Abstract
We consider the Grüneisen parameter and the magnetocaloric effect near a pressure and magnetic field controlled quantum critical point, respectively. Generically, the Grüneisen parameter (and the thermal expansion) displays a characteristic sign change close to the quantum-critical point signaling an accumulation of entropy. If the quantum critical point is the endpoint of a line of finite temperature phase transitions, , then we obtain for , (1) a characteristic increase of the Grüneisen parameter for , (2) a sign change in the Ginzburg regime of the classical transition, (3) possibly a peak at , (4) a second increase below for systems above the upper critical dimension, and (5) a saturation of . We argue that due to the characteristic divergencies and sign changes the thermal expansion, the Grüneisen parameter and magnetocaloric effect are excellent tools to detect and identify putative quantum critical points.
- Received 8 July 2005
DOI:https://doi.org/10.1103/PhysRevB.72.205129
©2005 American Physical Society