利用动力学平均场论和精确对角化方法研究了周期Anderson模型中的变磁性，模型中存在$\bm{k}$依赖的$c-f$混合.研究发现，$\bm{k}$依赖的$c-f$混合效应和$f$电子间库仑相互作用引起的强关联效应对确定磁化强度和质量增强因子都有重要意义.对于远离半填充的情况，结果与在CeRu $_2$ Si $_2$中观察到的变磁行为一致。
英文摘要：
We investigate the metamagnetism in the periodic Anderson model with the $\bm{k}$-dependent $c-f$ mixing by using the dynamical mean-field theory combined with the exact diagonalization method. It is found that both effects of the $\bm{k}$-dependent $c-f$ mixing and strong correlation due to the Coulomb interaction between $f$ electrons are significant for determining both the magnetization and the mass enhancement factor. For the case away from the half-filling, the results is consistent with the metamagnetic behavior observed in CeRu$_2$Si$_2$.
We describe a minimal model, based on a spin only Hamiltonian with a single energy scale for itinerant electron metamagnetism. Within this model the metamagnetic critical field is directly proportional to the temperature where a peak in the linear susceptibility occurs which in turn is related in a simple manner to the temperature where the nonlinear susceptibilities also peak. The spin dependent thermodynamic properties are derived in a straightforward manner and bear a striking resemblance to observations in such strongly correlated systems as heavy fermion materials. We also consider extens…
Anisotropic metamagnetism and magnetotransport of heavy rare-earth orthorhombic single-crystal TbAlGe
University of Maryland, College Park（马里兰大学帕克分校）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；National High Magnetic Field Laboratory, Tallahassee（国家高磁场实验室（塔拉哈西））
We investigated the thermodynamic property of the heavy fermion superconductor UTe$_2$ in pulsed high magnetic fields. The superconducting transition in zero field was observed at $T_{\rm c}$=1.65 K as a sharp heat capacity jump. Magnetocaloric effect measurements in pulsed-magnetic fields obviously detected a thermodynamic anomaly accompanied by a first-order metamagnetic transition at $μ$$_{0}$$H_{\rm m}$=36.0 T when the fields are applied nearly along the hard-magnetization $b$-axis. From the results of heat capacity measurements in magnetic fields, we found a drastic diverging electronic h…
Different metamagnetism between paramagnetic Ce and Yb isomorphs
为了解决重费米子系统中的变磁现象之谜，我们比较了顺磁同质结构Ce和Yb系统，CeNi $_2$ Ge $_2$和YbNi $_2$ Ge $_2$，它们都位于磁不稳定性附近。最有趣的结果是在脉冲磁场中的磁化测量发现了两个系统中的变磁性转变。这是Ce和Yb类质同象顺磁系统的变磁性的首次观测。类似于其他的变磁体，两种化合物的变磁性转变场都很好地由温度$T_χ^{\rm max}$来缩放，在该温度下磁化率显示出最大值。此外，CeNi $_2$ Ge $_2$的非线性磁化率$χ_3$的峰值出现在$T_χ^{\rm max}/2$附近，与其它重费米子超磁体一样。相反，YbNi $_2$ Ge $_2$在$T_χ^{\rm max}$处仅显示$χ_3$的符号变化，如在位于铁磁临界点附近的巡游变磁体中所观察到的。CeNi $_2$ Ge $_2$的变磁性对应于典型的近藤晶格系统，而YbNi $_2$ Ge $_2$的变磁性类似于近铁磁巡游系统。本文还讨论了YbNi $_2$ Ge $_2$变磁行为的其它可能性。
High-field metamagnetism in the antiferromagnet CeRh$_2$Si$_2$
本文研究了反铁磁体CeRh $_2$ Si $_2$在高达50特斯拉的脉冲磁场中的转矩、磁致伸缩和输运以及在高达13特斯拉的静磁场中的热膨胀。从这些测量中推导出CeRh $_2$ Si $_2$的磁场-温度相图，其中磁场沿易磁化轴$\mathbf{c}$施加。二级相变温度$T_{N}$和一级相变温度$T_{1,2}$（零场时分别为~36 K和26 K）随电场的增加而降低。场致反铁磁-顺磁边界线$H_c$在1.5 K时为26 T，从低温时的一阶变为高温时的二阶。磁场-温度相图被发现是由（至少）三个不同的反铁磁相。它们被一阶谱线$H_{1,2}$和$H_{2,3}$分开，前者对应于H=0时的$T_{1,2}$，后者在1.5 K时等于25.5 T。的最大值的$T^2$ -系数$A$的电阻率观察在发病的高场极化制度，这被解释为一个增强的有效质量的签名在场诱导的量子不稳定性。将CeRh $_2$ Si $_2$中$A$系数的磁场依赖性与其压力依赖性进行了比较，并与原型重费米子系统CeRu $_2$ Si $_2$中$A$的场依赖性进行了比较。
Symmetry-enforced heavy-fermion physics in the quadruple-perovskite CaCu3Ir4O12
重费米子材料主要是稀土或锕系金属间化合物，只有极少数d电子系统例外。这些d电子重费米子系统的物理机制仍然不清楚。在这里，通过研究四重钙钛矿CaCu 3 Ir 4 O 12，我们提出了一个基于量子力学的机制，可能会加强重费米子物理在d-电子系统。我们表明，相邻的Cu 3d轨道之间的电子跳跃受到晶体对称性的严格禁止，因此Cu 3d电子只能通过与其他更流动的能带杂交而变得离域，类似于典型的重费米子稀土金属间化合物中的情况。这为在d电子系统中加强重费米子物理提供了一种有用的方法，并可能有助于未来设计新的重费米子材料。
We study the topological properties of an antiferromagnetic phase with reflection symmetry in three-dimensional heavy-fermion systems. We here propose a reflection-symmetric topological state in the three-dimensional antiferromagnetic phase and demonstrate how the paramagnetic phase changes into the antiferromagnetic topological phase of f -electron materials such as SmB6.
The mechanism of strange metal (SM) with unconventional charge transport near magnetic phase transitions has become an outstanding open problem in correlated electron systems. Recently, an exotic quantum critical SM phase was observed in paramagnetic frustrated heavy-fermion materials near Kondo breakdown. We establish a controlled theoretical framework to this issue via a dynamical large-N fermionic multichannel approach to the two-dimensional Kondo-Heisenberg lattice model, where KB transition separates a heavy-Fermi liquid from fermionic spin-liquid state. With Kondo fluctuations being full…
Kondo Echo Dynamics of Terahertz-Pumped Heavy Fermions
Physikalisches Institut and Bethe Center for Theoretical Physics, Universität Bonn（波恩大学物理研究所与贝特理论物理中心）；Institute for Quantum Computing Analytics (PGI-12), Forschungszentrum Jülich（于利希研究中心量子计算分析研究所（PGI-12））；School of Physics and Astronomy, University of St. Andrews（圣安德鲁斯大学物理与天文学学院）
在某些镧系和锕系金属中，由于强的电子-电子相互作用，在低温下形成的比自由电子质量大得多的载流子的有效质量，包括钚形成的那些。这种重费米子质量反映在电子比热系数的显著增强$γ$中，对于元素钚本身来说，它比普通金属大得多。根据我们的定义，有12个钚基重费米子化合物，最近发现的，其基本性质是已知的和讨论。相对于其他例子，这些基于钚的重费米子系统特别复杂，部分原因是可能同时存在多个几乎简并的5 f $^n$构型。这种复杂性带来了重大的机遇和挑战，包括了解其中一些材料中非常规超导性的起源。
Applicability of Anderson and Hubbard model for Ce metal and cerium heavy fermion compounds
研究了在金属铈和铈重费米子化合物的电子结构计算中考虑格位间$f-f$杂化的重要性。我们证明，对于重费米子系统，如铈化合物CeCu $_2$ Si $_2$ $f-f$杂化可以忽略不计，安德森模型的应用是合理的。另一方面，对于铈金属，$f-f$杂化足够强以提供与$4f$和巡回电子之间的杂化相当的杂化功能的贡献。我们认为，在Ce的情况下，只有最一般的哈伯德和安德森模型相结合的哈密顿量应使用。
Antiferromagnetic criticality at a heavy-fermion quantum phase transition
对强关联电子系统磁相图的解释仍有争议。特别是，在零温度下发生的量子相变的物理学仍然是个谜。重费米子化合物是量子临界性的教科书例子，因为掺杂、压力或磁场的应用可以导致磁有序态和顺磁态之间的量子相变。一个中心问题涉及临界量子涨落的微观性质。它们是反铁磁的还是本地的？在这里，我们证明，使用非弹性中子散射实验，量子相变在重费米子系统Ce 1-xLaxRu 2 Si 2的反铁磁序参量的波动控制。至少对于这个重费米子家族来说，赫兹-米利斯-森谷自旋涨落方法似乎是描述量子反铁磁-顺磁不稳定性的可靠基础。
In heavy fermion systems, multipole degrees of freedom make possible the emergence of rich phenomena, such as hidden orders and superconductivities. However, many of them remain unsolved since the origin of higher-rank multipole interaction is not well understood. Among these issues, we focus on the quadrupole order in CeB$_6$, which is a famous multipolar heavy fermion system actively studied for decades. We analyze the multiorbital periodic Anderson model for CeB$_6$, and find that both magnetic, quadrupole, and octupole fluctuations develop cooperatively due to the strong inter-multipole co…
