CeO_{0.9} F_{0.1} Co_xAs的强电子-电子关联和弱局域化
Strong electron-electron correlation and weak localization in CeO_{0.9}F_{0.1}Fe_{1-x}Co_xAs
摘要：
通过氟（最大Tc ~ 43 K）或钴（最大Tc ~ 11 K）对半金属（CeOFeAs）进行电子掺杂导致超导电性。在这里，我们显示的过渡金属（Co）的替代在铁网站上的CeO 0.9F 0.1FeAs（Tc ~38 K）的超导性能的影响，以了解载流子在稀土-氧和Fe-As层的相互作用。在两个层中同时掺杂相等数量的载流子导致9.8 K的Tc，其低于当导电层（CeAs）或电荷储存层（CeO）单独掺杂时获得的Tc。这表明这两层之间有明显的相互作用来控制超导性。电阻率显示出T2依赖性（T >>Tc），这表明强的电子-电子相关。霍尔系数和热电功率表明增加的载流子浓度与钴掺杂CeO0.9F0.1FeAs。CeO0.9F0.1Fe0.95Co0.05As和CeO0.9F0.1FeAs的射频穿透深度都表现出指数温度依赖性，间隙值为~ 1.6和1.9 meV。在正常状态下，在Tc附近观察到电阻最小值，这也显示出负磁阻，并为弱局部化的发生提供了证据。
英文摘要：
Electron-doping of the semimetal (CeOFeAs) by either fluorine (max Tc ~ 43 K)or cobalt (max Tc ~ 11 K) leads to superconductivity. Here we show the effect of transition metal (Co) substitution at the iron site on the superconducting properties of CeO0.9F0.1FeAs (Tc ~38 K)to understand the interplay of charge carriers in both the rare earth-oxygen and Fe-As layers. Simultaneous doping of equivalent number of charge carriers in both layers leads to a Tc of 9.8 K which is lower than the Tc obtained when either the conducting layer (CeAs) or charge reservoir layer (CeO) is individually doped. This suggests a clear interplay between the two layers to control the superconductivity. The resistivity shows a T2 dependence (T >>Tc) which indicates strong electron-electron correlation. Hall coefficient and thermoelectric power indicate increased carrier concentration with cobalt doping in CeO0.9F0.1FeAs. The rf penetration depth both for CeO0.9F0.1Fe0.95Co0.05As and CeO0.9F0.1FeAs show an exponential temperature dependence with a gap value of ~ 1.6 and 1.9 meV. A resistance minimum is observed in the normal state near Tc which also shows negative magnetoresistance and provides evidence for the onset of weak localization.
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