PrBi：拓扑满足四极自由度
PrBi: Topology meets quadrupolar degrees of freedom
摘要：
具有除电荷之外的电子自由度（包括自旋、轨道或谷值）的新型材料\textit{et al}已表现出巨大的兴趣和应用潜力。近年来，多极自由度在电子关联效应中引起了人们的极大关注。本文在晶体电场理论的框架下，系统地研究了拓扑半金属候选化合物PrBi的输运、磁性和热力学性质。结果表明Pr $^{3+}$（4 $f^2$）离子的基态为$Γ_3$非Kramers双峰.该基态是基态，但携带非零四极矩$\langle\hat{O}_2^0\rangle$。在低于0.08 K时发生四极相变。没有发现明显的四极近藤效应。超高场量子振荡测量证实PrBi是一种具有非平凡Berry相和低总载流子密度0.06 /f. u的半金属。我们讨论了低载流子密度和$4f^2$四极矩之间的相互作用，并将弱四极有序和近藤效应归因于低载流子密度的后果。因此，PrBi打开了一个新的窗口，物理拓扑结构和强相关效应与四极自由度的低载流子密度限制，唤起需要重新审查的Nozières耗尽问题的背景下，多通道近藤效应。
英文摘要：
Novel materials incorporating electronic degrees of freedom other than charge, including spin, orbital or valley \textit{et al} have manifested themselves to be of the great interests and applicable potentials. Recently, the multipolar degrees of freedom have attracted remarkable attention in the electronic correlated effects. In this work, we systematically studied the transport, magnetic and thermodynamic properties of the topological semimetal candidate PrBi in the framework of crystalline electric field theory. Our results demonstrate the $Γ_3$ non-Kramers doublet as the ground state of Pr$^{3+}$ (4$f^2$) ions. This ground state is nonmagnetic but carries a non-zero quadrupolar moment $\langle\hat{O}_2^0\rangle$. A quadrupolar phase transition is inferred below 0.08 K. No obvious quadrupolar Kondo effect can be identified. Ultrahigh-field quantum oscillation measurements confirm PrBi as a semimetal with non-trivial Berry phase and low total carrier density 0.06 /f.u. We discuss the interplay between low carrier density and $4f^2$ quadrupolar moment, and ascribe the weak quadrupolar ordering and Kondo effect to consequences of the low carrier density. PrBi, thus, opens a new window to the physics of topology and strongly correlated effect with quadrupolar degrees of freedom in the low-carrier-density limit, evoking the need for a reexamination of the Nozières exhaustion problem in the context of multi-channel Kondo effect.
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