YbRh $_2$ Si $_2$中磁场Grüneisen比在量子临界点的发散
Divergence of the Magnetic Grüneisen Ratio at the Field-Induced Quantum Critical Point in YbRh$_2$Si$_2$
摘要：
用低温磁化$M(T)$和比热$C(T)$测量方法研究了重费米子化合物YbRh $_2$ Si $_2$在量子临界点附近的磁场（$H_c=0.06$ T，$H\perp c$）.在接近不稳定性时，$dM/dT$比$C(T)$更奇异，导致磁格吕奈森比$Γ_{\rm mag}=-(dM/dT)/C$发散。在Fermi液相区，$Γ_{\rm mag}=-G_r(H-H_c^{fit})$与$G_r=-0.30\pm 0.01$和$H_c^{fit}=(0.065\pm 0.005)$ T的关系与YbRh $_2$（Si $_{0.95}$ Ge $_{0.05}$）$_2$比热系数的标度行为一致. $dM/dT$的场依赖性表明，作为磁场的函数，在通过之前在霍尔和热力学测量中观察到的线$T^\star(H)$时，熵的拐点。
英文摘要：
The heavy fermion compound YbRh$_2$Si$_2$ is studied by low-temperature magnetization $M(T)$ and specific-heat $C(T)$ measurements at magnetic fields close to the quantum critical point ($H_c=0.06$ T, $H\perp c$). Upon approaching the instability, $dM/dT$ is more singular than $C(T)$, leading to a divergence of the magnetic Grüneisen ratio $Γ_{\rm mag}=-(dM/dT)/C$. Within the Fermi liquid regime, $Γ_{\rm mag}=-G_r(H-H_c^{fit})$ with $G_r=-0.30\pm 0.01$ and $H_c^{fit}=(0.065\pm 0.005)$ T which is consistent with scaling behavior of the specific-heat coefficient in YbRh$_2$(Si$_{0.95}$Ge$_{0.05}$)$_2$. The field-dependence of $dM/dT$ indicates an inflection point of the entropy as a function of magnetic field upon passing the line $T^\star(H)$ previously observed in Hall- and thermodynamic measurements.
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