Low-temperature thermodynamic properties near the field-induced quantum critical point in NiCl2-4SC(NH2)2

摘要: We present a comprehensive experimental and theoretical investigation of the thermodynamic properties: specific heat, magnetization, thermal expansion in vicinity field-induced quantum critical point (QCP) around lower field ${H}_{c1}\ensuremath{\approx}2$ T NiCl${}_{2}$-4SC(NH${}_{2}$)${}_{2}$. A ${T}^{3/2}$ behavior heat magnetization is observed at very low temperatures $H={H}_{c1}$, which consistent with universality class Bose-Einstein condensation magnons. The temperature dependence coefficient ${H}_{c1}$ shows minor deviations from expected ${T}^{1/2}$ behavior. Our study complemented by analytical calculations Monte Carlo simulations, reproduce nicely measured quantities. analyze magnetic Gr\"uneisen parameters, are ideal quantities to identify QCPs. Both parameters diverge ${T}^{\ensuremath{-}1}$ power law. By using Ehrenfest relations second-order phase transition, we able estimate pressure dependencies characteristic scales.