Nearly isotropic superconductivity in (Ba,K)Fe2As2
Nearly isotropic superconductivity in (Ba,K)Fe2As2
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(Ba,K)Fe2As2 具有近各向同性超导性
DOI：
10.1038/nature07676
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发表时间：
2009-01-29
期刊：
影响因子：
64.8
通讯作者：
Wang, N. L.
中科院分区：
文献类型：
--
作者：
Yuan, H. Q.;Singleton, J.;Wang, N. L.
最近在铁砷基化合物中观察到超导性，超导转变温度（Tc）高达56 K，自然提高了与高Tc铜氧化物的比较。铜氧化物具有准二维电子性质的层状晶体结构，这导致人们推测，降低维数（即极端各向异性）是在40 K以上温度下超导的必要先决条件（参考文献，）。早期对铁砷化合物的研究似乎支持这一观点。本文报道了（Ba，K）Fe_2As_2单晶在高达60 T磁场中的电阻率测量结果。我们发现，超导性质实际上是相当各向同性的，在低温下与外加磁场的方向无关。这种行为与所有先前已知的层状超导体有着惊人的不同，并表明这些化合物中的降维并不是“高温”超导性的先决条件。我们认为，这种情况的出现是因为潜在的铁砷化合物的电子结构，这似乎是更多的三维比铜氧化物。外推的低场单晶数据不正确地表明一个高的各向异性和一个大大夸大的零温度上临界场。
Superconductivity was recently observed,,,,,,in iron-arsenic-based compounds with a superconducting transition temperature (Tc) as high as 56 K, naturally raising comparisons with the high-Tccopper oxides. The copper oxides have layered crystal structures with quasi-two-dimensional electronic properties, which led to speculation that reduced dimensionality (that is, extreme anisotropy) is a necessary prerequisite for superconductivity at temperatures above 40 K (refs , ). Early work on the iron-arsenic compounds seemed to support this view,. Here we report measurements of the electrical resistivity in single crystals of (Ba,K)Fe2As2in a magnetic field up to 60 T. We find that the superconducting properties are in fact quite isotropic, being rather independent of the direction of the applied magnetic fields at low temperature. Such behaviour is strikingly different from all previously known layered superconductors,, and indicates that reduced dimensionality in these compounds is not a prerequisite for ‘high-temperature’ superconductivity. We suggest that this situation arises because of the underlying electronic structure of the iron-arsenic compounds, which appears to be much more three dimensional than that of the copper oxides. Extrapolations of low-field single-crystal data incorrectly suggest a high anisotropy and a greatly exaggerated zero-temperature upper critical field.