La_(2-x)Sr_xCuO_4单晶的各向异性热导率的测量

Measuring anisotropic thermal conductivity of La_(2-x)Sr_xCuO_4 single crystals

采用加热器和温差电偶搭建了低温热导率的稳态法测量装置,并研究了高温超导材料La_(2-x)Sr_xCuO_4(x=0.01~0.04)单晶的各向异性热导率.实验发现:热导率随温度的变化存在明显的声子峰,并且随着Sr掺杂量的增大,声子热导率逐渐被压制,声子峰的强度也逐渐变弱,该现象来源于掺杂引起的晶格无序度的增强.对于欠掺杂的样品,a方向的热导率总是比b方向的大,这可能源于自旋/电荷沿a轴方向形成准一维的条纹状分布,而准一维的条纹结构会对b方向传导的声子产生额外的散射作用.

A low-temperature thermal conductivity measurement system using a heater and a thermocouple was set up based on the steady-state-method,and the anisotropic thermal conductivity of high-Tcsuperconducting La_(2-x)Sr_xCuO_4(x=0.01~0.04)single crystals was studied.An obvious phonon peak was found in the temperature dependent thermal conductivity curve.The phonon conductivity was gradually suppressed,and the strength of the phonon peak was weakened with the increase of Sr doping.This phenomenon originated from the increase of the lattice disorder.On the other hand,for those underdoped materials,the a-axis thermal conductivity was always a little larger than the baxis thermal conductivity.This might be due to the quasi one-dimensional stripe distribution of the spin/charge along the a-axis.Such a quasi one-dimensional stripe structure would cause extra scattering on phonons along the b-axis.