Spectroscopic evidence of the existence of substantial Ca 3d derived states at the Fermi level in the Ca-intercalated graphite superconductor CaC6
Spectroscopic evidence of the existence of substantial Ca 3d derived states at the Fermi level in the Ca-intercalated graphite superconductor CaC6
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DOI：
10.1103/physrevb.80.035420
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发表时间：
2009-07-01
影响因子：
3.7
通讯作者：
Yokoya, T.
中科院分区：
文献类型：
--
作者：
Okazaki, H.;Yoshida, R.;Yokoya, T.
我们对钙嵌入石墨超导体CaC_6（Tc = 11.2K）进行了软X射线光电子能谱研究。价带谱显示出六种主要结构，在费米能级（E-F）处有一个峰，这与计算的DOS相对应。E-F峰的强度在Ca 2 p-3d阈值处共振增强，为Ca 3d电子在E-F处的存在提供了光谱证据，这在实验上是首次得到证实。Ca 2 p芯能级谱具有非常大的不对称线形，这进一步可能暗示Ca 3d衍生的传导电子在Ca位点的存在。这些结果有力地支持了Ca 3d衍生的层间带对这种具有相对高的Tc的材料的超导电性起着至关重要的作用的图片。
We have performed soft x-ray photoemission studies of Ca-intercalated graphite superconductor CaC6 (T-c=11.2 K). The valence-band spectrum shows six main structures, with a peak at the Fermi level (E-F), which correspond to those of calculated DOS. The intensity of the E-F peak is resonantly enhanced at the Ca 2p-3d threshold, providing spectroscopic evidence for the existence of Ca 3d electrons at E-F, which is confirmed experimentally for the first time. The Ca 2p core-level spectrum has a very large asymmetric line shape, which is further possible suggestion of the existence of Ca 3d derived conduction electrons at Ca sites. These results strongly support the picture where Ca 3d derived interlayer band plays a crucial role for the superconductivity of this material with relatively high T-c.