Anisotropic Thermal Expansion of α-YbAlB4

International Conference on Strongly Correlated Electron Systems 2016

Matsumoto, Yosuke^1 ; Kuga, K.^1 ; Tomita, T.^1 ; Küchler, R.^2 ; Nakatsuji, S.^1

Institute for Solid State Physics, University of Tokyo, Kashiwa

277-8581, Japan^1

Max Planck Institute for Chemical Physics of Solids, Dresden

D-01187, Germany^2

关键词: Anisotropic thermal expansion;    Capacitance dilatometry;    Characteristic temperature;    Crystal electric field;    Linear thermal expansion coefficients;    Powder X ray diffraction;    Thermal expansion measurements;    Valence fluctuations;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/807/2/022005/pdf
DOI  :  10.1088/1742-6596/807/2/022005

来源: IOP

【 摘 要 】

Thermal expansion measurements were performed for α-YbAlB4using powder X-ray diffraction and our high resolution capacitance dilatometry. Highly anisotropic thermal expansion, which is much larger along the c-axis compared to the a- and b-axes, was observed. In addition, high resolution capacitance dilatometry revealed negative thermal expansion appears below 90 K only along the a-axis, not along the c-axis. The observation is consistent with anisotropic hybridization stronger in the ab-plane, suggesting the formation of anisotripic heavy fermion well below the valence fluctuation temperature scale of 200 ∼ 300 K. Furthermore, linear thermal expansion coefficient along the a-axis starts to decrease below 115 K. The characteristic temperature scale of 90 - 115 K may correspond to the crystal electric field excited level. The in-plane negative thermal expansion can be regarded as a development of anisotropic hybridization due to |Jz= ±5/2 > crystal electric field ground states which becomes dominant on cooling below the excited states.