【摘要】 测量了在O2 中退火不同时间的Sm1 .85Ce0 .1 5CuO4 单晶样品的热电势S与电阻率 ρ的温度依赖关系 .所有的样品电阻率高温下呈现线性温度依赖行为 .未退火的样品在 14 8K发生超导转变 ,而退火后的样品在低温下发生金属 半导体相变 ,其超导电性消失 ,表明退火引起了载流子浓度下降 ,体系进入欠掺杂态 .随着温度降低 ,所有的样品S T和ρ T曲线在 2 0 0K附近 (T )都发生斜率的改变 ,可以用赝能隙现象解释 .热电势S在低温下出现一个正的曳引峰 ,意味着载流子符号发生改变 ,由电子型转变为空穴型更多还原

【Abstract】 The temperature dependence of thermopower S and resistivity ρ for Sm 1.85 Ce 0.15 CuO 4 crystalline samples annealed in flowing oxygen for different days has been measured.All samples show linear temperature dependence.The original sample transformed into superconductor in 14 8K,while the samples annealed in oxygen lost superconductivity and became semiconductors at low temperatures indicating that annealing causes the decrease of the concentration of carrier and leads the system into under doped satate.With the decrease of temperature,the ρ T and S T curves of all samples exhibited changes of slope,which can be explained with pseudogap.A positive excitation drag contribution for thermopower S near 50K is observed in all samples,indicating the changing of the sign of carriers.更多还原