拓扑绝缘体Bi_2Te_3的热膨胀系数研究

Research of thermal expansion coefficient of topological insulator Bi_2Te_3

利用低温X射线衍射研究了Bi2Te3晶体的线热膨胀系数.结果表明:拓扑绝缘体Bi2Te3晶体的线热膨胀系数α||和α⊥表现为各向异性,并遵从不同的温度依赖关系.反映a-a平面内的膨胀系数α⊥在较宽的温区内服从Debye关系,而反映垂直于a-a平面方向的膨胀系数α||在100 K左右就开始出现与Debye模型在定性上的差别.利用Debye模型并结合Bi2Te3晶体的面内和层间原子之间的键合特性对α||和α⊥所表现出的不同温度依赖特性进行了解释.

Topological insulator Bi2Te3 crystals were grown and their thermal expansion was studied with X-ray diffraction at various temperatures. It was shown that the linear thermal expansion coefficients, α｜｜ and α⊥, which reflect, respectively, the thermal expansion within and out-off a-a plane of the Bi2Te3 crystal, exhibit quite different temperature dependent features. The α⊥ obeys the Debye law in a relatively wide temperature range, while α｜｜ deviates qualitatively from the Debye law at 100 K. Possible mechanisms behind the observed phenomena were explained using the crystal structure and the bonding features between the atoms in Bi2Te3 crystal.