European Synchrotron Radiation Facility, 71 Avenue des Martyrs, CS 40220, 38043, Grenoble Cedex 9, France.
Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany.
Nat Commun. 2018 May 22;9(1):2011. doi: 10.1038/s41467-018-04438-8.
The Kondo model predicts that both the valence at low temperatures and its temperature dependence scale with the characteristic energy T of the Kondo interaction. Here, we study the evolution of the 4f occupancy with temperature in a series of Yb Kondo lattices using resonant X-ray emission spectroscopy. In agreement with simple theoretical models, we observe a scaling between the valence at low temperature and T obtained from thermodynamic measurements. In contrast, the temperature scale T at which the valence increases with temperature is almost the same in all investigated materials while the Kondo temperatures differ by almost four orders of magnitude. This observation is in remarkable contradiction to both naive expectation and precise theoretical predictions of the Kondo model, asking for further theoretical work in order to explain our findings. Our data exclude the presence of a quantum critical valence transition in YbRhSi.
近藤模型预测，低温下的价态及其对温度的依赖关系都与近藤相互作用的特征能量 T 成正比。在这里，我们使用共振 X 射线发射光谱研究了一系列 Yb 近藤晶格中 4f 占据数随温度的演化。与简单的理论模型一致，我们观察到低温下的价态与从热力学测量得到的 T 之间的标度关系。相比之下，在所有研究的材料中，价态随温度升高的温度标度 T 几乎相同，而近藤温度却相差近四个数量级。这一观察结果与近藤模型的简单预期和精确理论预测明显矛盾，需要进一步的理论工作来解释我们的发现。我们的数据排除了 YbRhSi 中存在量子临界价跃迁的可能性。
