --> 0. For CeNi2Ge2, our results are in accordance with the spin-density wave (SDW) scenario for three-dimensional critical spin-fluctuations. By contrast, the observed singularity in YbRh2$(Si$_{0.95}$Ge$_{0.05}$)$_2$ cannot be explained by the itinerant SDW theory but is qualitatively consistent with a locally quantum critical picture.

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R. Kuechler, N. Oeschler, P. Gegenwart, T. Cichorek, K. Neumaier, O. Tegus, C. Geibel, J. A. Mydosh, F. Steglich, Lijun Zhu, Qimiao Si. 2003-08-05. Divergence of the Grueneisen Ratio at Quantum Critical Points in Heavy Fermion Metals. https://doi.org/10.1103/physrevlett.91.066405

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