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arXiv 0812.1082cond-mat.str-el
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Yb $_3$ Pt $_4$:量子临界的新途径

Yb$_3$Pt$_4$: A New Route to Quantum Criticality

M. C. Bennett, D. A. Sokolov, M. S. Kim, Y. Janssen, Y. Yiu, W. J. Gannon, M. C. Aronson

摘要:

利用比热、磁化率和电阻率实验研究了重费米子Yb $_3$ Pt $_4$中弱一级反铁磁相变的演化.我们发现,磁场抑制尼尔温度,以及比热跳变,潜热,和熵的转变,驱动在1.2 K和1.5 T的临界端点。在更高的磁场下,反铁磁跃迁变为二级,并且这条跃迁线又终止于1.62 T的量子临界点。有序态和高场顺磁态在低温下都是费米液体,尽管前者具有更大的磁化率和更强的准粒子散射。与以前研究的量子临界系统不同,Yb $_3$ Pt $_4$中的准粒子质量在量子临界点处不发散,这意味着这里的准粒子相互作用驱动零温度跃迁。费米液体参数在有序状态下几乎与场无关,这表明波动从未成为完全临界的,因为它们的发散被一阶反铁磁转变打断。

英文摘要:

We have studied the evolution of the weakly first order antiferromagnetic transition in heavy fermion Yb$_3$Pt$_4$ using a combination of specific heat, magnetic susceptibility, and electrical resistivity experiments. We show that magnetic fields suppress the Neel temperature, as well as the specific heat jump, the latent heat, and the entropy of the transition, driving a critical endpoint at 1.2 K and 1.5 T. At higher fields, the antiferromagnetic transition becomes second order, and this line of transitions in turn terminates at a quantum critical point at 1.62 T. Both the ordered and high field paramagnetic states are Fermi liquids at low temperature, although the former has a much larger magnetic susceptibility and stronger quasiparticle scattering. Unlike previously studied quantum critical systems, the quasiparticle mass in Yb$_3$Pt$_4$ does not diverge at the quantum critical point, implying that here the quasiparticle interactions drive the zero temperature transition. The Fermi liquid parameters are nearly field-independent in the ordered state, indicating that the fluctuations never become fully critical, as their divergences are interrupted by the first order antiferromagnetic transition.

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