Low-temperature thermodynamic properties near the field-induced quantum critical point in NiCl2-4SC(NH2)2
Zapf, Vivien S.
Al-Hassanieh, Khaled A.
Batista, Cristian D.
Date of Issue2012
School of Physical and Mathematical Sciences
We present a comprehensive experimental and theoretical investigation of the thermodynamic properties: specific heat, magnetization, and thermal expansion in the vicinity of the field-induced quantum critical point (QCP) around the lower critical field Hc1≈2 T in NiCl2-4SC(NH2)2. A T3/2 behavior in the specific heat and magnetization is observed at very low temperatures at H=Hc1, which is consistent with the universality class of Bose-Einstein condensation of magnons. The temperature dependence of the thermal expansion coefficient at Hc1 shows minor deviations from the expected T1/2 behavior. Our experimental study is complemented by analytical calculations and quantum Monte Carlo simulations, which reproduce nicely the measured quantities. We analyze the thermal and the magnetic Grüneisen parameters, which are ideal quantities to identify QCPs. Both parameters diverge at Hc1 with the expected T−1 power law. By using the Ehrenfest relations at the second-order phase transition, we are able to estimate the pressure dependencies of the characteristic temperature and field scales.
DRNTU::Science::Physics::Heat and thermodynamics
Physical review B
© 2012 American Physical Society. This paper was published in Physical Review B and is made available as an electronic reprint (preprint) with permission of American Physical Society. The paper can be found at the following official DOI: [http://dx.doi.org/10.1103/PhysRevB.85.184408]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.