Spin Fluctuation Theory for Quantum Tricritical Point Arising in Proximity to First-Order Phase Transitions: Applications to Heavy-Fermion Systems, YbRh2Si2, CeRu2Si2, and beta-YbAlB4
Spin Fluctuation Theory for Quantum Tricritical Point Arising in Proximity to First-Order Phase Transitions: Applications to Heavy-Fermion Systems, YbRh2Si2, CeRu2Si2, and beta-YbAlB4
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DOI：
10.1143/jpsj.78.084707
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发表时间：
2009-05
期刊：
影响因子：
--
通讯作者：
Takahiro Misawa;Y. Yamaji;M. Imada
中科院分区：
文献类型：
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作者：
Takahiro Misawa;Y. Yamaji;M. Imada
提出了反铁磁量子三临界点（QTCP）的一阶相变在零温度下变为连续相变的现象自旋涨落理论。在磁场作用下，除了反铁磁量子临界点外，在反铁磁QTCP周围还会出现铁磁量子临界涨落，这与传统的反铁磁量子临界点形成了鲜明的对比。对于流动电子系统，我们证明了在反铁磁有序（铁磁）波数q= q （q=0）时，QTCP周围临界磁波动的温度依赖性为chiQ \propto T^{-3/2} （chi0\propto T^{-3/4}）。chi0^{-1}的凸温度依赖是QTCP的特征，这在传统的自旋涨落理论中从未见过。我们提出量子三临界性的一般理论，与特定的近道物理本身无关，解决了在重费米子系统（如YbRh2Si2， CeRu2Si2和β - ybalb4）中广泛观察到的量子临界性难题。对于YbRh2Si2，我们的理论通过选择合适的现象学参数，成功地再现了实验铁磁磁化率的定量行为和磁化曲线。量子三临界性也与其他物理性质的奇点一致，如比热、核磁弛豫时间1/T_1T和霍尔系数。对于CeRu2Si2和β - ybalb4，我们指出量子三临界性可能是在这些材料中观察到的均匀磁化率异常发散增强的原因。
We propose a phenomenological spin fluctuation theory for antiferromagnetic quantum tricritical point (QTCP), where the first-order phase transition changes into the continuous one at zero temperature. Under magnetic fields, ferromagnetic quantum critical fluctuations develop around the antiferromagnetic QTCP in addition to antiferromagnetic ones, which is in sharp contrast with the conventional antiferromagnetic quantum critical point. For itinerant electron systems,} we show that the temperature dependence of critical magnetic fluctuations around the QTCP are given as chiQ \propto T^{-3/2} (chi0\propto T^{-3/4}) at the antiferromagnetic ordering (ferromagnetic) wave number q=Q (q=0). The convex temperature dependence of chi0^{-1} is the characteristic feature of the QTCP, which is never seen in the conventional spin fluctuation theory. We propose that the general theory of quantum tricriticality that has nothing to do with the specific Kondo physics itself, solves puzzles of quantum criticalities widely observed in heavy-fermion systems such as YbRh2Si2, CeRu2Si2, and beta-YbAlB4. For YbRh2Si2, our theory successfully reproduces quantitative behaviors of the experimental ferromagnetic susceptibility and the magnetization curve by choosing the phenomenological parameters properly. The quantum tricriticality is also consistent with singularities of other physical properties such as specific heat, nuclear magnetic relaxation time 1/T_1T, and Hall coefficient. For CeRu2Si2 and beta-YbAlB4, we point out that the quantum tricriticality is a possible origin of the anomalous diverging enhancement of the uniform susceptibility observed in these materials.