Divergence of the grüneisen ratio at quantum critical points in heavy fermion metals.
We present low-temperature volume thermal expansion, beta, and specific heat, C, measurements on high-quality single crystals of CeNi2Ge2 and YbRh2(Si0.95Ge0.05)(2) which are located very near to quantum critical points. For both systems, beta shows a more singular temperature dependence than C, and thus the Grüneisen ratio Gamma proportional to beta/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(Si0.95Ge0.05)(2) cannot be explained by the itinerant SDW theory but is qualitatively consistent with a locally quantum critical picture.
Küchler
R
R
Max-Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany.
Oeschler
N
N
Gegenwart
P
P
Cichorek
T
T
Neumaier
K
K
Tegus
O
O
Geibel
C
C
Mydosh
J A
JA
Steglich
F
F
Zhu
L
L
Si
Q
Q