本文用磁化率$χ(T)$、比热$C(T)$、电阻率$ρ(T)$和X射线吸收谱研究了Ce Mo $_{2}$ Si $_{2}$ C中Ce的价态涨落。粉末X射线衍射表明CeMo $_{2}$ Si $_{2}$ C以CeCr $_{2}$ Si $_{2}$ C型层状四元晶体结构（空间群\textit{P4/mmm}）结晶。CeMo $_{2}$ Si $_{2}$ C的晶胞体积偏离预期的镧系收缩，表明该化合物中Ce离子的非三价态。磁化率的温度依赖性很弱，且磁化率值很低，说明Ce离子处于价态涨落状态。CeMo $_{2}$ Si $_{2}$ C $<$ $\widetildeν$ $>$中的正式$L_{III}$ Ce价态由X射线吸收光谱测量确定= 3.11远低于四价Ce化合物CeO中的值$<$ $\widetildeν$ $> \simeq$ 3.4 $_{2}$。比热的温度依赖性没有显示出任何异常下降到1.8 K，这排除了系统中的任何磁有序。从比热数据获得的索末菲系数为$γ$ = 23.4mJ/mol 1，K $^{2}$。电阻率在低于35 K的低温范围内遵循$T{^2}$行为，证实了费米液体行为。因此，Kadowaki Wood比$A/γ^{2}$和Sommerfeld Wilson比$χ(0)/γ$都在费米液体系统预期的范围内。为了得到一些关于电子态的信息，我们在密度泛函理论中计算了能带结构，尽管这种方法不能精确地处理4f电子。穿过费米能级的非$f$电子态主要具有Mo 4d特征.它们提供了与4f态强烈杂化的状态，导致中间价态。
英文摘要：
We report on the valence fluctuation of Ce in CeMo$_{2}$Si$_{2}$C as studied by means of magnetic susceptibility $χ(T)$, specific heat $C(T)$, electrical resistivity $ρ(T)$ and x-ray absorption spectroscopy. Powder x-ray diffraction revealed that CeMo$_{2}$Si$_{2}$C crystallizes in CeCr$_{2}$Si$_{2}$C-type layered tetragonal crystal structure (space group \textit{P4/mmm}). The unit cell volume of CeMo$_{2}$Si$_{2}$C deviates from the expected lanthanide contraction, indicating non-trivalent state of Ce ions in this compound. The observed weak temperature dependence of the magnetic susceptibility and its low value indicate that Ce ions are in valence fluctuating state. The formal $L_{III}$ Ce valence in CeMo$_{2}$Si$_{2}$C $<$$\widetildeν$$>$ = 3.11 as determined from x-ray absorption spectroscopy measurement is well bellow the value $<$$\widetildeν$$> \simeq$ 3.4 in tetravalent Ce compound CeO$_{2}$. The temperature dependence of specific heat does not show any anomaly down to 1.8 K which rules out any magnetic ordering in the system. The Sommerfeld coefficient obtained from the specific heat data is $γ$ = 23.4 mJ/mol\,K$^{2}$. The electrical resistivity follows the $T{^2}$ behavior in the low temperature range below 35 K confirming a Fermi liquid behavior. Accordingly both the Kadowaki Wood ratio $A/γ^{2}$ and the Sommerfeld Wilson ratio $χ(0)/γ$ are in the range expected for Fermi-liquid systems. In order to get some information on the electronic states, we calculated the band structure within the density functional theory, eventhough this approach is not able to treat 4f electrons accurately. The non-$f$ electron states crossing the Fermi level have mostly Mo 4d character. They provide the states with which the 4f sates are strongly hybridized, leading to the intermediate valent state.
X-ray magnetic circular dichroism and resonant inelastic X-ray scattering explained: role of many-body correlation and valence fluctuations
Seoul National University（首尔大学）；Institute for Basic Science（基础科学研究院）；SLAC National Accelerator Laboratory（斯坦福直线加速器国家实验室）；Fudan University（复旦大学）；University of California, Davis（加州大学戴维斯分校）；University of Illinois（伊利诺伊大学）；National Institute of Standards and Technology（美国国家标准与技术研究院）
Valence fluctuations in Sn(Pb)$_2$P$_2$S$_6$ ferroelectrics
Sn（Pb）$_2$ P $_2$ S $_6$半导体中与磷离子$P^{4+} + P^{4+}\rightarrow P^{3+} + P^{5+}$的电荷交换有关的价态涨落是铁电态和量子顺电态的起源。它们涉及SnPS $_3$或PbPS $_3$结构基团的再充电，其可以表示为晶格中的半填充位点。Sn $_2$ P $_2$ S $_6$化合物的温度-压力相图和（Pb $_y$ Sn $_{1-y}$）$_2$ P $_2$ S $_6$混晶，其包括三临界点并且其中相变的温度降低到0 K，以及在量子顺电态冷却时低能光学声子的软化和介电极化率的上升用GGA电子和声子计算方法分析了Pb $_2$ P $_2$ S $_6$，并与电子关联模型进行了比较.建立了非简谐量子振子模型，用于描述介电常数的相图和温度依赖关系。
Valence fluctuation in Ce$_{2}$Co$_{3}$Ge$_{5}$ and crystal field effect in Pr$_{2}$Co$_{3}$Ge$_{5}$
制备了三元稀土锗化物R $_{2}$ Co $_{3}$ Ge $_{5}$（R = La，Ce，Pr）多晶样品，并通过磁化率、等温磁化强度、电阻率和比热等测试方法进行了研究。这些化合物均为正交晶系U $_{2}$ Co $_{3}$ Si $_{5}$结构（空间群\textit{Ibam}）。在这些化合物中，没有观察到磁性或超导转变的证据，直到2K。Ce $_{2}$ Co $_{3}$ Ge $_{5}$的晶胞体积偏离预期的镧系收缩，表明该化合物中Ce离子的非三价态。与三价Ce离子的预期值相比，有效矩的减小值（$μ_{eff}$ $\approx$ 0.95 $μ_{B}$）进一步支持Ce $_{2}$ Co $_{3}$ Ge $_{5}$中Ce的价态波动性质。磁化率随温度的变化与离子组态间涨落（ICF）模型一致。Pr $_{2}$ Co $_{3}$ Ge $_{5}$的比热的磁性部分虽然没有明显的相变异常，但观察到一个宽的Schottky型异常。对$C_{mag}$数据的分析表明，Pr $_{2}$ Co $_{3}$ Ge $_{5}$中的单重基态与单重第一激发态的分离度为22 K，而在73 K处为双重第二激发态。
Charles University（查理大学）；VSB – Technical University of Ostrava（俄斯特拉发理工大学）；Max-Planck-Institut für Chemische Physik fester Stoffe（马克斯·普朗克固体化学物理研究所）；Czech Academy of Sciences（捷克科学院）
`Interaction annealing' to determine effective quantized valence and orbital structure: an illustration with ferro-orbital order in WTe$_2$
School of Physics and Astronomy and Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交通大学物理与天文学院和汤川秀树研究所）；University of Cambridge（剑桥大学）；Department of Materials Science and Metallurgy, University of Cambridge（剑桥大学材料科学与工程系）；School of Materials Science and Engineering, Shanghai Jiao Tong University（上海交通大学材料科学与工程学院）；Shanghai Branch Hefei National Laboratory（合肥国家实验室上海分部）
