高T_c超导体Bi_(1.7)Pb_(0.3)Sr_2CaCu_2O_(8+δ)中电四极相互作用与温度的关系  

TEMPERATURE DEPENDENCE OF ELECTRIC QUADRUPOLE INTERACTION IN HIGH T_c SUPERCONDUCTOR Bi_(1.7)Pb_(0.3)Sr_2CaCu_2O_(8+δ)

作　　者：董明理[1] 李建华[1] 杜树斌[1] 韩汝珊[2] 李广生[1] 李宏成[3] 李贵群[1] 慎伟琦 

机构地区：[1]中国原子能科学研究院,北京102413 [2]北京大学物理系,北京100871 [3]中国科学院物理研究所,北京100080

出　　处：《低温物理学报》1993年第4期294-299,共6页Low Temperature Physical Letters

基　　金：国家自然科学基金

摘　　要：用微分扰动角关联(DPAC)方法,在77—300K温度范围内,测量了高T_c超导体Bi_(1.7)Pb_(0.3)Sr_2CaCu_2O_(8+δ)中的电四极相互作用与温度的关系。由拟合DPAC谱,得出了二组非轴对称静态电场梯度,它们分别对应于Bi-O面上Bi_1位上和非公度调制的Bi_2位上的电场梯度。在102K和170K都观察到了两个Bi位上电场梯度不对称系数和电场梯度异常变化,这也许意味着在这两个温度点上有晶格位移而引起的类相变的发生。测量了驰豫常数随温度的变化,看到了在Bi-O面上的Bi有很强的核弛豫现象,说明存在动态场的作用。驰豫常数随温度的变化规律不同于BCS理论所预言的低温超导体中的变化规律。The temperature dependence of the electric quadrupole interaction in high Tc superconductor Bi1.7Pb0.3Sr2CaCu2O8+δ has been measured by means of the differential perturbed angular correlation (DPAC) from 77K to 300K. Two static, non-axially symmetric electric field gradients, which assigned to Bi1 and Bi2 sites in the Bi-O planes and the incommensurate modulation sites respectively have been derived from the fitting of DPAC spectra. Anomalous changes of the EFGs and their non-axially symmetric parameters of both the Bi sites were observed at 120K and 170K. It may indicate that a phase-like transition caused by the lattice displacing happens. The stronger nuclear relaxation phenomenon of Bu sites in the Bi-O planes can be found from the changes of relaxation constants measured with temperature. It shows that there is a fluctuation field in action. The behavior of the relaxation constants with temperature is different from the regularity of the low temperature superconductor expected by the BCS theory.

关 键 词：高TC 超导体 电四极 相互作用 温度 

分 类 号：O511.1[理学—低温物理]