Intermediate valence in single crystalline Yb2Si2Al

Yb2Si2Al may be a prototype for exploring different aspects of the Shastry-Sutherland lattice, formed by planes of orthogonally coupled Yb ions. Measurements of the magnetic susceptibility find incoherently fluctuating Yb3+ moments coexisting with a weakly correlated metallic state that is confirmed by measurements of the electrical resistivity. Increasing signs of Kondo coherence are found with decreasing temperature, including an enhanced Sommerfeld coefficient and Kadowaki-Woods ratio that signal that the metallic state found at the lowest temperatures is a Fermi liquid where correlations have become significantly stronger. A pronounced peak in the electronic and magnetic specific heat indicates that the coupling of the Yb moments to the conduction electrons leads to an effective Kondo temperature that is approximately 30 K. The valence of Yb2Si2Al has been investigated with electron spectroscopy methods. Yb2Si2Al is found to be strongly intermediate valent [v(F) = 2.68(2) at 80 K]. Taken together, these experimental data are consistent with a scenario where a coherent Kondo lattice forms in Yb2Si2Al from an incoherently fluctuating ensemble of Yb moments with incomplete Kondo compensation, and strong intermediate valence character.

Yb₂Si₂Al可能是探索Shastry - Sutherland晶格不同方面的一个原型，它由正交耦合的Yb离子平面构成。磁化率测量发现无规涨落的Yb³⁺磁矩与弱关联金属态共存，这通过电阻率测量得到了证实。随着温度降低，发现越来越多的近藤相干迹象，包括增强的索末菲系数和Kadowaki - Woods比，这表明在最低温度下发现的金属态是一种费米液体，其中关联变得明显更强。电子和磁比热中一个显著的峰值表明Yb磁矩与传导电子的耦合导致有效近藤温度约为30 K。已用电子能谱方法研究了Yb₂Si₂Al的价态。发现Yb₂Si₂Al具有很强的中间价态[在80 K时，v(F)=2.68(2)]。综合来看，这些实验数据与一种情形相符，即在Yb₂Si₂Al中，从具有不完全近藤补偿和强中间价态特征的无规涨落的Yb磁矩集合中形成了一个相干近藤晶格。