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In this short overview, we summarize the optical spectroscopy FeTezxSex and AxFe2-ySe2. We elaborate that optical spectroscopy band structure evolution across the AFM phase transition temperature, studies on iron selenide superconducting systems measurements yield fruitful information about the the electronic correlation effect, the superconduct- ing pairing energy gap, the condensed carrier density or penetration depth, the inhomogeneity and the nanoscale phase separation between superconductivity and antiferromagnetism in those systems. 相似文献
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Common Features in Electronic Structure of the Oxypnictide Superconductors from Photoemission Spectroscopy 下载免费PDF全文
贾小文 ;刘海云 ;张文涛 ;赵林 ;孟建桥 ;刘国东 ;董晓莉 ;吴刚 ;刘荣华 ;陈仙辉 ;任治安 ;衣纬 ;车广灿 ;陈根富 ;王楠林 ;王桂玲 ;周永 ;朱镛 ;王晓阳 ;赵忠贤 ;许祖彦 ;陈创天 ;周兴江 《中国物理快报》2008,25(10):3765-3768
High resolution photoemission measurements are carried out on non-superconducting LaFeAsO parent com- pound and various superconducting RFeAs(O1-ZFx) (R=La, Ce and Pr) compounds. It is found that the parent LaFeAsO compound shows a metallic character. By extensive measurements, several common features are identified in the electronic structure of these Fe-based compounds: (1) 0.2 eV feature in the valence band, (2) a universal 13-16 meV feature, (3) near EF spectral weight suppression with decreasing temperature. These uni- versal features can provide important information about band structure, superconducting gap and pseudogap in these Fe-based materials. 相似文献
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通过研究用自组装法制备的萘磺酸掺杂的纳米管结构聚苯胺(苯胺与萘磺酸的摩尔比分别为1∶025,1∶05,1∶1,1∶2,1∶3)的电阻率温度依赖关系(测量温区为80—300K),仔细分析聚苯胺的结构形貌特征,提出了变程跳跃隧道穿透混合模型:认为在萘磺酸掺杂的纳米管结构聚苯胺样品中,跳跃和隧穿两种机制同时起作用,载流子沿纳米管传导是变程跳跃过程起主要作用,而载流子在纳米管之间的传导是隧穿过程起主要作用.实验结果表明,不同浓度的萘磺酸掺杂对样品的低温电阻率的影响很大,随着掺杂浓度增加,载流子传导所需克服的能垒C0迅速减小,当掺杂接近饱和时,C0不再减小.实验中还研究了不同形貌对电阻率的影响,结果表明样品中纳米管所占比例的增大有利于载流子传导
关键词:
聚苯胺
纳米管
低温电阻率 相似文献
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本文对Bi-系高Tc氧化物超导体的元素替代效应进行了系统的评述。对由于元素替代所引起的晶体结构、氧含量、空穴浓度和超导临界温度等参量的变化进行了重点讨论。总结出元素替代的两种机制,即CuO_2平面外原子格点上以改变迁移载流子浓度为主要特征的和在CuO_2平面内Cu的格点上以破坏局部磁有序、产生直接拆对作用为特征的替代效应。 相似文献
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Results of charge-transport and magnetic measurements of nanotubular polyaniline (PANI) composites containing Fe_3O_4 nanoparticles (~10nm) synthesized by a "template-free" method are reported. The T^{-1/2} resistivity has been observed, and dc magnetic susceptibility data are fitted to an equation χ=χ^*_P+C/T. With increasing weight ratio of Fe_3O_4, the electrical conductivity and temperature- independent susceptibility χ^*_P increase, and the Curie-type susceptibility is suppressed at low temperatures. Further discussions have been given. The PANI-H_3PO_4/Fe_3O_4 composite containing 27wt% of Fe_3O_4 nanoparticles is superparamagnetic, exhibiting very little hysteresis even at 5K. 相似文献
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High quality single crystal CaFe4As3 was grown by using the Sn flux method. Unlike layered CaFe2As2, CaFe4As3 crystallizes in an orthorhombic three-dimensional structure. Two magnetic ordering transitions are observed at ~90 K and ~27 K, respectively. The high temperature transition is an antiferromagnetic(AF) ordering transition. However, the low temperature transition shows complex properties. It shows a ferromagnetic-like transition when a field is applied along b-axis, while antiferromagnetism-like transition when a field is applied perpendicular to b-axis. These results suggest that the low temperature transition at 27 K is a first-order transition from an AF state to a canted AF state. In addition, the low temperature electron specific heat coefficient reaches as high as 143 mJ/mol·K2, showing a heavy fermion behavior. 相似文献