Sm_(2-x)Ce_xCuO_4单晶的赝能隙行为研究  

THE PSEUDOGAP BEHAVIOR IN ELECTRO-DOPED Sm_(2-x)Ce_xCuO_4 SINGLE CRYSTAL

作　　者：柴一晟[1] 杨宏顺[1] 刘剑[1] 余旻[1] 曹烈兆[1] 

机构地区：[1]中国科学技术大学物理系结构分析开放实验室,合肥230026

出　　处：《低温物理学报》2004年第1期26-30,共5页Low Temperature Physical Letters

基　　金：国家重点基础研究项目资助的课题 (批准号 :G19990 6 4 6 )~~

摘　　要：我们在电子型超导体Sm1 .85Ce0 .1 5CuO4中首次观察到赝能隙的证据 .研究了在O2 中不同退火时间 ,单晶Sm1 .85Ce0 .1 5CuO4样品的电阻率 ρ和热电势S ,电阻率 ρ的测量结果显示退火后样品高温区电阻率 ρ、dρ/dT和热电势的斜率dS/dT斜率增加 ,意味着载流子浓度下降 ,与减小Ce掺杂量x的作用等效 .所有的样品S～T和 ρ～T曲线在某个温度T 下都发生斜率的改变 ,该转变温度随着退火时间的增加而向高温区移动 ,而且越来越明显 .这可能是因为该温度下赝能隙被打开 ,热电势曲线在某个温度下存在一个最小值 ,这是载流子局域化的表现 ;热电势曲线上 5 0K附近观察到一个明显的声子曳引峰 ,正的峰值表示载流子符号在低温区发生了改变 ,即由高温的电子型变为低温的空穴型 ,与霍尔系数实验中斜率变化一致 .The pseudogap-like behavior has been observed in electro-doped superconductor Sm_ 1.85 Ce_ 0.15 CuO_4 for the first time. The resistivity ρ and thermopower S of single crystal Sm_ 1.85 Ce_ 0.15 CuO_4 with different annealing times were measured. The data of temperature dependence of resistivity indicate that the high temperature resistivity ρ ,d ρ /d T and the slope of thermopower d S /d T increase with increasing annealing time,which presume a decrease of charge density and act as the decrease of Ce content x . In each annealing procedure,the curve of S～T and ρ～T change their slopes below a certain temperature T * . It moves to high temperature region with increase annealing time,and becomes more and more clear,indicating the opening of a pseudogap under this temperature. At the same time,a minimum value exists in the thermopower at certain temperature,which is the manifest of carrier localization. At about 50K,a clear peak of phonon-drag was observed in thermopower,and its positive value shows a change of sign in charge carrier at low temperature,which is in accordance with the change of slope in Hall coefficients.

关 键 词：超导物理学 电子型超导体 输运性质 热电势 赝能隙 退火时间 电阻率 载流子浓度 铈掺杂 

分 类 号：O731[理学—晶体学]