Sign change of the Grüneisen parameter and magnetocaloric effect near quantum critical points

Markus Garst and Achim Rosch
Phys. Rev. B 72, 205129 – Published 30 November 2005

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, Tc(pcp)Ψ, then we obtain for p<pc, (1) a characteristic increase ΓT1(νz) of the Grüneisen parameter Γ for T>Tc, (2) a sign change in the Ginzburg regime of the classical transition, (3) possibly a peak at Tc, (4) a second increase ΓT1(νz) below Tc for systems above the upper critical dimension, and (5) a saturation of Γ1(pcp). 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.

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  • Received 8 July 2005

DOI:https://doi.org/10.1103/PhysRevB.72.205129

©2005 American Physical Society

Authors & Affiliations

Markus Garst1 and Achim Rosch2

  • 1Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
  • 2Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany

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Vol. 72, Iss. 20 — 15 November 2005

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