Grüneisen divergence near the structural quantum phase transition in ScF3

The cubic perovskite ScF exhibits pronounced isotropic negative thermal expansion and a structural quantum phase transition. We present measurements of the thermal expansion from 200 K to about 1.6 K. We find evidence for stress effects at both high and low temperatures. The coefficient of volumetric thermal expansion and the Gruneisen parameter exhibit power-law temperature dependences above 12 K. The Gruneisen parameter changes sign near 2.4 K and reaches by 1.6 K. Our results are consistent with predictions of Gruneisen divergence on the ordered side of a quantum critical point.