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Nonlinear uniaxial pressure dependence of the resistivity in Sr_(1-x)Ba_xFe_(1.97)Ni_(0.03)As_2 下载免费PDF全文
Nematic order and its fluctuations have been widely found in iron-based superconductors. Above the nematic order transition temperature, the resistivity shows a linear relationship with the uniaxial pressure or strain along the nematic direction and the normalized slope is thought to be associated with nematic susceptibility. Here we systematically studied the uniaxial pressure dependence of the resistivity in Sr_(1-x)Ba_xFe_(1.97)Ni_(0.03)As_2, where nonlinear behaviors are observed near the nematic transition temperature. We show that it can be well explained by the Landau theory for the second-order phase transitions considering that the external field is not zero. The effect of the coupling between the isotropic and nematic channels is shown to be negligible. Moreover, our results suggest that the nature of the magnetic and nematic transitions in Sr_(1-x)Ba_xFe_2As_2 is determined by the strength of the magnetic-elastic coupling. 相似文献
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Effect of residual stress on nematic domains in BaFe_(2-x)Ni_xAs_2 studied by angular magnetoresistance 下载免费PDF全文
We have studied the angular magnetoresistance of iron pnictides BaFe_(2-x)Ni_xAs_2, which shows clear 180 degree periodicity as fitted by a cosine function. In the x = 0.065 sample, the phase of the two-fold symmetry changes 90 degrees above the tetragonal-to-orthorhombic structural transition temperature Ts. Since the phase at low temperature is associated with the rotation of orthorhombic domains by magnetic field, we show that even vacuum grease can push the presence of orthorhombic domains at temperatures much higher than Ts. Our results suggest that residual stress may have significant effects in studying the nematic orders and its fluctuations in iron pnictides. 相似文献
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电阻起源于载流子(电子或空穴)在材料中运动过程中受到的各种各样的阻尼.按照材料的常温电阻率从大到小可以分为绝缘体、半导体和导体.绝大部分金属都是良导体,他们在室温下的电阻率非常小但不为零,在10-12 mΩ·cm量级附近.自然界是否存在电阻为零的材料呢?答案是肯定的,这就是超导体.当把超导材料降到某个特定温度以下的时候,将进入超导态,这时电阻将突降为零(图1),同时所有外磁场磁力线将被排出超导体外,导致体内磁感应强度为零,即同时出现零电阻态和完全抗磁性.超导态开始出现的温度一般称为超导临界温度,表示为Tc.微观上来说,当超导材料处于超导临界温度之下时,材料中费米面附近的电子将通过相互作用媒介而两两配对,这些电子对将同时处于稳定的低能组态,叫“凝聚体”.在外加电场驱动下,所有电子对整体能够步调一致地运动,因此超导又属于宏观量子凝聚现象.对于零电阻态,实验上已经证实超导材料的电阻率小于10-23 mΩ·cm,在实验精度允许范围内已经可以认为是零.如果将超导体做成环状并感应产生电流,电流将在环中流动不止且几乎不衰减.超导体的完全抗磁性并不依赖于超导体降温和加场的次序,也称为迈斯纳(Meissner)效应.一个材料是否为超导体,零电阻态和完全抗磁性是必须同时具有的两个独立特征. 相似文献
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正梦想是一定要有的,万一实现了呢。——马云每个人都有各自的梦想,小时候我们梦想成为科学家、教师、宇航员、艺术家,长大后我们梦想追逐更加舒适的生活和富足的精神世界。只要有梦想在,生活似乎就总是充满期待和希望。从事超导研究 相似文献
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本文以纳米In_2O_3为传感元件,设计构建了快速检测三氯乙烯的催化发光传感器。该传感器对三氯乙烯具有灵敏度高、特异性好及响应快速等优点。在检测波长为440nm,工作温度为250℃条件下,催化发光信号强度与三氯乙烯浓度呈良好的线性关系,其线性范围为20~1 200mg/m~3(r=0.9984),检出限(S/N=3)为8.0mg/m~3。苯、甲苯、邻二甲苯、对二甲苯、间二甲苯、氨水、甲醇、乙醇、甲醛、乙醛、四氯化碳、甲酸、乙酸、乙酸乙酯、正己烷及环己烷经过此传感器时,只有乙醇产生弱的发光信号,其它物质不产生响应信号。在72h内24次测定100mg/m~3的三氯乙烯,所得相对标准偏差小于5.0%,表明传感器稳定性好,使用寿命长。将此传感器用于三氯乙烯的分析,加标回收率为93.2%~103%。 相似文献
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