Pressure-tuned quantum criticality in the antiferromagnetic Kondo semimetal CeNi2-δAs2
Pressure-tuned quantum criticality in the antiferromagnetic Kondo semimetal CeNi2-δAs2
复制标题
反铁磁近藤半金属 CeNi2-delta As2 中压力调节的量子临界性
DOI：
10.1073/pnas.1509581112
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发表时间：
2015-11-03
影响因子：
11.1
通讯作者：
Thompson, J. D.
中科院分区：
文献类型：
--
作者：
Luo, Yongkang;Ronning, F.;Thompson, J. D.
近藤晶格金属中相互竞争的相互作用之间容易调节的平衡允许在磁性有序和无序相之间实现零温度、连续的转变，这是一个量子临界点(QCP)。事实上，这些高度相关的电子材料是发现和探索量子临界态的原型。为了解释近藤晶格QCP周围出现的奇怪的热力学和电学输运性质，提出的理论模型假定存在无限数量的巡回电荷载流子。在这里，我们报道了近藤晶格系统CeNi2-Delta As2(约0.28)的输运和热力学研究，因为它的反铁磁序在压力和磁场的作用下被调谐到零温度边界。这些实验表明，CeNi2-deltaAs2中类似于0.032 e(-)/公式单元的非常小但有限的载流子密度导致了意外的量子临界输运特征，并随着温度的降低延迟了全相干Kondo晶格态的发展。这种近藤晶格材料的小载流子密度和相关的半金属性有利于非传统的局域矩类型的量子临界性，并引发了Nozieres穷竭思想的幽灵，即足够数量的传导电子自旋来单独屏蔽局域矩需要集体近藤筛选。
The easily tuned balance among competing interactions in Kondo-lattice metals allows access to a zero-temperature, continuous transition between magnetically ordered and disordered phases, a quantum-critical point (QCP). Indeed, these highly correlated electron materials are prototypes for discovering and exploring quantum-critical states. Theoretical models proposed to account for the strange thermodynamic and electrical transport properties that emerge around the QCP of a Kondo lattice assume the presence of an indefinitely large number of itinerant charge carriers. Here, we report a systematic transport and thermodynamic investigation of the Kondo-lattice system CeNi2-delta As2 (delta approximate to 0.28) as its antiferromagnetic order is tuned by pressure and magnetic field to zero-temperature boundaries. These experiments show that the very small but finite carrier density of similar to 0.032 e(-)/formular unit in CeNi2-delta As2 leads to un-expected transport signatures of quantum criticality and the delayed development of a fully coherent Kondo-lattice state with decreasing temperature. The small carrier density and associated semimetallicity of this Kondo-lattice material favor an unconventional, local-moment type of quantum criticality and raises the specter of the Nozieres exhaustion idea that an insufficient number of conduction- electron spins to separately screen local moments requires collective Kondo screening.